Saturday was the first of May, a day traditionally given over to the celebration of labor activism and, as I learned from the great sage Robert Anton Wilson, al fresco coital activities. But for New York birders, it’s also a key date when you size up the spring migration so far, and the spring migration still to come.

Spring migration so far: Kind of cruddy, until April 30. On that day, a sudden push of warm air from the southwest was followed by a sudden push of really appealing field reports from around the city.

By the next day, many of them had moved on (and a few, like the reported Cerulean Warbler I chased to Prospect Park, were suspected to be illusory.) But there was still lots to see.

Up until this trip, my New York warblers for the year had been Yellow-rumped, Orange-crowned, Palm, and Pine. All lovely birds, to be sure, but not the species that make a spring. Up until now, winter had a hold, however tremulous, on the avifauna of Prospect Park. (The foliage was another matter altogether.)

But no more. Gone the Shovelers, Ruddy Ducks, and most of the White-throated Sparrows – gone, we hope, to fruitful breeding seasons on abundant home ranges to the north.

I spotted a Northern Waterthrush along the edge of the lake almost immediately. Crossing the path to the foot of Lookout Hill got me my first of season Common Yellowthroat. Not exactly mind-blowing, but a promising start.

Chimney Swifts arced through the air high above the hill, emitting their vaguely disconcerting chittering cries (I love these birds, but they do sort of sound like they belong in a zombie-themed video game.) Black-and-White Warblers circled the trunks of trees while Northern Parulas and Yellow-rumps picked at the leaves. At the top of the hill, I ran into a large birding group, and an even larger group of birds – more Parulas and Yellow-rumps, Blue-gray Gnatcatcher, Black-throated Green Warbler, and of course some of our year-round birds like Red-bellied Woodpecker and Mourning Dove. Coming down the other side added Gray Catbird and Baltimore Oriole to the list of incoming migrants, along with more Parulas, Black-and-White Warblers, and Waterthrushes.

Even at the time, though, something was odd. Though I heard a handful of Black-throated Blue warblers, I saw none – and I didn’t find so much as a hint of a Redstart (though others reported them from the park the same day.) No Ovenbirds, either.

But hey, the season is young.