Arizona Field Ornithologist

Wedge-rumped Storm-Petrel (Oceanodroma tethys), Amado WTP, Pima County

These Wedge-rumped Storm-Petrels were found by Laurens Halsey on 07 September 2016 and photographed by Laurens Halsey, Larry Pratt, Chris Rohrer, and Bill Lisowsky on the same date.

Hurricane Newton formed roughly 220 mi southwest of Manzanillo, Colima, Mexico on 4 Sep 2016 and reached Arizona on 7 Sep 2016, bringing with it several notable species, including three species new to Arizona and one even new to the ABA area! This storm officially reached hurricane strength winds late on 5 Sep 2016 and reached peak intensity with wind speeds of 90 mph shortly before making landfall at Cabo San Lucas, Baja California Sur. Newton moved north and weakened over the Baja California Peninsula. The eyewall fell apart before it made a second landfall, after crossing the Gulf of California, near Bahia Kino, Sonora where it weakened to tropical storm status. Early afternoon on 7 Sep it crossed into Arizona in a weakened state. Despite the weakened state of the storm it managed to bring 5 species of “tubenoses” to Arizona, typically associated with stronger storms. Clearly we have a lot to learn about how hurricanes affect birds in our area! To see a track of the storm see here and to see windspeeds see here. For more information on the last tropical storm to bring tubenoses to Arizona, Nora, see here.

Multiple Wedge-rumped Storm-Petrels (15+) were reported during and just after the hurricane. Four of which were found at this location. This is the first time this species has been recorded in Arizona and there are ~12 records for offshore California, about half of which were photographed. Due to difficulty identifying this species from Townsend's Storm-Petrel it is possible that some sight records from the 1970's and 80's may have been Townsend's. The species is uncommon to fairly common off southern Baja California and in the Gulf of California. These represent the first inland records for the United States (though one slightly inland in central California after a storm). There are two subspecies (which may actually represent two different species) with one population breeding in the Galapagos and the other in Peru. It is not immeditely clear which are represented here though. They differ in size and extent of white rump. Several specimens have been obtained from the storm and they should be identifiable to subspecies.

Small dark strom-petrel with a white rump. The extensive all white rump, forked tail, and small size (note size compared to the Least Storm-Petrel in Laurens Halsey last photo behind on left side) rules out other similar species except for Townsend's Storm-Petrel, a recent split from Leach's Storm-Petrel. Note especially the extensive white rump patch which is wedge shape and only slightly rounded where it meets the back, the extensive white wrapping around onto the undertail coverts, shallow forked tail, broad "hand" of the wing giving it a more rounded look and the stout bill, large feet, and pale upper-wing bar that did not include the primary coverts typical of the "Halocyptena" storm-petrels (potential genus split including Least, Black, and Wedge-rumped).

07 September 2016, photo by Laurens Halsey

07 September 2016, photo by Larry Pratt


07 September 2016, photo by Chris Rohrer

07 September 2016, photo by Bill Lisowsky

All photos are copyrighted© by photographer

Submitted on 09 September 2016