Initially, birders rejoiced at the rare New York City sighting of a common merganser, an elegant-looking duck with a regal auburn crest, in Central Park.

But as photos of the duck spread quickly on social media, so did concern: a piece of discarded plastic appeared jammed in the duck’s distinctive narrow bill, preventing it from feeding.

“It showed behavior indicative of it not being well, of it being starved,” said David Barrett, a Manhattan birder who has been monitoring the duck. On Thursday, he posted some of the first photos of it.

New York City’s Parks Department became so concerned for the duck that it began putting together a rescue plan.