Scaup Comparison

Before this weekend I had only seen Greater Scaup four times and two of those were identified by birding experts in San Diego.  Obviously I haven't had much experience with this species in the field.  On the other hand, I've seen Lesser Scaup many times in Arizona where they are much more common than their slightly larger look-a-likes.  The identification challenge presented by these two species warrants extra pages in field guides and their own chapter in advanced field guides.

Last week, Cornell's big day birding team found a Greater Scaup at a wastewater treatment plant on the southern edge of my county.  On Sunday I took my chances and waited until the evening when the sun would be at my back.  The identification would be tough enough through binoculars even in ideal lighting.

I arrived at the Amado Wastewater Treatment Plant and found two scaup roaming around.  I was glad they didn't have their heads tucked away taking a nap!  I studied the closer of the two in my binoculars and noticed the peak at the back and top of the head, most likely a lesser.  I found the other scaup moving closer and immediately noticed a difference in the posture of the two birds.  The first bird held it's head higher than the second bird whose more relaxed posture made the head look more round.  A birder with a scope joined me and I had great scope views of both birds.  At one point they came close enough to get this decent comparison photo.

female Greater and Lesser Scaup

They don't always pose this nicely!  The more rounded head and larger bill make the bird on the left a greater, very rare for Pima County.  With the help of the scope and the cooperation of the birds, this identification challenge was much easier than it could have been.  Hopefully this will help me identify future scaup, but I won't count on it.