Posted on behalf of Hannah Hoag.
Almost half of Canada’s bird species are in a downward slide. Overall, Canadian breeding bird populations have dropped 12% since the 1970s, according to a report released today. The State of Canada’s Birds 2012 is the first comprehensive summary of the health of bird populations across Canada. The report carries both good and bad news, with some populations rebounding after devastating slumps and others continuing on a steep downward trajectory. It also stresses how what goes on in one country affects bird populations in others.
“We need to find ways to do better because right now we are in the process of losing species. It takes a big investment to recover a species and in a difficult economic time it will be very difficult to find these sorts of resources,” says Ted Cheskey, the manager of the bird conservation programme at Nature Canada, a not-for-profit conservation organization in Ottawa, Ontario, that contributed to the report.
Aerial insectivores, such as barn swallows (pictured), have been hit the hardest. Their numbers are now less than 40% of what they were in the 1970s, with 22 of the 26 species that breed in Canada in decline. The causes aren’t entirely known, but because their sole food source comes from flying insects, pesticides, other contaminants or shifts in insect population peaks due to climate change may be at the root. “Perhaps these birds are out of synch with the insect populations and they are having trouble feeding their young,” says Dick Cannings, a scientist at Bird Studies Canada in Port Rowan, Ontario, who contributed to the report.
Grassland birds are also showing a rapid decline. Populations on the Canadian prairies have dropped almost 40% since the 1970s. Similar trends have been documented in other regions. In the United States, grassland birds have declined 40% since the late 1960s (State of the Birds, United States of America, 2009).
Arctic birds have had mixed success. Arctic seabirds can feed more easily now that heavy sea ice occurs less frequently. On the other hand, some species that depend on sea ice for nesting, such as the thick-billed murre, aren’t producing as many offspring. “Much of our data for Arctic shorebirds comes from stopover sites, but it doesn’t tell us much about the cause of change,” says Charles Francis, the panel chair and a programme manager at the Canadian Wildlife Service, which is a part of Environment Canada. An international seabird-monitoring project aims to address that deficiency.
But the trends for raptors and waterfowl paint a rosy picture. Populations have rebounded after bans on persistent pesticides such as DDT, captive breeding programmes, and the management of hunting and wetland habitats. “We can bring them back again,” says Francis, “but that can only happen if we take action on time and promptly.”
Not all of the threats these birds face fall within Canadian boundaries. About three-fourths of Canada’s birds spend some part of their life cycle elsewhere. When the summer warmth and abundant food come to a close, they head south. The further a bird migrates to its over-wintering grounds, the steeper its decline has been. Populations of birds that migrate to South America have been halved. The clearing of grasslands and forests for agriculture and urban expansion means that hungry birds cannot find food or shelter along their migratory routes or upon arrival. This international migration emphasizes the need for more cooperation between countries, says Cheskey.