Analyses of Globally Threatened Anatidac in

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Analyses of Globally Threatened Anatidac in

Relation to Threats, Distribution, Migration

Patterns, and Habitat Use


Doñari.a Biological Station1 Avcnicla Maria Luisa s/n, Pabellón dcl Peru, 41013 Sevilla, Spain, email andy@ebdO3 eM csjces

Abstract: New World Conservation Union criteria for globally threatened status are applied to the Anatidae (ducks, geese, and swans) at the subspectfic level Various characteristics of the 48 threatened taxa are consist- erect These taxa are compared to the 180 taxa that are nonthreatened to explain what aspects of a tenon’s distribution, migration pattern, and habitat use make it likely to be globally threatened. Habitat loss, bunt­ ing, and exotic introductions are the major causes of globally threatened status, affecttng 73%, 48%, and 33% of threatened Anatidae respectively. Although the habitat use patterns of threatened and nonthreatened Anatidae are similar, inland lentic wetland and forest inhabitants are most threatened by habitat loss, whereas marine ecos,yistem, grassland, tundra, arable land, and scrub dwellers are least threatened. Insular taxa are more likely to be threatened or extinct than taxa occurring on continental land masses. Nonmigra­ tory taxa are more likely to be threatened or extinct than migratory taxa, but there is no slgnficant differ­ ence when insular ta.xa are excluded from the analysis. Taxa with their breeding distribution centered above a latitude of 20° north are less threatened than those found farther south. Taxa with their breeding distribu­ tion centered at or above 55° north are even less threatened Russia holds 14 threatened Anatidae tarn, more than any other country. There is an exceptional concentration of 7 threatened, migratory taxa confined to the east-Asian flyway. Despite the fact that the Ramsar Convention was established with the conservation of the Anatidne in mind, only 31% of globally threatened taxa have ever been recorded on the world’s 685 Ramsar sites. For the 21 highly threatened taxa this proportion drops to 10%. Compared with globally threatened birds in general, the threatened Anatidae have a different geographical distribution but share habitat loss as the most important threat. Hunting and introductions are more important threats to the Anati.dae, and trade and small population ranges are less important All these findings have important implications for waterbird and wetland conservation programs.
Análisis de La globalmente arnenazada Anatidac en relaciàn con amenazas, discribuciOn, patrones de migraciOn y use dcl hbitat

Resumen: Los nuevos criterios de La UniOn Mundial para Ia Naturateza para los taxones globahnente amenazados se aplican a las Andtidas (patos, gansosy cisnes) a nivel subespecfico Se consideran varios car­ acieres de los 48 taxones en peligro de extinciOn. Se comparan estos taxones con los 180 que no estdn amenazadospara explicar qu€’ aspectos de Ia distribuciOn del taxOn, pauta de migraciOn y uso del hdbitat lo convies-ten en objeto de amenaza global. Lapdrdlda del hdbitat, Ia cazay Ia introducciOn de especies exdticas son las causas 4tirincipaies del estalus de globalmente arnenazado, que afecta at 73%, 48% y 33% de las Andti­ das amenazadas respecttvamente. Aunque el uso del habitat por pane de las Anátidas tanto amenazadas como no es similar, los interiores ldnticosy los bosques son los hdbitats mds amenazados, mien­ tras que los ecosistemas marinos, los pastizales La tundra, La tierra tie cultivo y el matorral son los que menos peligro sufren. Los taxones insulares estdn inds ame-nazados de exlinciOn que los de Iris que habitan las a tensiones terrestres continentates. Los taxones no migratorios sufren mds probahilidades tie amenaz.a o de a

tznciôn que los inigratonos, pero no bay dijerenciac sigisQicativas cuando los taxones insuiaies se exciuj.’en del andlisis. Los taxones cuya dtstribución se centre por c’ncinia tic’ los 20°Nestán inenos ainenazarlos qeit’ los situados mds at sue. Aquetios cuya eli-en tie ala estd centiada en o por enchna tie los 55W esteln induso menos arnenazados. Rusia contiene 14 taxones tie Andtk(as anunznzeulas, snás que cualquier otro pats Haj’ una concentraciOn excepcionai tie side taxones migratorios confiitculos a In rota oriental asi4tica A pewi- tie que Ia ConvenciOn Rainsar sefundO con el objetivo tie In consert‘aeión tie las An/aldus, solainente aigana t‘ox se ha regisirado ci 31% etc los iaxones glot’almente ainenazados en todos los 685 sllzos Rainsar dcl inunda Para los 2! laxones en ci maxima peligra do extinciOn, esta proporción cue basta ci 10%. En comparaciOmi con las anes globalmente amenazadas en general, las An&ida.c asrienazadas tienen ann distribución geogrd­ fica distinta, pero compai-ten Ia pErdida del beth/tat cwno Ia anienaza suds tnt/xis-sante. La ce/zn j’ las intro­ ducciones representan las amnenazas relatizian-zente suds importantes pam-a las Andtidas, mnientras qua el tout­ ercio y las circus tie disiribucion o poblaciones pequeüas son relatitmaunente las menus Toelos estos ballazgos suponon iunpiicaciones importantespara losprogratnas tie conser&acidn tie noes acudtmcas zoneis hilnzedets.

The role of demographic and life-history variables in de­ termining the extinction risk of populations has been studied extensively (Terborgh & Winter 1980, Pimm et al 1988; Laurance 1991), and the results have been ap­ plied in a revision of the threatened specits categories used by the World Conservation Union (IUCN; Mace & linde 1991; Macc & Stuart 1994). A final version of the revised categories has recently been formally adopted by The World Conservation Union (1994).

Studies comparing Red Lists of threatened animals and

plants with nonthreatened taxa have usually been re­

stricted to a small region (Lahti et al. 1991; Berg et al

1994). Studies of cite biology arid disrribtrczort of rlireat­ ened organism groups at a global level, which are impor­ tant for nature conservation, are lacking (see, however, Laurila &järvinen 1989). One reason for this is that data on the status of organisms are usually lacking in some parts of the world. Information on the status and biology of the Anatidae (ducks, geese, and swans) ts relatively good on a worldwide scale (del Hoyo et al 1992; Rose & Scott 1994). In this study the new IIJCN red list catego­ ries (World Conservation Union 1994) are applied to the Anatidae at the subspecific level to produce a list of the globally threatened taxa. This list is justified in detail elsewhere (Green 1996) and follows from earlier at­ tempts to identify the globally threatened Anatidae (Ellis­ Joseph et al 1992; Green 1992; callaghan & Green 1993), which used an earlier version of the proposed new IUCN criteria (Mace & Lande 1991).

Humans have long had a unique relationship with the Anatidae, reflected in their widespread harvesting for food, domestication, breeding in captivity, and their in­ fluence on human culture (Kear 1990). In modern times conservationists have paid particular attention to Anatidac to minimize the impact of recreational hunting (Moser et al. 1993) and to attempt to resolve increasing problems of agricultural damage (van Roomen & Madsen 1992). The Anatidae have acquired great importance as flagships for wetland conservation (Kear 1990), and concern for their

status was central to the adoption of the first global treaty for nature conservation (Matthews 1993), the Ramsar Con­ vention (Convention on Wetlands of Intemational Impon tance, especially as Waterfowl Habitat [Ramsar 19711).

1 consider the various threats facing the globally threat­ ened Anatidae in order to establish which factors are most responsible for putting Anatidae at risk of extinction. I analyze the distribution of globally threatened taxa, identifying those countries and regions where they are concentrated. Their distribution is related to that of the growing network of wetlands protected under the Ram­ sar Convention to establish what protection this network provides to globally threatened Anatidae. I also compare the distribution and threats facing the globally threatened

.Anatidac and those for all globatly threatened birds, using analyses recently conducted by Collar et al. (1994) for all

threatened bird species (only 2% of which are Anatidae). The globally threatened Anatidae are compared to the

nonthreatened Anatidae in an effort to identify parame­

ters related to extinction risk, as identified by the IUCN categories, it is well known that extinction risk is corre­ lated with population size, range size, extent of fragmen­ tation, and extent of population fluctuation, and the new 1UCN criteria are based on such parameters (Mace

& Linde 1991; World Conservation Union 1994). Thus, these parameters will obviously differ for threatened and nonthreatened taxa. Previous work has shown that there are no clear differences between globally threat­ ened and nonthreatened Anatidae taxa in terms of Iite­ history traits such as body size and cltttch size (Laurila & jarvinen 1989). This study compares parameters of dis­ tribution, habitat use, and migration patterns. Island birds have been found to have a high extinction risk (Moors

1985; Terborgh & Winter 1980), and I compare the sta­ tus of insular and noninsular Anatidae. 1 also compare the latitudinal breeding distribution of threatened and nonthreatened Anatidac to identify the consequences of the concentration of economically developed countries and of arctic and subarctic land masses (exploited for breeding by migratory Anatidae) in the northern hemi­ sphere Anatictac arc recorded in a wide range of habitat

typcs, and diffcrent ratcs of destruction sean likcly to make taxa using certain habitats morc prone to cxtinc­ tion than others. Thus, I compare the habitat usc of thrcatcncd and nonthrcatcned taxa and consider thc sig­ nificance of habitat loss as a threat. ft might be predicted that migratory taxa are more likcly to bc thrcatcned bc­ cause they arc dependent on different areas during thc brecding scason, wintcr, and migration. A thrcat opcrat­ ing in just onc of these areas could have a severe impact (SalathE 1991). Therefore, Iconipare the status of migra­ tory and nonmigratory Anatidae. 1 am aware of only one previous study in which migrant or rcsident status has been related to extinction risk in birds (Pimm ct aL

1988). The results of these analyses have important mp­

lications for waterbird and wetland conservation pro­ grams and will be influential in shaping an IUCN action plan for the Anatidae, which is currently being prepared

by the Wetlands international and The Wildfowl & Wet­

lands Trust

The new ILJCN criteria (World Conservanon tJnLon 1994)

were applied to aD Anatidae at the subspecies level (Green

1996). The members of the Anatidac family considcred follow the taxonomy of Morony et al (1975). The list of subspecies considered is that of Madge and Burn (1988) and del Hoyo et al. (1992). The three globally threatened categories are, in order of increasing risk of extinction, vulnerable (VU), endangered (EN), and critically endan­ gcred of the thrce threatened categories are categorized as lower risk (LR).

Data on distribution, migratory status, and habitat use patterns for all Anatidae tan were taken from Madge and Burn (1988), Marchant and Higgins (1990), del Hoyo et al. (1992), Green (1992), and Callaghan and Green (1993). Rarnsar site directories (Ramsar 1990; jones 1993) together with access to the Ranasar site database held by the Wet­ lands International at Slimbridge, United Kingdom, iden­ tified which threatened taxa are recorded on the 685 wetlands in the world that are protected by the Ramsar Convention.

I divided taxa into those that are migratory and nonmi­

gratory, using a broad definition of migratory which in­ cluded aLl those taxa that regularly undergo movements across nationaL frontiers, incLuding partiaL migrants. Taxa

making predictablc, long-distance movements between brecding and wintcring grounds that do not cross na­ tional frontiers (c.g thc Alcutian Canada Goosc (Branta canactensis teucopareia]) were aLso included. Taxa that have both migratory and nonmigratory populations were categorized as migratory. Taxa wcre divided into those rcstrrcted to islands and those not restrictcd to islands. I uscd two size classcs of islands: smaD islands with an arca of up to 20,000 km2 (including the Falkland islands [to

United Kingdomj and the Kerguelen islands [to FranceI)

and large islands with an area of between 20,000 km2 and 110001000 km2 [Cereopsis novaeholtandiae griseaj and thc Alcu­ tian Canada Goosc), wcrc regarded as smaD-island taxa.

In analysts of habitat use I uscd the following broad

categories of habitat type: forcst (including woodland and mangroves); marine cnvironment

The thrcats assigned to each taxon arc those consid­ ered the major causes o its globally threatened status (Green 1992; Callaghan & Grecn 1993; Grccn 1996) and do not give a complete list of all thosc negative factors that are impinging on the taxon. The various threats are divided into the categories used by Collar et al (1994) for all threatened bird specics, with thc cxccption that a threat of hybridization duc to the introduction of a closely related taxon is treated separatcly from othcr cf­ fects of exotic introductions (of predators, compctitors, introduced plants, etc). “Habitat loss” includes all kinds of habitat alteration apart from pollution. “Hunting” in­ cludes egg-collecting, accidental trapping, and other kinds of persecution. “Small range” includcs small popu­ lation and is only listed as a threat when it is thc princi­ pal rcason thc taxon qualifies for globally threatened sta­ tus “Pollution” incltides poisoning from pesticides or other chcmicals Statistical analyses were conducted using x2 tcsts on contingency tables, joining some categories in habitat analyses in order to prevent cxccssively low ex­ pected frequencies (Siegel & Castellan 1988).

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