Field Observation: Migration

On April 7, 2020 from 1:00pm to 2:00pm, I went for a run around Burlington. I started on South Willard and ran up to South Prospect and then down to the waterfront and back up. The weather was beautiful- sunny and 50 degrees with very little wind. This field journal was a bit different than my others. I am currently quarantining in my apartment in Burlington, so I really only go outside to get exercise. I decided to combine my run with bird-watching. It was actually quite successful because there were so many birds out and about on this nice spring day, and the streets are very empty lately which may allow for birds to be more active. It was also super nice for me to get outside and bird-watching really takes my mind off of how far I'm running because I'm quizzing myself on bird calls and trying to spot different species. The only down-side to running and simultaneously bird-watching is that my ability to take pictures goes straight down hill, so I apologize in advance for the quality of my photos.

Going up college street, there are trees at the top (near South Prospect) that are bare with the exception of a few berries. Whenever I walk past these trees I head chickadee calls, but today was one of the only days that I actually saw the black-capped chickadee. I always forget how small they are! I have heard black-capped chickadees throughout the entire winter in Vermont because they are year-round residents. They find holes in trees to shelter themselves and keep warm in the winter, and they also 'huddle' up with others to retain body heat. The benefits of migrating must not outweigh the benefits of sticking around in Vermont, perhaps because they are an omnivorous species and have a somewhat generalist diet. There is no need to migrate south for food sources.

I then saw and heard approximately four American Robins while running down South Prospect St. It had rained earlier that morning, so I suspect the American Robins on the ground were searching for worms? This was the first time all winter that I saw robins foraging on the ground rather than in trees for berries. When researching the migratory range of American Robins, it seems that some do migrate south to Florida for the winter, but some also stick around in the North. There are still food sources here for them in the winter (berries), so I think they'd be likely to stick around. However, if there is a very harsh and cold winter, I would imagine that the robins would migrate south and switch their diet from worms and invertebrates to fruits and berries.

I also heard a Blue Jay near the American Robins. I have seen and heard Blue Jays in Vermont all winter, and I've even heard them on tops of ski mountains. They are able to tolerate the extreme temperatures by flocking in the winter to keep warm and also to reduce the amount of energy needed to be vigilant. Similarly to American Robins, Blue Jays shift their diet from insects in the summer to fruits and berries in the winter. It seems like their migratory patterns are not fully known yet, but most individuals tend to stick out the northern winters. During mild winters in Vermont, there are still berries on trees. So, perhaps there is less competition for food if they stay in the north rather than migrate south with all the other species to feed on fruits.

Then, while running down Maple Street, I practically ran into a Common Grackle that was walking along the sidewalk. As I got closer, the bird hopped further into the grass near a bush, and I spotted another one along with it. I hadn't seen any Common Grackles in Burlington before this day, so I suspected that they just arrived. I looked up a range map for this species, and it shows that they are permanent residents of New York and the rest of the southern states. Vermont is indicated as part of the species' breeding range. So, I think it's safe to say they just arrived in Vermont to prepare for their breeding season. It doesn't seem like there is a big difference between the NY and VT winters, but I suppose the only thing that changed for this species to move northward for breeding is that competition for food got more intense in the southern states as other birds also began to migrate back north for the spring/summer. There are also signs of spring in Vermont, as the ground is no longer frozen so they can feed on invertebrate arthropods (like beetles and caterpillars). They also feed on seeds (from agricultural grains such as corn and rice), so perhaps they are able to find these seeds in VT now as farmers begin to ready their fields for the season.

I'm hoping to come across more obligate migrants in the next couple of weeks as more and more start to arrive in Vermont!

Publicado el abril 8, 2020 03:57 TARDE por aneu