Bertram, D.F.Jones, I.L.Cooch, E.G.Knechtel, H.A.Cooke, F.2012-04-232012-04-232000-02The Condor 102(1):155-162. (2000)http://hdl.handle.net/10315/13795We estimated survival of Cassin's Auklet (Ptychoramphus aleuticus) and Rhinoceros Auklet (Cerorhincam onocerata) from recapture rates during 1994-1997. For both species, a two "age"-class model provided the best fit. Estimates of local adult survival were significantly lower for Cassin's Auklet (0.672 +/- 0.047) than for Rhinoceros Auklet (0.829 +/- 0.095). Our estimate of survival appears lower than that required for the maintenance of a stable population of Cassin's Auklets. The available information indicates that a low survival rate and a declining population at Triangle Island are plausible, particularly given the recent age scale oceanographic changes which have occurred in the North Pacific Ocean. Nevertheless, additional mark-recapture data and indexes of population size are required to rigorously demonstrate population declines at the world's largest Cassin's Auklet colony.enAlcidaeCassin's AukletCerorhinca monoceratademographyPtychoramphus aleuticusRhinoceros Aukletseabird conservation and managementArticlehttp://ucpressjournals.com/journal.php?j=condhttp://ucpressjournals.comhttp://www.jstor.org/stable/1370392