Seasonal Movements of the Short-Eared Owl (Asio flammeus) in Western North America as Revealed by Satellite Telemetry

Abstract

The Short-eared Owl (Asio flammeus) is a widespread raptor whose abundance and distribution fluctuates in response to the varying amplitudes of its prey, which are predominately microtines. Previous efforts to describe the seasonal movements of Short-eared Owls have been hindered by few band recoveries and the species' cryptic and irruptive behavior. We attached satellite transmitters to adult Short-eared Owls at breeding areas in western and interior Alaska in June 2009 and July 2010, and tracked their movements for up to 19 mo. Owls initiated long-distance southward movements from Alaska and most followed a corridor east of the Rocky Mountains into the Prairie provinces and Great Plains states. Four owls followed a coastal route west of the Rocky Mountains, including one owl that crossed the Gulf of Alaska. Completed autumn migration distances ranged from 3205-6886 km (mean ¼ 4722 6 1156 km [SD]). Wintering areas spanned 218 of latitude from central Montana to southern Texas, and 248 of longitude from central California to western Kansas. Subsequent seasonal migrations were generally northward in spring and southward in autumn; these movements were comparatively short-distance (mean ¼ 767.5 6 517.4 km [SD]) and the owls exhibited low site fidelity. The Short-eared Owls we tracked from two relatively local breeding areas in Alaska used a patchwork of diverse open habitats across a large area of North America, which highlights that effective conservation of this species requires a collaborative, continental-scale focus.

Niche partitioning of avian predators in northern grasslands amended by biosolids

“…Our results suggest that the owls cued in on this resource-rich environment; both species are irruptive nomads that select breeding areas where voles are at high densities (González-Rojas et al, 2017;Poulin et al, 2001;Selçuk et al, 2017). Short-eared Owls are strongly nomadic, enabling birds to choose nesting and overwintering sites that have locally abundant prey (Booms et al, 2014;Johnson et al, 2017;Reid et al, 2011). Long-eared Owls show some nomadism in relation to vole abundance (Korpimäki & Norrdahl, 1991;Tulis et al, 2015), but they are also generalist consumers across their large geographic range (Birrer, 2009;Village, 1981).…”

Temporal and spatial population dynamics of the nomadic short‐eared owl across the western United States

“…Abundance cycles of prey species are not synchronized across the range of the short‐eared owl (Myers 2018) and are not likely synchronized across our study area. Short‐eared owls regularly disperse great distances (e.g., >3,000 km; Johnson et al 2017) and have irruptive breeding and nomadic movements in response to prey availability (Village 1987, Korpimäki and Norrdahl 1991). Therefore, the most parsimonious explanation of high annual variation in occupancy at the state level, yet overall stability across the study area, is that birds are moving state to state in response to changes in local prey availability.…”

What is the airspeed velocity of an unladen swallow? Modeling numerical judgments of realisitc stimuli

“…For instance, the flight speed is related to size and mass of birds, but also phylogenetic effects play an important role, where species of the same group tend to fly at similar speeds (e.g., swans, geese & ducks fly faster than falcons, crows & songbirds, Alerstam et al, 2007). We extracted the maximum flight speed values from scientific articles, if possible (e.g., Johnson et al, 2017), or otherwise, used the values from the original quartets game.…”