Osprey (Pandion haliaetus) Population and the Availability of Menhaden (Brevoortia tyrannus) as Their Food Source in Chesapeake Bay: Historical and Present-day Comparison

Sources/Usage: Public Domain. View Media Details

What is at stake? 

Ospreys feed primarily on fish and during reproduction, they reduce their brood size to match prey availability. In the more saline portions of the lower Chesapeake Bay, menhaden comprise much of their diet. USGS is determining if the current menhaden availability is sufficient to support a demographically stable osprey population.  

What is our approach? 

Comparison of contemporary data to historic information will provide insight on the theory that a reduced fraction of menhaden is resulting in a decline of osprey in the higher salinity areas of the Chesapeake Bay. To determine if there is a lack of menhaden that is affecting osprey reproductive rates in portions of the Chesapeake, USGS is:  

1. Compiling and evaluating historic data on the osprey population, reproduction, food habits and environmental characteristics in the Chesapeake Bay region. 

2. Determining osprey reproductive rates for the sustainability of the local osprey population in regions of the Chesapeake Bay where menhaden availability may be changing due to commercial harvest or other environmental characteristics.  

3. Using game cameras to document the fish delivered to osprey nests during the nestling period to determine brood provisioning rates. 

What are the benefits? 

Determining if prey delivery to nestlings or other environmental factors are affecting osprey reproductive success in portions of the Chesapeake will help state agencies and management organizations like the Atlantic States Marine Fisheries Commission evaluate how well the current fish harvest policy supports non-commercial species like birds whose diet is almost exclusively fish.