Range Overlap Between Mid-Continent and Eastern Sandhill Cranes Revealed by GPS-Tracking

Sandhill cranes (Antigone canadensis) are long-lived birds with relatively low recruitment rates, making accurate knowledge of abundance and distribution critical for well-informed harvest management. Minnesota, USA, is one of few states containing portions of 2 distinct breeding populations of greater sandhill cranes (A. c. tabida)-the Mid-continent Population (MCP) and Eastern Population (EP). Historically, the breeding range of MCP cranes in Minnesota was restricted to the extreme northwestern portion of the state, whereas the breeding range of EP cranes was limited to the east-central part of the state with a large area of separation between the 2 populations. Whereas MCP cranes have exhibited stable population estimates over time, EP cranes are currently experiencing a significant increase in population size and a concurrent expansion of breeding range. Our objectives were to evaluate the current range boundaries of the 2 populations in Minnesota and determine whether the populations overlap on their breeding areas and autumn staging grounds. We captured and attached Global Positioning System-Global System for Mobile Communications transmitters to 50 cranes in the zone between the historical breeding-range boundaries of the 2 populations. Movements of cranes revealed that EP cranes have greatly expanded their breeding range in Minnesota while MCP cranes have experienced more moderate range expansion in the state. Results of this study provide the first documentation of overlap between the breeding ranges of EP and MCP sandhill cranes. Our results also suggest that staging areas in northwestern Minnesota, where recreational harvest targeted at MCP cranes was allowed beginning in 2010, are being used by both populations and there is overlap in migration corridors, as evidenced by 4 cranes that used both the Mississippi and Central Flyways. (C) 2017 The Wildlife Society.