The Migration South

Aug 28, 2019

 

Credit Don McCullough / bit.ly/2Zu02Hj

In the midst of this fall weather preview, it feels more natural to be talking about southbound bird migration. While the migration is sometimes subtle, with local birds like Orchard Orioles, Yellow Warblers, and Purple Martins quietly slipping away in the dark of night, shorebird migration is more obvious. 

And among the thousands of sandpipers and plovers of the common and expected species, there will always be those interesting and uncommon species who, like a person with an expensive new haircut, are waiting for you to notice them.

 


Representing the rogue individuals who choose to flout migratory convention and blaze their own trails, these vagrants and waifs are what get a lot of us birders out of bed in the morning. This week, one such bird was an American Avocet, a big, spectacular outlier of a shorebird. First found on North Monomoy Island, it was later seen by many at the substantially more accessible Forest Beach in Chatham.

Avocet apparently comes from the Italian “avosetta”, meaning “graceful bird”. Somewhere between a sandpiper and an egret in size and stature, American Avocets are mostly white with black wings when we see them, though breeding birds have a head and neck the color of rusty mustard. They have a strange and seemingly indecisive breeding distribution, occurring in ephemeral wetlands in the otherwise arid American west, and in large numbers around the Great Salt Lake of Utah and San Francisco Bay. 

They winter in wetlands both fresh and salt in the southwest and Mexico. Long, lean, and indeed graceful, they sport the only really obviously upturned bill among the shorebirds, looking as if it was produced by a door slammed in the birds face. The odd angle of the bill allows them to efficiently skim feed for small invertebrates on mud flats, an obscure behavior known as “scything”, after the old-school way of harvesting hay. With only about 20 contemporary records for the Cape and Islands, it’s worth putting up with a little end of summer traffic when they turn up.

Another uncommon western visitor was discovered in the seldom birded dunes north of High Head in Truro when a Lark Sparrow dropped in on the over-sand trail. Bigger and more boldly patterned than our typical sparrows, Lark Sparrows hail from western grasslands. They don’t turn up much at feeders, but are happy to hop around on lawns with other sparrows, so be sure to sort through those flocks of Chipping or Song Sparrows for an odd man out.

This week also brought an unusual pulse of migrating Cliff Swallows, the rarest of the breeding swallows in Massachusetts, and a species rarely encountered on the Cape and Islands. Birders noted four at Race Point in Provincetown, another in Brewster, and an impressive 7 at the west end of Nantucket. One was even seen from that beaked whale research vessel over 100 miles south of Nantucket.

Cliff Swallows breed very sparsely in Massachusetts, constructing colonies of completely enclosed mud nests under bridges or on barns. When scanning through flocks of our more common Barn and Tree Swallows, look for a dark swallow with a pale rump, a square tail, and a single “headlight” created by their pale forehead. The Cliff Swallow is the famed swallow of Capistrano, to which they have not returned in many years. They have declined precipitously here in Massachusetts as well, and no longer breed on the Cape. The demise of agriculture and competition with House Sparrows at nesting sites likely explain most of the decline.

In the coming weeks expect migration to intensify, especially following any cold fronts and their attendant northwest winds. What wacky winged visitors will drop in on our fields and flats, our thickets and dunes? Tune in here, as always, to find out.