Here is a quick comparative analysis between two female ducks that are notoriously tricky to differentiate between, the greater scaup, first picture, and the lesser scaup, second picture. At first glance, it is easy to see why they can be easily confused. A closer examination makes it a bit easier. Without the benefit of a side by side in person perspective, where the greater scaup is clearly much larger, you must look primarily at the shape and profile of the head. Greater scaup have a more rounded crown whereas the lesser scaup have a small peak or bump toward the back of the crown. This bump is much more prominent when the bird is calm and relaxed, as they flatten it while actively diving and before takeoff. The bill of the greater scaup is larger and more flattened. The degree of white at the base of the bill varies within the two species but in the birds here at Pinola Conservancy, the greater scaup females have a much greater degree of white than the lesser scaup. Beyond the head, there is much individualized variability between females and the levels of white on their backs and flanks can vary greatly. We have many examples of this here. When wings are outstretched, you can see further differences, mainly the white stripe on the upper wing of the greater scaup being larger and running down into the primaries, where the white stripe of the lesser scaup does not reach the primaries. One really helpful hint, at least for the birds pictured here, is the antenna on the back of this lesser scaup female. She was part of an important research project gauging the physiological effects of internal transmitters on nesting female lesser scaup. I’m happy to say that this female has had no issues nesting routinely!