WATER CONDITIONING AND WHOOPING CRANE SURVIVAL
AFTER RELEASE IN FLORIDAGEORGE F. GEE, USGS Patuxent Wildlife Research Center, 12011 Beech Forest Road, Laurel, MD 20708-4041, USA
JANE M. NICOLICH, USGS Patuxent Wildlife Research Center, 12302 Beech Forest Road, Laurel, MD 20708-4022, USA
STEPHEN A. NESBITT, Florida Fish and Wildlife Conservation Commission, 4005 S. Main St., Gainesville, FL 32601-9099, USA
JEFF S. HATFIELD, USGS Patuxent Wildlife Research Center, 11510 American Holly Drive, Laurel, MD 20708-4017, USA
DAVID H. ELLIS, USGS Patuxent Wildlife Research Center, 11410 American Holly Drive, Laurel, MD 20708-4019, USA
GLENN H. OLSEN, USGS Patuxent Wildlife Research Center, 12302 Beech Forest Road, Laurel, MD 20708-4022, USA
About 50% of the whooping cranes (Grus americana) released in Florida die within the first year of release. Most of these deaths and those in subsequent years result from bobcat (Lynx rufus) predation. Choosing release sites in open marshes away from bobcat habitat has improved survival. We hypothesized that exposure to ponds (water conditioning) at the rearing site would encourage birds to roost in deeper water marshes after release and such exposure would thereby reduce bobcat predation. In this study, we moved young birds (ca 50 days of age) to netted pens with large (15-m diameter), deep (30--60 cm) naturally vegetated ponds. We randomly assigned the costume-reared whooping cranes into 2 equal-sized groups at fledging. Some groups were placed in pens with a pond (experimental or ponded groups) and the others we reared without additional water exposure (control groups). All birds in the pens with ponds used the water. At night, they roosted at a depth of 36-46 cm. During the day, the birds used the ponds as well as other areas of the pen. We released 3 pairs of water-conditioned and control cohorts, 1 set in 1995 and 2 in 1996. No obvious behavioral differences were noted between the cohorts released in those years. Controls survived as expected (about 60% first year survival). The water-conditioned birds had much higher survival the first year (85%) and continued to survive better for the next 3 years.
PROCEEDINGS NORTH AMERICAN CRANE WORKSHOP 8:160-165
Key words: costume-rearing, Florida, Grus americana, parent-rearing, reintroduction, water conditioning, whooping crane.