Dec 02 2008
There are probably as many opinions about deer hunting as there are white-tailed deer in Pennsylvania. (That would be about 1.5 million.) As a birder, I hope the hunters are successful because a good hunt protects songbirds.
How can this be?
Persistent deer overpopulation results in a browse line, an area where nothing grows from the forest floor to the height of a deer. This buck is standing in such an area. You can tell because you can see straight through the forest behind him. It makes for a nice clear picture, but not for biodiversity.
Deer eat plants. When deer are too plentiful they reduce forest habitat and that in turn reduces songbird populations. I first heard of this effect back in 1999 when I learned the results of a decade-long study by the Smithsonian Institution’s Conservation and Research Center (CRC).
The CRC maintained 12 study plots near Front Royal, Virginia: six surrounded by deer exclosures to keep deer off the land, and six unfenced. By comparing the presence and absence of deer, the study found that high deer density resulted in two impacts on birds: direct competition for food (affecting wild turkeys) and destroyed understory habitat (affecting songbirds).
For songbirds to survive they need cover. When the understory is destroyed, their populations decline and nest survival falls to zero. In the CRC study, understory birds such as hooded warblers, eastern towhees, and wood thrushes increased dramatically when deer were excluded. The veery population doubled! Even birds who nest in trees – rose-breasted grosbeaks, cerulean warblers and scarlet tanagers – benefited from a reduced deer population.
Sadly many of these songbirds are in decline. Deer, on the other hand, are prolific and can double their population every two to three years. Even with hunting and car accidents southwestern Pennsylvania’s deer population is stable, even growing in some locations.
It’s possible to have both deer and songbirds but only if the deer herd is kept in check. So I’m glad it’s hunting season.
If you’re going out hiking or birding, don’t forget to wear blaze orange!
For further reading and videos about Pennsylvania deer management see the PA Game Commission website on white-tailed deer. If you want to read about a huge deer problem see the Fairfield County (Connecticut) Municipal Deer Management Alliance and their section on bird impacts.
(photo by Joe Kosack/PGC photo, courtesy of the Pennsylvania Game Commission public photo gallery)
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