[All photographs copyright, Gary Nunn 2015] – The potential diversity of storm-petrels to be found in San Diego County waters is a bit dizzying so this small boldly white-rumped individual certainly grabbed our attention on a pelagic trip here on 14 June 2015. Just when the bird looked like it was going to make a close pass by our boat the Grande, nope, it would turn away again flying some distance ahead! Watching it from the bow however the views were very good, and, with a long lens, the photographs documentation worthy.
We could see the extensive white rump that wrapped underneath the tail and the dangly legs looked very long indeed as it pitter-pattered frequently along the water surface with its feet. No real sign of a notched tail, quite fan like in appearance really, and the bird seemed to be in active molt of secondaries and inner primaries, with a molt gap in the right wing. This was indeed what we had hoped for, a very rare migrant to San Diego County waters Wilson’s Storm-Petrel Oceanites oceanicus all the way from the southern hemisphere.
We carefully eliminated one other species from consideration, the Townsend’s Storm-Petrel Oceanodroma (leucorhoa) socorroensis (currently considered a form of Leach’s Storm-Petrel by the AOU) from nearby Guadalupe Island, Mexico, but this species has a smaller tail with minimal white wrapping underneath, and lacks the characteristic extreme leg length which causes the feet to project clearly past the end of the tail as in Wilson’s Storm-Petrel. Close examination of the many photographs taken show the trailing feet poking out beyond the tail, super long legs, extensive white rump which wraps under the tail, and the active wing molt typical of Wilson’s Storm-Petrel at this date in the northern hemisphere.