WILKES-BARRE — You probably enjoy spotting a robin in a yard, or listening to bird songs on a warm summer day. A bright red cardinal flitting about in a leafy green tree can really catch the eye. Now imagine them all gone, just vanished without a trace.
It’s actually happening, Wilkes University’s Jeffrey Stratford said, and it’s happening at a pretty alarming rate.
“A paper was just published in the journal Science,” the ornithologist and associate biology professor said. “It was a team of ornithologists and statisticians. They analyzed several types of data sources and they all pointed to the same conclusion: There is a rapid decline of birds. It looks to be a loss of about 30 percent of them in almost 50 years.”
In numbers, that’s 2.9 billion fewer birds across the skies of Canada and North America, according to a New York Times story on the report. The Times quoted National Audubon Society President David Yarnold, who called the findings “a full-blown crisis.”
And while the world may be a bit used to the idea of some bird species becoming vulnerable to extinction, the report found steep drops even among commonly abundant species.
“One bird in steep decline is the wood thrush,” Stratford said, “which used to be very common in Pennsylvania. We have about 20 percent of what we had in the 1960s.” Golden warblers are nearly extinct, having dropped to about 10 percent of what used to be around.
“Habitat loss is the primary reason,” Stratford said, though cats preying on birds is another. There is also a pesticide with an ingredient that has an impact on bird nutrition. “They don’t gain as much weight as they need to make migration,” Stratford said.
While loss of habitat seems straightforward, Stratford said it’s proving more complicated. “A lot of forest birds are on the decline,” he said. “If it was just the loss of forest causing it we would expect all forest birds to decline, but for some reason it looks like some are worse off than others.”
The problem may be loss of specific habitat for certain species. “For example, for a Golden Wing Warbler their winter habitat is okay, but their breeding habitat in this area has been in decline. For the wood thrush, we’re actually gaining forest in Pennsylvania so they should increase, but because their winter habitat is in decline elsewhere they are in decline.”
Even when the loss of habitat is clear, the real reason can be less so. Stratford noted the wood thrush winters in Central America, and that their habitat has been lost for coffee growing, but it turns out the method of growing makes a difference. “Shade-grown coffee is very good for birds, and sun-grown coffee is very bad. Everything is more complicated than you expect.”
Riparian habitat — undeveloped land along river banks such as Kirby Park in Wilkes-Barre — is another important consideration because migrating birds often use the lush but small forest areas to rest during migration. And collision with buildings — the type with lots of glass reflecting a blue sky or green park, say — is “a high cause of mortality.”
A rapidly declining bird population matters because birds serve numerous important purposes, Stratford said. When raising young, birds eat a lot of caterpillars and insects that otherwise would be damaging trees or spreading diseases like West Nile virus. Experiments have shown trees grow faster when birds fly among them than when they are kept out with nets, making birds important to the lumber and paper industry. And birds disperse seeds, helping keep forests diverse.
The solution is to figure out what habitat birds need and try to preserve it or restore it, to practice building methods that don’t lure birds to their deaths, and to practice farming methods that help rather than hurt birds (such as shade-grown coffee)
If the decline is not stopped and reversed, Stratford said, “There will be unknown consequences.”
