ENDANGERED BIRDS

BIRDS
ENDANGERED
N.J. Collar
lntemdtiotal
BirdLife
t. Introduction
tI. The Identification of EndangeredBirds
I . Trends and Factors in the Endangerment of Birds
lv. Approaches to the Conservation of Threatened
Birds
GLOSSARY
biological species concept Concept of a species as a
population or series of populations that are reproductively isolated from other groups, as well as the
degree of morphological similarity.
endangerment Condition in which a sPeciesis at risk
oI extinction.
phylogenetic species concept Concept of a sPeciesin
*'hich speciesJevelidentity is determined by menbers sharins distinct characteristics.
ENDANGERED BIRDS ARE DEFINED CHIEFLY AT
THE SPECIESLEVEL (although the definition of "species" remains contentious), and at the global and narional levels. New global criteria apply thresholds on
decline rate, population size, and range size to ldentify
endangerment. Some I 10,6of the world's avifauna are
at risk, but altogether 20% of species give cause for
concem. Most endangered birds (70%) have popula-
tions of lessthan 10,000mature individuals. The Philippines, Indonesia,Brazil, and Colombia possessthe most
significant proportions of endangeredbirds. Tropical
forest loss is the greatest threat, but there are many
other reasonsfor elevatedvulnerability (through range
restriction, occurrenceon islands,use ofrestdcted habitat. etc.). Remedial actions include detailed research
and documentation, site and habitat protection, and
intensive multilaceted managementprograms.
I.INTRODUCTION
Endangerment is the condition in which a speciesor
subspeciesof animal or plant is at risk of extinction.
The nature of the impending extinction may be local,
national, or global. There is no vocabulary to differentiate between these conditions; as a consequ€nce,there
is often confusion over appropriate priority levels. A
trend to use extirpationto indicate nonglobal extinction
brings its own problems, since the active verb extirpate
is sy'non)-mouswith eradicate;thereis also the problem
that disappearing subspeciesof species may be both
extinct 4r1dextirpated (extinct as taxonomically distinct
forms, extirpated as representativesof a hiSher taxonomic unit). This article conc€ntratesprimarily on bird
speciesat risk of global extinction, but nationally and
locally endangeredforms, including subspecies,are also
consideredi so extiry*ted is here used to mean locally
extinct. The terms mdangered, threatened, and. at rish
Enq(lopeaia o! Biodrenitt, volude 2
Copyright
O 20ol by Acad.nic
Press. All rights of reProduction
in any tom
r6erved
395
396
E N D A NG E R E DB I R D S
are commonly used interchangeably; endangeredis
prevalent in U.S. usage,but IUCN/The World Conservation Union status categories\se threateted.as a generic term ^nd Endangered (with a capital E) for a
particular status. ln this article, endangered.
is preferred,
exceptin contexts involving the IUCN threat categories.
II. THEIDENTIFICATION
OF
ENDANGERED
BIRDS
A. Taxonomy
andtheldentification
of
TargetUnits
ln general,decision makers look to sciencein two ways
for help in establishing pdorities in speciesconservation: the first is the degreeof a taxon's risk o[extinction,
and the secondis the degreeofits evolutionary differentiation. Many people are surprised that these aspects,
particularly the second, remain hard to assess.Ever
since the passing of the United StatesEndangeredSpecies Act, the term "endangered species" has become
widely used in popular and indeed jocular English parlance; so it seems extraordinary that debate still rages
over what a speciesis. Nonetheless,its definition is a
pewasive problem, and the profile of this issue will
increaseas more morphologically distinct, local forms,
currently considered subspecies,come under pressure
from human developmentactivilies.
When considering closelyrelated taxa in which there
is no geographical contact, and therefore no test for
reproductive isolation (the key criterion under the prevalent Biological SpeciesConcept or BSC), taxonomists
are compelled to rely on the degreeoftheir morphological similarity to judge, subjectively, whether they are
conspecific or not. Among birds there are thousandsof
such cases,in part becauseflight has allowed them to
colonize so many offshore and oceanic islands, where
they have evolved features that distinguish them at
some level Irom continental or other island stock.
Some influential museum-basedomithologists have
recently advocateda narrow phylogenetic speciesconcept (PSC),which bestowsspecies-levelidentity on any
population whose members fully share distinct characters,irrespectiveof hybrid zones.Many ofthese populations currently have taxonomic standing as subspecies,
and proponents of the PSCexpect its adoption to cause
a doubling of the number o{ avian species, to about
20,000 from the roughly 9500 in current usage.However, BSC supporters contend that, rather than clarifying the status of disjunct populadons, the PSC shifts
the difficulty to a yetmore complex and subjectivelevel,
where very minor differences (sometimes biochemical
only, and certainly not used to recognize even subspecies) may or may not be regardedas suffrciently distinct
and consistent to admit species-levelstatus, so that no
final number ofavian speciescan be even approximated.
This debateis important, not leastbecausebiological
diversity is directly at stake.Someyearsago th€ Birdlife
Red Data Book program eliminated subspeciesfrom its
concern, on the basis that there were simply too many
to document and that specieshad to take prioriry. This
decision, made with the knowledge that many threatened subspecieswill benefit from site managementfor
threatened specieswith which they are sympatric, still
tends to exposesome subspecies,especiallythose with
small ranges and therefore with relatively constrained
populations, to the vagariesof deteriorating global conditions. Unless a country is as wealthy as the United
States,whose legislation embracessubspeciesand indeed populations, or has little or no other biological
heritage in which to invest (for birds, Barbadosis one
such). the chances of intervention on behalf of these
forms are relatively low.
Nevertheless,subspeciesare far less stable as taxonomic entities than are species,and are easily erected
and just as easily subsumed (prior to 1950 at least two
museum ornithologists, Oberholser and Koelz, each established over I00 subspeciesin the course of a single
paper!). Becauseof this, they are generally unwelcome
in law, which requires widespreadlong-tern agreement
on taxonomy to be able to function. Consequently,
speciesrather than subspeciesare the units of concern
in most national and international legislation.
Partly perhaps as a consequenceo[ this, many omithologists seemwilling to countenancethe steady,consistent "unlumping" of many forms, on the basis of
multiple character differences extending beyond morphology to voice, behavior, and even habitat. For conservation purposes this process needs to be expedited
to ensure that specific identity is not bestowed too late
forintervention. However, the elevationof many weakly
distinct forms to species level may actually make the
identification of conservation targets harder, for if resourcesare insufficient to support all the resulting endangered species, many deserving cases (in terms of
their evolutionary distinctiveness) might be lost amid
the compedng claims o[ virtual look-alikes.
B. Scale
andtheldentification
of
TargetUnits
Birds can be endangeredat the global, broad regional
(e.9., subcontinental), national, narrow regional (e.g.,
E N D A N G E R E DB I R D S
provincial), and local levels. It is entirely legidmate for
countries and specialist interests to seek to "red-list"
(i.e., list as endangered)bird taxa at thesevarious levels'
although as the scalebecornessmaller, the various legitimate causesmay, theoretically at least,begin to conflict
with one another. However, decreasingscale is widely
acceptedas correlating with decreasingPriority, so conflicts of interest are unusual.
Global endangermentis the most important priority
level, since total extinction is a far worse risk than any
other form. ln th€ past 35 years or so, global endangerment of birds has been registered principally through
the RedDataBook program ofthe lnternational Council
for Bird Preservation(now Birdlife lntemational). This
program, acceptedby IUCN/The World Conservation
Union as the official source of globally threatenedbird
listings, has developedinto a long-term, continent-oriented project to created€tailed profiles of every endangered species (Collar and Stuart, 1985; Coll^t et al.,
1992; Collar et al., 1999), based on the rationale that
all information relevant to a species's conservadon
should be included. This in turn has led to the need
for abbreviated global listings (Collar et aI , 1994).
The speciesthat have found their way into these full
and abbreviated Red Data Books are normally found
on national "red lists," but not always at the expected
priorit) level, owing to the various algorithms that nonglobal assessmenttends to involve. Thus an apparently
Iogical ranking system in the 1984 South AJrican Red
Dat.1Book; Birds resulted in widespread and common
speciessuch as EgJptian Vultu:'e (Neophronpercnopt'
enrs) and House M artin (Delichonurbica)-both found
in Europe, the latter in huge numbers-coming out
higher (2/102 ar:.d6/102, respectively) than the topranking globally threatened South African endemic
Rudd's Lark (HeteromiraJrq ruddii)(22/ 102) .
Much more frequently a speciesis declared nationally endangeredwithout being globally endangered,alrhough the issuesat stakemay sometimesbe so momentous that global endangerment is often assumed.This
is the case with the Houbara (Chlamydotis undulata),
judged by many to be unsustainably exploited by Gulf
State hunters in most of its range and yet on Central
Asian evid€nce still outside the IUCN criteria thresholds. Similarly, the Spotted Owl (Strir occidefillis) is
an endangeredspeciesunder U.S. law, but it still misses
the IUCN criteria because its populations north and
south o[ its U.S. range render it unlikely to die out
within a relatively short time frame.
However, clearly the most important red list after the
slobal list must be at the national level, and somewhat
iurprisingly this emphasis has been increased by the
397
recently inaugurated Convention on Biological Diversity. Although the Convention has a supposedlyglobal
remit and ovewiew, it has devolved responsibility for
actions in defenseof biodiversity to national agencies
as framed by natiotal perceptions. Parties to the Convention thus sornewhat unfortunately run the risk of
focusing only on elements of their natural Patrimony
that they regard as relevant, at the expense of species
identified through intemational perspectives.
of
C. Criteriafor theIdentification
TargetUnits
Under protocols still being developed by IUCN/The
World Conservation Union, the global redJisting of a
taxon may occur only if its conservationstatusisjudged
to satisfy at least one of a set of universal quandtative
criteria (IUCN Species Suwival Commission, I99't).
Since a species can only become extinct by decreases
in population and range size, these criteria set thresholds on these parametersas well as on decline rate by
which to measureeligibility for and degreeo[threatened
status. In IUCN terminology, the word thredtenedmeans
what has hitherto b een called otdangered, whereas "Endangered' denotes a specific conservation status.
ln crude form, the criteda stipulate that, to qualifu
as threaten€d,a speciesmust possessa total population
(A) declining at a rate (projected or past) of 20% over
I0 years or three generations,or (B) within a range of
less than 20,000 kmt and decLining,or (C) of less than
10,000 mature individuals and declining, or (DI) of
less than 1000 mature individuals, or (D2) within a
range of less than 100 kmr. SPeciesmeeting any one
of these criteria qualify as threatened with the category
Vulnerable; nested thresholds qualify species for the
categoriesEndangeredand Critically Endangered.Subspeciescan be subjected to the same criteria, but this
may result in the curious circumstancewhere all races
of a species qualify as at risk (e.8., all five races of
an island specieswith declining populations of under
10,000) but the speciesitselfdoes not (total population
still above 40,000).
The general experiencewith birds, almost certainly
as with all animals and plans, is that populations tend
to be significantly underestirnated: for example, one
observeron the N€w Caledonian island of Uveajudged
there to be 70-90 Uvea (Horned) Parakeets (Eunymphi'
cus (comutus) uvesnsis)in 1993, but more intensive
fieldwork later that year yielded a formal estimate of
617 'r i79- Similarlv, a CAMP (Conservation Assessment and Management Plan) run by the Captive Breeding SpecialistGroup of IUCN in 1992 suggesteda total
398
E N D A NG E R E DB I R D S
population oI som€ 5000 Tanimbar Corellas (Cacatua
goffni), whereas analysisof quantified data from fieldwork that same year produced an estimateof 300,000400,000 birds. Consequently,liss of threatenedspecies
cannot be expected to remain shbl€: while some will
be added over time as their situation deteriorates or
their taxonomy is revised. others will be removed as
their true status is revealed.
In 1988, 1030 bird specieswere idendfied as at risk
of extinction. In 1994, this figure, based on the new
IUCN criteria, rose to lll l. It was not, however, the
case that 8l specieswere added to the 1988 complement. ln fact only 816 specieswere common to both
lists. The 214 disappearancesfrom and 295 addirions
to the 1994 list largely resulted from new "pioneering"
knowledge (involving new areasor new identification
insights) rather than from "monitoring" updates that
disclosed a clear trend. Exploration is thus still the
strongest biological data source, and "rare" species(for
which see Kunin and Gaston, 1998) sometimes prove
to be relatively common in some part of their range,
or in some previously uninvestigated habitat. Consequently, attempts to predict future extincdon rates using changes in red lists have been premature: the
changesin question are not real-world events (Crosby
et 4.1..1996).
A degree of red list stability derives from some species being destined to remain endangeredin perpetuit)..
This is b€causeof their irremediably small ranges or
populations (a circumstance that has made the criteria
unpopular in some quart€rs,since no active threat need
exisl to lrigger the listing). These are species-avian
examples including the tava Gull (Larus Juliginosus),
with 300-400 pairs maximum, and the Tinian Monarch
(Monarcha ta.hatsuh4s4e),
on an island of less than I00
km2 despite its estimared 40,000 individuals-for
which the price of survival is eternal vigilance.
Appropriate criteria for use at the national level are
still under development by IUCN; meanwhile, a good
model is that of Avery ef al. (in Coulson and Crockford, 1995).
III, TRENDS
ANDFACTORS
IN THE
ENDANGERMENT
OFBIRDS
A. GloballyThreatened
Birdsin 1994:
Numbers,
Criteria,andExtinction
RatePredictions
The l11l bird speciesjudged to b€ at risk of extinction
in 1994 representedI l% of the world's avifauna.Mor€-
over, a further 66 (I%) specieswere then listed as Data
Deficient and 875 (9%) as Near-Threatened, so that
altogether over 20% of all bird specieswere identified
as being of some global conservation concem. The majority ofthreatened specieswere classifiedasVulnerable
(7O4,63ok),w1th235(2196)Endangeredand 168 (15%)
Critically Endangered.
The commonest criterion triggered by threatened
birds was C, which combines small population
(<10,000) with significant decline. As many as 764
species(approaching 70o6)of all rhreatenedbirds were
judged (or, under the precautionary principle, thought
likely) to fulfill this criterion; thus 8o/oofall bird species
are known or suspectedto have dangerouslylow populations. The other four criteria proved to be rather
evenly dist buted: A (rapid decline) and B (small range
with significant decline) were triggered b1' around 400
species each, with somewhat smaller numbers triggering D1 (very small population) and D2 (very
small range).
The new IUCN criteria attach hlporhetical probabilities o[ extinction to the differenr caregoriesof threat,
on which basis400 speciesma1'be expectedto become
extinct.without remedialacrion,in rhe comingcentury;
however.it will take 1750 years for 900,6of the llII
listed threatenedspeciesto disappear.Comparison with
the 1988 listing allo*,ed three differ€nr listing recruitment rates to be tested on rwo models, indicating that
q'ith current trends between 400 and 1200 speciesof
bird may die out within the nexr 100 years,with a rime
to extinction for half the planet's avilauna (ca.4850
species) of 800-2800 years (Crosby et al., 1996). Although these figures are less pessimistic than other
recent estimatesderived from less robust data, human
pressureson the environment will only increasein the
foreseeablefuture, so these extinction rates will probablv orove much too conservative.
B. GloballyThreatened
Birds:Regions,
Countries,
Habitats
The majority of threatened bird species occur in Asia
and the New World, with relatively few in Africa. The
top ten countries for the high€st numbers of threatened
speciesare lndonesia (104), Brazil (I03), Philippines
and China (both 86), lndia (71), Colombia (62). Peru
(60), Ecuador (50), United Sutes (46), and Vietnam
(45). Asian countries predominate in rhis list: the
United Statesranks high becauseof its Pacific territories. The highest African countdes, ranking 2lst and
22nd, are Tanzania (30) and Madagascar(28).
Prio ty countries might be selected on rhis basis,
E N D A N G E R E DB I R D S
but severalfurther filters can be applied. Becausespecies
in the higher categoriesof threat are likely to become
extinct sooner, a reranking involving just those 403
speciesthat are either Critically Endangeredor Endangered .vieldsa top ten of Brazil (47), Philippines (45),
Colombia (31), United Sates (25), lndonesia and Mexico (20 each), Peru (18), and Vietnam, Ecuador, and
.{rgentina (16 each). Using this category, the emphasis
shifts dramatically to the New world.
A further filter involves only those speciesfrom the
preceding analysisthat are nationally endemic, thereby
indicating the degree of "ultimate resPonsibility" that
falls to thesecountries as their most urgent bird conservation task. The Philippines (40) emerge far ahead of
Brazil (32). itsell far ahead of Colombia (24), United
States (17), Mexico (13), Indonesia and New Zealand
(12 each),Australia (II), Madagascar(10), and Peru
(9). Although it was fairly obvious from the first analysis, given their small land area, that the Philippines
would be a priority area, this refined analysis offers
startling evidenceofthe critical imPortanceofthe country in terms of avian biodiversity and its impending loss.
The catastrophic erasure o[ forests from the planet
in the course of the twentieth century means that most
threatened birds are (mostly tropical) forest dwellers;
the only surprising thing is that the figure is as low as
65%. Wetland species account for 9%, scrubland for
another 97o, and grassland for 6%. The reladvely low
forest representation can be explained in pan by the
fact that the largest tracts o[ forest, in Amazonia, the
Congo basin, and Borneo, are-despite the destruction
visited upon them-still too extensive,and the species
they contain too widespread, to have resulted in more
than a handful of listings from these areas.
in Birds
of Endangerment
C. Causes
Endangered birds suffer from a range of different
rhreats. Some 52oloof them are affectedby habitat loss
rnd degradation(although this figure is almost certainly
higher: indeed, low-level and hence unreported habitat
loss could probably safely be indicated for the other
48%); this theme is explored in the following paragraphs. The next most important threat is simPly restriction of range or population, involving 23% of all
threatened birds. Hunting afflicts 8%, introduced species 6%, and trade 3%.
Until recently the notion that habitat lossv/asimportant in the demise of the Passeng€rPigeon (Ectopist€s
migratoius) had not been entertained, but Bucher
(1992) showed how the specieswas a specialiston seeds
produced in masting eventswhose scaleand geographic
399
location varied from year to year, that is, that were
patchy in both space and time. Human settlement of
the east and center of the North American continent
fragmented the native forests to the point where the
lapsein both time and distancebetween masting events
simplybecame too great.Despite the settlers'prodigious
slaughter of birds, which has always been blamed for
their disappearance,it aPpearsthat it may have been
their axes, not their guns, that caused the loss of their
quarry; the last wild birds very possibly st4rvedto death.
An equally celebratedNorth AmericansPecies,Perhaps still extant, is the Eskimo Curlew (Numenius bore'
clis), which, like the PassengerPigeon, used to be
hunted in phenomenal nunbers in the nineteenth century and likewise never recovered after the slaughter
finally abated.It seemslikely, however, that the loss of
its Argentine grassland wintering grounds and North
American prairie spring stopover sites was to blame.
Loss of stopover habitat is beginning to supplant hunting (never a convincing case)as the best explanation for
rhe virtual disappearanceof the closely related Slenderbilled Curlew (N. tenuirostris),which breedsin westem
Siberia and migrates southwest to the Medit€nanean
basin, almost certainly using the once extensive eastwest Russian steppesalong the way.
Other notable examples of this space/time vulnerability include the Thick-billed Parrot (Rhynchopsittap4'
chy rhyncha), P urple-winged Ground-dove (Cl ar at is godeJnda), Andean (Phoenicopterusandinus), and Puna
Flamingos (P. jamesi), Lesser Florican (Sypheotides iv
dica), and Resplendent Quetzal (Pharomachrus mocinno). The parrot shows the sarnetrait as the Passenger
Pigeon,since it is dependenton pine seed,a notoriously
unpredictable resource. The speciesis nomadic, but as
its native pine forests in Mexico's Sierra Madre are further fragmented, there is a serious danger that a conecrop failure will leave the last populations "stranded"
too far from food for any to suruive. The ground-dove
specializeson the seedsof forest bamboo in southeast
Brazil. So much forest has been destroyed within its
range,and bamboo seedsetis so temporally patchy, that
the specieshas become one of the rarest in the country.
The flamingos move between lakes in search of appropriate conditions (which shift over tim€) and are
therefore exposed to the possibility that human damage
to even a small number of sites may one day leave
the species with nowhere to go. The florican selecs
different grassland sites from year to year in rMestem
India, depending on the effects of local rainfall. Grassland is under enormous human pressure in India, and
conserving tracts that may be empty of birds for several
yearsat a time isnot a simPleproposition. Post-breeding
400
E N D A N G E R E DB I R D S
quetzals are now known to make complex short-distancemovements to severaldifferent aleas.so that manv
more tracts o[ forest than one or two may be needei
to ensure the long-term survival of viable populations
of this species.
ln Australia, many birds have been affected by human alrcradon of the natural fire regime. The Paradise
Parrot (Psephotus pulcherimus) almost certainly became extinct (it may conceivably survive somewhere)
owing to new buming pattems that suited livestock but
not the grasseson whose seeds the parrot subsisted.
Similar problems afflict the food supply of the Goldenshouldered Parrot (P, chrysopterygius)and the habitat
of the Noisy Scrub-bird (Atichomis clamosus).
The reasonwhy restriction of range ranks so highly
in the list of thr€ats is becauseany cause of decline is
likely to affect the endre speciestoo quickly for human
intervention to help. Such speciesare often restricted
to islands, and when those islands are oceanic, the
birds have usually evolved in the absenceofcontinental
pressuresfrom mammalian predators.As a consequence
they are behaviorally and physically adapred in ways
that leave them highly vulnerable when continental
predators become established within their ranges,
through either the direct or indirect agencyo[ humans.
These behavioral adaptations are not degenerative.
The Dodo (Raphus cucullatus) was given its name from
the Portugueseslang for "stupid," doido.But island animals that are €ntirely tame, or that nest in what to
human eyesare ludicrously undefended places,or that
have lost the function of their wings ar€ not evolutionary failures. On the contrary, theseseeminglydisadvantageous attributes are th€ result of continuing evolutionary pressures. Wings cost en€rgy to carry and
maintain, and in the absenceof predators they offer no
retum on the investm€nt in such energy.Shynesscosts
its possessorsdearly if less shy creatures have more
time to exploit whatever resource is at stake. Nesting
in inaccessibleplacesis needlesslyexpensivei[ there is
no risk in nesting on the ground in the open. Moreover,
the relatively stable conditions on tropical islands tend
to promote marked K-selected traits (e.g., slow reproductive rates).So the very things that render island birds
so vulnerable to aggressive,fast-breeding,continental
animals have actually been selectedJor through narrower, often intraspecific competition.
Most avian extinctions since 1600 have been on islands (King, in Moors, 1985), and a significant number
of threatenedbirds today are island species.The impact
of rats has been and remains massive(seeAtkinson. in
Moors, 1985): Magenh Petrel (Pterodromamagentae),
Zino's Petrel (P. madeira), Tuamotu Sandpiper (Proso-
bonia cancellata), Po\.nesian Ground-dove (Gallicolumba erythroptera), Seychelles Paradise-flycatcher
(Terpsiphone comina), and Rarotonga Monarch (Pomorea dimidiata) are a few of the Critically Endangered
birds whose fate is directly linked to the invasion o[
their islands by rats. ln some caseswhere cats have also
been introduced, it is not clear which predator is the
greater culprit, and these affected speciesoften live on
larger islands where very little can be done to help. The
New Caledonian Rail (Gallirallus lclresncyus), Cuba's
Zapata Rail (Cyanolimnascen/erai), the SamoanMoorhen (Gqllinula sylvestris), and virtually the entire endemic avifauna of Hawaii (the linle of it that survives,
but notably the honeycreepers,Drepanididae) are good
examplesof this uncertainty and impotence. Cats alone
are responsible for the plight of some species,such as
Townsend's Shearwater (Puffnus auricularis), Socorro
Dove (Zenaido.graysoni), and the Marquesan Grounddove (Gallicolumbarubesrens).Mongooses,which were
often released to devour rats or control snakes, are
major threats to speciessuch as Hawaiian Duck (Ancs
w_yvilliana)and St Lucias Semper'sWarbler (Leucopeza semperi).
Ancient lakes, like oceanic islands, often harbor endemic faunas and floras that are highly susceptible ro
exotic introductions. Among the birds, the grebe family
Podicepitidae has been particularly hard hit, with the
Alaotra Grebe (TachybaptusruJolavatus)of Madagascar
and Junin Grebe (Podiceps taczarowshit) of Peru close
to extinction; the Aritldn Grebe (Podylimbus gigas) of
Guatemala and Colombian Grebe (Podiceps atdinus)
have already vanished.
Linear water bodies may similarly expose certain
speciesto extinction risks from a single event or sedes
o[ events: Scaly-sidedMerganser (Mergus squamatus),
Brazilian Merganser (M. octosetaceus),
Wrybill (Anarhynchus Jrontalis), Rufous-throated Dipper (Cinclus
schulzi), and Luzon Water-redstart (Rhyacomis bicolor)
are all vulnerable in this way. Moreover, species that
concentrate in a small area for even part of their life
cycle may be abnormally exposedto danger. For example, the entire world population of Ascension Frig^tebird.(Fregato.o.quila)breedson a single stack smaller
than a municipal parking lot- Even birds that are briefly
drawn to individual fruiting trees are liable to suffer:
as many as 40 VisayanWrinkled Hombills (Aceroswaldeni) were shot in a single tree over the course of a
single day in October, 1997,an event that quite possibly
killed 50% of the population.
The foregoing examples represent "spatial" threats.
Other threats are better characterized as "temooral-"
involving a seemingly innocenr event whose conse-
E N D A N G E R E DB I R D S
40t
ger (Conothraupis mesoleuca, Brazil), Cherry-throated
quencescannot be remedied by the time they become
Tanager(Nemosiarourei, Brazil),Ibadan Malimbe (Malapparent.Ne*'Zealand's Kaka (Nestorm endionalis)and
imbus ibadanansis,southem Nigeria), and lsabela Oriole
Yelloshead (Mohoua ochrocephala)face enormous dif(Oriolus
isabellae,Ltzon, Philippines) . All are bafflingly
ficuhies no$'that introduced waspscomPetewith them
(breedrarer-some are known only by a single museum speci[or honevde*. an extremely important foodstuff
men-than rnight be inferred from the habitat apparing successin the Kaka is directly correlated with honently availableto them. Unidentified factors must afflict
e\.deq inrake in the previous autumn). The whitethem all, and clear|y sometimesnatural causes may be
hcaded Duck (Oxyuralzucocephala)faceslong-term exin play, particularly unseen ones such as diseasesand
rincrion through hybridization with its New World
infestations(seeMay, in Coulson and Crockford, 1995),
counterpart, the Ruddy Duck (O. jamaicensis),which
which are known to afflict the lphis Monarch (Pomates
becameferal in Britain in the 1960s and is now spread-fhe
iphis) and Gouldian Finch (Erythrura gouldiae).
ing into its range. In both casesthe costs and logistics
safestassumpdon in casesof inexplicable rarity, at least
o[ eradicationare too great lo consider.
on condnents, is that habitat degradation or loss is in
Sometimes threats come not from exotics but lrom
some way involved.
natives expanding their ranges,often owing to human
modifications of habitat. The spread of cowbirds (Molothrus) through the Americas and the Caribbean is
TOTHE
IV. APPROACHES
particularly worr)4ng. Birds such as Kirtland's Warbler
(Dendroica hirtlandii) and Black-capped Vireo (Vireo
OF
CONSERVATION
atricapillvs) need constant-effort prograrns to r€duce
BIRDS
THREATENED
cowbird brood-parasitism to tolerable levels. Similarly
rhe spread through the Caribbean of the Pearly-eyed
andSynthesis
A. Research
Thrasher (Margarops fuscatus), a nest-hole competitor,
The primary consewation need of an endangeredspehas been viewed with alarm by the Puerto Rican Amacies is information. There is a common behavioral trait
zon (Amazonavittatd) recovery teams.
amongacademicsof ignoring literature much older than
Analysis of Neotropical data (Collar et al., 1997)
I0 years, presumably partly reflecting the assumpdon
shows that the avian families with significantly high
that the data contained in such literature are incorPonumbers of threarcned species suffer from particular
(Psittacidae)
rated into more recent work. Often, in fact, the informarhreats in combination. Thus the parrots
tion has been ignored; sometimes,however, it has been
have rhe greatestproportion of threatenedbirds in any
used but, on proper reconsid€ration,proves tobe faulty.
tamilr' (2806), closely followed by the curassows and
(TinamiThere is therefore considerable virtue in seeking out,
guans (Cracidae,26%), and then the tinamous
assembling,and critically evaluating all iuformation redae. I5"... still almost double the 8% rate of endangerlating to an endangeredspeciesbefore deciding on the
menr in the \ew World avifauna as a whole). All three
most appropriate remedial or m€rely investigative acfamilies arc sensitive to habitat loss; but the parros
tion. Despite the need for speed in casesof speciesat
also experience intensive trapping for trade purposes,
risk, precipiate intervention can waste hundreds of
and the cracrds and tinamous are no less intensively
thousands of dollars and even prejudice attitudes
exploited for food. Possessiono[ a distinct economic
against a specieswhen its real needs are finally recogvalue within a beleaguered habitat t'?e, particularly
nized. For example, captive breeding management for
one with some (bio-)geographic restriction, conlers a
the Philippine Eagle (PithecophagajefJeryi), a costly
strong likelihood oI endangerment.
long-term, but to dat€ unsuccessfulprogram, appears
However, there are manv endangered birds whose
to have come into being in responseto somewhat overrarity has abidingly obscure causes.Among these are
(Caitind
srutulnla,Southeast cautious estimatesof the bird's population size.
the White-winged Duck
Recent Birdlife Red Data Books have sought to preAsia), Giant lbis (Pseudibisgigantca,lndochina), Himas€nt detailed synth€seso[ relevant data, extending to
Iayan Mountain-quail (Ophrysic superciliosa, lndia),
(Polyplectron
schleiermach- translations from languag€swith which biologists may
Bomean Peacock-pheasant
(Ptilinopus
not be familiar, so that a clear picture of a situation
orc4nus,Neeri, Bomeo), Negros Fruit-dove
(Charmosyna
can rapidly be considered and the options objectively
gros, Philippines), Blue-headedLorlkeet
(C.
assessed.However, ther€ are many other examples of
toropri, Buru, lndonesia), New CaledonianLorikeet
the careful construction of evidencein endangeredspediqdema), Forest O wlet (Atheneblewitti, India) , Liberian
cies management. One of the most notable is the exGreenbul (Phl llast rephus leucolepis), Cone-billed Tana-
402
E ND A NG E R E DB IR D S
haustive 400-page review of the history, plight, and
management of the Puerto Rican Amazon (AmaTona
vitt4td) assembledby members of the team that spenr
some 20 years piecing together the facts (Snyder et
al., 1987).
The importance of individual study of endangered
birds cannot be overstated,although there can be difficulties (over logistics, permissions, the generation of
statistically uselul data) and dangers(sometimes to the
student, sometimesto the species)that militate srongly
against such work, For larg€r species,radio-tracking is
becomingincreasinglyvaluableasa meansofrecovering
large quandties of information from a relatively small
investment of effort: speciesas different as Black-faced
Spoonbill (Platalea minor) and MadagascarSerpent-eagle (E[triorchis astur) have yielded data on movemens
and daily behavior pattems rhat are crucial ro their
long-term management.
B. SiteandHabitatConservation
The conservation of sites at which endangered birds
occur, and of the habitat they are known to occupy, is
the primary management technique for ensudng their
suwival. The key tool is th€ protected area, which for
Iarger sitesis usually reflected in law as a national park,
indicating the clear public interest of serdng aside a
major proportion of a country lor noneconomic reasons. Smaller areas are often designated as nature or
biological reserves,and are frequently consideredmore
as refuges or scientific laboratories for research purposesthan as sites with a broader public service;public
access can be more difficult than in nadonal parks.
However, the site of many national parks is important
for consewing viable populations of larger, low-density
species.Naturally it is appropriate to seek to savethese
specieswhere they are s)'npatric, thereby maximizing
the efficiency of the expense.Evaluations such as those
by Wege and Long (1995), Stou et aL (1996), and
Stattersfield et al. (1998) provide clear rarionales for
the hrgeting of conservation resourcesin such a way
as to secur€ not just individual species but the key
representativ€sof biogeographic regions.
ln general, endangeredbirds on continents require
larger-scalehabitat conservation, whereas those on islands need intensive multi-faceted management (aspectsofwhich are treatedin SectionIII,D). The cardinal
element in successfulsite conservadonis local support,
backed of course by national govemment. In its work
since 1983 to conservethe montane foress of westem
Cameroon (to which 25 speciesof bird are endemic, 9
oI them threatened), Birdlife International has imple-
mented a major ICDP (integrated conservation and development project) ar Mt. Kilum-ljim to aid local human communities around the mountains, and this has
led to a widespread appreciation oI the biological value
of the forest withour generaring rhe kind of hostility
that goes with attempting to create strict exclusion
zones. The same kind of program operatesar ArabukoSokoke Forest in Kenya, home to six endangeredbirds.
Other conservation organizations have been using the
same fundamental formula-that local people must be
made part of the solution, not demonrzed as part of
the problem.
Campaigns to promote interest in and support for
species conservation programs are liral elements of
those programs. These may rake rhe form o[ extension
work related to ICDP promotion of sustainableuse oI
Iocal resources, or more direct appeals to people to
appreciate the unique value of rhe wildlife in their
C. TradeControls
and
Intemational
Legislation
Although trade is not a strong factor in the endangerment of birds in general,it is important for a lew groups
ofspecies, most notably the parrots. The major intemational instrument for the control o[ trade is the Washington Convention, universally knou'n as CTTES(Convention on International Trad€ in EndangeredSpecies),
which has been in operation since rhe 1970s. Animals
and plants maybe registeredin three \ays: on Appendix
I, which essentiallyprohibits all movement of the species in question:on Appendix II. rvhich prohibits all
commercialtradeexceptunder license:and on Appendix ttl. which allo*s a particular narion to prohibit
ttade across its borders irrespective of a species' status elsewhere.
Becauseo[ the immense volume oI traffic in parrots.
and the problemof identificanonin so diversea family
(around 350 species),all but three specieswere placed
on Appendix ll in 1981. This move had the intention
ifnot the effect of giving protection to the more endangered parros-naturally their rarity increasedrheir desirability among bird-fanciers-which, if listed alone
on the Appendix, could easily have been traded indiscriminately under other names without customs officials necessarilybeing able to idenrify them. Appendix
II species have quotas set by exporting countries, in
theory based on data that show the exploitation to be
sustainable.Where the evidence suggeststhat it is not,
movement to Appendix I is supposed to bestow immunity.
E N D A N G E R E DB I R D S
Curiouslv-but as a measureof the power that some
trade interests can exert-lisdng on APP€ndix I can
actualh stimulate trade (a) while the speciesis still at
rhe proposal stagefor upgrading but also (b) following
Iistrng. on the basis o[ its enhanced rarity value. This
happened to the Hyacinth Macaw (Anodorhynchushyacrnrhinrs). rvhoserarity in the wild today is primarily a
e,.,nsequence
of a trapping blitz in the 1980s.ln general,
(-ITES trade controls have some effect, and allow for
r cn useful monitoring of changesin trading fashions
ovcr time. However, for truly prized species such as
Lcar's Macaw (A. leari) and Spix's Macaw (Cyonopsittd
sptrii), both frorn Brazil, there is little that any control
s\stem can do to elirninate smuggling: the financial
inducements are simply too strong. The same tends to
be true in lndonesia for exquisite songsters like the
Straw-headedBulb:ul (Pycnonotuszeylanicus)and SoodlLrokers like the Bali Surling (Leucopsar rothschildi).
Other important international instruments for end.rngeredbirds are the RamsarConvention (ior imPorr.rnt u'etlands), Bonn Convention (for migratory specres). and Berne Conv€ndon (for European species).
The Convention on Biological Diversity, already mentioned, ought to be the comerstone of endangeredspecies conservation across the planet. but considerable
e[fort bl nongovernmental organizations is needed to
ensurethe inclusionof global prioritiesin the national
consenation strategiesthat each partl to the convention is obliged to produceand implemenl.
for "Critically
Techniques
D. Management
Endangered"
Birds
I. Habitat Restoradon
Major conservation projects almost invariably involve
some habitat restoration work. However, for speciesat
the brink ofextinction through habitat loss, the emphasis falls more directly on the rapid replanting of foodplants and land areas.Lear'sMacaw appearsto be constrained by the availabilitl o[ licuri palms (Syagrus
coronata),many srandsof which show no sign of regeneration owing to cattle-grazing: Programs have long
been planned to establish many new Sroveswithin the
species'range. The Cebu Flowerpecker (Dicaeumquadricolor) survives in an area of heavily degraded forest
rhat consists ol a mere 3 km2: efforts are under way to
r€forest adjacent areaswithin the next 30 years. There
is now an emerging discipline of restoration ecology,
and it is likely that a great deal of conservation energy
in the twenty-first century will be channeledinto reconfiguring habiuts that were ruined during the twentieth.
403
2. Control and/or Restriction of Aliens
and Natives
Eradication of exotic predators and pests from islands
hasbeen pioneeredin New Zealand,where severalsmall
offshore islands have been rid of various mammals in
order both to preserveresident breeding speciesand to
translocatestricken native sPeci€sfrom the main islands
(Clout and Craig, in Coulson and Crockford, 1995).
This painstakingly systematic restoration of islandsmainly involving the elimination of cats, rats, and mustelids-has been essentialto the survival of birds such
as the Black Perel (Procellariaparhinsoni) and Kakapo
(Stigops habroptilus), and the expertise generated is
now being exported to other islands in the Pacific and
lndian Oceans.
Researcherson Mauritius recently discovered why
the native, Critically EndangeredPink PiSeon(Nesoen4s
mayeri) and Mauritius Fody (Foudia rubra) have manag€d to persist in the face of rat predation. Thesebirds
now nest almost exclusively in a grove of exotic Cryptomeiq japonica, whose bark produces a sticky gum and
whose leaves consist of spiny needles,both of which
discouragerats lrom getting at nests. Curiously, then,
in rare casesit appearsthat exotic vegetation can help
rather than hinder native sp€cies in their struggle
against exotic predators; in this insbnce the plandng
o[ more Crlptomeric is clearly called for.
It is not always the casethat exotic predators are the
problem. ln New Zealand, the native weka (Gallirallus
4ustralis) has proved to be a significant influence in
depressingthe numbers of Little Spotted Kiwi (Apteryx
owenii) marooned on Kapiti lsland, of Cook's Petrel
(Pterodromacookii) on Codfish Island (until removed),
and of Chatham Oystercatcher (Haematopuschatha'
mersis) on various Chatham islands. On Bermuda,
White-tailed Tropicbirds (Phaethonlepturus) outcompete Cahows (Pterodromacahow) for nests and have to
be controlled. As already mentioned, brood-parasitism
by cowbirds requires intensive local control efforts to
prevent the suppression of breeding successin Kirtland's Warbler and Black-cappedVireo.
3. Captive Breeding
The role of captive breeding in endangeredbirds has
long been controversial. The prevailing view among
conservation biologists is that capdye breeding is not
a major managementtool for endangeredbirds, and that
indeed it can positively dishact attention and lesources
from serious problems that affect th€ species.The Philippine Eagle has already been mentionedi similarly,
cranesand parrots have in the past been launched into
401
E N D A N G E R E DB I R D S
ex situ prograrrs in the mistaken belief that maior benefits will resulr (bolh speciesimprint heavily.and parrots, many of which leam survival techniques through
observation of their parents, are particularly disadvantagedfor retum to the wild). Captive breeding hasmany
other drawbacks,notably the particular dangersof diseasetransmissionto wild birds from captive stock (Sny_
d.er et aL. L996).
Nevertheless,captive breeding has achieved several
outstanding successes.The Northem Bald Ibis (Geron_
ticus eremita.) and Califomia Condor (Gyunogps cali_
fomianus) both flourish in caprivity while efforts to
implove environmental conditions in the wild continue.
The Lord Howe Rail (Gallirallus qrlvestris) and Guam
Rail (G. owstoni), members of a notoriously vulnerable
family (since so many rails reached islands in the past
and proceededro lose the power of [light), probibly
only persist thank to er sittl regimes. The Socono
Dove (Zenaida graysoni) survives only becausea few
Californianbird-fanciersrook and bred specimensat
a time before its native island *u, ou"rrun by exotic
predators. ln Ig98 rhe Bali Starling (Leucopsar rothschildi) was within eight individuals of becoming extinct in lhe wild owing to relentlesspoachingtor trade.
but zoos throughout the world have bred the species
such that many hundredsand perhapsrhousandssur_
vive for possible reintroduction when poaching has finally been brought under control.
There is also a role for veterinarians in intensive in
situ managementprograms, through their expertise in
providing appropriate advice on roxicity ofnestbox ma_
rerials,control ofnest parasites.
compositionand secure
provision of supplementary foods, disease screening,
and minimization in cross-fosteringand translocation
exerc$es.
4. Reintroduction
and Translocation
The extirpation of a speciesat a discrete site may have
been caused by a shorGterm or remediable factor, so
that restocking with individuals from elsewherecan be
undertaken. This is usually relevant or worrhwhile only
when rhe speciesis globally endangered.bur whatevei
the urgency, the endeavor requires careful planning
(Black, I991). A seriesof feasibility assessmentsshould
determine rhe sire's continuing ecological suitability
(the original constraining factors must no longer opeiate), the threats it faces,the availability of appropriate
stock, the socioeconomic implications, and local, national, and international awarenessneeds. The birds
must be in optimal condition, and if captive-bred thev
should havebeenrearedin disease-free
condirionsani
in such a way as to be behaviorally and genetically fit
for independence in nature. Monitoring of the project
is crucial, and it should be documented for circulation
to other biologists contemplating such effors.
Bird speciesthat have benefited from well-desisned
reintroductionprogramsinclude rhe Neneor Hawaiian
Goose (Branta sandyicensis),California Condor, pere_
grine (Falco pereginus), and Chatham lslands Snipe
(Coenocorypha
pusilla). Those rhat have nor incluie
Cheer Pheasant (Cqtrexs wallichii) in Margalla Hills,
Pakistan (fox predation), Shore plover on Mangere ls_
land. New Zealandlthe birds flew back ro Souih Easr
lsland), and Thick-billed parrots in rhe Unired Stares
(the wild-caught birds flew back to Mexico; rhe captive_
bred ones flew nowhereat all).
Translocation to previously unoccupied siteshas be_
come a greatly valued technique, if onl) as a temporary
measurewhile efforts are concentratedon habitat resto_
ration or predator eradication at the native site. Benefi_
ciaries of rhis approach include Niuafoou Megapode
(Megapodiuspitchardii), Vini lorikeets. Kakapo. Guam
Rail lollowing captive breeding. Seychellei Magpierobin (Copsychussechellarum), and Sel.chellesWarLler
(Acrocephalusseychellsnsis).
The work done in Dreoara_
tion for the Seychelles
Warbler translocarrons
showed
that target islands had many times the insect abundance
of the host island, Cousin. This was clearly related to
the absenceof predation pressure on the insecr fauna,
and-unsurprisingly but still very strikingly-when
birds were releasedonto the target islands they began
breeding almost immediately, and very rapidly expanded their numbers. On Cousin the birds had been
so packed that they bred only very slowly, with one
offspring tending ro sray on territory and help at the
nest.waiting for a parenl to die { Komdeur, tqq}). This
observation underscoresthe value of the food resource
base in managing endangeredbirds, and leads to the
next point.
5. Supplementary
Feeding
The value of increasing food availability for sDecies
whose populations need rapid growlh s;ems t; have
been perceived only relatively recently, perhaps begin_
ning with work on Peregrines(seeTemple, 197g). ihe
techniquehas been adopredlor endangeredbirds on
Mauritius, principally with the Mauritius Kestrel (Falco
punctatus),for which extra food clearly enhancedreoroductive output Qoneser cl., in Coulsonand Crockford,
1995). New Zealand workers supporting efforrs on
Mauritius have found the same with the Kakano: nor_
mally rhe speciesbreeds only in responsero major
masting events,which may occur once every five years,
but wirh dietary supplements it appears to be capable
405
E N D A NG E R E DB I R D S
o[ bre€ding every year. On Hokkaido, Red-crowned
Cranes (Gms japorlensis)have recovered ftom nearcrtirpation through a combination of better protection
.rnd extensive food provision. Clearly, as a relatively
short-term measuresupplementary feeding can be crurral in producing an unnaturally rapid reproductive
output, a very desirable effect in critically low populations where the genetic value of every individual needs
to be maximized.
6. Nest-Site Provision or Enhancement
Where nest sites are limiting (often the casewith holenesting species),the provision of nestboxesor the enhancement of natural cavities may be appropriate.
Puerto Rican Amazons ignored the former butbenefited
from the latter. Mauritius Kestrels greatly benefited
from the creation o[ nesting ledges. The provision of
grilles at entrances has helped Prevent White-tailed
Tropicbirds from appropriating Cahow burrows. In the
Galipagos, a new, more secure colony of Dark-rumped
I'etrels (P. phaeopygia)was establishedby digging nest
burrows and playing calls among them at night.
7. Cross-Fostering and Cross-Breeding
Many large raptors and most cranes lay two eggs but
normally rear only one young, so biologiss attempting
to increase productivity of endangeredforms of such
birds have long sought to make use of the expendable
second eggs by taking them for hatching and captive
breeding. ln the case of the Whooping Crane (Grus
ameicano), an attempt was made to establisha second
population by placing such eggsin the nestsof Sandhill
Cranes (G. canadetsis). but this did not result in a
breeding population, possibly as a result of imprinting.
The most famous inshnce of cross-fosteringinvolved
the Black Robin (Petroica traversi), whose population
fell to five individuals in 1980 but recovered by the
placing of some eggs in the nests of Chatham Island
Tit (P. macrocephala).
Cross-breeding with another subspecies was regarded as the last hope of the Dusky SeasideSparrow
(Ammospizs ma"itimus nigrescens), but the last stock
died out before the endeavor could begin. However, it
has been used on the endemic Norfolk lsland race undulata of the New Zealand Boobook (Morepork, Ninox
noyaeseelondiae), which by 1986 had been reduced to
a single female. After nestboxeswere erected to overcome an irnmediate shortage, two male nominate male
boobooks were introduced to the island; one o[ them
paired with the female and in due course produced a
string of hybrid offspring. The taxonomic (and legal)
implications of this technique may not have been con-
sidered, but it clearly representsa means of presewing
genetic diversitY.
8. The RoIe of the Concerned Cltizen
Finally, it is worth stressingthat much of the advocacy
for endangered birds, and many of the insights into
their plight and salvation, comes from national and
international conservation organizations. One of the
most valuable things that any s)'rnpathetic individual
can do to help endangeredbirds is simply to join or
support such organizations. Their conservation effectiveness depends not only on the financial security derived from a broad membership base,but also on being
recognizedas the representativemouthpieces of a constituency consisting of millions o{ concerned citizens
SeeAlsotheFollowingArticles
EFFORTS'
OF . CONSERVATION
BIRDS.BIODIVERSITY
MAMMALS' ENDANGERED
ENDANGERED
CONTEMPORARY.
AND AMPHIBIANS' EXTINCTIONS,MODERN
REPTILES
OF
INSTANCES
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