Songbirds breeding earlier as climate changes, Pittsburgh study shows
April 20, 2017 9:40 AM
A Ruby Crowned Kinglet takes flight after having its measurements taken at the Powdermill Avian Research Center in Rector, Pa. on Tuesday, April 26, 2011.
A robin searches before finding a worm at North Park following a rainstorm, April 29, 2014.
Research assistant Marcia Arland, of the North Hills lets a Ruby Crowned Kinglet go after taking its measurements at the Powdermill Avian Research Center in Rector, Pa. on Tuesday, April 26, 2011.
Program coordinator Andrew Vitz blows on a Ruby Crowned Kinglet to determine the amount of fat it has stored at the Powdermill Avian Research Center in Rector, Pa. on Tuesday, April 26, 2011.
Seasonal assistant Blaine Carnes untangles a Ruby-crowned Kinglet from a netat the Powdermill Avian Research Center in Rector, Pa. on Tuesday, April 26, 2011.
Clothespins tagged with numbers that correspond to the various nets at the Powdermill Avian Research Center in Rector, Pa. are used to keep track of where a caught bird was captured on Wednesday, April 27, 2011.
A pond near the Powdermill Avian Research Center in the Powdermill Nature Reserve in Rector.
Bob Downing/Akron Beacon Journal
Powerdermill Run flows through the Carnegie Museum of Natural History's Powdermill Nature Reserve in Westmoreland County, Pennsylvania.
By John Hayes / Pittsburgh Post-Gazette
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.
“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 long-term 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 they were collected.
PG graphic: Powdermill Locator
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 1-degree change. A paper published last year by Mr. DeGroote and Ms. McDermott demonstrated that for every 1-degree Celsius of warming, migrating birds were breeding three days earlier, matching the increased spring budding rate.
“The earlier studies showed us that some of the birds in the southern United States may be migrating sooner, but the rest of the birds down in Venezuela and Central America, they have no idea 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 there’s a warmer, earlier spring, the leaves and insects have already emerged and there’s more food available during migration. The birds arrive here earlier because they are eating as they travel. They’re healthier and migrating faster.”
From the newest analysis of Powdermill data, Mr. Degroote and Ms. McDermott determined that the time between the birds’ arrival and start of breeding activity was getting shorter.
“They’re setting up territories, nesting and breeding more rapidly,” he said. “The early migrants -- sparrows, phoebes -- they’re more robust and can deal with snowstorms and other weather events. But some of the others, like Tennessee warblers, don’t seem to be coming much earlier, just a little.”
Some early-arriving birds -- ruby-crowned kinglets and Eastern phoebes -- are able to “clue in” to warmer springs, he said, because they’re already in the United States.
If migrating birds are eating insects on the way north, that could reduce the bugs’ impact on agriculture and spread of diseases, said Mr. DeGroote. If they migrate too soon and miss the peak spring insect period, they may not find enough food to feed their young and the insect population could grow to levels that force the agriculture industry to spend more money on insecticides, impacting waterways and raising grocery prices..
“Birds are breeding a lot earlier. Plants are budding a lot earlier,” said Mr. DeGroote. “This paper is the first to put all those pieces together.”
The new research found that three-fourths of the species studied were breeding earlier. In one-fourth of those, the impact on the birds was negative -- the number of young was fewer in warmer years. One quarter of those birds, however, had more young -- more plants, more insects, more food availability.
“That means that in half of those species that were breeding earlier, there was no impact at all. They’re just breeding earlier,” Mr. DeGroote said.
Jim Bonner, executive director of the Audubon Society of Western Pennsylvania, who did not participate in the study, said he found it interesting that all migrating birds did not respond the same to warmer spring weather.
“This kind of study reinforces the preponderance of evidence that climate change is happening and it does impact a wide range of creatures including migratory birds,” he said. “I think further good research like this will help us understand that, and make the appropriate adjustments.”
John Hayes: 412-263-1991, email@example.com.
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