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Global Warming and Boreal Birds

 
 

Worldwide, bird populations are predicted to suffer in response to global warming. A 2000 BirdLife International report found that 11% of the world’s bird species – that’s a total of 1,111 bird species – are considered to be at risk from global warming. As many as 200 of these species may disappear within the next 20 years. Optimal habitats for many species of bird may no longer exist as the planet heats up.1

Long-distance migratory birds may arrive too late to find food

Long distance migrants, such as many of those that summer in the Boreal Forest, face greater challenges in the face of global warming.  Research in eastern North America has documented that in the spring, short-distance migrant birds are arriving 12-14 days earlier now then they were 50-100 years ago, while long-distance migrants have seen an advance of spring arrival date by only 3-4 days.

Insects in the northern breeding grounds are also hatching earlier in the spring. When insects emerge sooner, birds must lay eggs sooner if they are to raise their young when caterpillars and other insects are at maximum abundance.2 Long distance migratory birds that winter in the tropics and summer in the boreal are at a disadvantage because they use seasonal changes in daylight rather than climatic cues to start their migrations northward.3 As a result, many of these birds may arrive on the breeding grounds too late to provide adequate food for their young.4

Spotlight: Gray Jay

Gray JayGlobal warming could affect the survival of Gray Jays and other food-hoarding birds. Gray Jays in the southern boreal have been most affected by recent warmer autumns, in which the cached food spoiled before it had a chance to freeze. The hoarded food is the Gray Jay’s only resource to get through the winter and early spring. The Gray Jays also rely on stores of frozen food to feed their young, which typically hatch in April. Scientists found that the birds had more young in years after cold autumns than after warm autumns. Gray Jays are extremely reliant on the boreal; 89% of the species population breeds there.  Global warming could similarly affect other hoarding species.5

Global warming could hit ducks hard

Wetlands critical to sustaining North America’s duck populations dot Canada’s boreal forest. Twelve to fourteen million ducks depend on this habitat each summer.6 Increasingly seen as rivaling in importance to the celebrated “prairie potholes” wetlands (prime breeding grounds for many of the continent’s ducks), the vast boreal forest breeding grounds could dry up from the high temperatures and drought associated with increasing global warming. Scientists have already observed widespread disappearance of small ponds and marshes in boreal forests, attributed to melting of subsurface permafrost.7 For example, since the 1950s, the total surface area of closed-basin ponds in Alaska’s boreal region under observation has decreased by 31% to 4%, and the total number of ponds has decreased from 54% to 5%.8

Spotlight: Whooping Crane

Whooping CraneThe recovering population of Whooping Cranes may suffer from global warming. Whooping Cranes were nearly extinct in 1941 with a population low of 15. Now, the population of the largest North American crane has reached a world-wide total of 468 birds in the wild and captivity. The Whooping Crane nests in bulrushes or other wetland vegetation. The migratory Whooping Crane population breeds entirely within the boreal, specifically in Wood Buffalo National Park.

The breeding success of the cranes is jeopardized in years of inadequate rainfall, and in dry years the Whooping Crane nests usually fail. Most global warming scenarios predict more dry years within the region where Whooping Cranes nest. The Whooping Crane’s wintering grounds are also subject to change with global warming. The migratory population of Whooping Cranes from the boreal winters in the Aransas National Wildlife Refuge in Texas, where birds feed on blue crabs and find habitat in the shallow marshes in the low-lying coastal land. Sea level rise as a result of global warming is expected to flood these marshes, erode beaches, and potentially increase the salinity of the rivers and groundwater, affecting the availability of the crabs for food.9

Changing tree and plant distribution as a result of warming will alter habitat suitability

Populations of boreal birds are likely to decrease as available habitat decreases from global warming. The Intergovernmental Panel on Climate Change (IPCC) predicts that the boreal, taiga, and tundra regions will shrink by as much as 36%. This means that there will be less available habitat for boreal birds, especially those that are almost entirely restricted to the boreal region.10


1 Collar, et al. BirdLife International (2000)
2 Crick, H.Q.P. The Impact of Climate Change on Birds. Ibis 146:48-56. (2004)
3 Janice Wormworth. Bird Species and Climate Change; a Global Status Report. A Climate Risk report to the World Wildlife Fund for Nature. (2006)
4 Crick, H.Q.P. The Impact of Climate Change on Birds. Ibis 146:48-56. (2004)
5 Doyle, Alister. Warming globe rots jay’s food stashes, report says. The Vancouver Sun, 8/21/2006.
6 Western Boreal Forest, Canada Region 5. Ducks Unlimited online, http://ducks.org/page2513.aspx
7 Riordan, B. and Verbyla, D.  Shrinking ponds in subarctic Alaska based on 1950-2002 remotely sensed images. Journal of Geophysical research, 111. (2006)
8 Ibid.
9 Schyler, Krista. Refugees at Risk; the Threat of Global Warming. Report by Defenders of Wildlife, (2006).
10 IPCC Special report on the regional impacts of climate change and assessment of vulnerability. http://www.grida.no/climate/ipcc/regional/index/htm.

   

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Dr. Fritz Reid, Director of Conservation, Ducks Unlimited

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Banner photo credit: CPAWS, by Juri Peepre