Abstract:
The Rookery Bay Estuarine Research Reserve in Naples, Florida, is comprised of a variety of different habitats within approximately 110,000 acres of protected land. In these various niches fed by the shallow estuary waters, as well as the deeper bays and sloughs, live dozens of species of wading and diving birds. On December 12th, 2010, the Marine Ecology class of Hiram College conducted a directional study of birds returning to a single rookery island in Rookery Bay in an hour and fifteen minute time period. We looked at the numbers and directions of flight of eight different species as they returned from feeding to roost on the island for the night. These species were the brown pelican, great egret, snowy egret, white ibis, glossy ibis, double-crested cormorant, little blue heron, and tri-colored heron. Our circular statistical analysis revealed that six of the eight observed species returned to the rookery from non-random directions. The mean vector bearings, or average angles of return, as well as the p-values for both the great egrets and glossy ibis, were found to be random in 2010. Five of the six species showing non-random orientation agreed with results from previous years' data. The double-crested cormorant, the only trend exception, has not been found to have a non-random return direction since 2004. The total numbers of each species recorded in 2010 have decreased since their observed peak in 2006, with the exception of the double-crested cormorant, whose numbers have increased since that time.