OSPREY (Pandion haliaëtus) NIGHT ROOSTING AT LOCK AND DAM 19, MISSISSIPPI RIVER.

Heather R. Grimm, T. C. Dunstan
Department of Biology, Western Illinois University, Macomb, IL, 61455.

During the fall migration period of 2001, osprey, Pandion haliaëtus, population 
size, night roost entry and exit times, and related behavior were studied at 
Lock and Dam 19, Mississippi River.  Data were gathered weekly (Friday evenings 
and Saturday mornings) on eight occasions from Aug 31 to Sep 21, 2001.  This 
study used ground observation surveys to document the number of ospreys 
foraging, resting and night roosting in the subject area along on the Illinois 
riverbank area.  The counts of ospreys varied between one to 36 ospreys per 
observation period.  Data on foraging activity as related to night roost morning 
exit and evening entry times were analyzed and plotted in relation to official 
sunrise and sunset times, respectively.  The locations for night roosting within 
the river ecosystem were identified, and the relative use of landscape was 
analyzed via Chi-Square and Simpson's Diversity analyses.  The study area is a 
multiple use area for fish-eating avian species and this pilot study provides 
information for future research and applied management for ospreys using the 
area during both fall and spring migration.

Keywords: Pandion haliaëtus, osprey, migration, Mississippi River, night 
roosting