I hate to sing the blues about our nation’s songbirds, but after reporting the story about the concerns for the future of the Carolina Chickadee, I think I should.
That’s because scientists say that since the end of World War II, there has been a decline in the songbird population over much of the eastern United States. And that includes the Carolina Chickadee.
It’s not an even decline, which makes it difficult to pinpoint the exact cause.
Audubon, the National Wildlife Federation, Cornell University and other researchers say it appears that bird species that migrate long distances to Central America and South America have suffered more population declines than songbirds that don’t migrate at all or that spend the winter in the southern United States.
The decline is also uneven when considering where the songbirds live. The loss of birds that live in woodlots and small tracts of forest is greater than the decline of bird populations that live in large stretches of forest such as Great Smoky Mountains National Park.
It would be safe to lump all of this into a simple phrase: so go the trees, so go the birds. After all, forests in the tropics, the birds’ wintering grounds, are being cut for timber production and farming. Development is taking a toll on forests in the U.S. as well.
But it might not be that simple.
A growing number of studies is showing that songbird declines are due to multiple factors, including what researchers are calling forest fragmentation. In populated areas, it means the reduction in the size of forest tracts, usually due to suburbanization and development. Large stretches of forest are chopped up into smaller tracts, with strip malls or neighborhoods in between. Tree protection laws do save trees, but as they apply to developments such as shopping centers or housing, the tracts of trees are small. It's not the size of forest the Carolina Chickadee would call home.
In less inhabited areas, such as western North Carolina, forest fragmentation refers to the isolation of one patch of forest from another by logging or by the building of roads or power lines.
Some birds thrive in and around the fragmented forests typical of a suburban landscape. But many, including warblers, require large, unbroken woodlands for protection from predators lurking on forest fringes.
And it’s not only habitat decline that threatens songbirds. Forest fragmentation also opens up remaining adjacent woodlands to the animals that follow people, including cats, raccoons, opossums, black bears and even blue jays. These predators then feast on the eggs and young of migrant songbirds, many of which build open nests vulnerably close to the ground.
There are a chorus of reasons songbirds are in trouble. Studies continue, but it’s clear, our forests and large tracts of forest must be protected or our spring mornings will be much quieter.
Frank Graff is a producer/reporter with UNC-TV, focusing on North Carolina Science Now, a weekly science series that airs Wednesdays, beginning in August 2013, as part of North Carolina Now on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!