Field Journal #3 ... A Sunday In Derway

Date --- 3/7/2021
Start Time --- 11:15 AM
End Time --- 12:30 PM
Location --- Derway Island Nature Trail off North Ave, Burlington, VT 05408
Weather --- (Temperature) =25 degrees Fahrenheit, or ~ -4 degrees Celsius ... (Wind) = 10mph N ... (Precipitation) = none
Habitats --- Area of land along Winooski River bank ... river covered by ice. Lots of ice and some snow on trails, surrounded by leafless trees and branch/twig litter on the ground. Some trees cut down were seen shredded into sawdust material.

Video observation of White-breasted Nuthatch can be viewed in notes of individual bird's observation (link attached)

We're already a week into March, but winter is here to stay for just a bit longer in Burlington. Upon venturing down to Derway Island bordering the Winooski River, the paths meant for safe travels were transformed into zones of slow and ultra-tiny steps thanks to the thick layers of ice. After getting past the hazardous portion of the walkways, we proceeded toward the river, right up near the edge to look for animal prints and scat; wind was strongest over in this area, whereas deeper into the island, wind remained minimal to nonexistent. A scan of the water bodies (Lake Champlain and Winooski River) with binoculars revealed no nearby water or shore birds. Coyote, racoon, and skunk tracks were found in various areas along the river. Deeper into the island's trails, where the snow and ice were not so treacherous, two Northern Cardinal (M+F) were spotted in southward flight. Three Black-capped Chickadees were seen in scattered trees, shivering and bopping from branch to branch. A singular Tufted Titmouse was observed curiously scoping a branch or two before flying off towards the northwest. After hearing light pecking on a tree, we saw a White-breasted Nuthatch facing downward on a tree, chirping and pecking frequently. The bird seemed to have found tiny insects within the bark of the tree to sustain himself.

These birds, like any animal when outside during winter, are exposed to the winds and surrounding temperature of the harshly cold season in the northeast. However, the warm blooded avian animals have evolved to maintain high internal temperatures while residing in this area of the United States. Like humans will do when feeling chilly, birds replicate this action to generate kinetic energy, transformed into body heat. We saw the Black-capped Chickadees doing this while resting (through the binoculars) on our adventure, where I assume they were taking a quick break from searching for nutritional value. According to (https://www.audubon.org/how-do-birds-cope-cold-winter), the opposing muscle contractions performed aid in retaining significant amounts of generated heat. The Tufted Titmouse we saw, who was relatively swift inspecting branch after branch, in what I suspect was foraging and relocating upon lack of success. When we heard the White-breasted Nuthatch tapping away at the tree, we quickly located it and witnessed it face-down clinging to a tree, about 20 feet above the ground. We took the video we linked in the observation comments, then slowly approached the base of the tree. The bird didn't seem to be phased by us whatsoever, as we craned our necks upward to admire its beauty. After a series of pecks, the bird would crane his neck away from the tree to ingest the insects just captured by its bill. The specific tree it was hanging on seemed to be full of what the bird was looking for, as it communicated yonder through minute calls. At the beginning of the linked video, one can hear a faint White-breasted nuthatch murmur from afar.

Birds that stay put during the winter months might alter their diet by favoring more "insulating" foods during this period of time. For example. the passerines we saw on this excursion were probably searching for nutritious items that allow them to retain heat. I know berries are often present and littered along the ground in Derway from plucking them off branches, but we did not see any today. Nor did we see any seeds, which would also be a hot commodity during this time. When insects return from their state of dormancy once warmer weather approaches, the passerines will look to nibble on them for nutrients.

Lots of snags were observed, and many had deep cavities created by various types of woodpeckers. While all were too high to even poke with a branch, I imagine an animal, whether it be a family of birds or chipmunks or squirrels, reside in these open spaces that provide shelter. According to Coombs, Bowman and Garroway (2010), southward-facing cavities are exposed to more light in the northern hemisphere, which in nature make these shelters warmer than their northward-facing counterparts. As a result, I'd expect that the tree cavities of Derway Island would have more residents in the southward-facing than northward-facing cavities.

Citations

Coombs, A., Bowman, J., & Garroway, C. (2010, November 1). Thermal properties of tree cavities during winter in a northern hardwood forest. Retrieved March 07, 2021, from https://bioone.org/journals/Journal-of-Wildlife-Management/volume-74/issue-8/2009-560/Thermal-Properties-of-Tree-Cavities-During-Winter-in-a-Northern/10.2193/2009-560.short

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