Yesterday I took a long beach walk as a storm threatened, and witnessed a surprising sanderling (Calidris alba) and Heermann’s gull (Larus heermanni) interaction. This time of year I often see sanderlings, which are winter Monterey Bay visitors. They’re the busy little shorebirds running up and down the beach with each successive wave, probing the sand for invertebrates (crabs, worms, etc.). Heermann’s gulls, also visitors, are the easiest of the adult gull species to identify (for me) with their red bills, black legs, and dark bodies and wings. Sanderlings and gulls accompany most of my winter walks and so I don’t usually pay much attention to them.
At one point a group of sanderlings that I had been shadowing took flight as if spooked. I looked around for a jogger or a dog (none) or an overhead predator (none). I couldn’t figure out what had disturbed them — all I saw were sanderlings and gulls.
I stood there and waited. An immature gull took flight… and took off after a sanderling.
The small bird dodged and darted, and the young gull followed in pursuit till it lost the sanderling. It landed, then took off again, after another (or maybe the same) sanderling. During these chases, the other sanderlings continued feeding at the surf’s edge (although they appeared a bit wary). The gull continued several attempts until it actually caught a sanderling. But when it landed in the surf with the little bird, the frantically flapping sanderling managed to pull loose.
There were three Heermann’s gulls on the beach, two immature and one mature, and over a period of about 15 minutes, I watched as each chased the sanderlings in the same manner. The drama ended when a dog pursuing a ball ran down to the surf.
All of the birds scattered. (Some of our beaches allow leash-free dogs.)
I’ve read that gulls will harass other shorebirds to get the prey that the smaller birds are catching (a bit of thievery), but this looked like predation by the gulls on the sanderlings (although I didn’t see a kill).
This experience captivated and startled me. We all know about predator-prey interactions and that we’re all part of a vast food web. (I think about that every time I paddle my kayak out into the bay.) And yet, we’re seldom confronted by it as I was on this walk. Empathetically, I wanted to vilify the predator and cheer the escaping prey, even though I knew it was natural and necessary. I reacted emotionally to the dog as well: it interrupted my experience while saving the sanderlings (at least temporarily). When I thought about it, the dog (and its owner) were just enjoying a day on the beach, as I was.
This event is a microcosm of current events on this planet — living our lives changes how everything else lives. The gulls, sanderlings and dog woke me from a somnambulist morning walk, and reminded me that whether we’re aware or not, we’re all active participants in our planet’s future, for better or worse, or both.