Diario de jessharkness2

Date: March 4th, 2019
Time: 1:47 PM
Location: Casavant Natural Area, Winooski, VT
Weather: -2 °C, very lightly snowing. Mostly sunny, light winds.
Habitat: mostly deciduous forest, lots of fallen trees. River habitat (Winooski river runs along portion of walking trail).

Many species of birds utilize specialized aspects of evolution and ecology to survive the cold winter months. The Black-capped Chickadee, a species I observed, is much tougher than meets the eye in terms of surviving the winter. Chickadees (and titmice- another species I observed today) utilize facultative hypothermia to actively down-regulate their body temperature. Essentially, their body intentionally enters a hypothermic state during the coldest hours of the night to minimize heat and energy loss. The Northern Cardinal, which usually has a slender shape, can puff up its feathers to look like a fuzzy red ball in order to retain body heat. Chickadees may also puff up their feathers to prevent heat loss, making them look much fatter than they actually are.

The water-bird species I observed also demonstrate some unique physiological mechanisms to help keep them warm in the winter. The Canada Goose deals with winter the same way humans do- they put on extra layers, by growing an extra set of insulating downy feathers in colder months. Ring-billed Gulls, and other wading birds, benefit from a countercurrent exchange of venous and arterial blood in their feet. This mechanism allows their bodies to keep warm blood circulating near vital organs, while allowing the extremities to cool down in order to prevent heat loss from the bird’s core. American Crows gather by the thousands during winter nights to form communal roosts where they sleep. In their communal roosts, crows can share information with each other about food locations, and they have a greater chance of surviving a predator attack and warning each other of danger in the night.

Many birds in the winter adapt a different foraging strategy, and often rely on different food sources. For example, the Black-capped Chickadee spends the majority of its daylight hours seeking fatty food sources, since fat makes for a great insulator and energy source. More than 10% of a chickadee’s winter body weight may be made of fat! Foods that may normally be consumed by a songbird, like insects or worms, are scarce in the winter, so many birds will switch to eating more seeds, winter fruits, and nuts. Canada Goose and Mallards are much larger than songbirds like chickadees and titmice, and therefore they have larger fat reserves. In spring and summer, geese concentrate their foraging on grasses and sedges, but switch to eating more berries and seeds in the fall and winter.

DATE: March 24, 2019
TIME: 1:00 PM
WEATHER: Sunny, mostly clear blue sky. 6 °C. Winds: S 9 mph.
LOCATION: Casavant Natural Area, Winooski, VT

Birds are constantly communicating with one another through calls, songs, bright flashes of plumage, or even drumming on a tree. By far the most abundant bird I encountered today was the American Robin. These robins were being very vocal, and I noticed them mostly on the ground of the forest, probably looking for food, judging by their calls and movements. There was a decent sized group of them, about 6-8 individuals, and they were almost constantly calling to one another, as if to say, “I found some food over here!” Now that it is officially Spring, robins are gearing up for their breeding season. Their mating song is very melodic, and sounds very different from the foraging calls I heard today. They have a number of other distinct vocalizations too, each serving a different purpose (ex: alarm calls, defense calls, etc.). Robins (along with many other species of songbirds) have a fine-tuned lexicon of vocal communication.
There was one particular robin that I was able to observe on for a minute or so. This robin was hopping around on the forest floor, probably looking for insects or some fallen berries/seeds. Considering that I went on my bird walk around 1 PM, I wasn’t surprised to see this robin, and the group that it was part of, foraging. The ground is cold and frozen in the morning and at night this time of year, but the sun is at its peak in the early afternoon, and therefore the ground is as thawed out as it is going to get at this time. This would be the optimal time to forage in the dirt. It’s also possible that this was a male robin, perhaps gathering materials to bring to his mate to build a nest, though it may be a bit early in the year for this behavior, and I did not notice any mating songs.
Communication between robins also involves visual cues. Robins are fiercely territorial over their nesting sites, mates, and resources. Male robins use their red breasts to settle territorial disputes, especially during the breeding season. Dominant, older males typically have a larger area of red on their breast, which sends a visual “back off” signal to other younger males. Robins weren’t the only “red” birds I observed today. I caught a quick glimpse of a male Northern Cardinal- but a glimpse is all you need to identify these birds. The males are bright red, all over, save for a black patch around their bill. The red plumage of a cardinal serves a different purpose than the red breast of a robin. Unlike the robin, male and female cardinals are very easy to tell apart. Cardinals exhibit a classic case of sexual dimorphism- while the male is a vibrant, flamboyant red, the female has a mute brown/orange body, with touches of red at the tips of her wings and tail. The bright red plumage of the male cardinal indicates to the female that he would be a mate worthy of choosing- the pigmentation and intensity of his plumage reflects his ability to find food that is rich in proteins and carotenoids. Both the robin and the cardinal display stunning red plumage, but for entirely different reasons.