Migratory connectivity in the Loggerhead Shrike (Lanius ludovicianus)

• Published in: Ecology and evolution Vol. 8; no. 22; pp. 10662 - 10672
• Main Authors: Chabot, Amy A., Hobson, Keith A., Van Wilgenburg, Steven L., Pérez, Guillermo E., Lougheed, Stephen C.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.11.2018; John Wiley and Sons Inc
• Subjects: Alluvial valleys; Bayesian analysis; Birds; Breeding grounds; Breeding seasons; Breeding success; Connectivity; deuterium; differential migration; Ecological monitoring; Evolutionary conservation; Genetic markers; Habitat loss; Lanius ludovicianus; leap‐frog migration; Limiting factors; Microsatellites; Migrants; Migration; migratory connectivity; Mountains; Original Research; Population decline; Populations; Reproduction; Stable isotopes; Wildlife conservation; United States > US; Mexico; North America; microsatellites; leap‐frog migration; stable isotopes; differential migration; deuterium; migratory connectivity
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.4415

Aim We 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. Location We 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. Methods Our 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. Results Migratory 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 conclusions Our 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. We combine genetic and stable isotope data to quantify patterns of migratory connectivity of Loggerhead Shrike, a species of conservation concern in North America, to assess how connectivity differs and impacts subpopulation trajectories. Our study used a Bayesian framework and species‐ and age‐specific δ2Hf isoscapes and genetic markers to distinguish between co‐occurring migratory and nonmigratory individuals on the wintering grounds.