I had a break on Florida’s Sanibel Island from our Michigan snow, sleet, and polar cold early this April . It was over 80 degrees every day, sunny and warm, so I wandered along the Gulf Coast beach in utter bliss with my toes in the waves.
All day long Brown Pelicans flew close to the shore, suddenly turning as if on a hinge to dive bomb schools of fish, sieving them up in their bills and throwing their heads back to swallow. There was a little pod of three pelicans accompanied by a small seagull, which flew over after every dive to join them.
I wondered, somewhat sentimentally, if this was a bird/bird friendship, like the companionship of cats with parrots and goats with baby hippos you sometime see on YouTube? I asked a fisherman what was going on, and he explained that the pelican’s explosive dive stuns schools of fish, leaving plenty to bob confusedly about for the gull to feed on.
Gulls are well-known scavengers – there were crowds of them circling and screaming around fishing boats returning to harbor, riding low with the day’s catch. The fishermen don’t get anything out of this gull companionship; neither, apparently, do the pelicans.
I have a handy-dandy Birder’s Handbook, which includes quirky informational essays. When I got home I consulted it, to learn that the pelican/gull relationship is not bird/bird friendliness but “commensal feeding.” A “follower bird” associates with a “beater species” which “stirs up the waters” like the pelican or flushes hidden food advantageously.
Birds don’t just follow other birds: the Cattle Egrets I saw along Florida highways follow tractors as well as cows, gleaning the stirred furrows; the tractors don’t seem to get anything from the relationship.
Birds of different species sometimes flock together for mutual protection, to “increase the number of eyes and ears available to detect predators and [confuse] them as many individuals flee at once.” Great Egrets hang around White Ibises not only for fish that the deep-delving Ibises stir up, but also, being taller, they detect and warn of approaching danger. Downy woodpeckers feed with Titmice and Chickadees to “use them as sentinels,” while Blue Jays alert my whole back yard until (including its squirrels) they are all yelling together about a menacing hawk.
Which explains a curious intermingling of species on the Sanibel Island beach: a flock of Sanderlings, tiny sandpipers scuttling in and out of the surf to probe for mollusks, crustaceans, and horseshoe crab eggs, will have a Plover with them; or a Willet that signals danger with a fluting warble will hang out with a group of Ruddy Turnstones.
Another strange thing on those beaches is how tame the shore birds are, standing around totally unperturbed by human approach. One day while I was swimming a Snowy Egret trotted from the tideline to my towel and seemed to be waiting there for me. My father, a professed pagan and ocean-lover, told us before he died that he might come back to see us some day as a big white bird, so, thinking it was him, I pulled my grandson from his swim to introduce them to each other.
Silly me: the next day I saw the Egret, with his big yellow feet and his wispy feathers blowing in the wind, sitting by another towel to await commensal feeding.