Western Grebes are almost exclusively fish-eaters but yesterday morning at Bear River MBR I photographed one consuming a crayfish (a crustacean).
1/1000, f/7.1 ISO 640, Canon 7D, Canon EF500mm f/4L IS II USM +1.4 tc, not baited, set up or called in
I’ve been photographing Western Grebes for almost eight years now and this is the first one I’ve ever seen eating anything other than a fish (though I have seen them consuming feathers which are a dietary aid for them rather than a food item).
1/800, f/7.1 ISO 640, Canon 7D, Canon EF500mm f/4L IS II USM +1.4 tc, not baited, set up or called in
It maneuvered the crayfish so it went down “tail”-first, probably to accommodate the awkward angle and large size of the chelipeds or claws (most prey items that are swallowed whole are swallowed head-first). The bird struggled a little to get it down but not much.
After seeing this feeding episode I wondered just how unusual this food item was so I did a little research. The Birds of North America Online (Cornell) has this to say about the diet of Western Grebes: “Fish reported to compose 81% to virtually 100% of diet.” Because of their fish-laden diet pellet casting in Western Grebes is unusual. It’s thought that when it does occur it probably does so with individual birds who have been eating invertebrates with chitinous exoskeletons (like crayfish).
I’ve photographed a variety of other species casting pellets and from my research I now know the behavior that immediately precedes pellet casting in Western Grebes (several drinking movements) so I’ve got to admit that I’ll now be looking for the very long-shot opportunity to photograph one of these birds casting a pellet. After all, I once photographed a Western Kingbird casting a pellet and at the time BNA said that they had “no information” on that behavior with the species.