Download Birds chapter chapter 4
Download Appendix 4.1 Breeding bird species in the Arctic
BIRDS (Chapter 4)
Lead Authors: Barbara Ganter and Anthony J. Gaston
Contributing Authors: Tycho Anker-Nilssen, Peter Blancher, David Boertmann, Brian Collins, Violet Ford, Arnþór Garðasson, Gilles Gauthier, Maria V. Gavrilo, Grant Gilchrist, Robert E. Gill, David Irons, Elena G. Lappo, Mark Mallory, Flemming Merkel, Guy Morrison, Tero Mustonen, Aevar Petersen, Humphrey P. Sitters, Paul Smith, Hallvard Strøm, Evgeny E. Syroechkovskiy and Pavel S. Tomkovich
The Arctic is seasonally populated by roughly 200 species of birds, corresponding to about 2% of global avian species diversity. In contrast to more southerly latitudes, the dominant ecological and taxonomic groups among Arctic birds are waterfowl, shorebirds and seabirds, while songbirds are less prominent and much less diverse than at lower latitudes. The vast majority of species only spends a small portion of each year in the Arctic – but it is here that reproduction takes place.
Of the 162 species for which more than half of their breeding range falls in the terrestrial or marine Arctic, about half have a circumpolar distribution while the others are confined to either the Nearctic or Palaearctic or to the Atlantic or Pacific ocean basins. A particularly high species richness is found on both sides of the Bering Strait. Overall, species diversity is more than twice as high in the low Arctic than in the high Arctic.
Because of the migratory nature of most Arctic birds, these animals connect the Arctic to all other parts of the globe. Arctic birds winter as far south as the southern tips of the continents, and some even reach Antarctica. The extent of migratory behavior also means that the population sizes and trends of Arctic birds are sometimes affected, either positively or negatively, by events and activities occurring outside the Arctic. There are many examples of such extra-Arctic effects. As a consequence, conservation of Arctic birds will almost always necessitate international cooperation throughout the range of the migratory species. This is especially critical for the endangered species among Arctic birds, such as the Siberian crane Leucogeranus leucogeranus or the spoon-billed sandpiper Eurynorhynchus pygmeus, the latter currently facing extinction.
I have started to notice birds which I used to only see on TV, little birds which have multi-coloured bills, that fly home with multiple cod in their beaks and that burrow into the soil. I think these are the puffi ns, which are located some distance south migrating north due to the disappearance of the ice cover during the summer months. Pijamin: Elders Conference on Climate Change 2001.
Global climate change has the potential to influence Arctic bird populations in many ways, through effects acting in the Arctic itself as well as on migration routes or in wintering areas. However, although there are some indications that climate-induced changes are already taking place, the anthropogenic factors that are independent of climate – disturbance, habitat loss, fishing, hunting, agricultural intensification – have a much larger impact on populations at present.
Despite its harsh environment, the Arctic is populated by a variety of different bird species. Arctic breeding birds benefit from a short but strong seasonal outburst of food availability, be it growing plants for herbivores, invertebrate biomass for insectivores or zooplankton for seabirds and their fish prey. This plentiful seasonal food supply is coupled with relative safety from predation created by continuous daylight, a low diversity of predators and the sheer numbers of prey swamping predator pressure (McKinnon et al. 2010). Diseases and parasites are also less prevalent than in warmer climates (Kutz et al. 2005). After the breeding season, however, most birds leave the Arctic to spend the winter in warmer climate zones; in fact, the majority of ’Arctic birds’ spend only a small fraction of each year on their Arctic breeding grounds (Meltofte 1996, Newton 2007). Their migrations connect the Arctic to all other parts of the globe.
Being highly visible and audible as well as diurnally active, birds are one of the groups of organisms that are best known to humans worldwide. Hence, Arctic birds also have a strong cultural significance to the indigenous peoples of the Arctic. The arrival and departure of migratory birds marks the changing of the seasons, and in addition to their significance as a food source birds also play a role for festivals and the planning of family and community events.
Roughly 200 bird species breed in the Arctic, amounting to 2% of the global avian biodiversity. However, the relative weight of higher taxonomic groups is different from the global total. The Anseriformes (waterfowl) and Charadriiformes (shorebirds, gulls, auks) make up the majority of avian diversity in the Arctic and are therefore treated in detail in separate sections of this chapter. By contrast, the songbirds, being the most diverse group elsewhere, are underrepresented in the Arctic and are treated together with the other ’landbirds’ below.
Whereas some species occur mostly in temperate latitudes and only reach the Arctic at the fringes of their distribution, others are more or less confined to the Arctic during the breeding season. These ‘true Arctic’ species will be the main focus of the analyses below. Among them there are species with a circumpolar distribution while others are confined to one of the hemispheres or have even more restricted distributions. In their sum, the distributions of the single species result in patterns of species richness that differ throughout the Arctic. In this chapter we address these species richness patterns as well as the current status, trends and future prospects of individual species.
CONCLUSIONS AND RECOMMENDATIONS
With about 2% of the global species total, the Arctic supports only a small fraction of the world’s avian biodiversity, but adaptation to the harsh Arctic environment has created a variety of highly specialised species and a number of Arctic endemics. Because almost all Arctic birds are migratory, population trends for many species are driven by events outside the Arctic. For year-round resident Arctic birds, little trend information is available. Where trends are known for migratory populations, the main pattern of trends can be summarized as follows: increases in many Nearctic and W Palaearctic waterfowl populations, especially geese; and decreases in many shorebird populations and waterfowl of the E Palaearctic. For some species wintering in E Asia, habitat loss and hunting in the wintering grounds have been identified as the main causes of population decline. Problems with food supply on critical staging areas have also been diagnosed for a few shorebirds migrating through the Americas. Because of the international nature of migratory birds, conservation action for endangered Arctic breeders must include international cooperation on a flyway level both in and outside the Arctic, to ensure safeguarding of critical habitats and proper management of hunting. This is especially critical for highly endangered migratory species such as the spoon-billed sandpiper and the Siberian crane.
On the Arctic breeding grounds, known causes of population changes have been excessive harvest and climate variability, while potential threats include oil, gas and mineral exploitation. Oil exploitation at sea and increased transport of oil through Arctic waters, with its associated risks of oil spills, is especially hazardous for the great number of marine and coastal birds of the Arctic. The aggregation of very large numbers of birds in breeding colonies or molting sites, often associated with areas of high productivity and a of high diversity of other taxa (e.g. fish, marine mammals), makes the protection of such colony and molting sites and adjacent waters from the risk of oil spills a priority. Breeding and molting birds can also be negatively affected by disturbance resulting from industrial development and tourism, which can increase predation and/or keep birds from using suitable habitats. Again, this is especially severe where large concentrations of birds are affected. The overharvesting of Arctic birds is a problem mainly of inhabited regions, principally in the sub-Arctic or the fringes of the Arctic. In some cases these problems are either solved or on the way to solution: eider populations affected by over-harvesting in the late 20th century are recovering, and the greatly diminished population of thick-billed murres in Novaya Zemlya have stabilized.
In the true Arctic, some heavily harvested species, particularly geese, are increasing rapidly. Because ‘overabundant’ geese are causing degradation of sensitive habitat in some Arctic areas, management efforts have been initiated to reduce population sizes through increased hunting outside the Arctic. The problem with use of hunting as a management tool is that the massive shooting needed to significantly reduce numbers may cause high crippling rates, greatly increased shyness and create widespread disturbance of other waterfowl species on the staging and wintering grounds (Madsen & Fox 1995, Noer & Madsen 1996).
Climate change may act on Arctic bird populations in various indirect ways (Boyd & Madsen 1997). These include changes in food supply; predators, prey, parasites and diseases; mis-match between the peak of availability of food and the timing of arrival on breeding grounds, hatch, brood rearing or migration. The northward shift of vegetation zones will affect both food and habitat, as well as habitat loss due to permafrost thawing in some areas. However, even though single effects have been shown at a local scale for some bird populations, the complexity of these interacting factors makes it very hard to predict future impacts of a warming climate on Arctic bird populations. Some effects, like the impact of egg-eating by polar bears, may attenuate, as bear populations at lower latitudes decline (see Reid et al., Chapter 3).
Some species found mostly or entirely in the Arctic are showing signs of population decline which may be related to climate change (ivory gull, thick-billed murre, gyrfalcon, perhaps snowy owl). The exact causes are unknown, but may relate directly or indirectly (e.g. through changes in their food supply) to increasing temperatures. We need much more extensive monitoring, especially in Canada and Siberia, to better assess the causes of population change. Greater integration of national monitoring programmes under the Arctic Monitoring and Assessment Programme, the Arctic Breeding Bird Condition Survey (ABBCS) and the Circumpolar Seabird Data Portal (Seabird Information Network 2012) would be useful and the CAFF seabird group could provide the necessary incentive. We particularly need better information on the non-game Arctic endemics: gyrfalcon, snowy owl, shorebirds, ivory, Sabine’s and Ross’s gulls, jaegers/skuas and little auks. With their breeding distributions restricted to Arctic biomes, these birds are likely to be the first to exhibit symptoms of climate change effects. Likewise, we need regular monitoring of important wintering areas for Arctic seabirds and waterfowl, such as SW Greenland (Boertmann et al. 2004), waters off Newfoundland and Labrador (Frederiksen et al. 2011) and polynyas supporting eiders in the N Bering Sea (Petersen & Douglas 2004).
If climate change proceeds as predicted, many of the bird species characteristic of the northern taiga and sub-Arctic are likely to expand northwards as temperatures increase. However, this cannot be viewed as an improvement in the richness of the Arctic avifauna, but rather constitutes a contraction in the area of the Arctic, as we have hitherto defined it in biological terms. Ultimately, much of the region now characterised by a high Arctic fauna may become low Arctic in character, and the eventual disappearance of typically high Arctic birds such as gyrfalcon, ivory gull and little auk seems probable.