Field Journal 3: Ecological Physiology

Start time: 1:30pm
End time: 3:30pm
Date: 03/06/21
Location: Blueberry Lake, Warren VT
Weather: 19℉ and cloudy
Habitat: Trail system through coniferous forest surrounded by farm fields.

On a chilly Saturday afternoon, I headed down to Warren, Vermont to do some bird watching. The trail system that I explored was around Blueberry Lake, consisting of mostly coniferous trees as well as some open farm fields. I did not see a lot of birds that I was able to identify, which may be due to the high amount of loud families and dogs that were also there that day. However, I did see two American Crows and suspect that there were quite a bit more out of sight.

American Crows have evolved to be able to survive in pretty chilly temperatures in the winter. Some behavioral adaptations that crows display to keep warm consist of fluffing their feathers, tucking a leg or beak into its feathers, shivering, sunning, and roosting. Additionally, crows will sun themselves and go into a state called “torpor”. When in this state, they will lie on the ground with their bills open and go into a state of unconsciousness where their core temperature drops 10-12 degrees. Additionally, their heart rate and respiration are reduced which allows the bird to save 20% of its energy. This saved energy goes towards keeping the bird warm.

American crows are pretty omnivorous and will scavenge whatever they can find. The bulk of their diet in the spring and summer consists of earthworms and other terrestrial invertebrates. In the winter, they rely mostly on waste grain. This could be one of the reasons why I saw American Crows on my walk, because I was near lots of farm fields. American Crows budget their time in the winter to be awake and active during the warmest part of the day. In order to be in the sun the longest, they leave their roost sites at sunrise and hunt for food/sun themselves throughout the day. In the evening, they roost with other crows to conserve body heat during the night.

I believe that the crows that I was observing were beginning to look for a roosting place. Roosting is a behavior that crows exhibit where they gather in large flocks at night to conserve body heat. Because the temperature was already starting to drop so rapidly, and it was a pretty cloudy day, the crows that I was observing may have been beginning to do just that.

Snags are important in the winter because they provide shelter for birds and other wildlife to spend the night in. Sleeping in a cavity can trap body heat, and raise the body temperature of a bird. Some bird species that are likely to use them are smaller songbirds that need to rely on sheltered areas to maintain their body temperature At the end of my walk, I observed two cavities. One was larger with a few holes in it and had a good-sized cavity. The other had a smaller cavity, which I suspect a woodpecker made.

Posted on March 8, 2021 03:46 AM by elenarbernier