Tristram's Storm-Petrel back on the Farallones!

March 19, 2015

Today our 2 new interns (Sean and Eva) found this fresh storm-petrel carcass (killed by a Burrowing Owl) on our first storm-petrel predation survey of the seabird season. Upon seeing the bird, I did a double take at it’s massive size and knew immediately that this was not one of the Ashy or Leach’s Storm-petrels that breed on the Farallones. After taking several morphological measurements and consulting with Peter Pyle and his extensive datasets on storm-petrel morphometrics, we have concluded this is a Tristram’s Storm-Petrel (Oceanodroma tristrami). The combination of morphological measurements collected from the specimen (including wing length, tail length and leg size) rule out all other likely species. This is a Hawaiian/Central and Western Pacific species which only has 2 previous North America records. The first of which was an individual that was caught in a mist net on SEFI in April of 2006. This is further evidence of warm water conditions in the Gulf of the Farallones this year and the corresponding occurrence of more tropical species. This specimen’s unfortunate demise also highlights the challenges we face with Burrowing Owl predation on Farallon storm-petrels.
-Russ Bradley, Farallon Program Manager

Fresh Tristram’s Storm Petrel carcass found on Southeast Farallon Island 3/18/2015
3rd North American Record!