Time for annual Christmas Bird Count
Data biases related to the varied collection methods of nonscientist collectors are offset, he said, by the huge numbers of participants.
“If we’re talking about hundreds of thousands of people reporting on tens of millions of birds over a century, that’s about as statistically accurate as data can be,” he said.
A couple of years ago the regional Audubon chapter was asked to compare the populations of several bird species in Pittsburgh with their numbers in other metropolitan cities east of the Mississippi River and generally in the north.
“I queried [Christmas Bird Count] data sets … and was able to use them to propose the ranking of 15 cities based on the frequency of finding those birds during the Pittsburgh Bird Count.”
Audubon has compared historical CBC data with weather records compiled by the U.S. Geological Survey to examine trends related to a changing climate.
“We were looking at individual species and comparing data over 118 years to see if the birds’ ranges were changing,” he said.
One of the findings was that a particular finch species has gradually moved north and away from the coasts at a time when southern latitudes and inland areas are getting warmer.
“That trend would suggest the bird is moving in the direction you would expect in a warmer climate,” said Mr. Shema. “There’s a direct correlation between the statistical weather data and bird data.”
Some birds, said Mr. Shema, are considered migratory in Pennsylvania but resident in other states and countries.
“We count hundreds of white-throated sparrows in the Christmas Bird Count, yet they are not here in summertime,” he said. “Dark-eyed junko is another that we don’t see until wintertime, but it’s considered a resident somewhere else. We’re providing information on a species that doesn’t breed here, and someone in the Northern Tier or Canada may be using our information on a bird that lives there.”
How to participate
According to the Aububon Society website, the local bird count takes place in circles that represent specific geographic areas — for example Fox Chapel or South Butler. A leader is assigned for each circle so birders of all experience levels can participate. Homeowners within a count circle may also count birds in their backyards. Phone numbers for the leaders and the areas they serve are on the website for the public to contact to get instructions on how to participate.
Counts that will take place on three dates on Audubon properties include Saturday at Todd Nature Reserve area in Buffalo Creek Valley at the new park site, 154 Monroe Road, Sarver, 16055; Dec. 30 at Beechwood Farms Nature Reserve, 614 Dorseyville Road (Fox Chapel), Pittsburgh, 15238; and Jan. 6 at Succop Nature Park, 185 Airport Road, Butler, 16002. Children’s activities also have been scheduled at these locations on those dates.
For more information about the Christmas Bird Count, data entry and access to historical data, visit the Audubon Society of Western Pennsylvania at www.aswp.org/pages/ christmas-bird-count.