A couple of nights ago we watched an interesting interaction on Salmon Creek Beach. A couple of young Bonaparte's Gulls (Chroicocephalus philadelphia) were following a flock of Sanderlings along the shoreline.
Although we never saw it actually happen, I'm pretty sure the Bonaparte's Gulls were waiting for the Sanderlings to come up with prey items so they could steal them — a form of kleptoparasitism.
As they usually do, the Sanderlings were feeding intensively along the swash zone. The Bonaparte's Gulls would sometimes run along with the Sanderlings (as above), other times they would fly in from another location and land in the middle of the Sanderling flock, and yet another strategy would be just to stand and watch the Sanderlings from slightly higher up the beach.
Bonaparte's Gulls are known to steal food from other species of birds. Has anyone else noticed them kleptoparasitizing Sanderlings before?
As one of the smallest gulls in North America, Bonaparte's Gulls can appear diminutive and "innocent," but watch for the little "bandits" in them!