Figure 3. - Limiting Bird Damage to Fruit Crops

Diet of American Kestrels in Michigan Cherry Orchards
Megan Shave ٠ Catherine Lindell
Zoology Department ٠ Michigan State University ٠ East Lansing, MI 48824
Kestrel female
Discussion & Conclusions
Introduction & Objective
American Kestrels (Falco sparverius) hunt in open
habitats, including agricultural fields and orchards1.
In addition, potential kestrel prey species (such as
voles, some passerine birds, and a variety of
insects) can cause damage in orchards. However,
the use of kestrels as a biological control species in
orchards has received limited investigation2,3.
Biological control via a native predator is an
appealing management strategy that concurrently
addresses agricultural and conservation needs4.
Results
Video Recordings
The kestrels made 708 total prey deliveries during the almost 125 hours of video
recordings. Figure 3 shows the relative proportions of different prey types among
these deliveries for each box. Figures 4 and 5 show examples of prey deliveries
captured by the recordings.
The typical kestrel diet includes both invertebrates
(mainly terrestrial arthropods) and small vertebrates
(mostly small mammals and birds)1; however, the
observed proportions of prey types in the diet vary
geographically and seasonally5.
1.00
This preliminary study aimed to assess the diets of
kestrels occupying nest boxes located in Michigan
cherry orchards, in order to determine whether
these kestrels are hunting the types of prey that
may cause damage in the orchards. During the
summer of 2013, the proportions of different prey
types delivered to kestrel nestlings were determined
by recording prey deliveries to nest boxes. In
addition, pellets and prey remains collected from
around and inside the boxes were used to identify
example prey at a taxonomic level more specific
than what may be possible from viewing the video
recordings.
0.60
16 hrs
22 hrs
24 hrs
23 hrs
16 hrs
8 hrs
11 hrs
4.5 hrs
0.90
0.80
0.70
0.50
22
138
187
106
99
41
94
21
0.40
arthropod
mammal
bird
herptile
mollusc
unknown
0.30
0.20
0.10
0.00
Box 1
Box 2
Box 3
Box 4
Box 5
Box 6
Box 7
Box 8
Figure 3. Relative proportions of different prey types among deliveries to kestrel nestlings.
Numbers within bars indicate total number of deliveries for each box. Numbers above bars
indicate total number of hours recorded for each box.
As shown in Figure 3, the majority of total prey
deliveries consisted of arthropods. The most
common arthropods were crickets, grasshoppers,
and beetles (grubs and adults). Some of these
insects may cause problems in Michigan orchards;
for example, increased numbers of grasshoppers
can cause significant leaf damage in young
orchards7.
Mammals and birds comprised nearly all of the
vertebrate deliveries. The videos indicated that most
of the mammals were voles. The bird deliveries
varied, and several species were represented in the
videos and prey remains, including two species
known to damage fruit crops: the European Starling
and American Robin (Fig. 6). Small mammal
trapping and bird surveys will be employed in
upcoming seasons to determine whether kestrel
predation influences the activity of these prey in
Michigan cherry orchards.
While the kestrel diet compositions seemed similar
across most nest boxes, it is notable that Box 1
appeared to have relatively more vertebrate prey
deliveries. A more robust dataset would allow for
statistical tests of whether diet composition varies
by box or by nestling age. Thus, video recordings
will continue during the summer of 2014 with the
goal of recording more occupied boxes, recording
each box for more days, and recording throughout
the entire ~30 day nestling period.
Methods
Literature Cited
Video Recordings
In early March 2013, weatherproof security cameras
(Opcom IP56) were installed in eight kestrel boxes
located in cherry orchards around Leelanau County,
MI (Fig. 1). All eight boxes were occupied by
breeding kestrels during the summer of 2013. Boxes
were recorded on a rotating basis using a digital
video recorder (SecurityMan HomeDVR) powered by
a rechargeable 12 V DC sealed lead acid battery
(Fig. 2)6. Most recordings were made from
approximately 09:00 to 17:00, though equipment
malfunctions altered this schedule in some cases.
Recordings were made between days 0 and 22 of
the ~ 30 day nestling period.
Figure 4. Adult kestrel delivering grasshopper
Figure 5. Adult kestrel delivering vole
Results
Pellets and Prey Remains
Pellets were found early in the breeding season and mostly contained small mammal
bones. Common prey remains found inside the boxes included a variety of arthropod
parts and the legs and wings of birds. Figures 6 – 8 show examples of collected
remains.
DVR
Camera
cord
Power
inverter
[1] Smallwood, J.A., and D.M. Bird. 2002. American Kestrel. The Birds
of North America [Online.] Available at http://bna.birds.cornell.edu/
bna/species/602.
[2] Askham, L.R. 1990. Effect of artificial perches and nests in
attracting raptors to orchards. Proceedings of the 14th Vertebrate Pest
Conference: 144-148.
[3] Paz, A., D. Jareño, L. Arroyo, J. Viñuela, B. Arroyo, F. Mougeot, J.J.
Luque-Larena and J.A. Fargallo. 2013. Avian predators as a biological
control system of common vole (Microtus arvalis) populations in northwestern Spain: experimental set-up and preliminary results. Pest
Management Science 69: 444 – 450.
[4] Kross, S.M., J.M. Tylianakis, and X.J. Nelson. 2012. Effects of
introducing threatened falcons into vineyards on abundance of
passeriformes and bird damage to grapes. Conservation Biology 26:
142-149.
[5] Sherrod, S.K. 1978. Diets of North American Falconiformes. Journal
of Raptor Research 12: 49-121.
[6] Steen, R. 2009. A portable digital video surveillance system to
monitor prey deliveries at raptor nests. Journal of Raptor Research 43:
69-74.
[7] Shane, B. and J. Wise. Increased populations of grasshoppers
cause problems in fruit crops. Michigan State University Extension
[Online]. Available at: http://msue.anr.msu.edu/news/increased_
populations_of_grasshoppers_cause_problems_in_fruit_crops.
Acknowledgements
12 v
battery
Funding Provided by:
Figure 1. Camera
installed inside nest
box
Kestrel male
Figure 2. Video recording setup
Collection of Pellets and Prey Remains
Pellets and remains found within a 30 m radius
around a box were collected during each box check
(checks occurred once in late April and then weekly
starting in late May). Prey remains were collected
from inside the box during banding of the nestlings
and again during cleaning of the boxes at the end of
the season.
Figure 6. Example bird remains. Left:
European Starling remains. Right: American
Robin wings.
Figure 7. Example mammal remains. Left:
Eastern Chipmunk remains. Right: Vole skull
and jaw with other small rodent bones
extracted from a pellet.
• North American Bluebird Society
• New York State Bluebird Society
• MSU Wallace Grant in Aid of Research
• MSU College of Natural Science Fellowship
• USDA SCRI Grant
Field Assistance
Provided by:
•  Shayna Wieferich
•  Ben Hawes
•  Rachael Eaton
•  Kate Howard
•  Jason St. Pierre
Kestrel Boxes Provided by:
Figure 8. Example arthropod remains. From left to
right: cricket leg, three beetle wing cases, two
grasshopper legs, cicada wing, and cicada head.
•  Melissa Brady
• Tom Comfort
And many thanks to the orchard owners and managers for
allowing the installation of kestrel nest boxes on their properties.