Adult Males in Breeding Plumage
Eric writes: Adult male Red-breasted and Common Mergansers have very distinct patterns thus they are quite easy to identify even at large distances. At close range, Red-breasted Mergansers appear grayish overall with a dark head, white neck patch, and reddish breast. Their wings have large white patches that include most of the secondaries and greater and lesser coverts. Common Mergansers have similarly dark heads but have an overall white-bodied look as opposed to the gray-bodied look of Red-breasted. Commons also have similar white wing patches but they are larger with more contrast then Red-breasted. Even at a distance these patterns are easily noticed.
|P2. Breeding plumaged male Red-breasted Merganser-Notice the overall gray-bodied look, dark green head, reddish breast and white wing patches.|
|P4. Breeding plumaged male Common Mergansers-notice the overall white-bodied look, distinct and contrasting dark head, and large white wing patches. Commons also have whiter underwings which lead to a more white overall appearance.|
Females and Non-breeding Males
I'll treat females and non-breeding males (including first year birds) the same, as the only major difference between the two is the amount of white in the wing. The adult males have white median and lesser coverts while the females and first year birds only have white secondaries and greater coverts.
From a distance, it is important to pay attention to overall patterns as well as shape. Red-breasted Mergansers appear mostly gray with a brownish head and white wing patches (amount of white in wing patches dependent on sex). Commons have a much colder appearance; overall they are white and pale gray with very similar white wing patches to Red-breasted.
|P1. Nonbreeding plumaged male Red-breasted Mergansers. Notice the overall grayish-brown appearance, low contrast between head and neck, and slightly upturned bills (doesn't always appear this way).|
|P6. Female Common Mergansers. Notice the overall cold gray/white appearance, high contrast between the head and neck, thick/straight neck, and the straight appearance to the bill.|
|P5. Female Common Merganser-notice the thick, straight necked appearance|
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