Date of this Version
Sherry, D.A., and F. Chavez-Ramirez. Use of wading birds as indicators of potential whooping crane wintering habitat. In Chavez-Ramirez, F, ed. 2005. Proceedings of the Ninth North American Crane Workshop, Jan 17-20, 2003. Sacramento, California: North American Crane Working Group. Pp. 127-132.
A search for suitable wintering sites on which to establish another migratory population of whooping crane (Grus americana) has been conducted and will continue. In addition to an evaluation of food availability for whooping cranes, wading birds that overlap highly in patterns of habitat utilization with whooping cranes may be useful as indirect indicators of suitable whooping crane habitat. We determined the extent to which several species of wading birds overlap in patterns of habitat utilization with whooping cranes on their current wintering grounds. We conducted aerial surveys of whooping cranes and wading birds at Aransas and Matagorda Island National Wildlife Refuges, Texas. We classified habitats used in order of increasing surface area as pools, ponds, lakes, and bays. We observed species which included whooping cranes (N= 638), great egrets (Casmerodius albus) (N=987), great blue herons (Ardea heroidias) (N=751), reddish egrets (Egretta rufescens) (N=301), snowy egrets (Egretta thula) (N=155) and tricolored herons (Egretta tricolor) (N=67). Specific overlap indices indicated that great egrets had the highest overlap with whooping cranes (0.97), and tricolored herons also overlapped significantly (0.87). Reddish egrets (0.74), snowy egrets (0.69), and great blue herons (0.60) overlapped to a much lesser extent. We recommend that surveys conducted for the purpose of locating suitable wintering habitat for whooping cranes should focus on habitats utilized by great egrets and tricolored herons.