Field Journal 5: Migration

Date: April 4, 2020
Start: 9:00
End: 10:30
Location: Aiken Center to the golf course and back
Weather: 34 degrees F, mostly cloudy, 7mph N winds
Habitat: buildings, patches of trees, fields, small wetlands

Some year-round resident species that we observed were Black-capped Chickadees, Northern Cardinals, and Blue Jays. They don't migrate because it is more beneficial for them to remain here. The benefits are that they save energy, they're able to keep their territory, and have more time to care for their young. These birds have many adaptations to survive in the same range year-round. One is that they can change their food preferences for the winter. For instance, the Black-capped Chickadee eats seeds, berries, and plant matter in the winter since the insects or spiders are not available in the winter. When spring comes around and the ground has thawed, their diet starts changing toward eating insects. Another adaptation that Chickadees perform during winter is communal roosting, which is when several birds crowd into cavities overnight so they can share body heat. Lastly, Chickadees tend to flock with their own species as well as with nuthatches, woodpeckers, and more. This creates a better chance of them finding food especially important in the winter when it's scarce.

A facultative migrant that we observed was Cooper's Hawk. They are a short to medium-distance migrant so the birds we saw today were likely from the lower states of New England or maybe down near Virginia. They may go toward Canada as their some of their breeding grounds are up there and there may be better resources for them however, Vermont is also a breeding ground so they may stay here. The environment allows the birds to gage when to leave their wintering area and travel up north. The growth of new plants, availability of food, increasing day length, and temperature increase all affect the timing of migration. For Cooper's Hawk, the migration of small birds that they eat likely triggers their migration. Other facultative migrants we saw were the Canada Goose, Red-winged Blackbird, Song sparrow, and American Robin. Sadly we did not observe any obligate migrants. An advantage of arriving in Burlington in early April as an obligate migrant would be that they get to scout out the best breeding grounds, territorial areas, and nesting sites before several more species make their way up. A disadvantage may be shortage of food due to the sometimes extended cold weather that occurs in Burlington.

Song Sparrows are both a year-round species as well as a medium distance migrant. The map that I examined showed that the closest nonbreeding ground to Burlington is in North Carolina. If the Song Sparrows we saw in Burlington came from North Carolina, they would have traveled about 796 miles in order to get here. However, it is more likely that they came from a year-round location a little closer to Vermont like lower Pennsylvania which would equate to about 500 miles total. Song Sparrows are also known to have a leapfrog migration, meaning the birds farthest North, in Canada and Alaska, fly to Southern United States and northern Mexico to winter while the birds in northern US might migrate but don't go as far as the Canadian and Alaskan birds. The rest of the calculations for the species observed are listed below, they are based off of non-breeding sites, from the "All About Birds" map, that are closest to Burlington. The species listed as zero are year-round residents, however, their mileage may be more than this as some move a bit further south in the winter.

(measurements in miles)
White-breasted Nuthatch: 0
Hairy Woodpecker: 0
American Crow: 0
American Goldfinch: 880
Dark-eyed Junco: 200
Black-capped Chickadee: 0
Blue Jay: 0
House Sparrow: 0
Rock Pigeon: 0
European Starling: 0
Mourning Dove: 2,400
Raven: 0
Ring-billed Gull: 200
American Robin: 1,400
Mallard: 850 miles
Red-winged Blackbird: 800
Canada Goose: 1,200
Song Sparrow: 500

Total: 8,430 miles

Julkaistu huhtikuu 4, 2021 08:03 IP. käyttäjältä avilensky