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Tonra, Christopher M.

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Tonra
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Christopher M.
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    Data from: Remote estimation of overwintering home ranges in an elusive migratory nocturnal bird
    (2021-01-29) Tonra, Christopher M.; Wright, James R.; Matthews, Stephen N.
    NOTE: An updated and larger version of this dataset is available. See https://doi.org/10.5441/001/1.k6s7916g. ABSTRACT: Due to a long running research bias toward the breeding season, there are major gaps in knowledge on the basic nonbreeding ecology of many species, preventing a full‐annual cycle focus in ecology and conservation. Exacerbating this problem is the fact that many species are extremely difficult to detect outside of breeding. Here, we demonstrate a partial solution to this problem by using archival GPS tags to examine the overwintering ecology of a migratory nocturnal bird, the eastern whip‐poor‐will (Antrostomus vociferous). We deployed tags on 21 individuals and were able to recover 11 (52%) one year later. Tags collected high precision (approx. 10 m) points throughout the nonbreeding period. With continuous time movement models, we used these data to estimate overwintering home ranges. All individuals exhibited at least one bounded home range during this phase of the annual cycle, three of eleven had two wintering locations, and home range area ranged from 0.50 to 10.85 ha. All overwintering home ranges contained closed‐canopy forest land cover (42%–100%), and no other land cover type represented >40% of any home range. We found some evidence, with caveats, that total edge within the landscape surrounding the home range was negatively related to home range area. The prevalence of contiguous closed‐canopy forest cover in overwintering home ranges contrasts with apparent breeding habitat preferences, which includes clear‐cuts and other, more open, habitats. This study is the first to reveal key aspects of overwintering space use in this species by using archival GPS to overcome both logistical and methodological limitations. Expanded use of such technology is critical to gathering basic ecological and distributional data, necessary for achieving a more complete understanding of full‐annual cycles of animal populations.
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    Data from: Concentration of a widespread breeding population in few critically important nonbreeding areas: migratory connectivity in the Prothonotary Warbler
    (2019-07-03) Tonra, Christopher M.; Hallworth, Michael T.; Boves, Than J.; Reese, Jessie; Bulluck, Lesley P.; Johnson, Matthew; Viverette, Cathy; Percy, Katie; Ames, Elizabeth M.; Matthews, Alix; Slevin, Morgan C.; Wilson, R. Randy; Johnson, Erik I.
    One of the greatest challenges to informed conservation of migratory animals is elucidating spatiotemporal variation in distributions. Without such information, it is impossible to understand full-annual-cycle ecology and effectively implement conservation actions that address where and when populations are most limited. We deployed and recovered light-level geolocators (n = 34) at 6 breeding sites in North America across the breeding range of a declining long-distance migratory bird, the Prothonotary Warbler (Protonotaria citrea). We sought to determine migratory routes, stopover location and duration, and the location of overwintering grounds. We found that the species exhibits a large-scale, east‒west split in migratory routes and weak migratory connectivity across its range. Specifically, almost all individuals, regardless of breeding origin, overlapped in their estimated wintering location in northern Colombia, in an area 20% the size of the breeding range. Additionally, most of the individuals across all breeding locations concentrated in well-defined stopover locations in Central America while en route to Colombia. Although error inherent in light-level geolocation cannot be fully ruled out, surprisingly much of the estimated wintering area included inland areas even though the Prothonotary Warbler is considered a specialist on coastal mangroves in winter. Based on these results, conservation efforts directed at very specific nonbreeding geographical areas will potentially have benefits across most of the breeding population. Our findings highlight the importance of using modern technologies to validate assumptions about little-studied portions of a species’ annual cycle, and the need to distribute sampling across its range.
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    Data from: Study "GPS tracking of eastern whip-poor-will"
    (2023-01-24) Skinner, Aaron A.; Ward, Michael P.; Souza-Cole, Ian; Wright, James R.; Thompson, Frank R., III; Benson, Thomas J.; Matthews, Stephen N.; Tonra, Christopher M.
    Aim: A full annual cycle approach to conservation and understanding of regional population trends requires an understanding of migratory connectivity. We present tracking data on the eastern whip-poor-will (Antrostomus vociferus), a Neotropical migrant that has declined by 70% in recent decades. When and where populations of this species are limited throughout the annual cycle is poorly understood. Location: Breeding area: midwestern United States; passage area and winter area: midwestern/southern United States, Mexico, Central America. Methods: We utilized data from 52 archival GPS tags from five breeding areas covering a 9.5-degree latitudinal span (~1000 km) of the whip-poor-will breeding range in the summers of 2017 and 2019. We identified migratory routes and spatiotemporal bottlenecks, stopover and wintering locations, calculated migratory connectivity throughout migration and on the wintering grounds and tested predictions for three latitudinal connectivity patterns. Results: Whip-poor-wills circumvented the Gulf of Mexico, and populations across a large latitudinal gradient came together in eastern Texas in early October, resulting in decreased connectivity throughout migration. Breeding-winter migratory connectivity was low (MC = 0.22 ± 0.12), with extensive overlap of core wintering areas in southern Mexico and Guatemala. The overlap of wintering areas by individuals from dispersed breeding latitudes suggests that whip-poor-wills most closely resemble telescopic migrants. Main conclusions: Circumventing the Gulf of Mexico influenced connectivity in the whip-poor-will, funnelling individuals into a small region in eastern Texas in migration and likely influencing breeding-winter connectivity. Thus, geographically dispersed breeding populations overlap in space and time during migration and winter, and non-breeding season conditions affecting populations (both positively and negatively) impact individuals from across the core breeding range. For example, extensive deforestation occurring in the whip-poor-will's core wintering area likely impacts individuals from all five deployment locations. We demonstrate that combining multiple indices of spatiotemporal cohesion is critical to fully understand how migratory animals are distributed in the non-breeding season.