Field Journal #5: Migration

On Tuesday, April 15th, I watched my backyard for birds, focusing on the bird feeder and pond, mainly. The weather was mid-50s and it was very windy, with only small periods of the sun breaking through the clouds. I watched from around 10:30am-12:30pm, and saw a range of species. I saw the pair of Mallard ducks that visit our pond every year, three Wild Turkeys along the edge of the woods (2 toms and 1 hen, at separate occasions), seven American Crows, a pair of Downy Woodpeckers (that made several reappearances), two Mourning Doves, one Eastern Phoebe, and eight Black-Capped Chickadees, and lots and lots of red squirrels and chipmunks.

Following is my list of resident bird species which stay in VT during the winter (mostly… I think some crows do occasionally migrate).
Black-capped Chickadee: These tiny songbirds have a lot of adaptations that make them well-suited for surviving winter. They have thick feather coats to conserve heat, are known to hide food, roost in tree cavities, and are able to go into controlled hypothermia at night to save energy. They also are able to put on a lot of fat during their daily foraging that allows them to have that extra energy stored for nighttime.
Downy Woodpecker: These birds can be found nesting in small tree cavities that they’ve hollowed out, where they will shelter for warmth. They feed mainly on trees, digging deeper into the bark during the winter (this means that their food is still plenty available during winter). They can also be found eating suet in backyards, as they do in mine.
American Crow: Crows are not picky eaters, so it is easier for them to find food during winter than for many other birds. They can eat carrion, be found at trash piles, or scavenging in other areas. Their larger size also probably helps them retain body heat compared to smaller birds. They also tend to flock in larger numbers during the winter, which allows them the advantage of finding food easier.
These birds forego migration because it is a massive expense, and lots of birds would die during the long flight south. If they are able to survive during the winter, it makes more sense (is safer) to stay than to go. The physiological and behavioral adaptations talked about above all help these birds to survive in the winter.

A facultative migrant is a bird that can choose whether or not to migrate, while obligate migrants have to migrate. An example of a migrant that should be arriving in Vermont now would be an Eastern Phoebe. They are coming from as far as Mexico, and go as far north as the upper latitudes of Canada during the breeding season. Phoebes eat mostly insects, but also some small berries (and seeds from a bird feeder, if there is one around). As spring rolls around, there is more of their food available, and the insects will be plentiful by early summer. It also becomes warm enough for them to not freeze overnight. One advantage of their migration in early April would be that they get here before other birds, and maybe get the best pick of habitat/location, and can scope out the area to know where the best food is. A disadvantage of arriving so early is that they might have trouble finding food (insects), or it might be too cold for them (overnight freezes, late snowfalls), and they are not suited for this.

Since the range of wintering habitat for most species is so broad, it is hard to determine where exactly/how many miles were flown by each incoming migrant, so I used a mid-range location. After adding up Mallard, Eastern Phoebe, and Mourning Dove, I have about 3,000 miles flown.

Posted on April 15, 2020 04:59 PM by mnwaterman