Diario de jessharkness2

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: 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.