Migratory Ecology and Movement Patterns of Mid-Continent and Eastern Sandhill Cranes

Abstract

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 is one of few states containing portions of 2 different breeding populations of greater sandhill cranes (A. c. tabida)—the Mid-continent Population (MCP), which has a harvest season in northwestern Minnesota in the fall, and Eastern Population (EP), which is not currently harvested in the state. Although the historical range boundaries of these populations have not been in close proximity during the 20th century, EP cranes are currently experiencing a significant increase in population size and a concurrent expansion of breeding range. A better understanding of range boundaries and information regarding fine-scale space use of cranes (both adults and juveniles) at different times of the year, is necessary to inform harvest management (e.g., determination of appropriate hunting zone boundaries and timing of harvest season). Our objectives were to 1) evaluate the current range boundaries of the 2 populations in Minnesota and whether the populations overlap on their breeding areas and autumn staging grounds; and 2) characterize the fine-scale movements and behavior of cranes after their arrival on breeding grounds in the spring until fall staging. 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. We were able to document, for the first time, overlap between the breeding ranges of EP and MCP sandhill cranes. EP and MCP cranes also both used some of the same staging areas in northwestern Minnesota, where recreational harvest targeted at MCP cranes began in 2010. Moreover, we observed multiple cranes using both Mississippi and Central flyways when migrating between breeding and wintering grounds; choice of flyway has historically been used to assign population affiliation (Mississippi Flyway = EP, Central Flyway = MCP). Juvenile and adult cranes exhibited different movement strategies during the spring and summer. Juveniles traversed larger areas and were more likely to display long-distance roaming behavior, whereas adults were more likely to revisit the same areas. We hypothesize that these differences may reflect constraints adults experience when nesting and brood rearing, and differential knowledge of the landscape between adult and juvenile birds.