FJ5: Migration
Date: 3/29/23
Start time: 2:15 pm
End time: 3:20 pm
Location: Oakledge Park
Weather: mid to high 40s, slight wind, partly cloudy
Habitat: park with deciduous forest, freshwater coast
For this excursion, I went to Oakledge Park. I walked on the trail first, and there were several areas of dense vegetation. In these areas, there were lots of smaller birds like the Black-capped Chickadees and Tufted Titmice. There were also several Ring-billed Gulls flying and calling out overhead since we were near the water, as well as American Crows. Going a little deeper onto the trail revealed a White-breasted Nuthatch hopping up and down a tree, a Northern Cardinal, and several Song Sparrows. After that, I exited the trail which came out to a large, flat field and saw more American Crows and a Mourning Dove (though I only heard it). I kept following the trail along the water's edge and was able to see a pair of Canada Goose as well as a pair of Common Mergansers (one male and one female!) on the lake. (I was excited at this point because it was my first time seeing Common Mergansers!) Continuing on into a neighborhood, I saw several House Sparrows by a feeder and Common Ravens as well as more American Crows.
Most of the species I observed on this excursion are year-round species, aside from the Canada Goose (who are here during breeding season) and the Ring-billed Gulls (who are here during the warmer months). The ones who stay in VT year-round like the Black-capped Chickadee undergo facultative hypothermia, which is a condition where the bird's body temperature drops below its normal level. This occurs as the result of internal clocks or a lack of food/energy, and helps the bird survive in low temperatures. Another way birds survive the winter temperatures is through torpor, which the Mourning Doves do. Torpor is a hibernation-like state in which the bird's body temperature drops much lower than usual (to around 8-20 C). This conserves energy since the bird is not moving or responding to stimuli and lessens the need for high food consumption. Birds like these have these strategies to survive the winter here in VT because it is more energy-effective to remain than it is to migrate long distances, especially for the smaller birds that don't have wings suited for that kind of flight.
Birds like American Robins and Red-Winged Blackbirds migrate up to VT during the summer months, likely due to the weather being cooler than in the south, the ground unfreezing (allowing insects to emerge), and berries starting to grow. These birds may not have the same techniques to stay warm during the winter, so they leave when it gets too cold but come back when it's warmer and the food supply is more abundant. Migrating birds arriving in early April may have the advantage of having more space to establish their territory/set up their homes.
Havainnot
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