Field Observation 4: Migration

I went out on a bird-walk on 4/6/18 from about 4:15pm to about 5:40pm in the Centennial Woods behind the UVM Rescue station. We walked from the hotel to the and stopped along the access road to walk about 30 yards into the woods in two spots before reaching the trail head and walking down the path. The snow started off as just a few flakes, and became an almost full white out until we entered the trail. From there, the trees filtered out most of the flakes. The trail was a nice mix of slushy mud covered in an inch of snow. We did not see any birds until we got further into the trail and the sounds of the road died away. Then we could make out a woodpecker drilling, and hear a Dark-eyed Junco trilling. We slid down the hill towards the stream and were able see some of what we were hearing. We saw some Black-capped chickadees that started on a low-hanging bush, and then flew up higher to an older hardwood when they were startled by us snapping branches as we walked. There were about four Black-capped Chickadees. In the hardwood that they flew up towards, we were able to spot the Hairy Woodpecker that had been tapping before. It was hopping around from branch to branch. From our vantage point, looking up the hill at the tree, it was not possible to get a clear picture. There always seemed to be a branch in the way or a phone died right when it was in position through binoculars. The only picture was of its wingtip as it moved behind the trunk. We could tell that it was a Hairy and not a Downy Woodpecker because its beak was a similar length to its head, whereas the beak of a Downy Woodpecker would have been shorter than the length of the head. The Black-capped Chickadees were also almost impossible to get a picture of. On the walk back along the access road, we spotted six American Robins foraging above a rainwater retention basin.
Not all American Robins migrate for winter. This may be due to the fact that they are chubby birds that are able to put on enough fat to survive the cold winter months. They are also omnivores, so it’s possible that they would be able to find food throughout the season, unlike some other birds that may eat only insects or only seeds. As for the Hairy Woodpecker, Vermont is not so far north that they would need to move south to survive. The population of Hairy Woodpeckers in Montreal or further north may have to migrate in order to survive. For the most part, the population in Burlington is able to stay year-round. Black-capped Chickadees are also common winter residents in Vermont. These three species are all omnivorous which may help them to find food throughout the winter. They would most likely change the specifics of what they each forage for depending on the time of year. When the temperature drops very low at night, it is highly likely that they all go into torpor to conserve energy.
An example of a facultative migrant would be the Great Blue Heron. Some choose to stay in Vermont for the winter, and some fly south for the winter. At this time of year, they would be preparing for migration, currently traveling or arriving at their final destinations. It all depends on the individuals and their goals. As mentioned in a previous journal, some may choose to raise their young in Florida, while others are surviving the winter in Vermont. To facilitate the arrival of a Great Blue Heron, the water in the area has to be open, meaning that the ice has to have cleared. Great Blue Herons need to be able to hunt in the shallows, and if there is still ice covering the water, they will be unable to hunt and unable to survive. If they were to be able to get to this area safely and to be able to hunt enough to provide for themselves, a Great Blue Heron would be at an advantage as it would be able to start building a nest for itself and to begin courting in preparation for mating. It would be able to pick a prime nesting location with access to water and hunting, while still being easy to protect from threats and weather. A disadvantage to arriving this early would be that there may still be a snap freeze, and the water would be closed off, not allowing the birds to hunt.

Publicado el 08 de abril de 2018 por esm398