Dietary Plasticity in a Specialist Predator, the Gyrfalcon (Falco rusticolus): New Insights into Diet During Brood Rearing

Abstract

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Bayesian stable isotope mixing models effectively characterize the diet of an Arctic raptor

“…We also calculated a TDF for gyrfalcon using the sider package in r, which applies a phylogenetic regression model to a database of TDFs published in the literature (Healy et al, 2018). To test model sensitivity to the incorporation of an informative prior, we generated gyrfalcon dietary proportions based on nest camera data for 20 nestyears over the 2014-2015 brood rearing periods on the Seward Peninsula published by Robinson et al (2019). Proportions were rescaled into Dirichlet hyperparameters before their incorporation into BSIMMs (following .…”

“…raptors; Ims & Fuglei, 2005). Arctic raptor diet studies have done so through the use of nest camera dietary analysis in recent years (e.g, Robinson et al., 2019), which provide high‐precision diet estimates for nestlings but are often constrained by sample size and geographic scope. There is an apparent need for a robust methodology to assess spatial and temporal trends in the diet of Arctic raptors.…”

Nonrandom territory occupancy by nesting Gyrfalcons (Falco rusticolus)

“…Rock Ptarmigan habitat is characterized as barren fellfields at higher elevations and on windblown ridges, with a dwarf shrub mat <0.4 m tall of Salix reticulata L., Empetrum nigrum L., Vaccinium spp., Saxifraga spp., and Dryas spp. As alternative prey, we considered those species with a mass ≥100 g that were observed as prey in Gyrfalcon nests on the Seward Peninsula in 2014 and 2015 (Robinson et al 2019) and for which AKGAP data were available (Arctic ground squirrel (Urocitellus parryii (Richardson, 1825)), Whimbrel (Numenius phaeopus (Linnaeus, 1758)), Long-tailed Jaeger (Stercorarius longicaudus Vieillot, 1819), American Golden-Plover, (Pluvialis dominica (Statius Muller, 1776)), and Pacific Golden-Plover (Pluvialis fulva (Gmelin, 1789)).…”

“…Because the incidence of alternative prey in Gyrfalcon diet increases during low ptarmigan years, the availability of alternative prey may be important for sustained occupancy of Gyrfalcon territories. We included species >100 g and >10 detections in prey samples from the Seward Peninsula and for which habitat data were available Burnham and Mattox 1984;Nielsen 1999;Booms and Fuller 2003;Robinson et al 2019 Area of primary and alternative prey habitat WIPT + ROPT + ALT Gyrfalcon diet is broadest during the nesting season. Greater amounts of habitat for primary and alternative prey may provide a diverse diet needed to raise young successfully and influence territory selection…”

“…The Gyrfalcon (Falco rusticolus Linnaeus, 1758) is an apex avian predator of the Arctic tundra (Watson et al 2011). Breeding as far north as 82°N latitude, it is considered a tundra specialist resident year-round at northern latitudes (Platt 1976;Nielsen and Cade 1990;Watson et al 2011) and a dietary specialist dependent primarily on one or two bird species in the genus Lagopus (Roseneau 1972;Booms and Fuller 2003;Nielsen 2003;Nyström et al 2006;Watson et al 2011), although exceptions to these characterizations exist (Burnham and Newton 2011;Robinson et al 2019). Because of its restricted range and diet, the Gyrfalcon is predicted to be one of the Arctic birds most vulnerable to climate change (Thomas et al 2004;Liebezeit et al 2012).…”