American woodcock migratory connectivity as indicated by hydrogen isotopes

Abstract

To identify factors contributing to the long‐term decline of American woodcock, a holistic understanding of range‐wide population connectivity throughout the annual cycle is needed. We used band recovery data and isotopic composition of primary (P1) and secondary (S13) feathers to estimate population sources and connectivity among natal, early fall, and winter ranges of hunter‐harvested juvenile American woodcock. We used P1 feathers from known‐origin pre‐fledged woodcock (n = 43) to create a hydrogen δ2Hf isoscape by regressing δ2Hf against expected growing‐season precipitation (δ2Hp). Modeled δ2Hp values explained 79% of the variance in P1 δ2Hf values, indicating good model fit for estimating woodcock natal origins. However, a poor relationship (r2 = 0.23) between known‐origin, S13 δ2Hf values, and expected δ2Hp values precluded assignment of early fall origins. We applied the δ2Hf isoscape to assign natal origins using P1 feathers from 494 hunter‐harvested juvenile woodcock in the United States and Canada during 2010–2011 and 2011–2012 hunting seasons. Overall, 64% of all woodcock origins were assigned to the northernmost (>44°N) portion of both the Central and Eastern Management Regions. In the Eastern Region, assignments were more uniformly distributed along the Atlantic coast, whereas in the Central Region, most woodcock were assigned to origins within and north of the Great Lakes region. We compared our origin assignments to spatial coverage of the annual American woodcock Singing Ground Survey (SGS) and evaluated whether the survey effectively encompasses the entire breeding range. When we removed the inadequately surveyed Softwood shield Bird Conservation Region (BCR) from the northern portion of the SGS area, only 48% of juvenile woodcock originated in areas currently surveyed by the SGS. Of the individuals assigned to the northernmost portions of the breeding range, several were harvested in the southern extent of the wintering range. Based upon this latitudinal winter stratification, we examined whether woodcock employed a leapfrog migration strategy. Using δ2Hf values and band‐recovery data, we found some support for this migration strategy hypothesis but not as a singular explanation. The large harvest derivation of individuals from the northernmost portions of the breeding range, and the difference in breeding distributions within each Management Region should be considered in future range‐wide conservation and harvest management planning for American woodcock. © 2016 The Wildlife Society.

Migratory connectivity of American woodcock derived using satellite telemetry

“…). The high proportion of woodcock in our sample that migrated to breeding sites in Canada during spring migration complements the high harvest derivation from the northern portion of the woodcock's range found by Sullins et al () using stable isotopes.…”

“…4). The high proportion of woodcock in our sample that migrated to breeding sites in Canada during spring migration complements the high harvest derivation from the northern portion of the woodcock's range found by Sullins et al (2016) using stable isotopes. Myatt and Krementz (2007) proposed a route similar to Glasgow's Western Route based on observations made using aerial radio-telemetry of woodcock marked with very high frequency transmitters before southward migration from Minnesota, Wisconsin, and the Upper Peninsula of Michigan.…”

“…Woodcock migration has been studied using band returns from hunters (Glasgow 1958, Sheldon 1967, Coon et al 1977, radio-telemetry (Krementz et al 1994, Myatt and Krementz 2007, Meunier et al 2008, phylogenetics (Rhymer et al 2005), and stable isotopes (Sullins et al 2016). These studies provided insight into woodcock migration; however, they were limited by focusing on a single geographic area, being unable to provide information on >1 relocation per individual, or only allowing inference at coarse temporal (phylogenetics) or spatial (stable isotopes) scales.…”

Disentangling data discrepancies with integrated population models

“…This discrepancy has yet to be addressed, precluding understanding of range-wide dynamics and development of robust management strategies. Although there have been analyses of American Woodcock population dynamics based on breeding surveys (Thogmartin et al 2007, Sauer et al 2008, localized nesting studies (Roboski andCausey 1981, McAuley et al 1990), seasonal survival from radio telemetry (Longcore et al 2000), harvest surveys (Padding et al 2010), and bandrecovery analyses (Krementz et al 2003, Mayhew andLuukkonen 2010), there have been few attempts to combine these data (e.g., Zimmerman et al 2010, Sullins et al 2016 and no attempts to use an IPM for a population-level analysis.…”

Using Stable Isotope Analysis to Infer Breeding Latitude and Migratory Timing of Juvenile Pacific-Slope Flycatchers (Empidonax Difficilis)

“…The analyses of contaminants, parasites, pathogens, trace elements, mitochondrial DNA, genome sequences, and stable isotopes are some of the intrinsic approaches that have been used to infer migratory movements of wildlife (Hobson & Norris, 2008;Ruegg et al, 2014). The analysis of mitochondrial DNA and stable isotopes are two of the preferred approaches being applied in many migratory connectivity studies (Boulet et al, 2006;Hobson & Norris, 2008;Paxton, Van Riper III, Theimer, & Paxton, 2007;Ruegg et al, 2014;Rundel et al, 2013;Sullins et al, 2016;Webster et al, 2002;Woodworth et al, 2016).…”