Noteworthy All 67 ocean bird species such as albatrosses, petrels, shearwaters, boobies, tropical terns, tropicbirds, frigatebirds, puffins and related species in U.S. waters show a medium or high vulnerability to climate change. Many seabirds possess traits that make them sensitive to effects of climate change, such as low reproductive potential; nesting on low-lying islands that may be inundated by rising sea levels; strong fidelity to breeding sites; and reliance on marine ecosystems that are sensitive to sudden change. Many effects have already been documented including increased water temperatures; decreased ice cover; altered water chemistry; more intense storms; and changes in marine diversity, population sizes, movements, and life cycles.
	Image: Magnificent Frigatebirds courtesy USFWS

Observations and Predictions

It is difficult to predict and measure climate change in marine systems because natural largescale changes occur naturally. These systems shift much more rapidly and over larger areas than in terrestrial systems where rooted plants and other physical conditions restrict the pace of change.

Warmer temperatures and changing wind patterns are predicted to affect the movement of ocean waters which can significantly alter ocean productivity and food webs. If upwellings are slowed or fail to occur, fewer nutrients are available for phytoplankton, which form the foundation of marine food chains. Birds may also be affected by changes in marine food webs as changing water temperatures cause coral bleaching and as increasing atmospheric carbon dioxide acidifies the ocean, preventing marine species from creating and maintaining their shells or skeletons.

Bird Species Vulnerability

Ocean birds are slow to adapt or recover from adverse conditions and are vulnerable to climate change because of their low reproductive potential (advanced age of first breeding, production of one egg each year or every other year, and the high mortality rate for young birds). Many seabirds forage over vast areas of ocean and are highly sensitive to the availability of marine food. This sensitivity is especially pronounced during breeding, when providing food for chicks can place enormous physiological strain on the parents.

Masked Booby by Eric VanderWerf

Even where scientists have determined that changing climate has influenced seabird populations, the exact mechanisms are not completely known. What is known is that climate influences reproduction, food resources, and population dynamics. Some species will be favored, others will not. Reproductive failure of seabirds resulting from changes in marine productivity is a documented natural occurrence, such as when Pacific Coast seabird chicks starve during El Niño years. If catastrophic events become more frequent, intense, or longer as a result of climate change, population recovery is less likely. Warmer waters have apparently led to decreases in the abundance of fish in Prince William Sound, the Gulf of Alaska, and the California Current region, which is likely to reduce the abundance of fish-eating birds.

The 67 ocean birds assessed have elevated vulnerability to climate change; 43 are at the highest level.

Seabirds such as Common Murres that time their breeding based on temperature cues may fail to raise any young if their chicks hatch at the wrong time, missing the window when food is abundant. Climate change may also cause prey to shift ranges, leading to declines in bird populations if the birds are unable to follow. For example, receding sea ice could make it difficult for arctic-breeding seabirds to reach productive foraging areas distant from their nesting sites. 

Horned Puffin by Vernon Bryd

Because ocean birds are highly vulnerable to climate change, we must reduce existing stressors, including fishing operations that result in bycatch of birds; pollution; introduced predators and plants that destroy nesting colonies; and overharvest of fish by fishing fleets.

Some seabirds now nesting on low-lying islands may be subject to sea level rise. The future of these birds is dependent on intense restoration and site protection on higher islands to provide them with suitable, predator-free breeding sites.

Because oceans are so important to birds, fish, and other resources, cooperative conservation efforts must be expanded to include marine and aquatic cooperatives. New marine protected areas, national wildlife refuges, monuments, and sanctuaries will protect important resource areas. 

Laysan and Black-footed albatross by Eric VanderWerf

Translocation of very threatened ocean birds is a possibility. During the last few years, Bermuda Petrel chicks have been moved from small, low, rocky islands to nearby Nonsuch Island where the higher elevation provides more security from hurricanes and sea-level rise. The chicks survived and produced the first record of petrels breeding on Nonsuch Island in more than 400 years. In New Zealand, eight species of burrow-nesting petrels and shearwaters have been translocated successfully. 

Regulations and voluntary measures to reduce bycatch have greatly reduced the number of seabirds accidently killed by long-line fisheries in Alaska and Hawai'i. The designation of National Wildlife Refuges and Marine National Monuments conserves foraging areas and many remote islands where seabirds nest.

 Previous Page                                                                 Next page