Repeatability in migration of Ferruginous Hawks (Buteo regalis) and implications for nomadism

Watson, James; Keren, Ilai N.

doi:10.1676/18-171

Cited by 16 publications

(17 citation statements)

References 33 publications

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“…Ferruginous hawks are large, migratory raptors found in central Canada and United States (Schmutz and Fyfe, 1987; Schmutz et al, 2008). The shortgrass prairies of southern Alberta, Canada represent the northern edge of this species’s breeding range, and birds breeding this far north make relatively long migrations to the southern Great Plains in the United States (Watson and Keren, 2019). Adult ferruginous hawks were captured at nest sites during the breeding season, using either a dho-gaza net or a bal-chatri trap (Watson, 2020).…”

Section: Methodsmentioning

confidence: 99%

“…The temporal resolution, or fix rate, of a movement dataset has a significant effect on the results of many movement analyses (Jerde and Visscher, 2005; Thurfjell et al, 2014), so we fit the model to the hawk movement tracks rarefied to 1-hour, 12-hour, and 24-hour fix rates. We bounded t 1 and t 2 such that t 2 − t 1 needed to be greater than 7 days, as anything shorter would represent a biologically unrealistic migration (Watson and Keren, 2019). We also estimated 95% confidence intervals for each individual migration using the parametric bootstrapping method described above.…”

Section: Methodsmentioning

confidence: 99%

“…Like many animal species, ferruginous hawks display complex migratory patterns including stopovers and pre-migratory dispersal (Watson et al, 2018; Watson and Keren, 2019). Stopover behaviour is defined as the interruption of migration over some temporal period (Rappole and Warner, 1976) and is very diverse, just like migration itself (Salewski et al, 2007; Evans and Bearhop, 2022; Schmaljohann et al, 2022).…”

Section: Methodsmentioning

confidence: 99%

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A parametric model for estimating the timing and intensity of animal migration

Thompson

Harrington

Mallory³

et al. 2023

Preprint

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Animals of many different species, trophic levels, and life history strategies migrate, and the improvement of animal tracking technology allows ecologists to collect increasing amounts of detailed data on these movements. Understanding when animals migrate is important for managing their populations, but is still difficult despite modelling advancements. We designed a model that parametrically estimates the timing of migration from animal tracking data. Our model identifies the beginning and end of migratory movements as signaled by changes in step length and turning angle distributions. To this end, we can also use the model to estimate how an animal's movement changes when it begins migrating. We tested our model on three datasets: migratory ferruginous hawks (Buteo regalis) in the Great Plains and barren-ground caribou (Rangifer tarandus groenlandicus) in northern Canada, and non-migratory brown bears (Ursus arctos) from the Canadian Arctic. We estimated the beginning and end of migration in caribou and hawks to the nearest day, while confirming a lack of migratory behaviour in the brown bear population. The flexibility of our modelling framework allowed us to assess intricacies associated with each dataset: long-term stopover behaviour in ferruginous hawks and a priori knowledge of caribou calving areas and behaviour. In addition to estimating when caribou and ferruginous hawks migrated, our model also identified differences in how the two populations migrated; ferruginous hawks achieved efficient migrations by increasing their movement rates while caribou migration was achieved through significant increases in directional persistence. Our approach is broadly applicable to many animal movement studies. We anticipate that rigorous assessment of migration metrics will aid understanding of both how and why animals move.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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A parametric model for estimating the timing and intensity of animal migration

Thompson

Harrington

Mallory³

et al. 2023

Preprint

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“…Nomadic movements can be made by young animals (prior to reaching breeding age) or by adults (during the breeding years). These last two types of movements are not always well differentiated in the literature, and prospecting by young animals sometimes can precede nomadism by adult animals (Watson et al, 2019; Watson & Keren, 2019).…”

Section: Introductionmentioning

confidence: 99%

Interpreting long‐distance movements of non‐migratory golden eagles: Prospecting and nomadism?

et al. 2022

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Movements by animals can serve different functions and occur over a variety of spatial and temporal scales. Routine movement types, such as residency (localized movements) and migration, have been well studied. However, nonroutine movement types, such as dispersal, prospecting, and nomadism, are less well understood. Documenting these rarely detected events requires tracking large numbers of individuals across all age classes. We studied >500 golden eagles (Aquila chrysaetos) tracked by telemetry over a 10‐year period in western North America, of which 160 engaged in nonroutine, long‐distance (>300 km) movements. We identified spatial and temporal correlates of those movements at both small and large scales, and we quantified movement timing and direction. We further tested which age and sex classes of eagles were more likely to engage in these movements. Our analysis of 88,093 daily tracks suggested that distances traveled by eagles were responsive to the updraft potential of the spatial and temporal landscape they encountered. Tracks covered longer distances at locations and times of higher updraft potential, and older birds traveled farther than younger birds. By contrast, after decomposing daily tracks into 563 nonroutine, long‐distance movements measured at a multiday scale, only the duration of travel was responsive to environmental conditions encountered by eagles. Multiday trips that were longer were those initiated in open and warm landscapes and those that ended in mountainous regions. Finally, long‐distance movements were more frequently made in seasons other than winter, in north–south directions, and by young birds. We documented clear correlates of nonroutine, long‐distance movements by golden eagles at small, local scales but found little evidence of such correlates at larger, regional scales. Most long‐distance movements we documented fit patterns associated with traditional definitions of prospecting and nomadism but not migration. Our study is the first to describe these movement types by golden eagles, and as such provides a foundation for subsequent study into the movement ecology of other species.

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“…Classifying movement types this way may not, however, be accurate at all spatial and temporal scales. Birds previously thought to be nomadic sometimes show predictable movements for a part of the year (Watson and Keren 2019), while some species exhibit partial migration, where individuals of a species thought to be migratory sometimes overwinter at their breeding grounds (Townsend et al 2018).…”

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confidence: 99%