Christmas Bird Count Trends

Manomet has participated in the National Audubon Society's Christmas Bird Count (CBC) for the past 40 years. During the count, volunteers across the United States, Canada and other Western Hemisphere countries go out over any 24-hour period during late December or early January to count birds. They follow specified routes, counting every bird they see or hear all day within a circle of diameter 15 miles (24 km).


The data are collected, compiled and made available online by the National Audubon Society, allowing researchers and conservation biologists to study the long-term health and status of bird populations across North America.


Manomet held its annual Christmas Bird Count in early January 2014. Every year, the Manomet team counts birds in the area around the Manomet headquarters in Plymouth County, Massachusetts. The data collected over Manomet's 40 years of participation suggest interesting trends in the populations of certain species.


General Graphs

The total number of bird species tallied has been steadily increasing in recent years. The number of species counted has exceeded the 40-year average for eight of the last ten years.



While the total number of bird species has increased, the total number of individual birds has been trending steadily downwards. This year's 6,163 birds, or 112 birds per party hour, was the lowest ever, continuing the decreasing number of individuals seen for the last eight years. These declines are driven primarily by diminishing numbers of wintering Canada Geese, American Black Duck, Common Eider and large gulls.




Species for Which Numbers Have Decreased

The American Kestrel is one species whose population has declined dramatically over the past 40 years. During Manomet's first year of CBC participation, 15 American Kestrels were counted. Now, we are unlikely to count a single kestrel. Reduced nesting cavity space due to a decreased number of standing dead trees and competition from other raptors whose populations in the northeastern United States are increasing, such as the Cooper's Hawk, are likely causes for this decline. Kestrels are also grassland-feeding birds, a declining habitat in the northeast.



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






Species for Which Numbers Have Increased

The numbers of southern species like Northern Cardinal and Red-bellied Woodpecker have increased in recent years. A large body of research suggests that the ranges of these species have been expanding northward, which may likely be indicative of responses to climate change.





Another species for which numbers have increased is the Hooded Merganser. Warmer air temperatures have led to an increase in the number of Hooded Mergansers wintering in the northeast. The amount of suitable habitat available to them has increased, with more open water in ponds and lakes during winter months. One could speculate that the recent increase in beaver numbers provides breeding habitat.




Additional Resources

Click here to view individual Christmas Bird Count summary reports by year.