Multi‐season occupancy models identify biotic and abiotic factors influencing a recovering Arctic Peregrine FalconFalco peregrinus tundriuspopulation

Abstract

Critical information for evaluating the effectiveness of management strategies for species of concern include distinguishing seldom occupied (or low-quality) habitat from habitat that is frequently occupied and thus contributes substantially to population trends. Using multi-season models that account for imperfect detection and a long-term (1981-2002) dataset on migratory Arctic Peregrine Falcons Falco peregrinus tundrius nesting along the Colville River, Alaska, we quantified the effects of previous year's productivity (i.e. site quality), amount of prey habitat, topography, climate, competition and year on occupancy dynamics across two spatial scales (nest-sites, cliffs) during recovery of the population. Initial occupancy probability was positively correlated with area of surrounding prey habitat and height of nest-sites above the Colville River. Colonization probability was positively correlated with nest height and negatively correlated with date of snowmelt. Local extinction probability was negatively correlated with productivity, area of prey habitat and nest height. Colonization and local extinction probabilities were also positively and negatively correlated, respectively, with year. Our results suggest that nest-sites (or cliffs) along the Colville River do not need equal protection measures. Nest-sites and cliffs with historically higher productivity were occupied most frequently and had lower probability of local extinction. These sites were on cliffs high above the river drainage, surrounded by adequate prey habitat and with southerly aspects associated with early snowmelt and warmer microclimates in spring. Protecting these sites is likely to encourage continued occupancy by Arctic Peregrine Falcons along the Colville River and other similar areas. Our findings also illustrate the importance of evaluating fitness parameters along with climate and habitat features when analysing occupancy dynamics, particularly with a long-term dataset spanning a range of annual climate variation.

Extreme weather affects Peregrine Falcon (Falco peregrinus tundrius) breeding success in South Greenland

“…The effect of weather on productivity is mediated by the parents' selection of a suitable protective nest ledge and Peregrines frequently return to successful nest sites and desert nesting sites that are exposed to direct rainfall or that have become wet or flooded already during the pre-laying period (Olsen & Olsen 1988, Bruggeman et al 2016. However, there is a limit to how effective this strategy is (Olsen & Olsen 1988, McDonald et al 2004: an experimental Arctic study reduced nesting mortality through rain events by installing nest boxes (Anctil et al 2014).…”

Incorporating productivity as a measure of fitness into models of breeding area quality of Arctic peregrine falcons

“…We detected Arctic peregrines at 108 unique nest-site locations during 24 years of surveys. Estimates of detection probability, as determined from previous work, were > 0.8 for the first survey in all years except 1982, when it was 0.7, and slightly lower for the second survey (Bruggeman et al 2016). Total number of times nest sites were occupied over 24 years ranged from 1-24 (mean = 12.0; SE = 0.655).…”

“…Second, during the recovery the Arctic peregrine population exhibited density dependence (Bruggeman et al 2015, Swem andMatz 2018), which may negatively affect productivity. We also used knowledge of factors related to Arctic peregrine occupancy of nest sites and abundance on nesting cliffs in the CRSA (Bruggeman et al 2015(Bruggeman et al , 2016 to select covariates describing nest-site attributes (e.g. habitat; topography; prey habitat availability) to evaluate in models.…”

Does Hopi Religious Harvest of Eaglets Affect Golden Eagle Territory Occupancy and Reproduction on the Navajo Nation?

“…The studies described above focused on relatively smaller areas chosen for high densities of nesting Golden Eagles, whereas we may have observed lower occupancy rates, in part, because our larger study area incorporated more marginally suitable habitat in which some territories were only sporadically occupied. This is the first study, to our knowledge, to estimate the occupancy dynamics of persistence and colonization for Golden Eagle territories, although dynamic occupancy models have been used to analyze longterm datasets on other raptors, including Peregrine Falcons (Falco peregrinus; Bruggeman et al 2016) and Spotted Owls (Strix occidentalis; Olson et al 2005, Dugger et al 2011. Persistence and colonization rates did not differ between study areas, suggesting habitat suitability was comparable across the study area.…”