Baird's sandpiper
Baird's sandpipers migrate through the middle of North America to and from the Arctic and South America. They are rare on the eastern seaboard, although a few juveniles are usually seen in late August and early September on their way south. Note the very long wings, bright feather edging on the back and buffy streaking on the breast. Photo by E. Vernon Laux

Late summer magic

By E. Vernon Laux - August 23, 2007

Things are getting very interesting in the great outdoors. Just past the mid-point of August, everything is changing dramatically in the bird world. The nesting season is over, and all birds, both adults and young of the year, are engaged in prolific feeding, growing new feathers and preparing for the upcoming winter. Sunrise and sunset are even more spectacular at this time of year as the sun seems to dwindle on and below the horizon creating spectacular lighting and colors.

For those species that engage in migration, the changes are most intense. Since this encompasses a majority of birds that one is likely to encounter, whether in one's yard or at the beach, migrants are already here, preparing to depart, or are passing through, as you read this. The flocks of gulls and terns at favored spots along the shoreline, the dense flocks of sandpipers and plovers on tidal flats or the flock of mixed species in local woodlands are all engaged in a critical phase of their lives, in migration or preparing to go.

While summer has a few weeks left on the calendar, as far as birds are concerned, it is autumn. The length of day is rapidly shrinking and sunsets are noticeably earlier. Migration is underway. On nights with northwest winds, land birds are moving and each dawn brings a new cast of characters to woods and fields.

It is an exciting and most pleasant time of year to be afield. Each day brings new opportunity and possibilities. The tidal flats are at their most productive right now and a slew of birds are utilizing these important feeding and resting areas.

All about terns

The Vineyard is particularly good for tern species in late August. Flocks of these social and highly gregarious birds move to Island waters after the breeding season, from nesting colonies in Nantucket Sound and Buzzard's Bay. Flocks primarily consist of mostly common terns but there are also roseate terns mixed in, often in substantial numbers and lots of other species to check for that will be encountered, sometimes frequently. Several black terns have been seen; a couple have been around since late July at Eel Pond in Edgartown. The most productive time of year for rare and unusual species is during the upcoming few weeks.

Species that have occurred sporadically at this season, some much rarer than others, include; Caspian tern, royal tern, Sandwich tern, gull-billed tern, Forster's tern, black tern, Sabine's gull, jaegers resting on the beach, and almost anything one can find in a North American field guide. Should a hurricane come close, then the ante is upped, so to speak, and all manner of tropical seabirds have a chance of appearing. Hurricanes are exciting for the ornithologists but bad for the birds and human inhabitants.

Least terns that nest on outer beaches in several spots on the Vineyard are still around in numbers. These smallest of terns, the Island's most common nesting species, breed in colonies and appear to have had a successful season. After fledging young in mid to late July, they begin to head south. They are present until around this time in August and then thin out very quickly, so that by early September they are virtually gone. Now you see them, then you don't. They just sort of drop off the radar screen each fall and won't be back until next May.

Cuckoos and caterpillars

There have been several reports of cuckoos this past week. Not the ones driving cars, bikes, or mopeds, but the birds, of which there are two species found on the Island. Black-billed and yellow-billed cuckoos are both here and often one species will outnumber the other, in any given year. They are unique amongst birds found in this part of the world, as they are the only birds that eat hairy caterpillars. In fact, they specialize in eating them.

The caterpillars that are colorful and hairy have various spines and poisons that make them unpalatable, to say the least, to most birds. Cuckoos, which eat these caterpillars and also behave differently than other birds by remaining motionless in trees and moving slowly in foliage, have developed a remarkable way to deal with all these gastronomic nightmares. While eating one of these caterpillars would cause most birds all kinds of discomfort and could even prove fatal, that is far from the case for cuckoos.

They can eat these virtually inedible, highly defended caterpillars because they are able to grow new stomach linings. That's right; they periodically slough off their stomach lining and cough it up with a new one in place. Planned wear and tear, all part of eating noxious caterpillars, has somehow enabled cuckoos to evolve this incredible ability. A species of penguin, the chinstrap penguin, also does this in response to toxic levels of iodine and other minerals in its primary food, krill. Amazing hardly seems an apt description to this evolutionary biological solution for dealing with toxic food.

Until next week - keep your eyes to the sky.

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