Field Journal 2

Field Journal 2
02/26/20

Time: 7:00am to 8:30am
Date: 02/26/2020
Clouds: 100% cloud cover
Wind: Slight breeze from the southwest
Temperature: 33 degrees
Precipitation: Lightly snowing and raining
Location: The woods near the Intervale community farms

As I walked the wooded trail running along the Winooski River, I saw four Common Mergansers swimming in the river where open water bordered water covered by ice. They were facing upstream without diving or moving much. Two females eventually climbed onto the ice and preened their breast feathers. The river provided an open space where birds were visible as they flew from one bank to the other, and I saw many indiscernible birds and one Canada Goose fly over the open expanse.

Watching the river flow under the ice, I wondered about the challenges faced by aquatic birds that overwinter in Vermont. As the Mergansers stood on the ice and paddled in the water, I imagined the countercurrent exchange taking place in their legs and feet. Possibly even the complete shunting of blood flow at the ankles to minimize heat lost through these large apteria. I also imagined the uropygial gland was hard at work as the female Mergansers preened, providing oils and waxes necessary to keep their feathers waterproof and airtight to maximize insulation. The Mergansers also behaved with energy-conservation in mind- they were paddling just enough to keep their place in the current, and those that left the water did not expend energy by traveling very far.

Further along the trail, approximately 5 Nuthatches were visible in the upper branches of trees. Two woodpeckers were pecking at a branch without bark, (They seemed too large to be Downy Woodpeckers, so I counted them as Hairy Woodpeckers). They were sharing the small branch peacefully, and in light of class discussion about personal space, I am guessing they were a pair due to the lack of territoriality over the branch resource. Three White-breasted Nuthatches and three Pileated Woodpeckers were further down the trail, still near the river. Pileated woodpeckers were all pecking in live trees high in the canopy, occasionally calling loudly. Five Blue Jays flew across the river and landed together in the top of a tree. One American Crow was perched in a tree, and two Black-Capped Chickadees and two Cardinals (male and female) were flushed out of the undergrowth when a ski-trail groomer drove by.

As I stood shivering in the light rain that had begun to fall, I wished I had downy plumage to puff up when temperatures drop below the thermoneutral zone. Overwintering birds such as Chickadees can shiver to produce more heat, and they can increase the insulative power of their feathers by puffing them out. They can also cover their legs with their feathers and tuck their bills under their wings as they perch or sleep to reduce loss from these apteria. Some birds will also build up fat reserves for the wintertime, which can provide extra energy necessary for shivering. Rather than expend lots of additional energy to keep themselves warm, some birds will decrease their body temperatures overnight in a controlled hypothermia or for a few weeks in a torpor. This is only beneficial in birds with extreme energy demands, however, due to high costs associated with a slow wake-up from these states.

I passed many snags as I walked, some with large holes and piles of shavings on the ground below (see picture). I stationed myself beside one snag with many holes. After a few minutes of no activity, I gently knocked on the trunk, but with no results. On a neighboring tree, however, a Black-capped Chickadee was pecking at the end of a dead branch (see picture). It appeared to be feeding on something- maybe some freshly exposed insect larvae or a fruiting fungus?

Snags hold valuable roles in forest ecosystems, among which are their services to overwintering birds. Birds may seek out holes in snags for shelter from the harsh weather, and some cavities may hold a large huddle of birds seeking increased insulation. Snags may also offer prime perching branches, seeing as they are spacious and clear of obstructive leaves. In addition to protection, snags offer good feeding grounds: many that I passed on my walk were riddled with fresh woodpecker holes that evidenced the bountiful insects and larvae residing inside the softer wood of snags. Cavities may also be used for food caches, which some species make to supplement their foraging over the winter. Black-capped Chickadees are known to store thousands of seeds and bits of animal fat from carcasses in multiple caches during harsh seasons.

Walking back along the trail, Back-capped Chickadee calls alerted me to a mixed-species flock. They flew descended from the trees after I pshhed, and I got a close-up view of one Brown Creeper, one Downy Woodpecker, three Tufted Titmice, five White-breasted Nuthatches, and seven Black-capped Chickadees! Mixed-species flocks such as this are one strategy adapted by birds to better survive the winter. Members of a flock benefit from increased eyes that can better both spot food-rich resources and predators, which increases the proportion of the time flock members can spend foraging. Niche-partitioning within a mixed-species flock reduces competition between its constituents. Bird species differ in the type/part of trees in which they forage, as well as the type of prey they seek, minimizing competition for scarce food resources.

After leaving the forest, I saw more birds along the roads. One Black-capped Chickadee, one Tufted Titmouse, three Eastern Phoebes, one American Crow, One gull, one White-breasted Nuthatch, and four Blue Jays were all in high branches along suburban roads.

Publicado el febrero 29, 2020 01:04 MAÑANA por gmsaveson