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Water conditioning and whooping crane survival after release in Florida

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Abstract

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.

Additional Publication Details

Publication type:
Book chapter
Publication Subtype:
Book Chapter
Title:
Water conditioning and whooping crane survival after release in Florida
Year Published:
2001
Language:
English
Publisher:
North American Crane Working Group
Publisher location:
Seattle, Washington
Contributing office(s):
Patuxent Wildlife Research Center
Description:
ix, 226
Larger Work Type:
Book
Larger Work Subtype:
Other Government Series
Larger Work Title:
Proceedings of the Eighth North American Crane Workshop
First page:
160
Last page:
165