Light-level geolocation reveals migration patterns of the Buff

research paper Wader Study 123(1): 29–43. doi: 10.18194/ws.00032
Light-level geolocation reveals migration patterns of the Buff-breasted
Sandpiper
Richard B. Lanctot1*, Stephen Yezerinac2, Joaquin Aldabe3#, Juliana Bosi de Almeida4#,
Gabriel Castresana5#, Stephen Brown6, Pablo Rocca3, Sarah T. Saalfeld1 & James W. Fox7
1
U.S. Fish and Wildlife Service, Migratory Bird Management Division, 1011 East Tudor Road, MS 201, Anchorage,
Alaska, 99503, USA
2
Mount Allison University, Biology Department, 63B York Street, Sackville, New Brunswick, E4L 1G7, Canada
3
Centro Universitario Regional del Este, Universidad de la República, Ruta 15(y Ruta 9), Km 28.5000, Departamento
de Rocha, Uruguay; and Departamento de Conservación, Aves Uruguay / BirdLife International, Canelones 1164,
Montevideo, Uruguay
4
SAVE Brasil/Birdlife International, Rua Fernão Dias, 219 cj. 2, Pinheiros, São Paulo, SP 05427-01, Brazil
5
Dirección de Áreas Naturales Protegidas, Organismo Provincial para el Desarrollo Sostenible, Ferrari 500 Gral,
Conesa, Buenos Aires, Argentina
6
Manomet, PO Box 545, Saxtons River, Vermont, 05154, USA
7
Migrate Technology Ltd, PO Box 749, Cambridge, CB1 0QY, UK
#
ese authors contributed equally to the paper; each led fieldwork in their respective countries.
*Corresponding author: [email protected]
Lanctot, R.B., S. Yezerinac, J. Aldabe, J. Bosi de Almeida, G. Castresana, S. Brown, P. Rocca, S.T. Saalfeld & J.W. Fox.
2016. Light-level geolocation reveals migration patterns of the Buff-breasted Sandpiper. Wader Study 123(1): 29–43.
Buff-breasted Sandpipers Calidris subruficollis have a small and apparently
declining population, and face threats both during migration and while wintering.
To document their migratory patterns, we equipped 62 Buff-breasted Sandpipers
with light-level loggers on their wintering sites in Argentina, Brazil, and Uruguay
during the austral summer of 2012/2013. A year later, we recovered data from
three birds (two females and one male) and tracked their movements for one
complete migratory cycle. During northbound migration, all three birds traveled
non-stop to Colombia, then to coastal Texas, followed by several smaller
movements within the Central Plains, and one last non-stop flight to their
breeding grounds in Canada and Alaska. Southward migration was similar except
stops in Bolivia and Paraguay were used. Birds took ~1.5 months and 4–7 stops
to travel north, and 2–2.5 months and 4–6 stops to travel south. Females each
traveled >33,000 km and the single male traveled >41,000 km during their
annual migratory cycles. The longer migration distance of the male appears to
be a result of him stopping, and possibly visiting leks, at two and possibly three
disjointed sites across the Arctic. The most important stopover sites for this
species appear to be in Colombia and coastal Texas (north and southbound
migrations), and Bolivia and Paraguay (southbound migration only). Additional
areas were used in the Great Plains but for less time, including the Eastern
Rainwater Basin of Nebraska and the Flint Hills of Kansas. The time spent at
stopovers varied between sites and the direction of migration, ranging from 2–4
weeks in Colombia and Texas, and 1–20 days in the Central Plains. Local
observations of birds indicate they likely spread over a broad area during
stopovers. To fully understand how the species uses the landscape will require
more precise locations from additional individuals and systematic ground
surveys.
Keywords
Buff-breasted Sandpiper
Calidris subruficollis
connectivity
geolocator
migration
stopover
Western Hemisphere
30 Wader Study 123(1) 2016
INTRODUCTION
Shorebird species in North America are facing serious
population declines (Bart et al. 2007, Andres et al. 2012),
declining faster than many other bird taxa (Zöckler et al.
2012, NABCI 2014). To stop these declines and recover
populations to the levels called for in the U.S. and Canadian
shorebird conservation plans (Donaldson et al. 2000,
Brown et al. 2001), conservation efforts may be needed
across species’ entire annual cycle. To do this, knowledge
of the geographic links between migratory populations at
different stages of their annual cycle is needed (Marra et
al. 1998, Webster et al. 2002). This is particularly true for
long-distance migrants, such as shorebirds, that travel
across geopolitical jurisdictions that vary in their conservation
and protective measures. Unfortunately, except in broad
generalities, for many taxa, little is known about how individual birds travel between breeding, migratory stopover,
and wintering sites. Knowing these patterns could give
insight into causes of the population trajectories for these
species and help identify key areas for conservation.
Until recently, tracking small animals, particularly birds,
throughout their entire migratory cycle has been difficult.
Satellite transmitters are too large for most birds, and
indirect measures such as stable isotopes and genetics
can typically only assign individuals to specific populations
(Haig et al. 1997, Franks et al. 2012, Miller et al. 2015).
Recent advances in the miniaturization of electronic
devices has led to the development of very small lightlevel loggers (a.k.a. geolocators) that can be attached to
small migratory birds for accurate individual tracking
(Clark et al. 2010). These loggers measure levels of sunlight
and store them along with a time stamp in their internal
memory. Birds are equipped with loggers at a location
where they can be recaptured later for data download.
Once recovered, the light levels can be analyzed to estimate
daily sunrise and sunset times. Latitude is then calculated
using day length and longitude is calculated using local
apparent noon and midnight. Errors of geolocations can
be ±200 km; accuracy is much greater for longitude and
both metrics can be greatly improved by averaging when
birds spend multiple days at a given locale, using habitat
knowledge, weather patterns, the geolocator’s conductivity
sensor, and other techniques (Porter & Smith 2013, S.
Yezerinac, pers. obs).
By providing tracking throughout the year, light-level
loggers can provide many new insights into the life history
of wild birds. For example, daily tracks can reveal migration
routes, travel speeds, stopover locations and turnover
rates, and the breeding or wintering locales for individuals
(the latter depending on where the bird is equipped).
This information can reveal inherent migratory differences
between individuals (Conklin et al. 2010, Egevang et al.
2010, Minton et al. 2010), degree of sexual and age segregation in migration routes and breeding/wintering locations,
and level of migratory connectivity between specific wintering, breeding, and stopover sites (Finch et al. 2015).
Such information can then be used to make site-level
conservation and management recommendations.
One species that is lacking information on migration
patterns is the Buff-breasted Sandpiper Calidris subruficollis.
This species is of high conservation concern because of
its small (~56,000 individuals; range: 35,000–78,000;
Andres et al. 2012) and apparently declining population,
with threats occurring both during migration and on
wintering grounds (Lanctot et al. 2010). Buff-breasted
Sandpipers are categorized as ‘Near Threatened’ by IUCN,
are included in Appendices I and II of the Convention on
Migratory Species of Wild Animals, and occur on conservation lists of countries throughout their range
(Argentina: Threatened, López-Lanús et al. 2008; Brazil:
Vulnerable, MMA 2014; Canada: Species of Special Concern, COSEWIC 2012; Paraguay, Near Threatened, del
Castillo et al. 2005; United States: Bird of Conservation
Concern, U.S. Shorebird Conservation Plan Partnership
2015; Uruguay: Priority Species for Conservation, Aldabe
et al. 2013).
The Buff-breasted Sandpiper is one of the longest-distance
migrants in the Western Hemisphere, breeding sporadically
in Arctic regions of Russia, Alaska, and Canada, and
wintering in southern South America (Lanctot & Laredo
1994). Roughly, it is thought that the species migrates
through central South America, across the Gulf of Mexico,
and through the central United States and Canada before
the birds reach the Arctic coast. Southbound migration
is thought to follow a similar route, but over a much
broader range, with juveniles frequently seen on the
Atlantic coast of North America. The species typically
migrates in small flocks but occasionally can be found in
large flocks numbering in the thousands on both staging
and wintering sites, apparently when habitat conditions
restrict suitable habitat availability (Lanctot et al. 2002;
K. Strum, B. Ortego, R. Russell, summaries of eBird and
state listserv data). Stopover sites do not appear to be
fixed at any given location, although general geographic
areas are used repeatedly (see Lanctot et al. 2010). To
date, no major north or southbound migration stopover
sites have been located in northern South America,
although sites with smaller numbers of birds have been
found (Ruiz-Guerra et al. 2013). Unfortunately, much of
the available information on this subject is based on incidental sightings of Buff-breasted Sandpipers by birders
and occasional organized surveyors. This type of data
has a high likelihood of being biased because observations
are primarily limited to areas accessible to people (e.g.,
roads; see Lanctot et al. 2008 for discussion on survey
bias). For this reason, authors of the recently published
Buff-breasted Sandpiper Conservation Plan suggested
that ascertaining migration patterns and geographic areas
of concentration, as well as linking breeding and nonbreeding locations, are the highest range-wide priorities
for this species (Lanctot et al. 2010).
Here, we summarize results from a light-level geolocation
study conducted on Buff-breasted Sandpipers in southern
South America. Unlike most other small shorebirds, this
species shows site-fidelity to wintering areas but not to
breeding areas (Lanctot & Weatherhead 1997, Almeida
2009), requiring loggers to be placed on birds on their
Lanctot et al. l Migration patterns of Buff-breasted Sandpipers 31
Fig. 1. Location of principal wintering locations (dark gray) of the Buff-breasted Sandpiper in southern South America
(after Lanctot et al. 2004). The three study sites where birds were captured are indicated with white dots. Coastal lagoons
are in light gray.
wintering areas so they can be recaptured and the data
downloaded. We report efforts to capture and recover
birds, the route and relative importance of stopover sites
along the species migration pathway, timing of migration
during both north and southbound migration, turnover
rates at stopover sites, general migratory connectivity, as
well as information on sex-ratio and within- and betweenyear site-fidelity to major wintering locations.
METHODS
We conducted field work at Laguna de Rocha in Uruguay
(34°38'S, 54°17'W), Lagoa do Peixe in Brazil (31°18'S,
51°00'W), and Bahía Samborombón in Argentina (36°00'S,
57°12'W; Fig. 1). All three sites are used consistently by
Buff-breasted Sandpipers, and prior marking studies suggested that 30–50% of the birds might return the following
year (Almeida 2009, Lanctot et al. 2010, J. Aldabe & P.
Rocca, pers. obs.). Teams of 4–6 people captured birds at
each site for about 2–4 weeks between mid-December
2012 and mid-January 2013. We used cannon nets and
wilsternets (Koopman & Hulscher 1979) during the day
and bright lights and cast nets at night. We measured and
weighed each bird, and then placed a numbered metal
band and one or two colored-engraved leg flag(s) on one
leg as specified by the Pan American Shorebird Program.
We placed a custom-made, size 1A, dark green flag with
an attached Intigeo-W65A9RK light-level logger (Migrate
Technology Ltd., Cambridge, UK) on the other leg of
most birds (Fig. 2). Loggers were attached to flags with
cyanocrylate glue, and logger and flag collectively weighed
about 1.1 grams (2.0% of average body mass). We attached
logger flags to the left tibia of birds such that the light
sensor faced distally when the logger pointed anteriorly.
These loggers were suitable for >1 year archival recording
of near full range ambient light with temperature and
conductivity indicators. We took pictures of the ventral
sides of most birds’ wings for later aging based on spotting
on the outer primaries (see Lanctot et al. 2010). The sex
of the birds was determined using a discriminant function
analysis based on the length of the total head (back of
head to tip of bill), diagonal tarsus, and flattened and
extended wing (Almeida 2009).
In December 2013 and January 2014, field crews returned
to the same study areas to search for previously marked
birds. We used spotting scopes and binoculars to search
for birds and visited fields where birds were initially
captured repeatedly for 3–4 weeks. Once a geolocatorequipped bird was found, we attempted to lethally collect
32 Wader Study 123(1) 2016
either travelling or stationary. Periods of travel were identified by consistent directional movement and distances
between consecutive fixes of over 200 km. In contrast,
stationary periods were identified by the absence of consistent directional change in latitude and longitude, and
distances between consecutive fixes that were within the
range shown by birds at stationary wintering locales.
Thus, it was possible in practice to discern the start and
end of each stopover or travel period with a resolution of
0.5–1 day.
Fig. 2. Buff-breasted Sandpiper with engraved flag on right
leg and geolocator on left leg. Inset: close-up of light-level
geolocator attached to leg flag (photo of bird: C. Alves da
Silva).
it (under appropriate permits; see Acknowledgements)
using either pellet guns or 22-caliber rifles, as recapturing
specific individuals was unsuccessful during trials the
previous season using a variety of capture methods such
as net guns and whoosh nets. Loggers were removed
from the collected birds and the birds were weighed and
frozen for later shipment to museums.
The geolocators sampled light level every minute and
recorded the maximum sampled in each 5-min period
on a 249-point logarithmic scale spanning from one to
74,000 lux. Each recovered logger had light records that
spanned from deployment through return to the site of
recapture. Each logger’s battery died before download, so
no correction could be made for clock drift. However,
clock drift was apparently minimal, as the longitudinal
fixes were equally accurate for the locations of deployment
and recapture. The sequences of light records were
analyzed with IntiProc software (v1.02, Migrate Technology
Ltd., Cambridge, UK) and a light-level threshold of 20
lux to identify daily times of sunrise and sunset. Both
sunrise-to-sunset and sunset-to-sunrise periods were
used to generate bird locations. To work out appropriate
sun-elevation angles to ascribe to the times of sun
transition for the calculation of geographic fixes, we used
the geolocation algorithms in the R package GeoLight
(v1.03; Lisovski & Hahn 2012, R Core Team 2013). For
the period that each bird remained static at the locale
where it was captured, we determined the average sunelevation angle (range –3.3° to –3.8°) that yielded the
lowest average deviation between the fixes and the actual
location where the bird was captured. This sun elevation
angle was used in further analyses. For one logger there
was a change of 0.5° in average sun-elevation angle from
the start to the end of deployment; we assumed this
logger changed in sensitivity, so we linearly interpolated
the change over the year.
We mapped tracks and stepped through them one fix at a
time to parse the fixes into periods when the bird was
Light-level geolocation data provide imprecise estimates
of location (see Fudickar et al. 2012, Lisovski et al. 2012).
The accuracy of fixes are reduced by factors such as
weather, latitude, longitudinal travel, and date proximity
to the equinoxes. Latitude uncertainty is particularly high
during the spring and fall equinoxes (21 March and 21
September). Degrees of longitude also have high uncertainty
when birds migrate north of the Arctic Circle due to the
increased spatial density of lines of longitude. Longitude
and especially latitude become more difficult to establish
as the dark night period reduces (into 24-hr daylight),
but generally a diurnal pattern is clear. In general, due to
the nature of the astronomy, longitudinal data tend to
have higher accuracy than latitude. To better understand
the magnitude of the uncertainty, we placed a test logger
in an ideal location (above ground in open pasture in
Argentina — far south of the equator at a place where
daylight length is more variable throughout the year)
and restricted our analyses to ideal conditions (i.e., days
with relatively clear skies and near the solstice) and determined how predicted fixes differed from actual fixes.
The range of fixes from this logger was ~230 km latitude
and ~100 km longitude from the actual site. The average
of all the fixes was ~38 km from the actual site. Thus, as
accuracy will be lower for loggers carried by birds due to
behavioral and environmental factors that reduce accuracy
of light records, a regional scale perspective should be
used when interpreting mapped locations.
Because error distributions for fixes are non-normal, we
mapped the mean latitude and longitude for each stopover
along with the 75th and 25th percentiles, respectively, of
all of the fixes that contributed to each stopover locale.
We depicted direct connections between stopovers (rather
than the actual fixes identified as belonging to periods of
travel) simply to aid in interpreting the sequence of
stopovers. These connections do not imply actual travel
routes, as uncertainty is high with light-level geolocation.
When birds were in areas without a sufficiently dark
night (i.e., breeding locales and one stopover/breeding
location), we did not estimate latitude, however we
estimated longitude using the midpoint (i.e., local
noon/midnight) of the diurnal cycle of declining and
increasing light as the sun descended and rose in the
southern sky. We ascribed midnight times for only those
days where the diurnal pattern was clear. However, such
days were the majority of days in the Arctic. Here, we
delimited possible breeding ranges for individuals by
restricting known breeding ranges of the species as
available on NatureServe (www.natureserve.org) using 66°
Lanctot et al. l Migration patterns of Buff-breasted Sandpipers 33
Fig. 3. Northbound (A) and southbound (B) movement of three Buff-breasted Sandpipers during the 2013 migration
periods as determined from light-level geolocation. Yellow shaded areas represent possible breeding locations and stars
indicate winter capture locations. The two red stars are the capture sites in Argentina and Brazil for the three recaptured
birds, while the open star is the capture site in Uruguay where no birds were recaptured. The red square represents a
second wintering site used by the recaptured male. The green line represents the c615 male, the purple line represents
c469 female, and the blue represents the c514 female (see Table 2 for more details at each location, and the text for
uncertainty associated with locations and lines connecting locations). The question marks (??) indicate the region where
the male either staged temporarily or bred, but the location was too uncertain to plot. Size of stopover dot indicates
length of stay. See Figs. 4–5 for more details on staging sites and their associated uncertainties in North and South
America.
(latitude of the Arctic Circle where continuous daylight
in the summer begins) and 78° (north of the most
northern known observation for the species) for the
southern and northern edges, respectively, and the mean
± 1 SD of all longitude locations for the western and
eastern edges. Weight values are reported as means ± SD.
RESULTS
We captured and deployed loggers on 62 Buff-breasted
Sandpipers between 15 December 2012 and 23 January
2013 (Table 1). An additional nine birds were captured
but did not have loggers attached. We placed loggers on
after-hatch year birds (62.3%), hatch year (20.9%), and
unknown age birds (17.7%; pictures were not taken of
wings so aging was impossible). Discriminate function
analyses indicated we placed loggers primarily on females
(61.3%). Of the birds captured (n = 71), the sex ratio was
1.4:1 females to males in Argentina, 1.5:1 in Uruguay,
and 1.5:1 in Brazil. Between December 2013 and January
2014, we collected and downloaded data from three Buffbreasted Sandpipers (two in Argentina and one in Brazil).
The male and one female lost 6.9 g and 2.0 g, respectively,
and the remaining female gained 1.0 g. We also observed
at least three other geolocator-equipped birds in the
austral summer of 2013/2014 (2 in Brazil, 1 in Argentina)
and one during the austral summer of 2014/2015 (1 in
Argentina), but could not capture them. We do not know
if the single returning bird in Argentina was the same in
both years.
34
Wader Study 123(1) 2016
Route and staging times at stopover sites
All three birds migrated north through the central region
of South America then through the Great Plains of North
America, and finally north to Arctic breeding areas (Figs.
3–5). A similar, but reverse route was used on the way
south. Birds took about 1.5 months to reach the breeding
grounds after leaving their wintering sites, 2–2.5 months
to reach the wintering grounds after leaving their breeding
sites, and had 4–7 and 4–6 stops (>1 days) during north
and southbound migrations, respectively (Table 2). During
their annual cycle, the two females traveled >32,000 km
each and the single male traveled >41,000 km (Table 2).
The extra distance traveled by the male was due to him
moving from the Central Arctic to western Alaska and
back to the Central Arctic before migrating south. This
shift cannot be explained by incubation affecting light
patterns because males do not incubate. The females stayed
in one area of the Central Arctic. The maximum time
spent by any bird migrating non-stop was five days; these
longer migration bouts were typically when birds traveled
between their wintering grounds in southern South America
and Colombia, and while crossing the Gulf of Mexico.
Northbound – All three birds employed several longer
migration ‘skips’ to reach North America from southern
South America, followed by several smaller ‘hops’ within
the Central Plains, and one last ‘skip’ across Canada to
reach their breeding grounds (see Warnock 2010 for
migration terminology; Fig. 3). The initial movement to
northern South America and then crossing the Gulf of
Mexico (Figs. 3 & 4) were longer than subsequent
movements, typically taking 2–4 days to reach Colombia
and 3–4.5 days to reach the Texas coast or nearby inland
areas (Table 2). In North America, birds typically flew
only 0.5–1 day between stops as they traveled through the
Central Plains from Texas to the upper Midwest (Fig. 5).
A final skip was made from the northern Central Plains
to breeding areas, taking a minimum of 1–2 days, but
likely longer, as exact locations were difficult to determine
once birds crossed the Arctic Circle.
Southbound – A similar migration pattern was observed
during southbound migration, except birds spent more
time at stopover sites, did not always use sites in Texas or
Colombia (which were used by all three birds during
northbound migration), and had additional stops in
South America (Figs. 3–5, Table 2). One bird bypassed the
Texas Coast and traveled directly from Kansas/Nebraska
to Colombia. Another bird bypassed Colombia and
traveled directly from Texas to Bolivia.
Turnover rates – The time birds spent at stopover sites
varied between sites and the direction of migration (Table
2). Birds staged the longest in coastal Texas during
southbound migration (27–27.5 d), followed by Bolivia
during southbound migration (11.5–24 d), then
Colombia during northbound (16–21.5 d) and
southbound migration (14–19 d). Birds stayed the
shortest times while migrating north through the Central
Plains of North America (typically 1–5.5 d), although one
bird stayed 20 days around the Nebraska/Kansas border
during southbound migration. Only one bird stopped in
Paraguay for a six day period before moving on to its
wintering location in Brazil.
Migratory connectivity
The three geolocator track lines suggest that birds wintering
in Argentina and Brazil use the same migration corridor
and breeding area, although the single male captured in
Argentina also traveled to Alaska, outside of the breeding
range of the two females (Fig. 3). During southbound
migration, our tracked birds separated after leaving
Bolivia, with the single recaptured bird from Brazil
Table 1. Information related to deployment of light-level loggers on Buff-breasted Sandpipers in Argentina, Brazil, and
Uruguay during 2012–2014.
# loggers
deployed by age
(AHY, HY, U)a
# loggers
deployed by sex
(f, m)b
Date range of
deployment
# collected/
resighted
Average weight
(g ± SD) at
capture (n)
Average weight
(g ± SD) at
recapture (n)
Argentina
21 (9, 2, 10)
21 (13, 8)
24 Dec 2012–
23 Jan 2013
2 / 1c
51.67 ± 4.51 (21)
48.0 ± 0 (2)
Brazil
26 (21, 5, 0)
26 (16, 10)
25 Dec 2012–
6 Jan 2013
1 / 2d
54.96 ± 6.43 (26)
51.0 (1)
Uruguay
15 (8, 6, 1)
15 (9, 6)
15 Dec 2012–
18 Jan 2013
0/0
56.00 ± 7.12 (15)
n/a
Country
a
AHY = after-hatch year, HY = hatch year, U = unknown; two and seven additional birds were marked with only engraved flags
in Argentina and Brazil, respectively.
b
f = female, m = male
c
One logger-equipped bird was resighted but not captured in Dec 2013 and Jan 2015, but we are unsure if it was the same bird.
d
More than two logger-equipped birds were likely present based on daily sightings.
Lanctot et al. l Migration patterns of Buff-breasted Sandpipers 35
Fig. 4. Northbound (A) and southbound (B) stopover (colored dots) and wintering (open circles) locations of three Buffbreasted Sandpipers in South America during the 2013 migration periods as determined from light-level geolocation.
The green dots represents the c615 male, the purple represents c469 female, and the blue represents the c514 female
(see Table 2 for more details at each location, and the text for uncertainty associated with locations and lines connecting
locations). Locations are shown as the mean latitude and longitude of the fixes comprising each stopover, while the
vertical and horizontal lines span from the 75th to the 25th percentile of the fixes, respectively. Horizontal lines are
covered up by circles in most cases due to their small size and the scale of this map.
traveling more eastwardly and stopping in Paraguay before
continuing onward to Lagoa do Peixe (Fig. 4). In contrast,
the two birds recaptured in Argentina traveled directly to
the wintering grounds in Argentina. The single recaptured
male had between one and three distinct breeding areas
and two wintering areas. In contrast, the females appeared
to use a single breeding and wintering area.
Departure and arrival dates
All three birds departed the wintering grounds between
6 and 13 April and arrived on the breeding grounds at
the end of May (Table 2). Departure from the breeding
grounds was more variable, ranging from 20 July to 2
August. Arrival to the wintering grounds was also variable,
ranging from 22 September to 14 October. The single
male left the breeding grounds after one female but before
the other; he arrived on the wintering grounds 3–4 weeks
earlier than the females.
Within- and between-year site fidelity to wintering
locations
Females collected in Argentina and Brazil stayed in the
same winter area throughout the study, spending 164
and 192 days at their capture locations, respectively (Table
2). The single male collected in Argentina used two sites:
his original capture site where he spent 125 days and a
second site in Central Argentina where he spent 63 days.
The second site was visited 10 days after his initial capture,
but not used in the second winter prior to his recapture.
DISCUSSION
Migration pattern
Our logger data were consistent with the overall migration
pattern previously suggested for this species (Lanctot &
Laredo 1994, Lanctot et al. 2002, 2010), with all three
N 30.0, W 96.0
N 40.3, W 96.7
N 43.4, W 100.0
N 49.2, W 105.5
Houston, TX
Border of Kansas/Nebraska
Southern South Dakota
Southern Saskatchewan
N 44.9, W 98.6
N 27.2, W 97.7
N 1.0, W 75.6
S 12.0, W 66.9
S 24.7, W 57.6
S 30.4, W 51.1
South Dakota
Corpus Christie, TX
Colombia
Northern Bolivia or Brazil
Paraguay
Lagoa do Peixe, Brazil
N 48.0, W 103.9
North Dakota/Montana
N 47.7, W 100.8
N 36.9, W 95.9
Oklahoma/Kansas
North Dakota
N 27.6, W 97.5
Corpus Christie, TX
north of 66.0, W 105.0
N 4.2, W 70.8
Colombia
Central Arctic
S 37.0, W 57.3
Bahia Samborombón, Argentina
Logger C514, Female, After-Hatch Year
N 48.9, W 99.3
Border of Manitoba/North Dakota
north of N 66.0, W 110.0
N 5.0, W 68.9
Colombia
Central Arctic
S 31.1, W 50.8
~latitude°,
longitude°
Lagoa do Peixe, Brazil
Logger C469, Female, After-Hatch Year
General location
fallstop1
breeding
springstop4
springstop3
springstop2
springstop1
wintering
wintering
fallstop6
fallstop5
fallstop4
fallstop3
fallstop2
fallstop1
breeding
springstop5
springstop4
springstop3
springstop2
springstop1
wintering
Period 1
5.5
64
3–8 Aug 2013
30 May–1 Aug 2013
25–29 May 2013
14–23 May 2013
9
4.5
11–13 May 2013
16 Apr–7 May 2013
south
south
north
north
north
north
north
stationary
19 Oct 2013–23 Dec 2013
when collected 2
Captured 26 Dec 2012,
departed 13 Apr 2013
south
south
south
south
south
south
south
north
north
north
north
north
north
Directional
movement from
this location
12–17 Oct 2013
17 Sep–9 Oct 2013
28 Aug–16 Sep 2013
28 Jul–24 Aug 2013
2.5
21.5
109
66
6
22.5
19
27
23–27 Jul 2013
21–22 Jul 2013
1
4.5
30 May–20 Jul 2013
24–28 May 2013
18–22 May 2013
14–17 May 2013
11–12 May 2013
18 Apr–5 May 2013
Captured 6 Jan 2013,
departed 13 Apr 2013
Dates at site
52
5
4.5
4
2
18.5
98
No. days
at site
0.5–1
1–2
1.5
1–1.5
0.5
3
2.5–3
Total distance
1
1–2
0.5–1
4.5–5
1
0.5
1
1.5
0.5–1
0.5
0.5–1
4–4.5
3.5–4
Flight duration
from this
location (days)
1,129
4,752
4,744
1,900
1,231
4,023
5,039
32,802
1,103
1,810
1,742
3,894
2,449
655
4,658
4,534
1,116
590
1,402
4,204
4,645
Distance from
this site to
the next (km)
Table 2. Dates and estimated locations of sites visited by three Buff-breasted Sandpipers captured in either Argentina or Brazil that were tracked with light-level loggers between
late December 2012 and early January 2014. Flight duration and distances flown (assuming straight line flight) between sites are also listed. See text for how sites were determined
and level of precision of locations.
36 Wader Study 123(1) 2016
fallstop3
fallstop4
wintering
N 3.4, W 74.1
S 13.1, W 64.5
S 35.3, W 56.8
Colombia
Beni Savanna, Bolivia
Bahia Samborombón, Argentina
fallstop4
S 10.0, W 67.3
S 35.6, W 57.1
Northern Bolivia or Brazil
Bahia Samborombón, Argentina
115
south
5–6 Aug 2013
south
stationary
22 Sep 2013–14 Jan 2014
when collected
south
9–20 Sep 2013
8 Aug–4 Sep 2013
south
0.5–1
south
18 Jun–29 Jul 2013 (active/
roost pattern from 2–12 Jul)
1–4 Aug 2013
2.5–3
west
2–11 Jun (as late as
17 Jun) 2013
Total distance
1–1.5
5
1.5–2
At least 1, up to 7
1
north
29 May–1 Jun 2013
41,420
3,418
5,603
1,896
571
4,904
4,802
3,762
3,951
995
752
1,294
353
4,033
4,512
574
33,232
2,990
2,121
5,303
Distance from
this site to
the next (km)
1
Wintering and breeding refer to when the bird was stationary on its wintering or breeding grounds, respectively. See Methods for how locations of stopover (stop) and movement were determined from light-level
geolocation data.
2
Light recording stopped on 17 Dec 2013.
wintering
11.5
fallstop3
N 29.7, W 96.6
1.5
27.5
fallstop2
N 43.3, W 94.7
Border of Minnesota/Iowa
West of Houston, TX
3
fallstop1
N 45.6, W 98.7
South Dakota
41
breeding3? and/or
post-breeding staging
north of N 66.0, W 97.0
Trajectory with western Hudson Bay
10–16
breeding2
north of N 66.0, W 160.0
Trajectory with Nulato Hills, AK
3.5
1.5
0.5–1
0.5–1
north
north
1–2
north
0.5
2.5–3
north
north
3–3.5
0.5
north
west
north
23–26 May 2013
19–22 May 2013
3.5
15–18 May 2013
4
12–13 May 2013
29 Apr–11 May 2013
10–26 Apr 2013
3 Feb–6 Apr 2013
Captured 24 Jan,
departed 2 Feb 2013
stationary
14 Oct 2013–4 Jan 2014
when collected
Total distance
2.5–3
south
17 Sep–11 Oct 2013
5
south
1
Flight duration
from this
location (days)
Directional
movement from
this location
south
3–16 Sep 2013
9–28 Aug 2013
Dates at site
3.5
2
12.5
16
63
10
83
24
14
20
No. days
at site
breed1? or springstop7?
north of N 66.0, W 117.0
springstop6
N 49.2, W 105.5
Southern Saskatchewan
Northwest Territories
springstop5
springstop4
springstop3
N 30.4, W 96.0
Northwest of Houston, TX
N 39.9, W 96.8
springstop2
N 28.0, W 97.6
Corpus Christie, TX
N 44.2, W 100.3
springstop1
N 3.8, W 71.6
Colombia
South Dakota
wintering2
S 33.4, W 60.7
Central Argentina
Border of Kansas/Nebraska
wintering
S 38.6, W 57.0
Bahia Samborombón, Argentina
Logger C615, Male, unknown age
fallstop2
N 40.6, W 98.5
Nebraska/Kansas
Period1
~latitude°,
longitude°
General location
Table 2 continued
Lanctot et al. l Migration patterns of Buff-breasted Sandpipers 37
38
Wader Study 123(1) 2016
birds traveling north through the central region of South
America, across the Gulf of Mexico, and through the
Great Plains of North America to reach Arctic breeding
areas (Figs. 3–5). Southbound migration followed a similar,
but reverse route as northbound. We did not observe any
birds traveling along the Atlantic Flyway of North America
as might be predicted, as this route is used primarily by
young-of-the-year traveling south from the breeding
grounds (Lanctot & Laredo 1994). The migration distances
documented for this species, especially by the male
(>41,000 km), may match or surpass prior annual migration
distances documented for the American Golden-Plover
Pluvialis dominica, Red Knot Calidris canutus rufa, and
White-rumped Sandpiper C. fuscicollis (Skagen 2006).
Estimated bird locations suggested that Colombia may
be an important staging site for Buff-breasted Sandpipers
as they prepare to cross, or replenish fuel from crossing,
the Gulf of Mexico (Fig. 4). Ruiz-Guerra et al. (2013)
speculated there might be a major northbound stopover
site in northern South America but their limited observations of the species were insufficient to confirm its
existence. The use of Colombia during southbound migration was even more surprising, as very few individuals
have been found in this area historically (Lanctot et al.
2002, 2010). Indeed, two of the three stopped in Colombia.
Our logger data also suggested the importance of sites in
Bolivia and Paraguay during southbound but not northbound migration (Fig. 4; Lanctot et al. 2010). Stopovers
overlapped generally with the Beni Savanna region of
Bolivia, and the Bahía de Asunción and adjacent rivers in
Paraguay. The Beni Savanna region is the first shortgrass area available for foraging after birds leave Colombia
and cross the Amazon Rainforest (B. Hennessy, pers.
comm.). Portions of the Beni Savanna and Bahía de
Asunción have been designated as Western Hemisphere
Shorebird Reserve Network Sites of Regional Importance
due to the fact that >1% of the global population of Buffbreasted Sandpipers stop there during fall migration
(http://www.whsrn.org/sites/list-sites).
The Central and Mississippi flyways of North America
were also used during both north and southbound migration (Fig. 5). Stopover sites were consistent with previous
studies that suggested the importance of coastal portions
of Texas, the Eastern Rainwater Basin of Nebraska, and
the Flint Hills of Kansas (Fellows et al. 2001, Jorgensen et
al. 2008, McCarty et al. 2015, Penner et al. 2015). The
latter two sites are or are being nominated to be landscape
Western Hemisphere Shorebird Reserve Network sites.
Heretofore unknown areas of use were found in Iowa,
South Dakota, and North Dakota, states where this species
is considered a rarity (Kent & Dinsmore 1996, Tallman et
al. 2002, Lanctot et al. 2010). Perhaps not surprising
given the number of locations with ground observations
(Fig. 9 in Lanctot et al. 2010), the logger data indicated
the three birds stopped at many different locations during
their north and southbound migrations. This suggests
the species disperses broadly over the landscape and may
go largely unnoticed unless present in high numbers.
Such broad use of the habitat may bode well for the
species given the ephemeral nature of stopover sites in
this region (Skagen 2006, McCarty et al. 2009), with site
quality varying due to hydrology alteration (e.g., precipitation, flooding of wetlands, drought) and agricultural
practices (e.g., tillage, seeding, burning, grazing, land
conversion).
Timing of migration
All three birds left the wintering grounds in early to midApril, about 1–2 weeks later than prior reports suggested
was likely (Table 2; Myers & Myers 1979, Almeida 2009).
All birds staged in Colombia during late April and early
May for about 2–3 weeks, before flying to the Texas coast.
Stopover durations in the Midwest were in general quite
variable, ranging from one to 20 days (but most were <5
d). These estimates were generally longer than estimates
based on radio transmitter data from the Rainwater Basin
in Nebraska that estimated a turnover rate of only two
days (McCarty et al. 2009, 2015, J. Jorgensen, pers. comm.).
However, due to the inaccuracy of logger locations, we
were unable to determine exactly when birds left a
particular field or pasture.
All three birds arrived on the breeding grounds at the
end of May, which coincides with prior reports of males
and females arriving together in late May (Table 2; Lanctot
& Laredo 1994). The departure from the breeding grounds
in late July/early August suggests a long post-breeding
period, as breeding activity by males is typically completed
by mid- to late June (Lanctot & Weatherhead 1997) and
by mid-July for successful breeding females (Lanctot &
Laredo 1994). Although post-breeding staging is thought
to be unusual or at least reduced in length for most
shorebird species (Meltofte et al. 2007, but see Taylor et
al. 2011), Lindström et al. (2002) reported juvenile Buffbreasted Sandpipers to be some of the fattest shorebirds
captured during their expedition across northern Canada
in July and August 1999. Perhaps post-breeding staging
is needed so individuals can complete the first major
southbound jump to the mid-prairie region near the
United States/Canada border. Alternatively the birds may
be postponing southbound migration to avoid predators
(Jamieson et al. 2014).
Like many other Nearctic migrants traveling to wintering
areas (Jehl 1979, Senner & Martinez 1982, Alerstam &
Lindström 1990), Buff-breasted Sandpipers migrated
south at a more leisurely pace (Table 2). Although the
overall number of stopover sites was similar to that during
northbound migration, the length of stay at each was
generally longer. For example, birds stayed in coastal
Texas for about 27 days during southbound migration
but did not exceed 12.5 days during northbound migration.
The lack of urgency in migrating south was also evident
from birds stopping in Bolivia and Paraguay, which added
2–3 weeks to their southward trip. The stopover length of
six days in Paraguay is very close to the estimated seven
day length suggested by Lesterhuis & Clay (2001, A.
Lesterhuis, pers. comm.). The pace Buff-breasted Sandpipers
use during southbound migration may be at least partially
Lanctot et al. l Migration patterns of Buff-breasted Sandpipers 39
Fig. 5. Northbound (A) and southbound (B) stopover locations of three Buff-breasted Sandpipers in the Central Great
Plains of North America during the 2013 migration period as determined from light-level geolocation. The green dots
represents the c615 male, the purple represents c469 female, and the blue represents the c514 female (see Table 2 for
more details at each location, and the text for uncertainty associated with locations and lines connecting locations).
Locations are shown as the mean latitude and longitude of the fixes comprising each stopover, while the vertical and
horizontal lines span from the 75th to the 25th percentile of the fixes, respectively.
influenced by the timing of available habitat. For example,
in Bolivia, arrival of Buff-breasted Sandpipers in the Beni
Savani coincides with heavy grazing of cattle and the
exposure of river and lake margins during the dry season
(B. Hennessey, pers. comm.); both conditions likely
provide good forage opportunities. Similarly, use of areas
in the Amazon and Paraná-Paraguay watersheds appear
to be tied to dropping water levels, which are essential to
expose sandbanks and mudflats used for foraging (Antas
1983, R. Clay, pers. comm.). The arrival of Buff-breasted
Sandpipers on the wintering grounds in September–
October was similar to that reported previously (Almeida
2009).
Breeding and wintering locations
Despite our inability to know the latitude at which birds
bred, it is clear from longitude estimates that all 3 birds
used different regions of the Arctic (Fig. 3). Both females
used the Central Arctic throughout the summer, whereas
the male used one to three areas distributed across the
Arctic to breed. Lanctot & Weatherhead (1997) suggested
males display at multiple leks across a broad landscape,
but until now, no data on Arctic-wide movements by
birds have been available. Similar landscape-scale movements have been observed in male Pectoral Sandpipers
Calidris melanotos (B. Kempenaers & M. Valcu, pers.
comm.), suggesting that other species also may be using
this reproductive strategy.
The single westward movement on the wintering grounds
by the geolocator-equipped male suggests that these inland
sites may function as additional wintering areas or perhaps
as staging areas where birds fatten up prior to migrating
north. Inland sites were presumed by Lanctot et al. (2002)
to have low use based on the paucity of historic records
and their extensive agriculture and human development.
However, the fact that the male spent 63 days in the
region suggests inland areas should be investigated more.
40
Wader Study 123(1) 2016
Clearly, additional information is needed to determine
the relative extent of local and regional movements within
the wintering grounds, and the importance of non-core
wintering sites such as the inland portions of the Rio de
La Plata Grassland, the Puna Ecoregion in western Argentina
and southern Bolivia, and the Colorado and Negro Rivers
in northern Patagonia (Lanctot et al. 2002).
Low rates of logger recovery
We documented the return of only six (9.7%) geolocatorequipped birds to our study sites. This is much lower
than the 27 and 64% return rates reported by Almeida
(2009) and may be an underestimate due to our inability
to differentiate between individual tagged birds in the
field and the fact that geolocator-equipped birds were
observed daily in Brazil. Our low return rates may have
been due to a lower level of search effort compared to
that made by Almeida (2009), and/or equipping birds in
suboptimal habitats in Uruguay (birds were captured in
lower quality agricultural areas as high rainfall made
grasslands, where birds had been seen in good numbers
in prior years, unsuitable) that may have decreased
detection in the second year of the study, and/or higher
mortality due to the burden of carrying the logger. The
latter point seems unlikely however, as we also failed to
observe eight of the nine birds marked with only leg
flags.
Sex ratio of birds
Almeida’s (2009) extensive winter ecology study in Lagoa
de Peixe, Brazil during 2002–2005 indicated that there
were 2.7 females to every male. This strong female-biased
sex ratio in the northern portion of the species’ wintering
range prompted her to speculate that males might be
more prevalent than females farther south. Our sample
of 71 birds containing 42 females (sex ratios in each
country ranged from 1.44–1.54) does not support her
prediction, but rather, may indicate that a female-biased
sex ratio exists throughout the entire wintering range.
This finding is consistent with analyses showing that
species where males tend to be polygamous and lack
parental care, such as in the Buff-breasted Sandpiper
(Lanctot et al. 1997), also tend to have female-biased sex
ratios (Zwarts et al. 2009, Liker et al. 2013). If differences
in migration distances between the single male and two
females observed here are representative of the overall
population, this could explain the female-biased sex ratio,
as the greater migration distance of the males may have
both direct and indirect survival costs (Lok et al. 2015).
The mixture of both sexes (and ages) at all sites, contrasts
with other monogamous species that show geographic
segregation on the wintering grounds (Nebel et al. 2002,
Nebel 2006, 2007). From a management point of view,
these sex- and age-ratio patterns suggest that prior concerns
about the need to protect multiple areas within the species
wintering range may not be as important as previously
thought. However, caution must be used as our capture
data may have been biased due to small sample sizes or
temporal patterns in our sampling. Maintaining these
areas could also be important if there is connectivity
between wintering areas and different portions of the
breeding grounds — something we still do not know.
Summary and future efforts
Clearly, tracking of more birds is needed to ensure the
migratory patterns observed here are reflective of the
entire population. Also, more accurate tracking is needed
to understand how birds use particular habitat types so
that they can be better managed to ensure habitat availability
during north and southbound migrations (Vermillion
2012) and on the wintering grounds. For example, the use
of GPS enabled tags would help to understand how the
species uses the landscape at a micro-scale. Such knowledge
would help managers evaluate site-based conservation of
grasslands (and wetlands), assess impacts from and plan
for urban and energy development (e.g., wind turbine
farms), and assess whether this species is likely exposed
to agrochemicals (Strum et al. 2010). An extensive band
and resighting program would also provide information
on migratory connectivity and habitat use. Such work is
relatively cheap and banding has already been initiated in
portions of the species’ range. Well-designed surveys in
key stopover areas that incorporate ‘citizen scientists’,
combined with the turnover rates reported here or generated
in the future, will also be useful for generating new population estimates for the species (see e.g., Penner et al.
2015). Repeating counts in the Eastern Rainwater Basin
(Jorgensen et al. 2008) would be especially valuable as
this work would allow us to generate the first reliable
trend estimate for the species. Finally, more information
is needed on how birds distribute and use the breeding
grounds. This may be particularly important if climate
changes result in less suitable habitat.
ACKNOWLEDGMENTS
Field work included many individuals who worked long
hours deploying loggers, and searching for and collecting
birds. We thank especially Fabiano José de Souza, Riti
Soares dos Santos, Héctor Caymaris, Eduardo Chiarani,
Terry Doyle, Brooke Hill, Leo Lencina, Melina Lunardelli,
Omar Nievas, Juan Ordoñez, Daniel Rabbers, Pablo Rojas,
Paola Russo, Daniel and Andres Sosa, Terri Taylor, and
Ezequiel Velazques for their dedication and enthusiasm.
We also thank the many landowners in each country
who kindly allowed us access to their properties. In
Argentina, Silvia Duhalde allowed us to work on his
farm and Abel Lencina allowed us to store equipment in
his barn. In Brazil, Lagoa do Peixe National Park provided
housing and personnel, Renato Bender allowed access to
Fazenda Boiadeiro, Claudir Jorge Gomes Lima and Jair
Marques da Silveira provided support within their ranch,
and Pousada Parque (Eulália and Abel Sessim) provided
housing and logistical support. In Uruguay, Mercedes
Rivas provided institutional support, Gerardo Evia facilitated
housing, Javier Vitancurt facilitated permits for capturing
birds in protected areas near Laguna de Rocha, the Centro
Universitario de la Región Este and the Universidad de la
República provided trucks and equipment, Aves Uruguay
Lanctot et al. l Migration patterns of Buff-breasted Sandpipers-- 41
facilitated administration, PROBIDES provided housing,
and the Sistema Nacional de Áreas Protegidas provided
permits for working in the area. We thank Brent Ortego,
Khara Strum and Bob Russell for summarizing eBird
data. Permits to capture, uniquely mark and equip Buffbreasted Sandpipers with geolocators were obtained from
the U.S. Geological Survey’s Bird Banding Laboratory
and CEMAVE, Brazil. The Provincial Agency for Sustainable
Development (Organismo Provincial Para el Desarrollo
Sostenible) within the Province of Buenos Aires (Buenos
Aires La Provincia) provided a permit to collect birds in
Argentina. The Ministry of the Environment (Ministério
do Meio Ambiente – MMA) through the Chico Mendes
Institute for Biodiversity Conservation (Instituto Chico
Mendes de Conservação da Biodiversidade – ICMBio)
provided permit #28478-4 to conduct research and collect
birds within Lagoa do Peixe National Park in Brazil. The
Territorial Ministry of Housing System Environment
(Ministerio de Vivienda Ordenamiento Territorial v Medio
Ambiente) provided a permit to collect birds in Uruguay.
The study was approved by the Mount Allison’s Animal
Care Committee (protocol #12-22). Financial assistance
to conduct the study was provided by the Neotropical
Migratory Bird Conservation Act; Buenos Aires La Provincia, Argentina; Juliana Bosi de Almeida; Aves Uruguay;
Universidad de la Republica, Uruguay; Manomet, Inc.;
Mount Allison University; and the U.S. Fish and Wildlife
Service. The findings and conclusions in this article are
those of the authors and do not necessarily represent the
views of the U.S. Fish and Wildlife Service.
REFERENCES
Aldabe, J., E. Arballo, D. Caballero-Sadi, S. Claramunt, J.
Cravino & P. Rocca. 2013. Aves. Pp. 149–173 in: Especies
Proritarias Para la Conservación En Uruguay. Vertebrados,
Moluscos Continentales y Plantas vasculares (A. Soutullo,
C. Clavijo & J.A. Martínez-Lanfranco, Eds.). SNAP/
DINAMA/MVOTMA y DICYT/MEC, Montevideo,
Uruguay. [In Spanish]
Brown, S., C. Hickey, B. Harrington & R. Gill (Eds.).
2001. The U.S. Shorebird Conservation Plan, 2nd edition.
Manomet Center for Conservation Sciences, Manomet,
Massachusetts.
Clark, N.A., C.D.T. Minton, J.W. Fox, K. Gosbell, R.B.
Lanctot, R. Porter & S. Yezerinac. 2010. The use of
geolocators to study wader movements. Wader Study
Group Bulletin 117: 173–178.
Conklin, J.R., P.F. Battley, M.A. Potter & J.W. Fox. 2010.
Breeding latitude drives individual schedules in a transhemispheric migrant bird. Nature Communications 1: 67.
Committee on the Status of Endangered Wildlife in Canada
(COSEWIC). 2012. COSEWIC assessment and status
report on the Buff-breasted Sandpiper Tryngites subruficollis
in Canada. COSEWIC, Ottawa, Ontario. Accessed Dec
2015 at: www.registrelep-sararegistry.gc.ca/default_e.cfm.
del Castillo, H., R.P. Clay, J. de Egea, O. Rodas, H. Cabral
Beconi, V. Morales & S. Centrón. 2005. Atlas De Las Aves
Del Paraguay. Guyra Paraguay, Asunción, Paraguay. [In
Spanish]
Donaldson, G., C. Hyslop, G. Morrison, L. Dickson & I.
Davidson (Eds.). 2000. Canadian Shorebird Conservation
Plan. Canadian Wildlife Service, Ottawa, Ontario.
Egevang, C., I.J. Stenhouse, R.A. Phillips, A. Petersen, J.W.
Fox & J.R.D. Silk. 2010. Tracking of Arctic Terns Sterna
paradisaea reveals longest animal migration. Proceedings
of the National Academy of Sciences 107: 2078–2081.
Fellows, S., K. Stone, S. Jones, N. Damude & S. Brown.
2001. Central Plains/Playa Lakes Regional Shorebird Conservation Plan. Version 1.0. U.S. Fish & Wildlife Service,
Denver, Colorado.
Finch, T., P. Saunders, J.M. Avilés, A. Bermejo, I. Catry, J.
de la Puente, T. Emmenegger, I. Mardega, P. Mayet, D.
Parejo, E. Račinskis, J. Rodríguez-Ruiz, P. Sackl, T.
Schwartz, M. Tiefenbach, F. Valera, C. Hewson, A.
Franco & S.J. Butler. 2015. A pan-European, multipopulation assessment of migratory connectivity in a nearthreatened migrant bird. Diversity & Distributions 21:
1051–1062.
Almeida, J. Bosi de. 2009. Wintering ecology of Buff-breasted
Sandpipers (Tryngites subruficollis) in Southern Brazil.
PhD thesis, University of Nevada, Reno.
Franks, S., D.R. Norris, T.K. Kyser, G. Fernández, B.
Schwarz, R. Carmona, M.A. Colwell, J. Correa Sandoval,
A. Dondua, H.R. Gates, B. Haase, D.J. Hodkinson, A.
Jiménez, R.B. Lanctot, B. Ortego, B.K. Sandercock, F.
Sanders, J.Y. Takekawa, N. Warnock, R.C. Ydenberg &
D.B. Lank. 2012. Range-wide patterns of migratory connectivity in the Western Sandpiper Calidris mauri. Journal
of Avian Biology 43: 1–13.
Andres, B.A., P.A. Smith, R.I.G. Morrison, C.L. GrattoTrevor, S.C. Brown & C.A. Friss. 2012. Population
estimates of North American shorebirds, 2012. Wader
Study Group Bulletin 119: 178–194.
Fudickar, A.M., M. Wikelski & J. Partecke. 2012. Tracking
migratory songbirds: Accuracy of light‐level loggers
(geolocators) in forest habitats. Methods in Ecology &
Evolution 3: 47–52.
Antas, P.T.Z. 1983. Migration of Nearctic shorebirds (Charadriidae and Scolopacidae) in Brasil - flyways and their
different seasonal use. Wader Study Group Bulletin 39:
52–56.
Haig, S.M., C.L. Gratto-Trevor, T.D. Mullins & M.A.
Colwell. 1997. Population identification of western hemisphere shorebirds throughout the annual cycle. Molecular
Ecology 6: 413–427.
Bart, J., S. Brown, B. Harrington & R.I.G. Morrison. 2007.
Survey trends of North American shorebirds: population
declines or shifting distributons? Journal of Avian Biology
38: 73–82.
Jamieson, S.E., R.C. Ydenberg & D.B. Lank. 2014. Does
predation danger on southward migration curtail parental
investment by female Western Sandpipers? Animal Migration 2: 34–43.
Alerstam, T. & Å. Lindström. 1990. Optimal bird migration:
the relative importance of time, energy, and safety. Pp.
331–351 in: Bird Migration: Physiology & Ecophysiology
(E. Gwinner, Ed.). Springer-Verlag, Berlin.
42
Wader Study 123(1) 2016
Jehl, J.R., Jr. 1979. The autumnal migration of Baird’s Sandpipers. Studies in Avian Biology 2: 55–68.
Jorgensen, J.G., J.P. McCarty & L.L. Wolfenbarger. 2008.
Buff-breasted Sandpiper (Tryngites subruficollis) density
and numbers during migratory stopover in the Rainwater
Basin, Nebraska. Condor 110: 63–69.
Kent, T.H. & J.J. Dinsmore. 1996. Birds in Iowa. Published
by the authors, Iowa City & Ames, Iowa.
Koopman, K. & J.B. Hulscher. 1979. Catching waders with
a “wilsternet”. Wader Study Group Bulletin 26: 10–12.
Lanctot, R.B. & C.D. Laredo. 1994. Buff-breasted Sandpiper
(Tryngites subruficollis). In: The Birds of North America,
No. 91. (A. Poole & F. Gill, Eds.). Philadelphia: The
Academy of Natural Sciences; Washington, D.C.: The
American Ornithologists’ Union. Accessed at:
http://bna.birds.cornell.edu/bna/ species/091.
Lisovski, S., C.M. Hewson, R.H. Klaassen, F. Korner-Nievergelt, M.W. Kristensen & S. Hahn. 2012. Geolocation
by light: accuracy and precision affected by environmental
factors. Methods in Ecology & Evolution 3: 603–612.
Lok, T., O. Overdijk & T. Piersma. 2015. The cost of
migration: spoonbills suffer higher mortality during transSaharan spring migrations only. Biology Letters 11:
20140944.
López-Lanús, B., P. Grilli, E. Coconier, A. Di Giacomo &
R. Banchs. 2008. Categorización de las aves de la Argentina
según su estado de conservación. Informe de Aves Argentinas
/AOP y Secretaría de Ambiente y Desarrollo Sustentable.
Buenos Aires, Argentina. [In Spanish]
Marra, P., K.A. Hobson & R.T. Holmes. 1998. Linking
winter and summer events in a migratory bird by using
stable-carbon isotopes. Science 282: 1884–1886.
Lanctot, R.B. & P.J. Weatherhead. 1997. Ephemeral lekking
behavior in the Buff-breasted Sandpiper, Tryngites subruficollis. Behavioral Ecology 8: 268–278.
McCarty, J.P., J.G. Jorgensen & L.L. Wolfenbarger. 2009.
Behavior of Buff-Breasted Sandpipers (Tryngites subruficollis) during migratory stopover in agricultural fields.
PLoS ONE 4: e8000.
Lanctot, R.B., J. Aldabe, J.B. Almeida, D. Blanco, J. Jorgensen, P. Rocca & K. Strum. 2010. Conservation plan
for the Buff-breasted Sandpiper (Tryngites subruficollis).
Version 1.1. Manomet Center for Conservation Science,
Manomet, Massachusetts, and U.S. Fish & Wildlife Service,
Anchorage, Alaska.
McCarty, J.P., J.G. Jorgensen, J.M. Michaud & L.L. Wolfenbarger. 2015. Buff-breasted Sandpiper stopover duration
in the Rainwater Basin, Nebraska, in relation to the
temporal and spatial migration patterns in the Great
Plains of North America. Wader Study 122: 243–254.
Lanctot, R.B., D.E. Blanco, R.A. Dias, J.P. Isacch, V.A.
Gill, J.B. Almeida, K. Delhey, P. F. Petracci, G.A. Bencke
& R. Balbueno. 2002. Conservation status of the Buffbreasted Sandpiper: historic and contemporary distribution
and abundance in South America. Wilson Bulletin 114:
44–72.
Lanctot, R.B., D.E. Blanco, M. Oesterheld, R.A. Balbueno,
J.P. Guerschman & G. Piñeiro. 2004. Assessing habitat
availability and use by Buff-breasted Sandpipers (Tryngites
subruficollis) wintering in South America. Ornitologia
Neotropical 15 (Suppl.): 367–376.
Lanctot, R.B., A. Hartman, L.W. Oring & R.I.G. Morrison.
2008. Response to Farmer (2008): Limitations of statistically
derived population estimates, and suggestions for deriving
national population estimates for shorebirds. Auk 124:
983–985.
Lanctot, R.B., K. Scribner, B. Kempenaers & P.J. Weatherhead. 1997. Lekking without a paradox in the Buffbreasted Sandpiper. American Naturalist 149: 1051–1070.
Lesterhuis, A.J. & R.P. Clay. 2001. Nearctic shorebirds in
Bahía de Asunción, Paraguay. Wader Study Group Bulletin
95: 19.
Liker, A., R.P. Freckleton & T. Székely. 2013. The evolution
of sex roles in birds is related to adult sex ratio. Nature
Communications 4: 1587.
Lindström, Å., M. Klaassen, T. Piersma, N. Holmgren &
L. Wennerberg. 2002. Fuel stores of juvenile waders on
autumn migration in High Arctic Canada. Ardea 90: 93–
101.
Lisovski, S. & S. Hahn. 2012. GeoLight–processing and
analysing light‐based geolocator data in R. Methods in
Ecology & Evolution 3: 1055–1059.
Meltofte, H., T. Piersma, H. Boyd, B. McCaffery, B. Ganter,
V.V. Golovnyuk, K. Graham, C.L. Gratto-Trevor, R.I.G.
Morrison, E. Nol, H.-U. Rösner, D. Schamel, H. Schekkerman, M.Y. Soloviev, P.S. Tomkovich, D.M. Tracy, I.
Tulp & L. Wennerberg. 2007. Effects of climate variation
on the breeding ecology of Arctic shorebirds. Bioscience
59: 1–48.
Miller, M.P., S.M. Haig, T.D. Mullins, L. Ruan, B. Casler,
A. Dondua, H.R. Gates, J.M. Johnson, S. Kendall, P.S.
Tomkovich, D. Tracy, O.P. Valchuk & R.B. Lanctot.
2015. Intercontinental genetic structure and gene flow in
Dunlin (Calidris alpina), a natural vector of avian influenza.
Evolutionary Applications 8: 149–171.
Ministério do Meio Ambiente (MMA). 2014. Portaria Nº
444, de 17 de dezembro de 2014. Reconhece a Lista
Nacional Oficial de Espécies da Fauna Ameaçadas de
Extinção. Diário Oficial da União – Seção 1, Nº 245, pp.
121–126. [In Portuguese]
Minton, C., K. Gosbell, P. Johns, M. Christie, J.W. Fox &
V. Afanasyev. 2010. Initial results from light level geolocator
trials on Ruddy Turnstone Arenaria interpres reveal unexpected migration route. Wader Study Group Bulletin 117:
9–14.
Myers, J.P. & L.P. Myers. 1979. Shorebirds of Coastal Buenos
Aires Province, Argentina. Ibis 121: 186–200.
Nebel, S. 2006. Latitudinal clines in sex ratio, bill, and wing
length in Least Sandpipers. Journal of Field Ornithology
77: 39–45.
Nebel, S. 2007. Differential migration of shorebirds in the
East Asian-Australasian Flyway. Emu 107: 4–18.
Nebel, S., D.B. Lank, P.D. O’Hara, G. Fernandez, B. Haase,
F. Delgado, F.A. Estela, L.J. Evans Ogden, B. Harrington,
B.E. Kus, J.E. Lyons, F. Mercier, B. Ortego, J.Y. Takekawa,
Lanctot et al. l Migration patterns of Buff-breasted Sandpipers-- 43
N. Warnock & S.E. Warnock. 2002. Western Sandpipers
(Calidris mauri) during the nonbreeding season: spatial
segregation on a hemispheric scale. Auk 119: 922–928.
nonbreeding migratory shorebirds to cholinesteraseinhibiting contaminants in the Western Hemisphere.
Condor 112: 15–28.
North American Bird Conservation Initiative, U.S. Committee (NABCI). 2014. The State of the Birds 2014 Report.
U.S. Department of Interior, Washington, D.C.
Tallman, D.A., D.L. Swanson & J.S. Palmer. 2002. Birds of
South Dakota. South Dakota Ornithologists’ Union,
Aberdeen, South Dakota.
Penner, R.L., B.A. Andres, J.E. Lyons & E.A. Young. 2015.
Spring surveys (2011–2014) for American Golden-plovers
(Pluvialis dominica), Upland Sandpipers (Bartramia longicauda), and Buff-breasted Sandpipers (Calidris subruficollis)
in the Flint Hills. Kansas Ornithological Society Bulletin
66: 37–52.
Taylor, A.R., R.B. Lanctot, A.N. Powell, S.J. Kendall &
D.A. Nigro. 2011. Residence time and movement patterns
of postbreeding shorebirds on Alaska’s northern coast.
Condor 113: 779–794.
Porter, R. & P.A. Smith. 2013. Techniques to improve the
accuracy of location estimation using light-level geolocation
to track shorebirds. Wader Study Group Bulletin 120:
147–158.
R Core Team. 2013. R: A language and environment for statistical computing. R Foundation for Statistical Computing,
Vienna, Austria. Accessed Dec 2015 at: http://www.Rproject.org.
Ruiz-Guerra, C., D. Eusse-González, C. Arango, L. Miranda
& Y.A. Beltrán. 2013. Spring status of Buff-breasted
Sandpipers in Colombia. Wader Study Group Bulletin
120: 202–205.
Senner, S.E. & E.F. Martiez. 1982. A review of Western
Sandpiper migration in Interior North America. Southwestern Naturalist 27: 149–159.
Skagen, S.K. 2006. Migration stopovers and the conservation
of Arctic-breeding Calidridine sandpipers. Auk 123: 313–
322.
Strum, K.M., M.J. Hooper, K.A. Johnson, R.B. Lanctot,
M.E. Zaccagnini & B.K. Sandercock. 2010. Exposure of
U.S. Shorebird Conservation Plan Partnership. 2015. U.S.
Shorebirds of Conservation Concern ─ 2015. Accessed
Dec 2015 at: http://www.shorebirdplan.org/science/assessment-conservation-status-shorebirds/.
Vermillion, W.G. 2012. Fall habitat objectives for priority
Gulf Coast Joint Venture shorebird species using managed
wetlands and grasslands. Version 4.0. Gulf Coast Joint
Venture, Lafayette, Louisiana.
Warnock, N. 2010. Stopping vs. staging: the difference
between a hop and a jump. Journal of Avian Biology 41:
621–626.
Webster, M.S., P.P. Marra, S.M. Haig, S. Bensch & R.T.
Holmes. 2002. Links between worlds: unraveling migratory
connectivity. Trends in Ecology & Evolution 17: 76–83.
Zöckler, C., R. Lanctot, S. Brown & E. Syroechkovskiy.
2012. Waders (Shorebirds). Pp. 92–102 in: Arctic Report
Card. Accessed Dec 2015 at: http://www.arctic.noaa.gov/
reportcard.
Zwarts, L., R.G. Bijlsma, J. van der Kamp & E. Wymenga.
2009. Living on the edge: Wetlands and birds in a changing
Sahel. KNNV Publishing, Zeist, The Netherlands.