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The American Robin, House Sparrow, Black-Capped Chickadee, Northern Cardinal and American Crow all use aspects of evolution and ecology to survive in the wintertime. During my field observation, I noticed around 15 American Robins all in one tree. They were all eating berries and seemed to be getting along just fine. I returned to the same spot about 20 minutes later and there were no birds to be found. I believe they were gathered around this one tree because their resource distribution is pretty clumped in the winter. Burlington only has so many fruiting trees and this tree was the only one on the street with berries/birds on it. Normally, American Robins can spread out relatively evenly, foraging for worms and insects, but those creatures are much harder to find when it starts getting cold. Additionally, they were practicing cooperative feeding, a social strategy that can increase foraging efficiency, protection from and awareness of predators, as well as create some agonistic encounters between individuals.

Black-capped chickadees are a commonly seen backyard bird, particularly during the cold months. I saw around 5 individuals on my walk. They carefully hide certain food items, have dense winter coats, specially selected winter roost cavities, and the ability to go into nightly hypothermia, helping conserve large amounts of energy and increasing the chances of survival. They eat enough seeds and frozen insects to gain an additional 10% or more of their body weight each day and use this excess body fat to shiver all night to keep warm. Birches provide good roosting conditions for them and help insulate them at night when temperatures really plummet.

Torpor, hypothermia, and countercurrent exchange are all tools that birds can use to stay warm in the winter and retain body heat. Many of the species that I noticed on my walk had fluffed up their feathers in order to trap air underneath those feathers and warm that air. Many birds also stand on one leg at a time while the other is tucked up warmly in its feathers. Some birds bury their beaks into their feathers to prevent evaporative cooling that occurs when a bird breaths out of its nares. Birds that can’t handle the cold of the winter may migrate south and then return once the weather starts to change.

On my walk, I saw at least 30 house sparrows and 17 American Crows (they really like the dumpster in my driveway). The house sparrows were not all together but I would see them every 50 feet or so with a handful of them hanging out in shrubbery and bushes. The American Crows were either up in tree branches or they were on the ground or pavement searching for discarded food. Both of these species are scavengers that have hitched their wagons to humans very successfully. We provide year-round foraging and our structures provide them with shelter as well. I’ve seen hundreds up crows roosting together in the canopy of deciduous trees and I’ve seen house sparrows be extremely aggressive towards birds of other species, pecking and using their calls and mob mentality to ward off intruders in their territory. House sparrows are highly social birds that return repeatedly to the same hierarchically-organized flock to forage and roost during the winter. A sparrow pair can produce multiple broods in one year depending in part on environmental factors and they've already started to look for nesting sites by early November.

I saw 4 Northern Cardinals on my walk, three of which were males, and none were flocking together. Each individual was pretty far apart from the other, perched on different phone lines. In the winter, they spend their time foraging while hopping on the ground or in low bushes, readily coming to bird feeders and particularly enjoying sunflower seeds. During the winter, when insects are scarcer, they’ll eat berries and vegetable matter. All of the birds I saw on my walk were either feeding, flying, or having some sort of interaction with each other. Birds burn a lot of energy staying warm, so constant feeding helps them regulate their bodily functions.

Standing dead trees, or snags, provide birds and mammals with shelter to raise young, stay warm and other functions. Woodpeckers and creepers are the most likely to utilize snags but around 30 bird species are capable of making their own nest cavities in trees. The insulation of a tree trunk home allows wildlife to survive high summer and low winter temperature extremes. Tree cavities and loose bark are used by many animals to store their food supplies, while insects living inside the dead wood eat thousands of forest pests. When they eventually fall, fish, amphibians, and other wildlife can use this structure for protection and habitat.

Time: 2:20pm - 4:00pm
Date: 03/22/2020
Weather: 35 degrees, partly sunny
Habitat: farmstead with open pasture, a pond, and mixed deciduous and conifer stands in the backyard

I visited my friend’s farm in Craftsbury this weekend. He lives in a pretty remote part of Vermont, and his house is at least a few miles from any other structure in any direction. He wanted to work on his car and replace the hood and pull out the carpets, and I decided it would be a perfect opportunity for me to explore his property and look for birds! At first, it was hard to find anything besides American Crows and one pesky Hairy Woodpecker that’s been eating away at the side of their barn for the past several weeks. I could hear many other species of birds while I was near his house, I just couldn’t see them. But, once I walked about a mile or two into the forest, I started to hear and see so much!

Birds are constantly interacting using posture, plumage, and vocal message. I immediately noticed that there was this one relatively large American Crow perched pretty low on a branch and raising its feathers and screeching at any bird that flew above it, regardless of the species. When a bird came too close to his branch, tree or the compost pile, he issued a series of warning calls, fluffed his feathers, and immediately went into aerial attack. Then I noticed that he was in the perfect position to pick vegetable and fruit seeds out of the large compost pile next to the barn. I started wondering if he set up shop in that same spot every day to get the best food scraps? He did seem much meatier than other American Crows, and maybe this extra source of food helped him through the winter and the extra weight gave him an advantage over other males when breeding season comes along.

Contrasting to this American Crow’s agonistic behavior towards other birds, I walked down to one of the ponds on my friend’s property and there were 3 mated pairs of Common Mergansers that were clearly enjoying one of the first sunny days in a while. The females have really funny tufts of brown feathers on their heads that make them look like they’ve just woken up with some major bedhead, and it always makes me chuckle. Each pair was allopreening, and when one of the males got too close to one of the females that was not his mate, you could see a reaction from the male where his posture completely changed and he would swim over and push his mate away while making small warning quacks at the intruding male. Most male birds I’ve seen (those that travel with their mate) are quite aggressive towards other males coming into their space, which we can probably connect to human behavior as well. Common Merganser males use countershading (white belly with black and other melanin’s on the back and the head) to avoid predation but they also have pretty bold colorations with iridescent greenish-blue on their face and some repeating patterns along their wings. These patterns help males when advertising for females and can also send warning signals to other males.

The patterns on Mergansers are very different than the ones on Eastern Phoebe’s and House Sparrows, which appear mostly to be used for camouflage, helping them blend in with the trees and greenery in the background of their habitat and protect themselves from predators like hawks and falcons. I watched a group of House Sparrows resting and chirping in a bush on the edge of the forest habitat. Right now, many birds are migrating back to Vermont from warmer places down South. As this event is occurring, the length of each day is growing and soon we will see many species arriving at breeding grounds and beginning nesting behavior and ovulation. The length of daylight is an essential environmental cue that triggers sex hormones and increases the size of gonads. Males proclaim their territories with songs and sometimes fights, pair bonds are established or reaffirmed, and mating takes place. One particular house sparrow was sleeping with its head scrunched down into its feathers. This was towards the end of my walk when it was getting to be around 4:00 pm, and the sun wasn’t as strong and the birds seemed less active.

I attempted to solicit "pish" calls while I was around the group of House Sparrows and experimented doing it quietly and then loudly at different volumes and timbres. They were not having it, and almost completely ignored me, with some retreating even farther into the brambles. Alas, I will have to work on my spishing skills and try them out on some other foraging species. All together I had a great experience and saw a lot of activity!