Kirsti Carr – Field Research Assistant
Update March 3, 2022
Staff continues to track our five Rough-legged Hawks from this winter and two Red-tailed Hawks from last season. Four out of the five Rough-legs have left Vermont and are now in New York. Two of the birds crossed paths and spent several days in close proximity near Hudson NY, approximately 120 miles away from Addison County. They were initially captured six miles apart in Vermont but never overlapped while in the state. The last bird has set up a winter range in the fields surrounding its initial encounter location. We will watch their movements as spring approaches and the birds begin their migration back to the arctic. In spring we will begin conducting Broad-winged Hawk nest surveys throughout the state and start monitoring for American Kestrel use of boxes in our network. We will also monitor amphibian crossing locations near the nature center and start work on numerous other projects.
The week started off icy, with an Arctic north wind blowing drifts into the remaining snow cover. Neil Paprocki, a Ph.D. student at the University of Idaho, was on his way to join VINS staff in Addison county. His Ph.D. research is focused on expanding work Jeff Kidd began in 2014 to address knowledge gaps about the movement ecology of Rough-legged Hawks throughout the country. The frigid weather was fitting for our “target” species. These birds are in the same family as Red-tails, Red-shoulders and Broad-winged Hawks, however their breeding grounds are restricted to the arctic tundra throughout the world, and they are well-adapted for extreme cold. In North America, they breed in Northern Canada and Alaska, and migrate south into the “lower 48” states for the winter. Neil has put out GPS transmitters on Rough-leggeds across the country, and aims to address multiple questions about the species’ migratory patterns. We were excited to assist Neil in deploying transmitters on his first Vermont birds, as we are hoping to learn more about their wintering habits in our state, and where the ones who spend their winter here might breed come summer!
Capture success is always unpredictable, and Neil had a limited amount of time before he had to leave New England for the next stop on his winter tour. We planned to drive the county, focusing on areas we have been regularly surveying since December, looking for Rough-legged Hawks perched on trees or telephone poles close to the road. When we found a suitable bird, we used a small trap called a bal-chatri, which is a weighted metal mesh box with a mouse inside (unreachable by a raptor). The trap is covered in monofilament loops that will self-tighten around a raptor’s foot or talon if it tries to grab the mouse. We watch from a safe distance away, using our cars as a blind, and grab the bird immediately after it is successfully caught in one of the loops. Versions of bal-chatris have been used as a safe trapping method for hundreds of years, originating with falconers in India. The capture, however, depends on the bird’s response to the trap. Some are too wary, not hungry, or for some other unknown reason uninterested in the trap. VINS provided Neil’s project with three tracking units, and Neil had a goal of deploying two more after that. When we set out for our first trapping day, we had no idea how the birds in this area might respond.
Lucky for us, the birds were interested. Right away we had Rough-leggeds fly over to the trap almost immediately after setting it. It wasn’t long before one showed initial interest, and committed enough to get caught. Our first bird was a juvenile female. She hatched this past summer (2021), and is now experiencing her first winter. We have no way of knowing where she hatched and fledged, but if all goes well, this coming summer we will see if and where she attempts her own nest! We caught one more juvenile female, and our first day was over with overwhelming success. The next day our luck continued, and we started the day with a beautiful third-year (hatched in 2020) male, a dark morph. Rough-leggeds have incredibly variable plumage, some with a pale breast, underwings and tail with variable brown, black and sometimes reddish banding and patterning, considered a “light morph.” Others have very dark brown or black breasts and underwings, with very patterned tails, “dark morph.” Better seen in photographs than described, it seems no two individuals are quite alike, and although there are two categories, the reality is a vast spectrum.
We knew the exact age of this third-year bird because he still had old, retained flight feathers in his wings. In the photo below, the first four feathers of the wing (technically called primaries 10, 9, 8 and 7) are dull brown and slightly worn compared to the next feather which is fresh, glossy and black. Lower in the wing, in what are considered secondary feathers, there are five visible feathers that are slightly shorter than the rest, with a thinner and lighter band at the tip. The difference in appearance of these feathers – shorter, plainer, less marked – signify that these are old juvenile feathers, i.e. the feathers the bird was wearing when he left his nest. Raptors typically undergo an annual molt, but often do not replace all feathers. When they hang on to a few, like this bird has, it is a helpful clue into how long the bird has been alive.
We ended up putting out all five transmitters in 2.5 days. They were put on three juvenile, light morph females, the dark morph adult male, and a dark morph adult female. It was a coincidence that both adults were dark morphs and the juveniles were all female, and our sample size is too small to make any assumptions about the demographics of the birds in the area. However in our roadside surveys we have confirmed a good number of dark morph Rough-legged Hawks, which are typically considered far less common than light morphs. We look forward to summarizing our survey data to look more closely at seasonal trends!
We had a great few days with Neil and are very excited he has added Vermont to his far-reaching study of Rough-legged Hawks. Thanks again, Neil!
These photos of the variability of the plumage are super helpful!