Birds turn up in ‘odd’ places, ornithologists cite climate change

Twenty years from now, birds are going to be seen in weird places, predicts Cornell ornithologist Andrew Farnsworth. Due to climate change and human impact on the environment, he said many bird species could change the time and place where they breed and perhaps migrate. 

“You’re going to see some very odd things happen,” Farnsworth said. 

Bird species with large populations that migrate long distances will be able to adapt to changes in temperature and urban sprawl, but species with smaller populations and narrow livable environmental conditions will experience catastrophic changes, according to Farnsworth. 

Humans amplify the speed of climate change with the emission of greenhouse gases and drastically alter the environment with the spread of urban areas and forest fragmentation, he said. As a result, birds are struggling to make the necessary evolutionary changes for survival. 

“In places where it’s getting warmer earlier, birds no doubt can be under really extreme selection pressure because of climate change,” Farnsworth said. “If they don’t arrive early enough, they’d miss an explosion of insects.”

He said birds migrate when situations get bad, and as early as this past spring, at least a couple species of birds, such as the red crossbill, broke “the norm” and were on the move because of climate and habitat change. Many species appeared two or three weeks earlier on breeding grounds and departed early due to mild weather.

Of the 836 species of birds protected under the Migratory Bird Treaty Act, approximately one fourth are known to be in trouble, according to the U.S. Fish and Wildlife Service, however population data on one third of these species is lacking.

Migration is the annual, large-scale movement of millions of birds between their ancestral breeding summer grounds and their nonbreeding winter grounds, according to the Cornell Lab of Ornithology. The majority of all bird species migrate to move from areas of low or decreasing food and habitat resources to areas of high or increasing resources.

Although changes in day length, lower temperatures and changes in food supply can trigger migration, Farnsworth said there are definite genetic predispositions to where and when birds migrate.

“There are all these cool cues that they have,” he said. “Waves crashing against the coastline, the alignment of the stars, the position of the sun. It’s much more evolutionary than just, ‘I’m going to fly somewhere and look for somewhere good.’” 

Since birds have been following roughly the same patterns of migration for the past billion years or so, it can be difficult for certain species to respond to drastic climate and habitat changes. Severe storms, just one byproduct of global warming, cause many birds to die while crossing large bodies of water, causing a dramatic decline in populations, Farnsworth said. 

Forest fragmentation and urban sprawl alter habitats where avian species stay for the winter, breed and stopover during migration, inevitably causing birds to migrate over large cities with artificial light and skyscrapers. Farnsworth said the artificial light confuses birds and makes them more prone to collide with tall buildings.

A 2009 study of 24 communication towers in Michigan showed that 50 to 71 percent of bird fatalities can be reduced through the elimination of steady-burning lights, according to the National Park Service.

Farnsworth studies the nocturnal migratory calls of birds and said he found that these short, urgent calls are most frequent when birds are disoriented from artificial lights and cloud cover. The calls are used as a means of communicating group positions so that birds can stay together and avoid collision.