Journal archives for February 2019

February 21, 2019

2/14 Lone Rock Point

I observed a pair of Common Ravens flying to and from a roost site on a cliff in the vicinity of Lone Rock Point at dusk. I was lying literally two feet above them on the top of the cliff when they flushed from their perch, so I was able to observe their flight from a position directly level with them. When flushed, they took off using long, gliding wingbeats and banked around the edge of the cliff and out of site. ~20 minutes later, when they returned to the roost site, their flight was steady and level, with even and relatively rapid wingbeats that made a strong swooshing sound as they passed in front of me. Ravens' wings are broad and quite long, close in size to those of an accipiter, and they are able to use them for both gliding and flying (unlike crows, which generally do not soar). The individuals I observed clearly demonstrated the functionality of their wing morphology for multiple flight styles, both of which relate to their ecological niche - long, steady flight allows ravens to efficiently cover large areas in search of food, while agile maneuvering combined with intermittent soaring are used to defend territory, display to mates, and make use of hard-to-access nest sites.

Although I didn't see any other birds in flight during this walk, I did spend ~10 minutes listening to the behavior of a small chickadee flock in a mature coniferous stand as the sun was nearing the western horizon. The constantly shifting contact calls of these birds in the upper branches of white pine and hemlock suggested what I already knew about chickadee wing morphology and flight behavior. Chickadees are highly active and inquisitive feeders. Their wings are graceful, but shaped for bounding flight from point-to-point rather than the long, steady, occasionally gliding flight of the Common Raven. As such, they are shorter and more arced relative to the bird's body. When I got particularly close, I could actually hear the small sound of their wings beating. It is not hard to imagine the behavior that would produce this sound. The chickadees were hopping and flitting between branches, sometimes using their wings as airbrakes to briefly hover as they approached and then dangled from the tips of pine and hemlock cones. Observing chickadee behavior this winter, I've become quite familiar with the sound of chickadees foraging in this manner, and find that it is distinctive, even if contact calls or territorial "chick-a-dee" calls are absent. No other bird that I know of dangles from the underside of hemlock branches to feed from the cones - a distinctive behavior and habitat niche enabled by the chickadee's particular flight pattern.

It is altogether not too surprising that I didn't find many birds on this walk. I was out in the hour before dusk, a time for birds in winter to be finding shelter/sleeping sites and to be consuming energetic foods, if available. The exposed edge of Lake Champlain is a relatively barren and harsh site for birds in winter, especially compared with the feeders of suburban Burlington or the fruit trees of downtown. Early morning would be a better time to find birds in this area. Also, an approach through the Episcopal Diocese trails, which pass through a much wider variety of habitats and are generally more sheltered, would probably yield more sightings.

Posted on February 21, 2019 03:27 by sam_blair sam_blair | 3 observations | 0 comments | Leave a comment

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