For years, warm weather in the East Village has been heralded by an influx of young, tattooed visitors carrying backpacks and bedrolls and wearing clothes so stiffened with grit that they have come to be known in the neighborhood as crusties.

Their arrival in Tompkins Square Park has become a predictable harbinger of spring, a surviving custom in a neighborhood that has undergone various upheavals and changes over the past several decades.

But this year, they have not materialized. People have reported stray sightings of one or two visitors, but nothing like what the neighborhood has come to expect. No one knows if they are simply late this year or if, for some reason, they will not come at all. Either way, their absence has been conspicuous.

“It’s like the birds aren’t migrating this year; the salmon aren’t swimming upstream,” said Chris Flash, an East Village resident who runs a local bike courier service and an underground newspaper called The Shadow. “The whole ecology of the neighborhood is out of whack.”