CHANGES IN WINTER WHOOPING CRANE TERRITORIES AND RANGE 1950-2006

Authors

THOMAS V. STEHN, U.S. Fish and Wildlife Service
FELIPE PRIETO, U.S. Fish and Wildlife Service

Date of this Version

2010

Document Type

Article

Citation

Stehn, T.V., and F. Prieto. Changes in winter whooping crane territories and range 1950-2006.In: Hartup, Barry K., ed., Proceedings of the Eleventh North American Crane Workshop, Sep 23-27, 2008, Wisconsin Dells, Wisconsin (Baraboo, WI: North American Crane Working Group, 2010), pp. 40-56.

Comments

Reproduced by permission of the North American Crane Working Group.

Abstract

The whooping crane (Grus americana) winters on the Texas coast primarily in salt marsh habitat. The location of adult whooping crane winter territories during 9 winters between 1950 and 2006 was derived from aerial census data digitized onto infrared photos using GIS software. Range expansion, including changes in distribution and size of winter territories, was analyzed over a 57-year period as flock size increased by 765%. Crane pairs have opted to establish territories in or close to the traditional winter area rather than moving long distances along the coast. This distribution seems based on the preference of the male crane to establish a territory as close as possible to its parents. Colonizing occurred to the nearby areas of Matagorda Island in 1958, San Jose Island in 1969, Lamar Peninsula in 1971, and Welder Flats in 1973. Minimum territory sizes were calculated to be 101 ha for Aransas National Wildlife Refuge and West St. Charles Bay, 139 ha for Welder Flats, 204 ha for Matagorda Island and Welder Flats, and 304 ha for San Jose Island. Salt marsh habitat was measured to determine if enough winter area is present to reach recovery targets and to predict expected use patterns for the near future. Based on an average winter territory size of 172 ha, the current winter range and contiguous areas can support up to 576 whooping cranes. Additional salt marsh habitat was measured in a 111-km radius from Aransas National Wildlife Refuge. If suitable, this noncontiguous area could support an additional 580 whooping cranes to reach a total flock size of 1,156. However, with the Texas coast undergoing rapid development and sea level rise, there is insufficient protected habitat for whooping cranes to reach recovery targets.