- Study: High deer populations mean fewer songbirds, The Bulletin, April 20, 2017
A team used lasers to build 3-D maps of English woods, and discovered that places with high deer populations had less than one-third the shrubbery under 2 meters tall that deer-free forests enjoyed. “It is clear from our research that if we want to encourage more woodland birds, then we need to take action to restore the woodland structures they require,” Eichhorn said in a news release. “But in many areas it will need a drastic reduction in deer to have any real impact.
Deer eat the bushes and saplings birds need for cover, forage and nesting material. And when concentrated in urban areas, safe from natural predators, they can become an ecological pest.
- Success and Predation of Bird Nests in Grasslands at Valley Forge National Historical Park [Abstract], Northeast Naturalist, March 2016
Estimated nest-success probability for Eastern Meadowlark at Valley Forge was 0.25 (0.04–0.65, n = 7) and similar to estimates from the Midwest, but slightly lower than other studies in the Northeast. Nest success for Field Sparrow; 0.77 [0.31–0.98, n = 8] and Red-winged Blackbird; 0.48 [0.18–0.80, n = 10] was higher than estimates from other studies. The local predator community identified at Valley Forge was less diverse than documented in other studies, with only 4 species depredating 8 of 25 monitored nests. The primary predator was Odocoileus virginianus (White-tailed Deer; 38% of nest predation events) followed by Vulpes vulpes (Red Fox; 25%); Procyon lotor (Raccoon; 13%), and a probable Mustela sp. (weasel; 13%).
- Woodland and Forest Birds: The Role of Sustainable Management, Audobon New York, July 20, 2015
- White-tailed Deer and Their Influence on Forest Vegetation, Long Island Natural History Conference, Tom Rawinski of the U.S. Forest Service, April 2015
- Deer Are Major Songbird Nestling Predators, Top Birding Tours, March 8, 2015
Deer are apparently much more than opportunists. In 2000, scientists with the U.S. Geological Survey (USGS) used mini video cameras to document systematic predation of songbird chicks in North Dakota. As was the case in earlier predation episodes, the deer were filmed eating nestlings at night.
- Researchers Document Deer Eating Birds, Field and Stream, March 6, 2015
Researchers keep on finding evidence that deer like a protein snack of bird from time to time. Deer eating birds opportunistically seems to be a wider-spread phenomenon than we previously thought. Scientists in North Dakota watching song birds via “nest cams” in a recent study found whitetails raiding more nests than either foxes or weasels.
- Deer Have Been Eating Birds For Years… They Will Eat Us Next, Huffington Post, March 5, 2015
For those of you thinking we can kill our way out of this predicament, please put your hunting devices away. It’s too late. Our collective fate is sealed. There is a certain calm that washes over you when you accept your doom. Don’t fight it, let it bring you peace.
- Field Cameras Catch Deer Eating Birds—Wait, Why Do Deer Eat Birds?, io9, March 4, 2015
These supposed herbivores placidly ate living nestlings right out of the nest. And if you’re thinking that it must be a mistake, that the deer were chewing their way through some vegetation and happened to get a mouthful of bird, think again. Up in Canada, a group of ornithologists were studying adult birds. In order to examine them closely, the researchers used “mist-nets.” These nets, usually draped between trees, are designed to trap birds or bats gently so they could be collected, studied, and released. When a herd of deer came by, they deer walked up to the struggling birds and ate them alive, right out of the nets.
- Abundant Deer Hurt Bird Populations, AboutNews, Jan 23, 2015
Recent studies provide some good insight about the relationships between deer and songbirds:
In one study in Quebec where researchers used a manipulative approach, areas where white-tailed deer density was experimentally reduced saw important increases in bird abundance and diversity (Cardinal et al., 2012).
Similar results were found in a series of small islands off British Columbia where deer (mule deer in this case) occur at various densities. On the islands with no deer, abundance and diversity of birds was highest (Martin et al., 2011).
Another study examined all the existing research done on deer and birds across North America, and then analyzed Breeding Bird Survey data, a very large citizen-science dataset. The authors report strong evidence for a continent-wide, negative effect of deer on the abundance of ground nesting or ground foraging birds (Chollet & Martin, 2013).
- The Meat-eating Habits of Deer, Outdoorhub, Dec 9, 2013
“If they come across a nest, where the food doesn’t move or run away, they’ll take advantage of it,” Pietz said. Other small animals are game too, as long as the deer can actually eat them.
- Specific Threats to Connecticut’s Birds, Connecticut Audubon Society, 2007
- Effects of Deer Herbivory on Birds, Wisconsin Bird Conservation Initiative, Sept. 2010
- White-tailed Deer (Odocoileus virginianus) Predation on Grassland Songbird Nestlings, USGS Northern Prairie Wildlife Research Center, Feb 2013
- Abundant Deer Hurt Bird Populations, About.com: Environmental Issues, 2013
- Wisconsin Bird Conservatory Initiative
- White-tailed DeerAlter Diversity of Songbirds And Their Habitat in Northwestern Pennsylvania, Pennsylvania Birds, 1996
- US songbirds decline as deer populations rise, Invasive Species Council, Sept 21, 2012
- DEER POPULATION AFFECTS BIRD POPULATION, Fairfield County, CT, 2010
- Managing the Abundance and Diversity of Breeding Bird Populations through Manipulation of Deer Populations, Conservation Biology, 2001
Deer densities in forests of eastern North America are thought to have significant effects on the abundance and diversity of forest birds through the role deer play in structuring forest understories. We tested the ability of deer to affect forest bird populations by monitoring the density and diversity of vegetation and birds for 9 years at eight 4-ha sites in northern Virginia, four of which were fenced to exclude deer. Both the density and diversity of understory woody plants increased following deer exclosure. The numerical response of the shrubs to deer exclosure was significantly predicted by the soil quality (ratio of organic carbon to nitrogen) at the sites. Bird populations as a whole increased following exclosure of deer, particularly for ground and intermediate canopy species.
- EFFECT OF WHITE-TAILED DEER ON SONGBIRDS WITHIN MANAGED FORESTS IN PENNSYLVANIA, Journal of Wildlife Management, 1999
- Deer Behind Britain’s Great Bird Decline?, National Geographic, October 28, 2010
- A perfect storm: two ecosystem engineers interact to degrade deciduous forests of New Jersey, Biol Invasions, 2008
We look at how two ecosystem engineers, the white-tailed deer and the invasive plant Japanese stilt grass, interact to completely alter the structure and composition of the subcanopy within northern deciduous forests. This interaction has wide-ranging repercussions on forest food webs which we explore through a case study of breeding woodland birds in the state of New Jersey. We show that the guilds of birds that rely on the subcanopy have experienced greater declines from 1980 to 2005 than birds that specialize on the intact upper canopy of impacted forests.
- Deer Culling – A Critical Tool for Conserving Local Habitat Diversity: A Green Paper by the Bird Conservation Network, Bird Conservation Network, Nov 2007
This paper outlines concerns that habitat within forest preserves and other natural areas in the region are being adversely affected by widespread overpopulation of white-tailed deer, and recommends ongoing proactive efforts to reduce this deer overpopulation
Improving Bird Habitat Through Forestry, Feb 17, 2017