I was down at Air Force Beach in Comox, British Columbia doing some birding this past weekend and was amazed at the amount of red seaweed washed up on the beach – in places it was at least thigh deep and was so thick that it was holding the incoming tide back from flooding the beach. Hundreds of gulls worked the seaweed eating small invertebrates and Scathophaga intermedia flies which were busy on the seaweed as well. It was a windy day at Air Force Beach and these flies were constantly flying into my face and gathered in the lee of my body and my backpack. Many rested in the safety of the driftwood above the high tide line and out of reach of the hungry gulls. Note the similarity in the appearance of this fly with Scathophaga stercoraria which I photographed on seaweed we put on on our backyard garden.
Because the gulls were focused on feeding (and avoiding the occasional dog off leash) I was able to sit in the driftwood and observe and photograph a number of different species of gulls in this large mixed flock at close range. Three were particularly interesting as they all sort of look alike – medium sized and black wing tips – and it was good to have the chance to take a look at them and sort out the field marks that help to identify them.
There were several Ring-billed Gulls (Larus delawarensis) in this flock and they were relatively easy to pick out. The key features used to identify this gull are black wing-tips, the black ring around the bill, yellow legs, and a yellow eye.
A number of California Gulls (Larus californicus) were also in attendance. These gulls also have yellow/greenish/gray legs and black wing-tips, but their eyes are darker and they have a black and red spot on their bills.
Rounding out this trio were a few Thayer’s Gulls (Larus thayeri). At first glance they seem very similar to the California Gulls, but a close look at the legs and bill are generally enough to separate them. Of these three, Thayer’s are the only gulls have “bubble-gum pink” legs and a single red spot on the bill (third winter birds may have a ring-like dark mark on the bill but the leg colour is useful to rule out Ring-billed Gull. The pink is often quite bright and stands out even in a flock of other pinkish legged gulls.
Three very similar looking gulls at first glance but pretty easy to separate using leg colour and bill markings. Keep an eye out for them on winter beaches on Vancouver Island!