ABSTRACT. 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. Il y avait une faible évidence de survie réduite de 0,07 ± 0,04 en moyenne pour les océanites qui occupaient des parcelles dans lesquelles se trouvaient aussi des Goélands argentés (Larus argentatus) et leurs poussins; toutefois, ce résultat n'était pas significatif sur le plan statistique (95 % IC = -0,15 à 0,02). La faible survie des adultes est un signe précurseur que cette colonie d'importance est exposée à des contraintes. Par ailleurs, d'autres travaux sont nécessaires pour de déterminer si la colonie diminue réellement et, le cas échéant, de trouver les causes de la diminution afin d'y remédier. Survie apparente des Océanites cul-blanc (Oceanodroma

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Arctic tern (Sterna paradisaea) populations are thought to be in decline across much of their range. For long-lived seabirds, determining adult survival rates is key to understanding current population trends and predicting trajectories. We therefore examined adult survival of terns banded at our field site in the Canadian High Arctic between 2007 and 2016. Apparent adult survival was 0.883, comparable to values for other tern species and for other Arctic larids. However, using this survival rate plus first year survival values from a recent study in Iceland, we project a declining trend for terns in the Canadian High Arctic, consistent with recent reports from local ecological knowledge and limited regional surveys. Our data suggest that low adult survival is not responsible for declining tern populations, and that studies should investigate whether dispersal to new nesting locations may be underway, or that young terns are not surviving well or recruiting to the population.

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