Pelicans have mobbed the North Basin, cormorants followed, and now it was the turn of the grebes. More than 50 of them clustered together at high tide in midday, far out from the eastern edge of the park and probably nearer the Berkeley mainland than to the park. They mostly looked like Clark’s but from this distance it was impossible to tell for sure. A pair of clearly Western Grebes trolled the waters far away from this flock.
I did not notice these birds the day before. They may have been even farther toward the eastern shore of the North Basin and escaped my eyes. They may have been the same flock I saw at the end of August. Or they may have flown in by night. They are said to be among the bird species that migrate preferentially by night. How they manage that remains one of the great scientific topics of investigation. It’s possible that birds can actually “see” the earth’s magnetic field.
Unlike the pelicans and the cormorants, who were clearly feeding, these grebes looked like they were resting, and a few of them had their heads tucked back into their wings, asleep. I checked the online sources to see whether these grebes could dive as effectively as cormorants, but came up blank. There’s a mountain of discussion about these birds’ taxonomy — their differences and similarities to the Western Grebe — but not that much detail about their foraging prowess. It’s probably fair to say that little fish, crustaceans, and other marine proteins should consider leaving the area or going deep into the mud when these bearers of long, sharp beaks patrol the surface.