Last week we talked about Black Skimmers, one of the southern waterbird species that seem to be on the rise in Massachusetts, as evidenced by an all-time high count recently recorded on the Vineyard. But there’s a second bird of more southerly affinities that has been quietly on the increase in these parts – the Yellow-crowned Night-Heron.
You may know the more common Black-crowned Night-Heron, which has always been one of our regular breeding herons in Massachusetts. The squawk of a Black-crowned flying in the fading light of dusk, or the sight of their hunched forms along a herring run, are familiar ornithological experiences on the Cape and Islands. But their yellow-crowned southern cousin has always been more of a bird-of-mystery.
This species doesn’t breed regularly north of Connecticut, and very few nests have been found here in Massachusetts. While skimmers tend to hang out in the open on sandy beaches, night-herons are skulking and nocturnal, making them more difficult to find and count. And because we are at the extreme northern edge of their range, they tend to nest as single pairs rather than in noisy colonies like our other herons and egrets, making breeding records tough to pin down.
Most wading birds - we’re talking heron and egrets here - will eat anything they can catch, including of course fish, but also mammals and even other birds. In Florida, I’ve watched Great Egrets snatching tired migrant warblers off the ground, and a Great Blue Heron choking down a foot-long rodent called a Round-tailed Muskrat. And Black-crowned Night-Herons are famous around here for getting into the tern colonies at night and chowing down on the chicks.
But the Yellow-crowned is a dietary specialist – all crabs, all the time. Fiddler crabs, green crabs, blue crabs, and, importantly, a mysterious nocturnal crab known as the square-backed marsh crab. This obscure and previously uncommon crab spends its nights grazing on marsh grass, and their apparent population boom in recent years is thought to be a cause of significant and worrisome salt marsh loss in Wellfleet and other places. I’ve found parts of these crabs in pellets coughed up by Yellow-crowned Night-Herons roosting at Wellfleet Bay sanctuary. If they are in fact becoming a regular part of our breeding avifauna, maybe they can help bring populations of this marsh-devouring crab back down to earth.
In a hopeful sign on this front, a Mass Audubon heron watch program at Hemenway Landing in Eastham recently tallied an impressive 22 Yellow-crowned Night-Herons, along with 43 Black-crowneds, flying out of the roost at dusk to feed in Nauset Marsh. This represents an all-time high count for Massachusetts, where ornithological records go back more than 150 years. Because of their skulky habits, it’s not clear how many of these birds represent local breeders versus post-breeding dispersers from other states, but either way, this crab-crunching wader is getting more common around here.
So if you notice a night-heron flying over at dusk, or hanging out along a creek bank, check for the lankier legs, longer neck, and slimmer proportions of a Yellow-crowned Night-Heron. Frankly, I’m not sure how they maintain that trim physique with those dietary habits – I was always told to avoid eating crabs after 8pm. Or was that “carbs”?
