Christmas Bird Count Data Reveal Population Declines

The National Audubon Society’s analysis of 40 years of Christmas Bird Count (CBC) data has revealed alarming declines in the populations of many bird species.

 

During the annual CBC, volunteers across the United States, Canada and other Western Hemisphere countries count birds over any 24-hour period from late December through early January and submit the data to the Audubon Society to be compiled.

 

The average population of the common birds in steepest decline, including Northern Bobwhite, Evening Grosbeak, and Northern Pintail Duck, has fallen by 68 percent since 1967. All 20 birds on the national Common Birds in Decline list lost at least half their populations in only four decades.

 

The findings, the Audubon Society suggests, point to serious problems with both local habitats and global environmental trends like climate change.

 

For the past 39 years, Manomet staff and supporters have participated in the CBC.

 

“For nine of the past ten years, the Manomet team’s number of species counted has exceeded the 39-year average,” said Banding Director Trevor Lloyd-Evans. “This year, we tallied an above-average 105 species.”

 

While the number of species counted has increased in recent years, the total number of individual birds has been trending steadily downwards. This year, the Manomet team tallied 10,871 birds, or 175 birds per hour of counting.

 

 “This was the second lowest number of birds we’ve ever tallied, continuing the low number of individuals seen for the past seven years,” said Lloyd-Evans. “These declines are partially driven by diminishing numbers of wintering Canada Geese, American Black Duck, Common Eider and large gull species.”

 

Numbers of large gulls like Herring Gulls and Great Black-backed Gulls tallied have been decreasing steadily in recent years. According to Lloyd-Evans, the closing of garbage dumps where gulls tend to feed and declines in the populations of many important New England fish species due to overfishing are likely causes.

 

In recent years, the Manomet CBC team has counted growing numbers of permanent residents from the south that are expanding their ranges northward, including Red-bellied Woodpecker, Tufted Titmouse, Carolina Wren and Northern Cardinal. According to Lloyd-Evans, the same trends have been observed at Manomet’s landbird banding laboratory. These range shifts, he suggests, are likely indicative of responses to climate change.

 

 “Trends being observed in certain bird populations stress the importance of landbird banding programs like Manomet’s,” Lloyd-Evans said. “Programs like ours, coupled with citizen-science programs like the Christmas Bird Count, allow us to better understand population trends, what their causes may be, and when necessary, what can be done to reverse them.”

 

For More Information:

 

Read our full Christmas Bird Count report with a breakdown of the number of birds of each species tallied:

 

https://www.manomet.org/sites/default/files/publications_and_tools/CBC%2...

 

Read more about how information gathered through the Christmas Bird Count is used to inform research and conservation action in the Audubon Society’s "Birds & Climate Change" report:

 

http://birdsandclimate.audubon.org/

 

- Haley Jordan