Point Counts Underestimate the Importance of Arctic Foxes as Avian Nest Predators: Evidence from Remote Video Cameras in Arctic Alaskan Oil Fields

Abstract

ABSTRACT. We used video cameras to identify nest predators at active shorebird and passerine nests and conducted point count surveys separately to determine species richness and detection frequency of potential nest predators in the Prudhoe Bay region of Alaska. From the surveys, we identified 16 potential nest predators, with glaucous gulls (Larus hyperboreus) and parasitic jaegers (Stercorarius parasiticus) making up more than 80% of the observations. From the video evidence, however, we identified arctic foxes (Alopex lagopus) as the predators in five of six predation events recorded with the cameras. These results indicate that estimated abundances of predators alone may not accurately reflect their true or proportional importance as nest predators. We also found that the identified predators removed all eggs and left the nests intact. Thus, attempts to identify predators solely on the basis of nest remains are not reliable for smaller bird species in this region. We found no evidence that camera-monitored nests were at greater risk of predation or desertion than camera-free nests. Overall, our ability to film predation events was hampered by the brief, highly synchronized breeding season, the harsh climate, and the higher nest survivorship for shorebirds in this region relative to temperate-breeding passerines, which have been the focus of most studies that use camera systems in attempts to identify nest predators at active nests.Key words: Arctic Alaska, Kuparuk, oil fields, nest predators, nest predation, passerines, Prudhoe Bay, shorebirds, video camera RÉSUMÉ. Nous avons recouru à des cameras vidéo pour repérer les prédateurs de nids actifs d'oiseaux de rivage et de passériformes, puis nous avons effectué des calculs séparément afin de déterminer la richesse des espèces et la fréquence de détection de prédateurs de nids potentiels dans la région de la baie de Prudhoe, en Alaska. À partir des calculs, nous avons dénombré 16 prédateurs de nids potentiels, les goélands bourgmestres (Larus hyperboreus) et les labbes parasites (Stercorarius parasiticus) représentant plus de 80 % des observations. Cependant, à partir des vidéos, nous avons pu constater que les renards arctiques (Alopex lagopus) étaient les prédateurs dans cinq des six cas de prédation enregistrés au moyen des caméras. Ces résultats laissent croire que seules, les abondances estimées de prédateurs ne reflètent pas nécessairement leur importance véritable ou proportionnelle à titre de prédateurs de nids. Nous avons également constaté que les prédateurs en question prenaient tous les oeufs, sans toutefois toucher aux nids. Par conséquent, la possibilité d'identifier les prédateurs seulement en fonction des restes de nids n'est pas fiable dans le cas des plus petites espèces d'oiseaux de cette région. Rien ne nous a laissé croire que les nids surveillés à l'aide d'une caméra étaient plus vulnérables à la prédation ou à l'abandon que les nids n'étant pas dotés de caméras. Dans l'ensemble, la saison de reproduction hautement synchronisée -bien que ...

Breeding Ecology of Birds at Teshekpuk Lake: A Key Habitat Site on the Arctic Coastal Plain of Alaska

“…Point counts were separated by at least 200 m and conducted at least 10 minutes apart. We counted all visual and aural detections of documented or suspected potential nest predators (Poole et al, 2003;Liebezeit and Zack, 2008) within an area 300 m beyond the plot boundary. We avoided re-counting individual predators by noting differences in plumage (e.g., light morph versus dark morph jaegers) and pelage (arctic fox) and by tracking active predator nests and fox den activity on or near study plots.…”

“…While we cannot say with certainty that this finding is related to negative impacts from oilfield development, it does agree with findings from Liebezeit et al (2009) that documented lower longspur survivorship closer to oilfield infrastructure. In addition, at least one potential nest predator, the glaucous gull, was more numerous at Prudhoe Bay, although most evidence suggests that the arctic fox was the more important predator at this site (Liebezeit and Zack, 2008). Lemming abundance was included as a variable in the top models, with years of higher lemming numbers corresponding to lower predation rates.…”

Shorebird Responses to Construction and Operation of a Landfill on the Arctic Coastal Plain

“…despite these greater numbers, nest-survival rates were generally high both in and outside the landfill throughout our study. perhaps this should not have been surprising because other studies in the Arctic have found Glaucous Gulls to have little effect on survival of shorebird nests (Smith et al 2007, Liebezeit andZack 2008). The small effect Glaucous Gulls have on nests was also apparent in a study of the species' diet in the barrow area from 2007 to 2009: only 4% of all samples of the Glaucous Gull's diet contained avian eggs (E. L. Weiser, pers.…”

“…We also have other circumstantial evidence that supports the notion that greater nest survival was due to the exclusion of foxes from the landfill. first, foxes are rarely observed during predator surveys but often depredate large numbers of arctic shorebird nests (Liebezeit and Zack 2008). Second, there is a direct correspondence between the lower nest-success rates outside the landfill in 2009 and a change to less effective trapping methods for the arctic fox in that year (Savory et al 2009).…”

Full Issue

“…Because predator point counts can underestimate the importance of mammalian predators (Liebezeit and Zack 2008), we used data from an arctic fox (Vulpes lagopus) removal program conducted to enhance Steller's Eider (Polysticta stelleri) productivity (see Gilsdorf and Rossi 2008, Savory et al 2009, Bair et al 2011) as an index of mammalian predator levels. Between 2005 and 2012, trappers removed adults and kits at dens and opportunistically shot and trapped adult foxes from mid-late-May to mid-July across~220 km 2 that included the greater Barrow area and our study plots.…”