To conduct a comprehensive survey for Chesapeake Bay ospreys during the breeding seasons of 1995-1996, revealing their status, distribution, substrate use. Also, to assess spatial variation in population growth during the time period between two comprehensive surveys.

Project Description:

We surveyed the tidal portions of the Chesapeake Bay for nesting Ospreys (Pandion haliaetus) during the breeding seasons of 1995-1996. The population was estimated to contain 3473 ± 75 (SE) breeding pairs. The population has more than doubled since the comprehensive survey conducted in 1973. During this recovery, there has been considerable spatial variation in the rates of population growth. Mean doubling times for well-defined subregions varied from a low of 4.3 yr to more than 40 yr. In general, growth rates have been highest in the tidal fresh and upper estuarine areas, where pairs occurred in 1973. Based on the pattern and magnitude of the recovery, it seems that the Chesapeake Bay population experienced a greater decline during the post-World War II era than was previously believed. Nesting substrate use by Chesapeake Bay Ospreys has shifted since1 973. The use of trees for nesting has declined from 31.7-7.2% in 23 yr. Channel markers accounted for 53.5% of all nest structures in the current study. Platforms established specifically for Ospreys supported1 2.1% of pairs. The proliferation and diversification of artificial substrates throughout the Chesapeake Bay has been one of the most important factors contributing to recent population expansion.

Years: 1995 – 1996
Status: Complete
Project Partners: Funding was provided by the Legacy Program of the U.S. Department of Defense and The Center for Conservation Biology
CCB Staff: Bryan Watts, Mitchell Byrd, Marian Watts
Project Contact: Bryan Watts bdwatt@wm.edu (757) 221-2247

Watts, B. D., M. A. Byrd, and M. U. Watts. 2004. Status and distribution of breeding Ospreys in the Chesapeake Bay: 1995-1996. Journal of Raptor Research 38:47-54.

View this data in the CCB Mapping Portal.