By Christina Schmidt
SHERIDAN — For the past few months, the Sheridan area has had an influx of visitors. These guests did not stay in Sheridan hotels or eat at local restaurants, but they did provide some helpful community services — reducing the rodent populations and cleaning up the carcasses of road and winter-killed animals.
“What you are seeing the most of is buteos,” said Dr. Jackie Canterbury, ornithologist and president of the Bighorn Audubon Society.
Buteos is a term for medium to large-sized birds of prey, such as hawks and buzzards. This winter, any short drive out of town or even keen observation in town has revealed a large number of buteos and other raptors, such as eagles, sitting in trees or on fences and poles or in flight.
Though this part of the state is home to a variety of year-round raptors, and the lack of foliage on trees in winter makes them easier to see, there is a true increase in numbers of some species during these months. Some of these birds make their way down to Wyoming after a summer in the northern Arctic, avoiding winter weather conditions that make Wyoming look downright balmy. However, it is not warm weather these birds are seeking, but sustenance.
“It is all related to food resources,” said Canterbury.
Perhaps the most abundant and easily visible visitor this winter has been the rough-legged hawk.
Rough-leggeds breed and nest in the high Arctic of Alaska and the northern stretches of Canada. Come winter, the distances they migrate are impressive. Wyoming is at the northern tip of their winter range. Some birds will stop in Wyoming while others press southward to states such as Oklahoma, Texas, Nevada, Colorado and Nevada — journeys of thousands of miles.
Canterbury says rough-leggeds are irrupting this year, meaning that more northern populations have come south in larger numbers than usual and congregated in the area, again likely due to good food resources, providing plentiful viewing opportunities for birders this year.
They begin arriving here in late September and are returning to the Arctic now and into April.
They primarily eat rodents, but Canterbury has also seen them eating on road kill.
They can be difficult to identify, with males and females and adults and juveniles sporting different plumage. However, in general, look for a white breast, a dark belly band and feathered legs. When in flight, their tail feathers are tipped in black.
“This is the toughest group to identify I think,” said Canterbury. “Until you look at redtails.”
Red-tailed hawks are widely distributed and common in Wyoming, but many leave for the winter and begin returning this time of year. Like their name implies, they can often be identified by their striking red tail feathers.
However, there are at leave five ‘races’ of red-tails in the U.S. and some of them, confusingly, have white tails. The western race, common in Wyoming, features a brown body with deep red tail feathers. However, the Krider’s and Harlan’s race, both of which are found in Wyoming, can have buff, white or salmon colored tails rather than red.
“Red tails are really complicated to identify except for two features in adults, a red tail and dark feathers on the leading edge of the wing that you can see when it is in flight,” said Canterbury. “That is the key. If you can see that in all these different color morphs, it is a red tail.”
Red-tails are voracious rodent-eaters and occupy a wide variety of habitats.
Golden eagles are Wyoming’s largest bird and easily identifiable as adults. Males and females look alike, with chocolate brown bodies and bronze-colored heads, but females are significantly larger than males. Juveniles have white patches on the underwings and tail, which shrink as they age. It takes five years for adult plumage to develop.
While the state has a year-round population, the winter population increases with migrating birds from northern populations in Canada and Alaska arriving in September and October.
“They are thought to be nonmigratory,” said Canterbury, of the state’s golden eagles. “But migrants from more northern populations (that do migrate) augment our local population so you have no idea who is who or where they are from.”
Goldens use a variety of habitats in Wyoming but are generally adapted for open grasslands where they feast on prairie dogs, jackrabbits, ground squirrels and other small mammals.
Adult bald eagles are perhaps the easiest raptor to identify, with their distinctive white heads and tails. However, this plumage is only found on adult birds 5 years or older. For the first four years of life, the birds molt their feathers annually, which are predominantly dark but with varying degrees of white splotches on the chest and visible on underwings in flight.
Juveniles also have dark eyes and a dark bill, which transition to yellow eyes and a yellow bill as they mature.
The area has a population of resident bald eagles, but numbers swell in the winter as migrants from the north arrive and mingle with the locals. They are often seen communally roosting in significant numbers in large trees such as cottonwoods. They are also often seen on roadsides.
“Bald eagles are big time carrion eaters,” said Canterbury. “They will eat about anything that is dead.”
During the 2017 mid-winter bald eagle survey of the Powder River Basin, volunteers counted 198 bald eagles and 102 golden eagles.
Though a member of the finch family and not a bird of prey, Canterbury said that, like the rough-legged hawk, this year appears to be an irruption year for the common redpoll, and it has been widely reported in the county.
They feed on birch, willow, alder and spruce seeds and will readily help themselves at bird feeders, where they are most often seen. They can be identified by their rose-colored breast and a deep red cap on their head.
They have a year-round range in northern Canada and are Arctic breeders further north. They usually go as far south as southern Canada, but this year they dipped farther south into the Wyoming area.
“They have really unusual features to help them deal with cold,” said Canterbury. “They can burrow deep into a snow bank and make a tunnel. They are very snow adapted.”