North American Crane Working Group

 

Date of this Version

2005

Document Type

Article

Citation

Westwood, C.M., and F. Chavez- Ramirez. Patterns of food use of wintering whooping cranes on the Texas coast. 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. 133-140.

Comments

Reproduced by permission of the NACWG.

Abstract

Whooping Crane (Grus americana) fecal samples were collected from Matagorda Island National Wildlife Refuge (MINWR) during winter and fall of 1993-94 (Winter-1; n = 59), and Aransas National Wildlife Refuge (ANWR) during winter and fall of 1993-94 (n = 102) and 1994-95 (Winter-2; n = 257) to study crane diets and compare patterns of food use in these areas. Food items varied between areas, across months, and between years in both frequency and percent volume. Blue crab (Callinectes sapidus), wolfberry fruit (Lycium carolinianum), horn snail (Cerithidea pliculasa), razor clam (Tagellus plebius), and orthopteran insects were present in feces samples at both ANWR (both winters) and MINWR during parts of the winter. Blue crab increased in both frequency and percent volume throughout the two winters on ANWR, and MINWR (Winter-1), while wolfberry fruit use declined. Horn snail presence in ANWR samples increased in frequency throughout both winters, while percent volume remained constant. No frequency trend was observed for horn snails in samples from MINWR, however, percent volume increased in the middle of the study period. Food niche breadth (dietary diversity estimated by 1/Σpi 2) was higher both years at ANWR (4.41 in Winter-1; 5.17 in Winter-2), than at MINWR (3.62). Dietary overlap was higher between Winters-1 and 2 on ANWR (91%) than between ANWR (Winter-1) and MINWR (82%). Dietary overlap between months indicate a change in diet which could be due to a loss of the wolfberry in the diet.