Diario de jessharkness2

DATE: April 21, 2019
TIME: 2:20 PM
LOCATION: Casavant Natural Area, Winooski, VT
WEATHER: Warm. 21°C. Light winds SSW at 12 mph. Mostly sunny (UV: 6/10).
HABITAT: Deciduous forest with a river running through it. Dense canopy. Very flooded on this date.
Spring is a productive time of year for birds. The weather is warming up again, food is becoming more abundant, and for many species, it is time to find a mate. For bird species that are returning from their spring migration, the males typically arrive before the females. The male Red-winged Blackbird needs to do a lot of preparation before the females show up. The quality of the territory that he is able to defend from other males is the main incentive for a female to choose him as her mate. I heard a male blackbird perform its signature “conk-la-ree!” song, coming from a patch of trees on the edge of a pond. He uses this song to invite females to come over and evaluate the territory he has been defending for their return. He may also have been using this song for territorial reasons. Many of the songs and calls that can be heard this time of year are based in mate attraction. For the Song Sparrow and the Black-capped Chickadee, both the males and females vocalize songs in a call and response fashion, giving each other clues about their locations. The male is also giving the female clues about his fitness through his song. If she likes what she hears, she may fly over and choose him as a mate. A similar arrangement is practiced by woodpeckers, with both the male and female utilizing their species-specific drumming pattern to attract each other.
Once a bird has found its mate, a decision must be made concerning their nest. The female American Robin will most likely decide to construct her nest in the lower half of a tree, typically hidden just below a layer of leaves. Any robins looking to nest in the Casavant Natural Area may have to wait a bit longer until the deciduous forest sprouts its leaves once again. A robin requires dead grass, twigs, and mud to make a sturdy nest. The Hairy Woodpecker will excavate and build its nest in a snag, and if this cavity becomes abandoned by the woodpecker, a chickadee might take it over for its own nest. There are lots of snags that can be found throughout the natural area, especially as one travels deeper into the forest and further away from the riverbank. The woodpecker doesn’t require many materials to build its nest once it has successfully created a cavity. The cavity is typically bare except for a bed of woodchips at the bottom. The Red-winged Blackbird will ideally build its nest in marsh vegetation or shrubs. An ideal spot in the natural area would be along the banks of the Winooski river, or on the edges of neighboring ponds. Females will typically choose to construct the nest near the ground in dense, grass-like vegetation. She will construct the nest by winding stringy plant material around upright stems, and weaving in wet vegetation. She will also add wet leaves, wood, and mud inside of the nest, and line the nest with a final layer of dry grasses. The robin, woodpecker, and blackbird have all fine-tuned their methods for nesting. Each method has its pros and cons: for example, the woodpecker nest will be difficult for aerial predators to see from above, but the eggs still face predation risks by tree-climbing predators such as the grey squirrel. Different species of birds have varying preferences and have to actively choose between ecological trade-offs when it comes to deciding where to place their nests.

Date: April 6th, 2019
Time: 2:30 PM
Weather: 7 °C, cloudy. Winds: SW, 5 mph.
Location: Casavant Natural Area, Winooski, VT
Habitat: Deciduous forest along a river. Grassy, sandy areas along river edge. Dense forest cover.
Some bird species may migrate south in the winter, chasing quality food and habitat that they can no longer find in their breeding grounds during the colder and darker months of the year. Other species can tough it out and stay in place by utilizing specialized behavioral and physiological adaptations. For example, one of the species that I observed today, the Hairy Woodpecker, is a persistent year-round resident bird species in Vermont. Woodpeckers are expert climbers, with strong feet and claws that allow it to cling to tree trunks, positioning itself so that it can be shielded from the winter winds. The Hairy Woodpecker is a widespread generalist, able to survive in a wide variety of habitats with an assortment of foods. This helps them remain in place all year, because they do not rely on one seasonal food source. They can adapt to changes in food and habitat availability, so long as they can find dead trees for excavating. Hairy Woodpeckers can re-decorate their habitat by drumming holes into trees, which they use for nesting and for shelter. Other year-round residents, such as the Black-capped Chickadee and White-breasted Nuthatch, will also utilize the holes that woodpeckers create for shelter and warmth in the winter months. Black-capped Chickadees are also able to stay warm by the physiological process of facultative hypothermia, in which their body temperature is actively down-regulated to a specific level to reduce heat loss and save energy to help them survive the cold.
One species that may be somewhat less abundant in Burlington these days is the Canada Goose. Geese that breed in the High Arctic fly south throughout the United States for the winter, but they are returning to their breeding grounds far north in Canada and Alaska around this time of year. However, in recent years, as lawns have proliferated, these grassland-adapted geese may stay put in urban and suburban areas year-round. There are multiple triggers for a bird’s migration to and from its breeding grounds. The most prominent factors influencing migration are resource availability (food, nesting locations) and changes in day length. The Canada Goose is migrating northward this time of year to take advantage of budding plants and an abundance of nesting locations in the far north. It’s also possible that there is a genetic drive for migration in some bird species, described as “migratory restlessness.” This is a type of impatient, anxious locomotor activity observed just before the onset of a migration, indicative of an urge to migrate.

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.

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.

I began my bird walk in Winooski on February 17th, 2019, around 3:30 PM. It was a bright, sunny, and very cold (-7 °C) afternoon with light winds. At the entry of the Casavant Natural Area, I saw a group of Canada Geese and Mallards flocked on the frozen Winooski River, some bathing in the frigid water while others stayed on the ice. As I continued my walk along the river, a small flock of American Crows flew overhead. Their flight style was a mix of smooth wingbeats and occasional, short gliding. They seemed like they were capable of flying for a while, easily traveling into and out of my field of view without touching down. Shortly after, a small songbird that I was unable to identify flew a short distance between trees. This bird had an undulating flight style, dipping and rising before landing on a branch and taking off again, flapping its wings in a a blur. Although I'm not certain what species of bird this was, I can say for sure it wasn't a sparrow or a wren, since they typically fly in a straight and level path. On the other hand, it may have been a woodpecker or a finch, who utilize a "bouncing" flight style.

There are many differences between a small songbird and a crow- it is improbable to visually mistake one for the other. I would not really need to examine their flight styles to tell them apart. However, if I were trying to tell the difference between a crow and a raven in flight, I would need to pay special attention to variations in flight style. For example, the crow has a fan shaped tail in flight, while the raven has a more round looking tail- this would a key identifier for telling the two apart. Ravens also flap less than crows do, and tend to soar/glide for longer periods of time. Flight styles can be very revealing identifiers between two visually similar species.

Small songbirds and crows occupy different environmental niches, which can be somewhat interpreted from their flight styles. Crows are scavengers, eating pretty much anything they come upon. A songbird's diet usually consists of seeds, fruits, and/or insects. Their diet doesn't typically require them to look for food from above, whether it be mice, roadkill, or garbage scraps- they can hop from tree to tree, and usually find what they're looking for. Perhaps differences in diet have contributed to the drastically different flight styles between a crow and the songbird I observed. While the crow scavenges for food from its vantage point above, the songbird flits through the forest and doesn't have to sustain flight for too long before it reaches the next tree over, where it is likely to find an insect or some berries.