Birds on the Move: Spring Migration

Near Farrell Park in Burlington Vermont, a path winds from soccer field, along farm fields, and through the woods. A detour off the trail to the right after crossing the bridge, leads to the UVM ropes course where I spent some time exploring. It was a very chilly morning with a fresh coating of April snow on the ground at about 11:00 am. I saw the regular year-round residents because they are the easiest for me to identify after a winter of listening to them regularly. These birds included American Crows, Blue Jays, a Black-capped Chickadee, a Brown Creeper, and a Tufted Titmouse.

These birds don’t need to leave this area in the cold months because food does not limit them. They have adapted to stay here where it is is uncrowded and forage for the remaining foods, thus their diet is not as specific and limited as those that left for the winter. Crows and jays are known to forage for a wide range of foods and are generalists which help in surviving the winter. In urban areas like here, they are able to find foods near people’s homes and substantial amounts of roadkill. Other birds that stay will eat remaining nuts and seeds larva of insects particularly in tree-bark and rotted wood.

Staying warm and conserving energy is essential for overwintering here so these birds will add on extra weight in down feathers that will insulate them. Additionally, birds such as the Black-capped Chickadee will overnight in tree cavities for warmth and insulation. These birds might excavate their own cavities or use a preexisting one.

While I have not seen this bird since December, I have heard rumor that the much sought Snowy Owls in Burlington have begun to migrate back north. This year they had an interruption and came down this south because they had a large population in the Arctic so they are in VT seeking food. Now that the temperatures are beginning to rise I speculate that they would be able to return to the Arctic for a better food supply. Unlike other birds, surviving the harsh cold temperature is not a driving force for these birds. While daylight might assist in reminding this bird to return north, ultimate factors of food abundance and weather are what will drive these birds back north.

An obligate species that has a regular and strict migration cycle that would primarily be driven by daylight, might arrive at this time in April and struggle with the lingering winter weather, snow, and cold temperatures. These species may have a difficult few weeks back in VT until the temperatures are consistently above freezing and the insects come out.

Because I found no migratory birds that don’t live year-round in north-western Vermont, I choose to look at the breeding ground of the Red-wingged Blackbird. These bird’s year-round habitat ends around Lake Chaplain so it is not unreasonable that they are here. I calculated the distance they might have traveled from central NY which is about 250-300 miles. Of course, they could migrate from anywhere in the US where they are year round residents but it seems unlikely they would go so far to Vermont. I have recently been seeing and hearing the Red-wingged Blackbird in centennial woods and along roadsides where their are open marshy areas.

Posted on 09 de abril de 2018, 02:44 AM by jnorris2