For the Birds Radio Program: Deer Eating Baby Birds
I love reading original scientific papers-the kind that appear in journals before anyone dilutes the information for the popular literature. A paper that appeared in the most recent journal of the American Midland Naturalist, which my chemist husband Russ heard about from a guy he works with at the EPA in Duluth, Al Jarvinen . The paper is titled, “White-tailed Deer predation on Grassland Songbird Nestlings,” and that’s exactly what it’s about.
If you, like me, assumed that white-tailed deer are vegetarians, the black-and-white photos taken as grown-up Bambis chomped down on tiny nestling Savannah, Grasshopper, and Clay-colored Sparrows, and blackbirds and cowbirds will forever dispel that notion. Pamela Pietz and Diane Granfors, the authors, had set up miniature black-and-white video cameras at a total of 132 grassland nests to monitor activity and predation. 57 of the nests were depredated, four by white-tailed deer.
The deer left no evidence, such as droppings, tracks, or disturbed vegetation, to indicate that they had taken the nestlings. Without the videotaped proof, no one monitoring the nests in traditional ways would have realized what had happened, because all the incidents happened at night. The deer took baby birds out of canopied ground nests and from open cup nests 15 and 40 centimeters above the ground in shrubs. One of the nests had an infertile egg which the deer didn’t take. However, the authors monitored some deer in pens after placing some quail eggs on the ground, and found that indeed, some of the deer took them as well.
Pietz and Granfors note that although these depredations were probably opportunistic, they were clearly deliberate, and they conclude that very likely deer eat baby birds more often than generally believed.
After reading the incidents captured by their videocamera, I agree. Their descriptions of the predation events were graphic. I’ll quote their observation at one nest:
An adult Savannah Sparrow flushed from a canopied ground nest that contained to sparrow nestlings and two Brown-headed Cowbird nestlings about 7 days old. [11 seconds later] a deer appeared at the nest for 3 seconds and removed one nestling from camera view. 32 seconds later the deer was in view for 4 seconds and removed a second nestling. [11 seconds later] one nestling moved out of the nest but was still in camera view [for 10 seconds]. The deer caught it outside the nest. Fourteen seconds later the deer returned to the nest and removed the fourth nestling withing four seconds. [10 seconds later] the deer examined the empty nest for 5 seconds. In short, the deer removed all four nestlings in 14 sec during a span of 1.4 minutes.
Maybe what with the election and everything, this is the season for disillusioning discoveries. Bambi’s first word was “bird”-I hate imagining that his first solid meal was also ” bird.” Suddenly those big brown eyes on White-tailed Deer don’t seem nearly so innocent. But in reality, deer are the exact same animals they always were.The truth may be confusing and sometimes disillusioning, but it is only when truth is squelched or hidden that life becomes chaos.