ABSTRACT. The documentation of anticoagulant rodenticides (AR) in nontarget species has centered around wildlife that inhabit urban or agricultural settings. However, recent studies in California have shown that AR use in remote forest settings has escalated and has exposed and killed forest carnivores. Anticoagulant rodenticides have been documented as physiological stressors for avian species. Northern Spotted Owl (Strix occidentalis caurina) critical and occupied habitat overlaps the areas where these studies occurred, yet no data were previously available to demonstrate whether this species was similarly affected. We investigated whether avian predators are also exposed to these specific pesticides and whether Barred Owls (Strix varia) may be a surrogate to indicate exposure rates in Northern Spotted Owls. We documented that 70% of Northern Spotted Owls and 40% of Barred Owls were exposed to one or more anticoagulant rodenticides. None of the rodent prey species sampled within the study area were positive for ARs. There were no spatial clusters for either low or high rates of exposure, though we detected low temporal trend early on throughout the study area. We hypothesize a recent change in land-use toward marijuana cultivation may have led to the increased use of AR in this area. This study demonstrates environmental contamination within occupied Northern Spotted Owl habitat and that Barred Owls can be used as adequate surrogates for detecting these pollutants in a rare species such as the Northern Spotted Owl. Furthermore, additional studies should focus on whether these pesticides are also affecting prey availability for these forest avian species.Exposition aux rodenticides chez les Chouettes tachetée du Nord et rayée dans les terres forestières éloignées du nord-ouest de la Californie : indice de contamination du réseau alimentaire RÉSUMÉ. Les cas d'exposition à des rodenticides anticoagulants (RA) chez les espèces non ciblées ont surtout été documentés pour la faune habitant les milieux urbains ou agricoles. Toutefois, de récentes études en Californie ont montré que l'utilisation de RA dans les environnements forestiers éloignés a grimpé, et des carnivores forestiers y ont été exposés et en sont morts. On a aussi documenté que les RA sont des facteurs de stress physiologique pour les espèces aviaires. L'habitat critique occupé par la Chouette tachetée du Nord (Strix occidentalis caurina) chevauche les endroits où ces études ont eu lieu, mais aucune donnée n'était auparavant disponible pour déterminer si cette espèce était aussi touchée. Nous avons examiné la possibilité que les prédateurs aviaires soient aussi exposés à ces pesticides spécifiques, et si les Chouettes rayées (Strix varia) pouvaient servir d'indicateur pour les taux d'exposition des Chouettes tachetées du Nord. Nous avons quantifié que 70 % des Chouettes tachetées du Nord et 40 % des Chouettes rayées étaient exposées à au moins un RA. Aucune des espèces proies de rongeurs échantillonnées dans notre aire d'étude ne se sont révélées posit...

22. Results of logistic regression on the effect of nesting success in the prior year on the probability that adult Southwestern Willow Flycatchers would remain on the same breeding territory in the subsequent year at the upper San Luis Rey River monitoring area,

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The literature on ecosystem services has been criticized for inadequately acknowledging culture values and for de‐emphasizing economic disservices. While economic loss due to tree damage by American black bears (Ursus americanus, hereafter bears) may negatively affect timber production, it also alters forest structure and habitat that may contribute to forest wildlife diversity, including culturally significant species. We examined the relationship between bear damage to Douglas‐fir trees (Pseudotsuga menziesii var. menziesii) and response of cavity‐nesting birds on the Hoopa Valley Indian Reservation. We measured disservices from bear damage by calculating current and future timber revenue loss, and ecosystem services by calculating forest structural complexity, abundance and diversity of cavity‐nesting birds, and woodpecker activity. Bear damage was correlated negatively with tree growth and positively with estimated timber loss. Forest structural complexity was positively correlated with bear damage, and cavity‐nester abundance and woodpecker foraging activity were positively correlated with forest structural complexity and bear damage. Pileated woodpeckers (Dryocopus pileatus) and red‐breasted sapsuckers (Sphyrapicus ruber) used bear‐damaged trees out of proportion to their availability, and pileated woodpeckers selected for more structurally complex sample units. Information from this study advances our understanding of the potential for bear foraging to negatively affect economic revenue and the trade‐offs with habitat conditions favoring other important wildlife species. Understanding the costs and benefits of bear damage can help guide management decisions vital to forest managers both on and off tribal lands.