Every year, thousands of volunteers identify and count birds during Audubon’s Christmas Bird Count (CBC). The annual count – which is in its 114th year – helps researchers, conservation biologists and others study North American bird populations over time. What have they learned?
Winter bird ranges are shifting. Audubon’s Birds & Climate Change analysis shows that from 1966-2005 – a 40-year period when the average January temperature in the lower 48 states rose by over 5 degrees Fahrenheit – 58 percent of observed bird species shifted their ranges north. Sixty species shifted their ranges by more than 100 miles. The U.S. EPA included these range shifts as one of 26 Climate Change Indicators in the United States.
Doves are expanding their ranges. Since 1950, the number of CBC counts reporting mourning doves has increased by 20 percent. White-winged dove counts are increasing from Texas to Florida and the Eurasian collared-dove, first reported in the 1980s in south Florida, is expanding its range in Florida and neighboring states. Why so many doves? Many dove species prefer urban and suburban areas, so they are benefiting from increased urbanization. Expansion of agriculture and backyard bird feeding also helps doves. And, warmer winter temperatures may also be giving doves a hand – the feet of some dove species are susceptible to frostbite during extreme cold snaps.
Some bird populations are recovering, others are declining. CBC data has shown the recovery of birds like the peregrine falcon and bald eagle. It has also documented the decline and disappearance of other species. Bewick’s wren – a familiar bird in the western U.S. – showed up in eastern U.S. counts from 1949 through the late 1970s. But by 1977, the eastern population began to crash and it hasn’t recovered. Some scientists think that competition from the more aggressive house wren contributed to the decline.
Viewer Tip: Learn more and find a count near you. Anyone can participate in the Christmas Bird Count, which takes place from December 14, 2013 to January 5, 2014. The CBC takes place in “count circles” that focus on specific geographic areas. Every circle has a leader, so even if you are a beginner birdwatcher, you’ll be able to count birds with an experienced birder and contribute data to the longest-running wildlife census. If your home happens to be within the boundaries of a count circle, you can count the birds that visit your backyard feeder.
Photo by Jerry Acton, courtesy of National Audubon Society.
(Sources: National Audubon Society. “Christmas Bird Count.” http://birds.audubon.org/christmas-bird-count; “Birds and Climate Change.” http://birdsandclimate.audubon.org/cbcanalysis.html; “Dynamic Dove Expansions Citizen Science illustrates the spectacular range expansions taking place throughout North America,” http://birds.audubon.org/dynamic-dove-expansions-citizen-science-illustrates-spectacular-range-expansions-taking-place-throug; “Demise of the Eastern Bewick’s Wren,” http://birds.audubon.org/demise-eastern-bewicks-wren)