Identifying waterbirds in winter

STILL IDENTIFIABLE: A Mallard, a Common Loon, and a Red-necked Grebe, all sleeping in the posture characteristic of their families. (Illustrations not to scale.) Art by David Sibley

For birders, winter is a time for standing on frozen shorelines and struggling to identify distant waterbirds. That means focusing on bill shape, head shape, body proportions, and behavior, among other things. It’s understandable that you would be discouraged when you come across a bird that’s sleeping because all of those features will be partly or completely hidden. On the bright side, a sleeping waterbird reveals other useful field marks and in some cases is easier to identify than a bird that is awake.

Even though part of the head is hidden on a sleeping bird, what you can see is still useful. A bird that is awake is constantly moving — preening, stretching, alert, relaxed, courting, sparring, diving, etc. The head shape changes as feathers are raised and lowered with the bird’s mood and activity. A sleeping bird is just asleep. Its head shape stays the same.

Distinguishing Greater and Lesser Scaup, or Barrow’s and Common Goldeneyes, can be easier when they are sleeping, simply because their head shape is more consistent and reliable then. On a broader level, sleeping postures can help to distinguish the different families of waterbirds.

The posture of a sleeping duck is familiar to everyone. Ducks turn their head 180 degrees, tuck their bill into the feathers of their back, and rest there. When birds sleep on the water, they go for maximum buoyancy and tend to float high in the water with their tail raised. This change is especially noticeable in diving ducks, like scoters or mergansers. When they are active, these species ride low in the water with their tails flat on the surface. If you’re used to seeing them like that, it can be confusing to see their high rounded backs and raised tails when they are sleeping.

Loons, like ducks, tuck their bill into the back feathers to sleep, but even when they sleep, they have a very low profile with the head resting flat on their shoulders.

Grebes have a unique sleeping posture. Unlike other birds, they do not turn around. They simply lay their neck down onto their back and tuck their bill in alongside the neck. This creates an entirely different silhouette than ducks or loons and instantly identifies the bird as a grebe.

Cormorants simply never sleep while swimming.

Identifying distant waterbirds is hard, but don’t ignore the sleeping birds. They might reveal clues that you won’t see when they’re awake.

This article was first published in the November December 2019 issue of BirdWatching magazine. Subscribe now.

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David Sibley

David Sibley

David Sibley writes the column “ID Toolkit” in every issue of BirdWatching. He published the Sibley Guide to Birds in 2000, the Sibley Guide to Bird Life and Behavior in 2001, and Sibley’s Birding Basics in 2002. He is also the author of the Sibley Guide to Trees (2009), the Sibley Guide to Birds-Second Edition (2014), and guides to birds of eastern and western North America (2016). He is the recipient of the American Birding Association’s Roger Tory Peterson Award for lifetime achievement in promoting the cause of birding and a recognition award from the National Wildlife Refuge System for his support of bird conservation.

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