Do turkeys eat grouse? Why are some areas that used to have more grouse seeing more turkeys and less grouse?
In this episode of Wildlife Matters, the Masked Biologist tackles these questions.
I have often heard people blame turkeys for reduced grouse numbers in Wisconsin. Are turkeys rampaging across the countryside, gobbling up any other game birds in their path? Or could there be another explanation?
First, ruffed grouse and turkeys really don’t extensively share habitats. An aspen forest attracts and holds grouse, but may not be ideal habitat for turkeys. As aspen forests age, and are not rejuvenated by cutting, they slowly fall apart. Hardwood species invade, possibly maples, basswood, and oak. As these species mature, they produce the kind of food and habitat that attracts turkeys, but may not hold as many grouse as the aspen used to years before. The turkeys haven’t eaten the grouse, they have simply followed the habitat; the grouse have moved on to other areas that provide the food and cover they prefer. So, if you have a forest where you used to see more grouse decades ago and now all you see is turkeys, maybe this is a symptom of a change in habitat type, not interspecific competition.
Let’s look at the biology of the birds as well. Turkeys are large birds, and they have a fair amount of variety in their diet. However, probably 90% of their diet is plant matter (seeds, fruits, nuts, grass, clover, even aspen buds) and only 10% is animal protein (like insects and animals). If they were foraging in the grass and a really small chick ran in front, a turkey might snap at it. However, there is no evidence that turkeys intentionally target chicks or poults. Their beaks are not designed to eat birds or eggs. They don’t have meat-tearing beaks like hawks, eagles, or vultures. They don’t have sharp, chiseled beaks like jays, crows, or ravens. Yet it is not too difficult to find someone who heard a story about a turkey ransacking a grouse nest.
A few years back I was walking a private forest with now retired Ruffed Grouse Society biologist Gary Zimmer; we were talking about this very topic. He pointed out that several studies have used motion sensing game cameras set up on bird nests to detect predators. Nest robbers are usually animals like raccoons, skunks, foxes, and other small furbearers. Crows and jays probably raid nests as well. I have even seen a couple of studies that showed deer eating eggs and chicks. Turkeys were not detected in the studies that Gary mentioned.
Gary presented an explanation that makes a lot of sense. If a hen grouse successfully hatches her brood, she leads them away from the nest. All that remains is an empty nest with empty egg shells. Birds seek the calcium in egg shells, and will gladly come to the nest to eat these shells—including turkeys. It is possible that these people saw a turkey cleaning up a nest after the hatching is complete, and in fact the birds are safe a good distance away. Another possibility, I suppose, would be if a nesting hen were killed by a predator and the nest was left unguarded. Any opportunistic hungry wildlife would take an easy, high protein meal if the opportunity presented itself. However, in that case, the nest was definitely going to fail anyway, and the depredation is actually scavenging of something that was already dead.
Finally, Wisconsin’s weather has changed markedly over the last half century. According to a study done by University of Wisconsin-Madison scientists, our annual average temperature rose by 1.1°F from 1950 to 2006. This may not seem like much to humans whose lives revolve around buildings and vehicles with heating and air conditioning, but it has a notable impact to the ecosystem. Wintertime temperatures have seen an average increase of 2.5°F. The state is seeing fewer extended subzero stretches, and overnight temperatures have become milder. Statewide, the first fall freeze occurs almost a week later than it did in 1950. Winters are shortening, and the growing season is slowly increasing. Ruffed grouse are well adapted to winter; they grow specialized snowshoes, called pectinations, to walk on snow in winter, and they burrow into the deep snow to stay warm and try to avoid predation. Turkeys, on the other hand, either sink in the snow or walk on a crust, and they have to find thermal cover like evergreens to stay warm. So, with the changes we have seen in our seasons, especially winter, it is no surprise that turkeys have begun to do better and ruffed grouse might struggle more to survive and thrive in less than ideal conditions.
Striving to make new things familiar and familiar things new, this is the masked biologist coming to you from the heart of wisconsin’s great Northwoods.