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Date - 4/3/21
Start Time - 9:08am
End Time - 10:33
Location - University of Vermont Redstone Campus and Burlington Country Club
Temperature - 30 deg F
Wind 20mph NW
~100% clear
Zero precipitation
Habitats were open, grassy grounds of the Gutterson field, the swampy-pond area near the Redstone Lofts, and up past the Redstone Commons to walk the path at the Burlington Country Club. Many birds individually and in groups flitted between trees and glided on the clear air, almost in a leisurely way. The areas where we observed them were very open, leaving a clear view of their perches on fences, vegetation, and trees.

Some of the year-round species we observed were the House Finch, Black-capped Chickadee, Common Raven, Rock Pigeon, and Ring-billed Gulls, who overwinter in the Northeast and don’t need to travel far to adjust to the colder temperatures and changed food availability. Their diets primarily consist of invertebrates (e.g. worms), seeds, and fruits that still exist during the winter months. Their bills are short, stubby and even conical (like the House Finches), to better adapt to cracking open and eating seeds. In a similar vein, Gulls have a primarily piscivorous diet allowing them to hunt fish in Lake Champlain during the winter as they can in the summer.

Facultative migrants we came across were the American Robin and the House and Song Sparrows. On average the straight line distance these species travel from their wintering grounds to Burlington is ~1000-2000mi. Their migration is dependent upon the food availability of the year, and if they do decide to migrate they don’t go too far into the tropics, typically staying in the southern US range. Their diets are the most adaptable - omnivorous and generalist - often making them opportunist species. Facultative migrants can survive on the same diet as year-round species, able to take advantage of the fruits, seeds, and invertebrates available during the winter, or able to migrate down south and feed on insects if need be like the obligate migrants do. Sometimes, as with the American Robin, some members of a population stay in the Northeast during the winter while some of the population migrate because of the intraspecific competition occurring. When the more competitively advantageous population members start to feed, there is less food availability for the less competitively “fit” population members. Other times the limited food availability comes from the conditions of the year itself. The Song Sparrow is a species that we have only been starting to see on our field trips, most likely arriving from somewhere in the Southern US and coming into Burlington as the weather gets warmed and a higher variety of overall food is available, so they do not need to compete as hard to eat. This is in contrast with the American Robin, who we’ve been seeing since our first field trip and whom the majority of likely did not migrate during the winter, given the proliferation of fruit and seeds in the area.

Obligate migrants we saw were the Eastern Phoebe and Red-winged Blackbird, likely coming from tropical areas back to Burlington as the weather gets warmer. On average the straight line distance these species travel from their wintering grounds to Burlington is anywhere from ~2500-5000mi. These species are insectivores, and need to migrate down south due to the lack of insect availability in colder climates. Changing climatic conditions, however, complicates these natural circannual cycles of the different bird species. The timing of spring has been very erratic for the past few years in light of worldwide warming temperatures and anthropogenic disturbance. During some weeks the weather here is warm as though it’s on the verge of spring, and in the next week it snows. A huge disadvantage of these obligate migratory species arriving in early April is that it will continue to snow some weeks and give them a competitive disadvantage when searching for food in a climate they are not adapted to. Snow likely confuses their circannual cycles and causes a further energy deficit that was already spent from migrating back to the northeastern US. On the other hand, an potential advantage to this early arrival could be that early mating and reproduction offset this lack of initial food availability and give the birds a competitive advantage over other later arrivals for finding mates. Changing climatic conditions also makes the categories of migratory birds themselves very fluid. Tufted Titmice are omnivores but are generally non-migratory species, favoring a seed-based diet overall. However, recent changing seed availability has led them to appear further south in the US. Conversely, more and more facultative migrants are seen to be sticking around in the Northeastern US in recent years, likely due to the weather staying warmer for longer and reducing competition for those species.

Sources:
https://www.allaboutbirds.org/news/
https://journeynorth.org/tm/robin/facts_migration.html

Date 4/17
Start Time - 1:11 pm
End Time - 2:45
Temp - 45 degrees Fahrenheit
Wind - ~20mph NE
100% cloud cover at the start - 65% cloud cover after around half an hour
Location - Redstone Campus and Downtown Burlington
Habitat was primarily open within a built environment, populated by buildings and telephone wires among the open streets and grassy areas. Some sparse trees populated the environment along streets as well. The habitat had heavy human habitation and influence, with many people constantly present either walking or from vehicles, and many of the "natural" areas human-made.

Date - 4/24/21
Start Time - 9:05am
End Time - 10:30
Location - University of Vermont Redstone Campus
Temperature - 54 deg F
Wind 10mph S/SE
~100% cloud cover
Zero precipitation
Habitat was mostly very suburban, with numerous buildings populating open, grassy areas, and sparse trees. Spent some time around a swampy-pond area within the residential areas.

The main behaviors related to territory/nest/mate selection were defensive strategies against other birds both of the same and different species. An American Crow chased a Red-tailed Hawk between the trees to defend its territory. Two male American Robins stood near each other outside one of the Redstone dorms, either getting ready to fight or having just gotten out of one and probably trying to defend nesting territory and/or mates. These interactions took place near trees and shrubs next to tall buildings - aka places that nests likely reside. Crows typically build their nests in tree crotches or on branches, while Robins make their nests among shrubby bushes and conifers and can be found in residential areas! Generally, early nesting birds like the Robin as well as Northern Cardinals and Chipping Sparrows use conifers and shrubs as their nesting sites to gain the most cover, and which are also near sources of food like seeds and fruit. As demonstrated, Robins can be very territorial, and they only make about one nest per bush. Other species similarly need cover when choosing their nesting sites, and which must be closer to their own respective sources of food. Red-winged Blackbirds build their nests 1-1.5ft above areas of water amongst dense vegetation like cattails - close to the water surface so they can feed on insects, frogs, and snails, with no real need to go out to the trees. Similarly, Canada Geese make their nests right near the water in order to feed on fish, insects, and the vegetation on the banks.
We found a Red-bellied Woodpecker singing very loudly on a tall tree right outside of a house. It was the only one of its species there. In one sense it might not be defending very good territory, because there are not as many sources of food around the house as there might be within woods (there was really only one or two trees on the property). Depending on the species, human interference might also pose a real survival problem. Additionally, the lack of other birds around the property could be a sign that the territory is not the most desired and fruitful. However, in another sense the house and other materials on the property might provide plenty of cover for the Woodpecker, and the tall tree the Woodpecker was on might itself be enough of a source of food and cover just for that bird. Some people may also have bird-feeders on their property as well. Furthermore, perhaps human presence is a good deterrent to rival species of birds that are not as well-adapted to human activities. Overall I’d say the Red-bellied Woodpecker seemed pretty well off for itself and was defending fairly good territory compared to other members of its species, indicating that that bird had high fitness compared to those other members as well.
The main nests that we observed were the nests of American Robins, made of dead twigs, grasses, hairs, and even some mud and dirt. The bottoms were very solid. Generally, the coarser materials were on the outside of the nest while the finer, more valuable materials made up the center, making it easy for the birds to rebuild their nests if the outside was destroyed. The bird would have to carefully scout the ground for twigs, grasses, and hairs. Much of their materials would probably be concentrated on the ground around forests, near trees and vegetation. Most of the nests we saw were also made in the center of shrubs where most of the deader branches reside, making it quite easy for birds to acquire those materials in the same spot they intend to make their nests! Some of the materials like hairs might also be found closer to residential areas rather than forests, and of course, human-planted shrubs and trees also conveniently exist on those properties as well.