get ready for fall migration
By Peter Alden
By late summer, birds all over North America have cared for and fledged one or even two broods of youngsters. Our habitats in late summer and autumn are often somewhat quieter as males see no reason to defend territories any longer once their babies are fledged. On the plus side there are two or three times as many individuals around or passing through compared to springtime.
Bird Identification in Autumn
Many adult birds that have a distinct non-breeding plumage in autumn have a ”basic” plumage that can be a challenge for new birders. Adult males will now resemble females and the young of both sexes often resemble their mothers. Note that their shapes, sizes, beaks, legs, behavior, actions and habitats are fairly constant.
After breeding and caring for youngsters, adults generally molt and gradually grow new crisp feathers to face either migration or the upcoming colder months if remaining locally. They do this at the peak of late summer when there is food availability in insects, nectar and fruit. Woodland birds which are no longer singing can be hard to see as they may fly poorly, are exhausted from all the parenting, and see no need to call attention to themselves.
Most sandpipers and plovers breed in the arctic tundra. Adults often abandon their chicks after a few days and fly southeast to the mudflats of New England arriving here from mid-July to early September. Their young remain up north for a month or more snapping at mosquitoes and awaiting new feathers. They fly the same route as their parents and arrive on our shores from late August into October. Color is useless in identification with them. It is size, shape, calls, proportions, actions, bill shape, leg length and habitats that key them out.
Do consider a pelagic trip on a whale-watching cruise, party fishing boat or your own boat on a calm day. Late summer/early fall is the best time to see gannets, shearwaters, storm-petrels, jaegers, some gulls and swimming sandpipers called phalaropes. A calm day later in the fall may yield Razorbills, Atlantic Puffins and murres as well.
Waterfowl go through a dull “eclipse” plumage and may be flightless for a few weeks. Herons and other wading birds may have young offspring that look distinct from adult plumage but they are the same size, shape as adults. A highlight on our coastal marshes and heathlands are vast flocks of Tree Swallows in August and September that feed on salt-marsh mosquitoes and ripening bayberries.
In September and October, many birders check the weather maps and head to mountain tops and coastal sites to view and count the many hawks, eagles, falcons and vultures heading south. In our upcoming Fall Birding in New England course we will highlight where to go when there will likely be a river of raptors in the sky.
Birds will be moving south throughout New England in broad fronts whenever there are still nights or tailwinds. No bird wishes to expend hard-earned energy flying into a headwind or weighted down by rain. Most of our insectivorous songbirds migrate southbound at night from late August into early October. Later fall migrants are mostly diurnal migrants.
A special feature of New England are the strong cool winds from the northwest that come through a half dozen times or so each autumn. Most of these birds are planning to fly southwesterly to the southeastern states before crossing the Gulf of Mexico or Caribbean to winter in Latin American tropics. The night fliers are blown off course and many wake up at dawn over the Atlantic Ocean. This forces them to fly into the wind to reach the nearest island, cape or shore to hide out, feed a little and rest before continuing.
October is when many of our sparrows and other seed-eating birds arrive from points north after the first frosty night that kills most insects. Some of our overwintering birds such as juncos and White-throated Sparrows come down from the mountains at this time.
A number of scarce migrants from the western U.S. stray east or get caught in the northwesterly winds and end up here. Due to all the fires out west we wonder if there will be more or less of these vagrants in 2021.