What about the Birds?

Thick-billed murre (Uria lomvia) colony on Coats Island, Nunavut

When we think about ocean animals, we often forget to include birds. Many of us associate birds with forests and grasslands, but there are thousands of seabirds found along the world's coastlines that depend heavily on the oceans to survive. The Pacific Ocean covers a third of the planet and in the North Pacific alone, there are at least 137 seabird species, numbering close to 200 million individuals [1]. With Canada having the world's longest coastline, millions of birds use our 243,792 kilometers of shores, and are impacted by how the oceans and land are being altered by abrupt climate change.

Climate change is affecting bird populations worldwide in many different ways. Warmer temperatures are leading to shifting territorial ranges, changes in food supply, and reduced habitat. With ocean temperatures predicted to continue increasing, many seabird and coastal-bird populations may be threatened.

Disappearing ice

In the Canadian Arctic, the warming climate is reducing the amount of sea ice in many areas. One of the birds found there is the Thick-billed Murre, a species that depends on sea ice to feed [2]. As the sea ice has disappeared earlier each year over the last several decades, the egg-laying date for these birds has shifted to earlier in the year as well. Decreased ice cover is also connected to slower chick growth and lower adult body mass as there is less food available, including Arctic cod a fish species which is highly dependent on ice. Reduced chick growth and adult mass can delay reproduction, and thus the survival of these birds. [2]

Thick-billed murres on welcomed summer ice floe in northern Hudson's Bay

Since the 1970s the sea ice in Antarctica has also been diminishing, effectively decreasing the range of viable habitat for penguins and other ice-dependant seabirds. As the sea ice retreats pole-ward, so do the birds. Studies dating back to 1970 reveal that Emperor Penguins have disappeared from the edges and margins of their most northern, peripheral sites around Antarctica [3]. Further reductions in sea ice will lead to increased pressure on Emperor Penguins and other seabirds as resource and habitat become increasingly scarce.

Shifting food sources

Warming waters have also led to shifting food sources for many birds. Situated near the northwest tip of Vancouver Island, Triangle Island is the largest seabird colony in Western Canada and is considered the crown jewel of British Columbia 's family of Ecological Reserves. The island is home to thousands of Rhinoceros Auklets that hatch and raise their chicks there each year. The colony was first observed in the 1970s and is still monitored today to track population size and chick development. A thirty-year study shows that as sea surface temperature increases, the birds' main fish prey species, the Pacific Sand Lance, is less abundant and chick development slows [4], making their survival to adulthood much more challenging.

Habitat loss

Along with warmer waters, rising sea levels will also affect birds along the coast. Shorebirds around the world depend on mudflats and beaches in order to feed and nest. With sea levels expected to rise between 0.1 m and 0.9 m in the next 100 years, shore birds will be impacted on a global scale [6]. Large bays, such as the Bay of Fundy, will lose between 18% to 70% of the areas used by birds [7]. With shorebirds dependant on several areas on the coast along migration routes, the reduction of mudflats in any number of areas may lead to large decreases in bird populations.

Surf scoters (Melanitta perspicillata) in the North Pacific Ocean

Storm threats

Increased storm activity is a major threat to birds. On the southeast coast of North America, many species of birds congregate in large numbers in coastal areas and wetlands, areas that are particularly vulnerable to hurricanes. During the breeding season these sites provide nesting areas and food for sizeable seabird populations [6], making the impact of a single hurricane potentially catastrophic to an entire population of seabirds. During the past 30 years, as a result of global warming, the destructiveness, length, and intensity of storms have all increased leading to a major disturbance to seabird populations [8].

Birds can also be swept thousands of kilometers off course by severe tropical storms. Each autumn, birds across the continent move south for the winter, seeking refuge from low winter temperatures and food scarcity. In October 2006, when two hurricanes joined over the Atlantic Ocean in the Caribbean and moved north onto land in Eastern Canada, they carried with them a plethora of migrating birds. For the next month, bird observers watched with astonishment as birds from Western North America and the West Indies migrated south across the eastern United States back towards their wintering locations! [9]

After Hurricane Katrina in 2005, and despite all the destruction around them, dedicated bird enthusiasts on the Gulf Coast continued with the 106^th Audubon Christmas Bird Count. They found pristine habitats and usually rich areas silent and devoid of almost all life. Although their work was difficult, the observations of these keen birders will help us understand how wildlife returns after a disaster. [9]

The importance of birds

The potential loss of bird species will affect ecosystems worldwide. Bird species are important in maintaining insect populations and may limit the diseases they spread. Moreover, seed pollination and dispersal in ecosystems such as rainforests and grasslands is dependent on birds. Their role in the food chain is essential to maintaining the delicate balance that allows ecosystems to exist across the planet. Found on every continent, birds have adapted to numerous eco-regions and are indicators of ecosystem health.

With a recent report indicating that 12% of all bird species on the planet are threatened, understanding how climate change will continue to affect bird populations is critical [10]. Seabird species from the Arctic to the tropics are challenged by warming waters, shifts in prey abundance, and habitat loss due to the changing global climate.

Sea Bird Adaptation and Survival lesson plan

Glaucous gull (Larus hyperboreus) chicks
in the low Canadian Arctic in July

1. Mallory, M.L., et al., Marine birds as indicators of Arctic marine ecosystem health: linking the Northern ecosystem initiative to long-term studies. Environmental Monitoring and Assessment, 2006. 113 : p. 31-48.

2. Gaston, A.J., H.G. Gilchrist, and J.M. Hipfner, Climate change, ice conditions and reproduction in an Arctic nesting marine bird: Brunnich's guillemot (Uria lomvia L.). Journal of Animal Ecology, 2005. 74 : p. 832-841.

3. Parmesan, C., Ecological and Evolutionary responses to recent climate change. Review of Ecological and Evolution Systems, 2006. 37 : p. 637-669.

4. Hedd, A., et al., Effects of interdecadel climate variability on marine trophic interactions: rhinoceros auklets and their fish prey. Marine Ecology Progress Series, 2006. 309 : p. 263-278.

5. Robertson, G.J. and H.G. Gilchrist, Evidence of population declines among Common Eiders breeding in the Belcher Islands, Northwest Territories. Arctic, 1998. 51 (4): p. 378-385.

6. Mclean, R., et al., Chapter 6: Coastal zones and marine ecosystems, in Climate Change 2001: Impacts, Adaptation and Vulnerability, L. Bijlsma and I. Sanchez-Arevalo, Editors. 2001, Intergovernmental Panel on Climate Change.

7. Galbraith, H., et al., Global climate change and sea level rise: potential losses of intertidal habitat for shorebirds. Waterbirds, 2002. 25 (2): p. 173-183.

8. Emanuel, K., Increasing destructiveness of tropical cyclones over the past 30 years. Nature, 2005. 436 : p. 686-688.

9. LeBaron, G.S., The 106th Christmas Bird Count , in American Birds . 2007.

10. Pegg, J., One in four bird species could disappear by century's end . 2004, Environment News Service.