Migrant and Year-round Resident Species
April 7, 2020 at 3:30 PM, Stratton Brook State Park, Simsbury, Connecticut, habitat was forested, with deciduous and evergreen trees. Pond and stream going through forest, tree density is high. The ground had no snow, some mud, but mostly dry ground. The weather was sunny and 63 degrees, with no wind speed in the center of the forest.
On my bird walk, I observed various residential and migrant species. However, for many species, such as the American Robin and the American Crow, it is up to the individual whether they migrate south for the winter or whether they stay put. According to Cornell, when some individuals migrate and others do not, it's called "partial migration", or "facultative." There are adaptations that these birds have that allows them to winter in cold places such as Connecticut. For example, they can live off of berries and seeds, and do not fully rely on eating insects to survive. It is impossible for me to know whether the American Crow and the American Robins that I saw migrated or not, but they are now here for the breeding season.
On the other hand, there are some species that definitely do migrate from Connecticut to the South for the winter. These include the Great Blue Heron and the Mallard. These two species have probably just recently come from the southern United States, such as Florida, Louisiana, etc. Since these birds spend a lot of their lives in water and they depend on water for feeding, they have no choice to migrate south in the winter when all of the water in the North freezes. The warmer weather here in Connecticut has definitely facilitated the arrival of these species because the ponds, lakes, and rivers are not frozen so they can reside there and catch the food they need to survive.
Obligate migrants face a tough choice, deciding whether to migrate early or wait a little until later. An earlier migration means that they would get “first pick” for the territory that they will reside it, which means they would get the area with the most food. However, if they decide to migrate early, they could run into an unexpected snowstorm or other inclimate weather that they are not adapted to survive in. This would mean they would have to fly a couple hundred miles south or not survive this type of inclimate weather. These challenges can make it very difficult for obligate migrants to time when they are going to migrate back to the North.
It is crazy to think about how far these birds fly when they are migrating! A straight line from Simsbury, Connecticut to Southern Florida, say Miami, Florida is about 1,400 miles. That means every year, these birds, such as the Great Blue Heron and the Mallard travel about 2,800 miles.
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