Songbirds breeding earlier as climate changes, study shows
Carnegie Museum research documents their habits
The early bird still gets the worm. But the early arrival of migrating flocks in Western Pennsylvania has led to earlier breeding activity, and that could have an impact on not only the robins, sparrows and other birds but also insects, diseases and farmers’ crops.
A new study by researchers from the Carnegie Museum of Natural History collects and analyzes 50 years of bird-banding data from the museum’s Powdermill Nature Reserve, an environmental research center near Rector, Westmoreland County.
In the study published April 12 in the peer-reviewed journal PLOS One, Luke DeGroote, avian research coordinator at Powdermill, and Molly McDermott, a postdoctoral data analyst, say that warmer and earlier spring weather leads to changes in birds’ breeding behavior.
“What we were asking was, are they breeding earlier because they’re migrating earlier or are they breeding sooner after they arrive,” said Mr. DeGroote. “What we found was that the window from when they arrive to when they start breeding is getting shorter.”
The report relied on longterm data from Powdermill, one of the oldest continually operating bird-banding centers. Established in 1962, the program live-captures nearly 13,000 migrating birds per year. Before they are released, birds are given leg bands listing data about that individual and where and when it was collected.
Over 50 years, Powdermill researchers have tallied more than 500,000 original bandings. With a recapture rate of almost 20 percent, researchers have documented data on more than 100,000 birds and nearly 200 species.
“When they started this banding program, they couldn’t have anticipated how we’d be using the data today,” said Mr. DeGroote. “It was really the core of our research.”
The new report is predicated on two previous studies that also used Powdermill data. A 2005 paper showed that migrating birds arrived in Western Pennsylvania one day earlier for every 1-degree Celsius that the temperature warmed. Buds on bushes in the study opened three days earlier for every 1degree change. A paper published last year by Mr. DeGroote and Ms. McDermott demonstrated that for every 1degree Celsius of warming, migrating birds were breeding three days earlier, matching the increased spring budding rate.
“The earlier studies showed
what temperature it is in the United States,” said Mr. DeGroote.
“Migration is based on photoperiod [the hours of light in a day]. The emergence of plants and insects is tied to the actual climate. If