When my friend Stacy McNulty, a biologist at the Adirondack Ecological Center in Newcomb, New York, told me about a snippet of video that graduate student Shannon Buckley had caught on a trail camera, I was astonished. Buckley, who shared the details with me by email, was studying rusty blackbirds in Maine and New Hampshire. She was looking specifically at the habitats of the birds and the raiding of their nests by predators. Once common in wet, boreal woods in northern New England and the Adirondacks, rusties seem to be experiencing a dramatic decline. Trail cameras—motion-sensitive devices used mostly by high-tech hunters tracking the timing and movements of whitetail deer—were set up at nests with the hope of catching any plunderers in the act.
One nest, located in a dead northern white-cedar and only a few feet off the ground, had gone quiet. Shannon and her field assistant retrieved the memory card from the nearby camera. On it were extraordinary images. Instead of showing a squirrel, fox, raccoon, weasel, jay, crow, or raven, the card contained video of a whitetail deer—a doe. The deer approaches the nest, noses in, and devours the contents, which may have been eggs or may have been hatchlings. Red squirrels were the most frequent predators at rusty blackbird nests, Buckley found, but in this case, the precious contents had been plundered by an animal most of us know, or think we know, as a strict herbivore.
Preconceptions aside, it turns out that the behavior Buckley witnessed on video might not be entirely out of character. Although carnivorous whitetails have flown under the radar of most of us, scientists have been catching them in the act, not often but occasionally, for years.
To track down further reports of bird eating by deer (coining a word, we might call it ornithophagy), I began by consulting my favorite go-to resource for all things concerning eastern mammals: Alfred Godin’s thorough and meticulously researched Wild Mammals of New England (Johns Hopkins, 1977). To my surprise, I came up empty-handed. Godin’s account of whitetail eating habits contained a detailed list of the plants whitetails are known to eat, but neither rusty blackbirds nor birds of any other kind appeared in his lengthy survey of the deer’s diet.
Just for fun, before turning to the scientific literature I decided to do the twenty-first century thing: I went trolling on YouTube. Instantly, I had a tug on my line. On May 16, 2010, a woman named Linda Ford Looper had uploaded a video titled “Deer Eating Bird.” When I watched it a few months ago, it had already had 1,687,707 views.
Looper’s video shows an injured bird, species uncertain, flapping on the ground. Along comes a deer. It picks up the bird in its mouth and, as the camera zooms in, chews the bird, of which there is no more sign. Meanwhile, Looper provides commentary. “Michael, he ate a bird!” she says. And she continues: “Did you see that? Oh, my word!”
Another YouTube bird-eaten-by-deer video was posted May 16, 2003. The source of this one, which had 117,381 views when I found it, was someone listed as G. Goss. The viewer observes two deer in a pen, with a white dog watching from outside the fence. A buck with short antlers in velvet, which might be a young male called a “spike” or might be an older buck with antlers just beginning to grow, picks up a dead bird, species also uncertain, and proceeds to eat it or try to. A male voice reports, “That’s Opie eatin’ a bird.”
The bird-eating deer in Looper’s video is also a buck and also in velvet, its antlers either just beginning to grow or small because the animal is young. Is it a coincidence that the deer in these videos have developing antlers? Both videos were uploaded in the month of May, a time when bucks (producing antlers at that time) and does (usually in the final weeks of gestating fawns) have a higher than usual need for dietary calcium.
A third deer-eating-bird video on YouTube was shot by Birdmama5 on May 26, 2011, and uploaded the following day. It shows a Key deer, a small subspecies of the whitetail native to the Florida Keys, picking up and chewing a dead mourning dove. This deer is a doe. If, in fact, it was pregnant with a fawn, the bird’s bones might have supplied calcium the mammal was seeking.
Also on YouTube are two videos of deer eating squirrels. In each case, the squirrel looks long dead. It’s hard enough to get one’s mind around deer eating eggs and baby birds out of nests without having to stretch one’s thinking to include them stalking and killing squirrels.
Completing my quick foray on the Internet, on a website called Outdoor Hub I found a report of a deer eating a Canada goose. A goose, I imagine, would be a mouthful and then some.
Turning to the scientific literature, I found further evidence of the designs at least some deer have on birds. A 1988 paper by R.W. Furness in the Journal of Zoology told of red deer on the Inner Hebrides, an island group lying off the west coast of Scotland. They ate the heads off of Manx shearwater chicks and also munched on the birds’ legs. “Killing of birds and the selective ingestion of bone-rich parts by ruminants,” the author notes, “has not previously been widely documented.” He posits that deer are driven to add bones to their diet when minerals such as calcium exist in low quantities in the plants that they eat.
In the United States, a 1975 study in Michigan showed deer plucking birds out of mist nets set up by bird banders. The species devoured by those deer make an impressive list that includes common nighthawk, northern flicker, blue jay, hermit thrush, American robin, cedar waxwing, and dark-eyed junco. North of the border, in Canada, a researcher reported a deer consuming a mourning warbler that it pulled from a net.
Although enough evidence exists to prove beyond doubt that deer are bird-eaters, at least to a limited degree, the general feeling among biologists is that this behavior is more of an exception than it is the rule. A wide-ranging study of 749 bobwhite nests in Georgia, for example, showed that although deer raided quail nurseries from time to time, they were guilty of only three-tenths of one percent of nest failures overall.
Still, at least in certain circumstances, deer may be significant players in the tragic realm of songbird nest predation. In a paper titled “White-tailed Deer (Odocoileus virginanus) Predation on Grassland Songbird Nestlings,” published in the American Midland Naturalist in 2000, biologists Pam Pietz and Diane Granfors tell of work they did on grassland birds in North Dakota. They collected video of deer raiding four songbird nests and report that during the course of their study, deer ate one red-winged blackbird, three brown-headed cowbirds, one clay-colored sparrow, two grasshopper sparrows, and two Savannah sparrows, all nestlings. Their conclusion: “Although probably opportunistic, deer predations clearly were deliberate and likely are more common than believed.”
Which brings me back to my late twenties and early thirties, when my friend John Van Valkenburg and I used to photograph warblers at their nests. John did most of the nest finding. He was better at it—a genius, really—than anyone I’ve ever known. The nest of the worm-eating warbler is famously hard to find, so camouflaged and challenging to spy on a forest floor that even Hal Harrison, author of the birds’ nest guide in the Peterson series, found only two in a celebrated lifetime of nest hunting. John found two in one day.
Over several years of roaming the woods together and photographing birds’ nests, John and I came to realize that a shockingly high percentage of nests are plundered. We weren’t scientists, and we didn’t keep formal records, but we were out in the field day after day and saw a clear pattern. Yet, we were clueless when it came to who, or what, was emptying those nests. Automated motion-sensitive trail cameras didn’t exist in those days. All we knew is that if we spied a ground nest full of ovenbird hatchlings one morning, it would as likely as not be empty the next.
A lineup of suspects in those murders would have to be long. There were no ravens in those Hudson Valley woods then, but crows were there, and they’re notorious nest raiders. Others with motive and opportunity were blue jays, common grackles, long-tailed weasels, short-tailed weasels, mink, raccoons, skunks, opossums, eastern rat snakes, eastern milk snakes, northern black racers, northern copperheads, southern flying squirrels, gray squirrels, and yes, those cute and famously herbivorous (but secretly non-vegetarian) ground squirrels we call chipmunks.
Still, when I think back, I remember the deer occurring in near plague proportions in those woods. There wouldn’t have been a single outing in search of birds’ nests when we wouldn’t have spooked one or more deer at every turn. Some of those animals might have been out searching for birds’ nests, too. Why not? The season of eggs and baby birds is also, as it happens, the time when whitetails are gestating or nursing fawns and growing antlers, and have their greatest need for calcium. And in overgrazed woods, a calcium-hungry deer must have to go to great lengths to satisfy its needs.
The negative impact of high deer densities on bird populations has long been noted, but the mechanism by which the impact occurs is generally assumed to involve the loss of food plants, an associated decline in numbers of bugs and worms, the diminishment of cover, and the reduction of trees and shrubs to nest in. Yet, Shannon Buckley’s experience with rusty blackbirds, carnivorous deer videos on YouTube, and the scientific literature all suggest that there could be more to it than that. A deer may have designs on your tulips, yes, but it may also crave your warblers.