Nests

At lunchtime, I went for a walk at Baylands Nature Preserve along the Bay in Palo Alto. One of the first things I saw was a baby American Avocet, still with downy plumage, sweeping the water for small invertebrates. American Avocets are a precocial species, so this little baby was pretty much on its own; there were no adult birds nearby.

A little further on I saw a line of Cliff Swallow nests on a building. The swallows pick up some mud in their bills, then fly up and apply it to the nest, gradually building the structure out so as to completely enclose the nesting birds except for small entry holes. The two nests closest to the camera are darker around the entry holes; that’s where mud has been recently applied, and the damp mud is darker than the dried mud.

I kept walking out the dike along Charleston Slough, past other birds that are I guessed were nesting, though I didn’t actually see a nest or babies: Forster’s Terns, Marsh Wrens, a Northern Harrier, Snowy Egrets, Mallards. About a mile and a quarter from the parking lot, I could finally see the California Gull nesting colony. The gulls were screaming and flying in swirling circles above the colony, and as I got closer I could see why: two researchers had kayaked out to the colony, and were walking around with clipboards checking out the nests. The gulls were divebombing them, and through my binoculars, I could see that the researchers were wearing helmets and jackets for protection.

I watched for a while; I like watching gull nesting colonies, and the addition of the invading researchers made it even more entertaining. Then it was time to head back to work, so I walked back to the parking lot, my mind completely emptied of everything except for birds, sun, mud, and nests.

Summer

At lunch time, I drove down to the marshes at Baylands Nature Preserve. A baby American Avocet stood at the edge of the water swishing its tiny beak back and forth to gather insects and other invertebrates from the water, just like the adult avocets a few yards away. Out in deeper water, a Mallard hen watched carefully over two baby Mallards swimming on either side of her. I couldn’t help noticing the difference in the way the two species raise their young: the American Avocet is a precocial species whose young are on their own from hatching, while the Mallard is an altricial species whose adults care for their babies for some time. It seemed that everywhere I looked I saw birds nesting or getting ready to nest: Cliff Swallows building their nests of clay on the side of a building, Forster’s Terns apparently nesting on a tiny island in the middle of the marsh, Marsh Wrens warbling madly in the rushes.

I looked across the bay at the green hills of the East Bay. Except some of the lower hills at the far end of the Dumbarton Bridge don’t look all that green any more. It’s been warm for the past few days, and it looks like the rains are finally over and gone, and now some of the low hills are turning summer-brown. The higher hills and mountains are still brilliant green, but it won’t be long before they turn brown, too.

Baby birds and hills turning brown: these two markers in time are as good as any to mark the end of the winter-wet season, and the beginning of the summer-dry season.

Silly Rynchops niger

In one of the few breaks in the rain this week, I managed to take a walk along the old salt ponds at the edge of San Francisco Bay in Palo Alto, now the Baylands nature preserve. It was low tide, so there were birds everywhere: shorebirds, gulls, diving ducks and dabbling ducks, egrets, grebes, geese, a White-Tailed Kite out hunting. And sitting among some California Gulls were half a dozen Black Skimmers (Rynchops niger), standing on the mud flats, all facing in the same northwesterly direction. Black Skimmers make me smile; they are such silly-looking birds, with their ridiculously large orange-and-black bills with the lower mandible sticking way out past the upper mandible, and black-and-white plumage on their heads that makes them look as though they’re wearing a baseball cap pushed to the back of their heads, and gawky red-orange legs.

But they’re not ridiculous at all. Their bill may look silly to me, but it is a precisely engineered product of natural selection and evolution, allowing the birds to skim fish from the surface of the water as they fly along. No doubt their plumage also has an evolutionary function; their legs only look a little gawky because these are birds that are meant for precision flying, not for walking around on dry ground. Black Skimmers are not silly at all, they are amazingly successful organisms: “This skimmer has undergone a remarkable range expansion north from Mexico into California since 8 Sept. 1962, when the first bird was found at the mouth of the Santa Ana River…” Arnold Small, California Birds: Their Range and Distribution, 1994.