Horseshoe crabs aren’t edible. In fact, I’m sure they probably taste absolutely disgusting, at least to us. Their eggs, however, are a favorite snack for seabirds up and down the Atlantic coast. On the mid-Atlantic coast, hundreds of thousands of migrating red knots, ruddy turnstones, sandpipers, and plovers spend weeks gorging themselves en route to the Arctic from South America. Here on Cape Cod, the birds also show up to feast while the crabs are spawning. The birds seem to mostly eat whatever eggs get washed out of the nests and rise to the surface, where they collect in the valleys of the patterns left by the waves.

You can hear the birds before you see them. From the other side of the marsh, you can only see clustered silhouettes, but their calls carry quite well. The most abundant birds lately have been willets and laughing gulls. Willets are unassuming brown birds with long beaks, as long as they’re standing around. When they take flight, they have black and white wing bars that flash as they flap around. It’s startling, which I suppose is the point. Their call is a high, warbly “will willet” that is rather incessant and can even sound a bit panicked, especially if they get disturbed by, oh, say, a scientist sloshing nearby. Much like a song can transport you back to a certain time, place, or event, the sound of willets is inseparable from the feeling of spending summer in a salt marsh — the grasses in thick strips of variegated greens, the odiferous mud between my toes, and the way the heat rises off the mudflat so that distant houses float mirage-like on the horizon.

My other constant companions at the edge of the marsh are the visually striking laughing gulls. Their bodies are mostly white, their heads are black with white around the eyes, and their wings fade from light gray to black when they are adults and in breeding plumage. Immature laughing gulls are mostly brown. Their name comes from their call, which does indeed sound like laughter, although I find the sound a bit unnerving. Sometimes it seems like nervous laughter, like when someone tells a joke that makes you feel really uncomfortable. Other times it sounds rather manic. Occasionally I think it sounds like the “hoo hoo ha ha” of someone trying to imitate a monkey.

The other day an immature laughing gull decided to follow me, hovering 10 feet above my head. It flew one way, then the other, then back, its oscillations centered directly above me. Perhaps it was trying to exact revenge because I was interfering with its eating, and was getting a lock on a target so its droppings would hit me. That one sounded manic.

Besides these species, there are usually quite a few others lining the water’s edge trying to get in on the spawning smorgasbord. The ever-present herring gulls bossily harass the laughing gulls. A few black-backed gulls stand around, pecking here and there. They don’t seem to have as much of an attitude as the herring gulls, probably because they are the largest gulls around and don’t need to be annoying. Herring gulls are sort of the prototypical “seagull,” with gray wings, white body, and yellow beak. They’re the gulls that will approach you at a clam shack expecting you to share with them. Black-backed gulls are larger, have black wings, and seem to have better things to do. Both have the typical seaside-soundtrack “seagull” call, often mixed in with clanging buoys, blowing foghorns, and crashing waves on relaxation tapes or coastal soft rock stations. Truthfully, I don’t really find gull calls as relaxing as I’m sure the people who make those tapes hope.