Field Journal #5: 4/8/2020

It is approximately 4 pm, and today’s date is April 8th, 2020. My bird walk today is being conducted along the natural areas around Trinity Campus, as that’s pretty much the only natural area I have access to due to the COVID-19 stay at home order. The temperature is about 45°F, and the sky is pretty cloudy. The habitat behind the “back 5” on Trinity is very covered with trees, and there is a good amount of underbrush. From what I can tell, there are mostly pines and other coniferous trees. I can also tell that there is a good amount of maples as well. There is a relatively small body of water nearby, which indicates a water source for nearby birds and other animals.
One species that I have been observing a lot during many of my bird walks is the Rock Pigeon. The Rock Pigeon is a year-round resident species in Vermont, which means that it is a bird that does not migrate. The Rock Pigeon is a species of bird that has learned how to effectively coexist among humans. Rock Pigeons are really popular city birds, which explains why I have seen them during my bird walks in areas that I would not think a bird would be, such as inside or on top of dumpsters, hanging out relatively close to the street where cars are constantly moving, and being nearby the sidewalks despite there being a lot of movement by people and their pets in very close proximity. One of the main reasons that Rock Pigeons don’t migrate is probably because of their ability to live so close to people, and with living close to people comes a food source, which is trash and other food scraps in this case. Rock Pigeons are able to find food year-round in their habitat, so it does not make sense to migrate somewhere else, as migration is an extremely energetically expensive process. One of the main drivers of migration in birds is to find food, which Rock Pigeons have access to year-round in Burlington.
Another common species I’ve observed throughout my field journal assignments is the American Robin, which is a migratory species. American Robins tend to return to Vermont in mid to late March, which is a perfect explanation as to why I’ve been seeing them relatively more often as it gets later into the spring. American Robins migrate south for the winter in large flocks. This migratory flocking behavior of American Robins is beneficial because traveling in flocks provides increased protection against predators, which can be useful when migrating long distances. In addition to increased protection, flocking behavior also means that there is increased foraging ability, which can prove useful when groups of birds are in areas that are unfamiliar to them. Finding food is likely very difficult for birds who are in ranges outside their comfort zone, and so this increased foraging ability likely helps keep a lot of the members of the flock fed and alive.
American Robins mainly migrate because of limited food resources, not temperature changes. This means that the local American Robins likely waited to migrate until the local food resources were depleted. Food availability is likely the factor that signals when to migrate to American Robins. Since the weather is warming up in Burlington, there are buds beginning to grow on the trees and the ground is pretty thawed. These are likely cues that cause the local American Robins to migrate back to Burlington, as they signify that food availability has begun to increase for the season. Arriving back in Burlington in early April has many benefits. The first benefit being that the birds returning in early April have the “first pick” of territories and home ranges and only have to work around the birds that have been in Burlington all season. Another advantage of returning to Burlington early is the found availability. There is likely minimal competition as the ground is thawed and the trees are budding, but only the early migrants and year-round species are currently in Burlington. Lastly, the American Robins that return to Burlington in early April may have better luck finding mates than those that return later in the season.

Posted on April 12, 2020 05:32 PM by emilyw603