Migratory patterns and connectivity of two North American grassland bird species.

Jason M Hill,Rosalind B Renfrew

doi:10.1002/ece3.4795

Abstract

Effective management and conservation of migratory bird populations require knowledge and incorporation of their movement patterns and space use throughout the annual cycle. To investigate the little‐known migratory patterns of two grassland bird species, we deployed 180 light‐level geolocators on Grasshopper Sparrows (Ammodramus savannarum) and 29 Argos‐GPS tags on Eastern Meadowlarks (Sturnella magna) at Konza Prairie, Kansas, USA, and six US Department of Defense (DoD) installations distributed across the species' breeding ranges. We analyzed location data from 34 light‐level geolocators and five Argos‐GPS tags attached for 1 year to Grasshopper Sparrows and Eastern Meadowlarks, respectively. Grasshopper Sparrows were present on the breeding grounds from mid‐April through early October, substantially longer than previously estimated, and migrated on average ~2,500 km over ~30 days. Grasshopper Sparrows exhibited strong migratory connectivity only at a continental scale. The North American Great Lakes region likely serves as a migratory divide for Midwest and East Coast Grasshopper Sparrows; Midwest populations (Kansas, Wisconsin, and North Dakota; n = 13) largely wintered in Texas or Mexico, whereas East Coast populations (Maryland and Massachusetts, n = 20) wintered in the northern Caribbean or Florida. Our data from Eastern Meadowlarks provided evidence for a diversity of stationary and short‐ and long‐distance migration strategies. By providing the most extensive examination of the nonbreeding movement ecology for these two North American grassland bird species to date, we refine information gaps and provide key insight for their management and conservation.

Highlights

Effective management and conservation of migratory bird popula‐ tions require an understanding of their patterns of movement, be‐ cause individual condition, survival, and breeding performance can be linked by processes that occur across thousands of kilometers and at different stages of the annual cycle (Fretwell, 1972; Norris & Marra, 2007; Renfrew et al, 2013; Rubenstein & Hobson, 2004)
Migratory connectivity refers to the degree of geographic linkage between populations throughout the annual cycle (Fraser et al, 2012; Marra, Studds, & Webster, 2010; Syroechkovski & Rogacheva, 1995)
To elucidate the migratory routes and connectivity of these grassland bird species, we deployed geolocators on Grasshopper Sparrows and GPS tags on Eastern Meadowlarks across six US states distrib‐ uted across their respective breeding ranges

Summary

| INTRODUCTION

Effective management and conservation of migratory bird popula‐ tions require an understanding of their patterns of movement, be‐ cause individual condition, survival, and breeding performance can be linked by processes that occur across thousands of kilometers and at different stages of the annual cycle (Fretwell, 1972; Norris & Marra, 2007; Renfrew et al, 2013; Rubenstein & Hobson, 2004). For migratory grassland bird species, basic in‐ formation about migratory connectivity and key nonbreeding areas could facilitate collaborative conservation efforts and iden‐ tify factors limiting population growth throughout their annual cycle (Robinson et al, 2010; Webster & Marra, 2005), while min‐ iaturized light‐level geolocators (hereafter geolocators) and GPS tags provide new means of revealing needed data (Bächler et al, 2010; DeLuca et al, 2015). Grasshopper Sparrows migrate nocturnally, likely within small groups of conspecifics or as individuals, and are difficult to detect outside of the breeding season when on the ground and not sing‐ ing (Evans & Mellinger, 1999; Vickery, 1996) They winter across the southeastern United States, on some Caribbean Islands, and south to Nicaragua, but migratory connectivity is essentially un‐ known (Vickery, 1996). To elucidate the migratory routes and connectivity of these grassland bird species, we deployed geolocators on Grasshopper Sparrows and GPS tags on Eastern Meadowlarks across six US states distrib‐ uted across their respective breeding ranges

| METHODS

Findings

| DISCUSSION