Migratory connectivity in the Loggerhead Shrike (Lanius ludovicianus)

Abstract

AimWe combine genetic and stable isotope data to quantify migration patterns in Loggerhead Shrike (Lanius ludovicianus), a species of conservation concern in North America, to assess how connectivity differs and impacts population evolution, ecology, and conservation.LocationWe sampled shrikes across the majority of their nonbreeding range, from the Atlantic Coast to the western United States east of the Rocky Mountains and throughout Mexico.MethodsOur study used a Bayesian framework using δ2Hf from a breeding season origin feather and nuclear genetic microsatellite markers to distinguish between co‐occurring migratory and nonmigratory individuals on the wintering grounds and, for migrants, to assign individuals to a breeding ground origin and genetic group.ResultsMigratory shrikes were present throughout the nonbreeding range but the proportion differed among sample areas. Four main wintering areas were identified. Connectivity ranged from weakly negative in birds wintering on the Atlantic Coast to strongly positive between wintering grounds in the southwestern United States and Mexico and northwestern breeding populations. Connectivity was weakest in L. l. migrans, and strongest in L. l. mexicanus and L. l. excubitorides. Although believed to be nonmigratory, long‐distance movements of individuals were observed in L. ludovicianus and L. l. mexicanus. Our data support a pattern of chain migration, again most notable in the western half of the species nonbreeding range, and differential migration based on age.Main conclusionsOur study provides of one such of the first quantitative measures of migratory connectivity and is among the first studies of a short‐distance migratory passerine in North America. The higher migratory connectivity among western, versus eastern populations, and less severe population declines attributable to habitat loss or reproductive success, may result in more localized and/or less severe limiting factors for western populations and more severe on the Atlantic coast and Mississippi Alluvial Valley wintering grounds.

High spatiotemporal overlap in the non‐breeding season despite geographically dispersed breeding locations in the eastern whip‐poor‐will (Antrostomus vociferus)

“…Briefly, chain migration is when breeding and wintering populations exist in the same latitudinal sequence on the breeding and wintering grounds (migration distance is similar between different breeding populations, but wintering latitude is different; e.g. Chabot et al, 2018). Leapfrog migration is when the latitudinal sequence of populations is reversed during the breeding and winter periods (migration distance increases with breeding latitude, and wintering latitude is different; e.g.…”

Clustering community science data to infer songbird migratory connectivity in the Western Hemisphere

“…In cases where other data, such as band records, migratory tracks, stable isotopes, are available for a given species, the Bayesian framework can be used to refine migratory connectivity estimates according to new sources of information when parallel migration can be reasonably assumed. Indeed, methodologies that incorporate genetic markers and stable isotopes ratios into a Bayesian framework are already available in the literature (see, for e.g., Chabot et al, 2018; Rundel et al, 2013), and eBird data specifically have already been used to constrain migratory estimates derived from stable isotopes (Fournier et al, 2017). If the assumption of broadscale parallel migration can be made, our methodology can be easily used alongside other data types without adding significant costs.…”

Phenotypic differentiation despite gene flow: Beak morphology, bite performance, and population genetics of Loggerhead Shrikes (Lanius ludovicianus)

“…These subspecies, and more specifically the shrikes that inhabit the latitudinal range of our study, are primarily resident (Yosef, 1996(Yosef, , 2008. However, we cannot exclude the possibility that some winter migrants were intermixed with the resident birds that we captured (e.g., Pérez & Hobson, 2007;Chabot et al, 2018).…”