Field Observation 2: Physiology

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.

Publicado el marzo 7, 2019 02:59 MAÑANA por jessharkness2