Friday, October 19, 2012

"Fri-D" - Cormorants

 [Immature Great Cormorant, left, and adult Double-crested Cormorant, right, from the Cape May Point hawkwatch, October 13 2012. Compare proportions, especially wing thickness and length, neck and head thickness. Click to enlarge photos.]

Plumage and bill/chin color differences are distinctive between the two eastern cormorants if you can see them well enough, which is often a big if. Cormorants tend to appear as distant lines of birds, or perched way out on buoys or jetties.

On plumage, young Greats have white bellies and brown necks, while that pattern tends to be reversed on Double-crested, with the belly being dark and the upper breast and neck pale - but see the juvenile Double-crested pictured below for a measurre of "caution advised." Greats always show a white chin, which of course stands out on the breeding adult, and the yellow/orange on the bare parts is confined to the chin and does not extend out to the bill as it does on Double-crested.

When they're together, Great is obviously bigger. It weighs almost twice as much, and while it averages only 3 inches longer in total length, it is proportionately longer winged (63 inches to 52 inches), and the wings on Great are broader, too. They both fly with a crook in the neck, but Great has a thicker neck and heavier head.

[Juvenile Double-crested Cormorant, one of the whiter ones with a white belly like Great - but the neck and breast are white, too. October 13, 2012 at Cape May Point, NJ.]

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