Populations of Leach's Storm-petrel (Oceanodroma leucorhoa; hereafter storm-petrel), one of the most widespread procellariiform seabirds in the world, appear to be declining in many parts of their breeding range. As part of a regional effort to assess status of storm-petrel colonies in eastern North America, we estimated apparent survival and recapture probabilities from 2009 to 2014 for adults on Bon Portage Island (43° 28' N, 65° 44' W), located off the southwestern coast of Nova Scotia, Canada. Mean annual survival estimated for this colony was low (0.78 ± 0.04) compared with other procellariiforms, e.g., > 0.90 for many albatrosses and petrels. Storm-petrels that were fitted with very high frequency (VHF) radio tags had an average of 0.11 ± 0.05 (95% confidence interval [CI] = 0.01 to 0.21) higher survival probabilities than those that were not, possibly because VHF tags were attached to known, established breeders. There was weak evidence that survival was reduced by an average of 0.07 ± 0.04 for storm-petrels in study plots that were occupied by Herring Gulls (Larus argentatus) and their chicks; however, this result was not statistically significant (95% CI: -0.15 to 0.02). Low adult survival is an early indication that this important colony may be under stress. However, further work is needed to determine if the colony is indeed declining and, if so, to determine the cause(s) of the decline so that they may be addressed.
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