Several species of birds that call southwestern Pennsylvania home are breeding as much as three weeks sooner than they did 50 years ago.
If the shift continues, bird populations could begin to decline, according to Powdermill Nature Reserve Avian Research Coordinator Luke DeGroote.
Researchers at the facility in Westmoreland County, run by the Carnegie Museum of Natural History, have been capturing and banding birds since 1961 and have seen a shift, which DeGroote links to climate change.
Most birds time their migration by the length of day, but link their breeding to the time when their food source is most abundant. That means there is less time between arrival in the region and the best time to breed.
“If it continues to shift, the birds could be in danger of not being able to time their breeding,” DeGroote said. “We are seeing some indication that some species are even now having trouble adapting.”
DeGroote said they have factored out the year-to-year fluctuations in weather. The study finds that some species are breeding nearly as soon as they arrive.
“If that peek abundance of insects happens before they breed, they wouldn’t have as much food to put into making the young,” DeGroote said.
The research is based on when different types of birds are first caught in the Nature Reserve’s research nets and when they first catch the newly fledged birds.
DeGroote said they have found late season birds such as gold finches are waiting longer to breed because summers are getting longer which means food sources such as thistle seeds are becoming available later in the year.
