For Marin’s shorebirds, autumn is already here

It still feels like summer to people, but for some birds, autumn is well advanced. This is particularly true of the shorebirds, the branch of the avian world whose fall migration first reaches Marin. A dozen species can already be seen on beaches and mudflats around the Bay Area, from sandpipers and yellowlegs to godwits and curlews — with more to come.

Seeking shorebirds offers many rewards: the sight of strange and extravagantly diverse creatures, dramatic swirling flocks of thousands of birds and a visceral sense of the changing seasons as the Earth makes its slow orbit around the sun and the great flocks of birds undertake their journeys across the continent.

What are shorebirds? The term refers to members of a few bird families, almost all of which regularly frequent shorelines of various kinds, the overlap of land and water where their general adaptations of long legs and bills routinely come in handy. Not all birds that associate with water are shorebirds. Herons, egrets, ducks, waterfowl, gulls and terns all fall outside of the shorebird designation.

While the shorebirds themselves are highly diverse, a few generally shared traits can be pointed out. As those long legs and bills suggest, these are birds of the shore — the shallow water and its neighboring beaches and mudflats — rather than swimming birds. Most are migratory, with most shorebirds leaving Marin in summer to breed either in the far north or in interior prairies and wetlands. And most flock in fall and winter, whether in loose assemblages of a handful of individuals to great swirling flocks containing thousands of birds.

Now is the season when those flocks arrive. While most winter songbirds, waterfowl and raptors don’t become abundant until October, shorebird numbers start picking up as early as late June, with many species becoming abundant in July and August. (A few species — stilts and avocets, snowy plovers and killdeers — do breed here in small numbers.) Visit wetlands near the bay such as Rush Creek Open Space Preserve, the Hamilton Wetlands, the Corte Madera Marsh or the Sonoma Baylands near Sears Point, the rocky shorelines of the San Rafael Bay Trail and Loch Lomond Marina, or coastal locations like Bolinas Lagoon, Limantour Beach and Abbotts Lagoon to experience our diverse array of shorebirds.

We are now entering the peak autumnal season for these birds, with a great many shorebirds passing through the Bay Area as they travel to wintering grounds farther south. A few species, notably the phalaropes — odd and unusual birds with brighter-colored females than males and an endearing habit of spinning in circles to stir up food — are seen only in migration and will be essentially gone from Marin after October. Most of our other shorebirds are present through the “winter,” understood in the broadest sense possible. The last spring migrants may trickle northward in May, while early southbound birds appear in July.

What birds are we talking about? Marin is home to more than 20 regularly occurring shorebirds, spread across four taxonomic families. The Recurvirostridae is represented by the black-necked stilt and American avocet, both elegant black and white birds with extravagantly long legs and bills (avocets are the only one of our shorebirds with a notably upturned bill).

The plover family, or Charadriidae, have four local representatives, all sharing a relatively portly form with shorter bills: killdeers, black-bellied plovers, semipalmated plovers and the threatened snowy plovers.

Our lone representative of the Haematopodidae family is the black oystercatcher, a strikingly black, chicken-sized shorebird with an intensely long and red bill that favors rocky shorelines.

The Scolopacidae, or sandpiper family, is the largest and most diverse, with around 20 different local representatives of hugely variable shape and size. On the small end of the spectrum are the tiny least and western sandpipers, miniscule scurrying birds that gather into majestic swirling flocks along with their slightly larger cousins the dunlins, and which are collectively known by the affectionate generality of “peeps.” Common mid-sized birds of this family include the greater yellowlegs and willet, both with long legs and long, straight bills. And on the largest end of the scale, marbled godwits, whimbrels, and the magnificently endowed long-billed curlew enrich Marin with their strange and striking forms.

Jack Gedney’s On the Wing runs every other Monday. He is a co-owner of Wild Birds Unlimited in Novato and author of “The Private Lives of Public Birds.” You can reach him at jack@natureinnovato.com.