Ecological Physiology

Date: Feb. 28, 2019
Time: 6:30-7:45 AM
Location: Forest behind Raven Ridge, Huntington, VT
Weather: Clear and sunny, around 12 degrees, no wind. 1.5 inches of fresh powder over old snowpack, about 9 inches deep.
Habitat: New growth softwood forest consisting of birches, maples, oaks, aspen, with a dense patch of mature hemlock. Backed by a steep rocky ridge with lots of staghorn sumac, close to a tiny stream and a nearby small neighborhood with cleared fields.

Early in the morning after a cold night with fresh snow, I noticed that many birds were not yet up and about. After an hour, I heard more activity than I did around 6:30am. This is likely due to the way that small birds conserve energy overnight by lowering their body temperature and metabolism. Once the sun comes up, ambient temperature begins to rise, making it easier for birds to move around with less energy expenditure going towards body heat.

I heard Black-capped Chickadees singing their territorial fee-bee songs once the air got warmer. I wonder if some of these individuals had just emerged from a nightly torpor. Up on the rocky ridge, I found several nooks and crannies in the ledge where I think some of them passed the night. In a few crevices, I found some scuff marks where the rock was worn, and a little plumulaceous feather along with a bit of defecation.

I was unable to visually observe any chickadees due to the dense hemlock canopy, but if I had seen them, I expect they would have been plump and puffed up against the cold instead of sleek and thin like they are in the summer. The Cornell Lab of Ornithology tells me their diet is mostly seeds and fruit in the winter, whereas in the summer their diet switches to 80% insects. With the songs coming from the Eastern Hemlock stand, I wonder if they were eating hemlock cones or picking hibernating bugs out from under the folds of bark. Chickadees only eat their food where they feel safe under cover, so they often carry their food to a hidden spot to eat it. When it's cold, it would benefit them to find a food source that also provides cover to minimize handling time and maximize profitability in terms of energy expenditure, so maybe that's why they were in the Eastern Hemlocks.

Over the course of my walk, I found 5 dead snags. 4 were about a foot in diameter, and varied in height from around 10-15 feet tall. These snags were deciduous, and had cavities the size of quarters or golf balls. I rapped on the trunks and pressed my ear against them, but heard and saw nothing. The last snag I saw was from a massive White Pine that was likely a pasture tree at one point (there is barbed wire in the area). The trunk was about three feet in diameter, with lots of short stumps of branches still attached. The trunk broke off about 12 feet up, and I don't know if it was hollow or solid inside. I didn't find any cavities in this one, maybe because the wood was much harder and not yet very decomposed.

Snags are very important for Black-capped Chickadees because their cavities provide insulated spaces for the tiny birds to spend the night. Without them, chickadees would likely freeze during the winter. Tree cavities are also important for chickadees in the summer, because they build their nests and raise their young inside them. Tree cavities provide year-round protection from predators and the elements for Black-capped Chickadees.

Posted on March 8, 2019 04:39 PM by zoey_november