Date: 03/025/2024
Start time: 12:25
End time: 13:31
Location: Green Mountain Audubon Center, VT
Weather: Sunny, Beaufort scale 0, 32ºF
Habitat: Forest edge/sugarbush- lots of old, live trees as well as snags. Both coniferous and deciduous
I observed three species: two year-round residents and one migratory species. The two year-round residents that I saw were the black-capped chickadee and the tufted titmouse. These species stay year-round because their a) food sources are plentiful enough to be found in quantity throughout the winter months and b) because they have adapted to it. Migration is dangerous and energy-expensive for birds, so it makes sense that they would want to stay in place for the winter. Chickadees and titmice survive the winter by puffing out their feathers to preserve body heat, utilizing countercurrent heating in their legs and feet (i.e. warm blood running through vessels next to vessels containing cold blood to heat it up), and, specifically to chickadees, by sticking together in loose foraging groups.
The migratory species I observed, the American robin, feeds primarily on insects, worms, and berries, so when insects and worms die/become dormant in winter, their food source decreases in climes where it is too cold. These birds migrate so that they can keep eating, but are not obligate migrants- they can still survive in Vermont off of what food is left as the winter goes on. Right now, robins are coming back from as far as the the Southwest, the Gulf Coast, and Mexico. When food becomes more available further north as temperatures rise, they follow it.
Vermont weather is very unpredictable- this year, for example, we received a foot of snow in one day just a few days ago. This is abnormal, definitely, but not out of character by any means for Vermont. This kind of unpredictability makes it rather tricky for birds to time their arrival correctly so that there is enough food and high enough temperatures for them to survive. There are some advantages to arriving early however- birds that arrive early get food (if there is food) with little competition, and they get the best territory.
American robin winter range goes as far south as mid-Mexico. Mapped out in a straight line from Mexico to Burlington, VT, they can cover as much as 1,300 miles.