Explanation of Indicator
Given its status as a threatened species in Florida and its dependence on a high quality coastal habitat, the eastern brown pelican is important as an indicator of the state’s coastal environmental health and the declining abundance of coastal habitat. M
angroves are the preferred nesting substrate in Florida. Loss of or reduction in nesting substrate may result in a decline in nesting effort. Additionally, without the proper nutritional base to support nesting efforts, pelicans will not nest. Therefor
e declining trends in nesting populations of eastern brown pelicans may indicate degradation of nesting substrates or fluctuations in the food supply.
Data Characteristics
SOURCE
Annual reports are maintained by the Florida Game and Fresh Water Fish Commission, Bureau of Wildlife Research. They are available from Brad Gruver at 620 South Meridian Street, Tallahassee, Florida 32399-1600, or at (904) 488-3831. The raw data can be
obtained from Steve Nesbitt at the Florida Game and Fresh Water Fish Commission, Wildlife Research Laboratory, 4005 South Main Street, Gainesville, Florida 32601, or at (904) 955-2230.
ACQUISITION
Reports are produced in hard copy format, and raw data are available on floppy disk in database format at no cost.
COLLECTION
The Florida Game and Fresh Water Fish Commission has been collecting brown pelican data since 1968. In 1983 data collection efforts were changed to a biennial survey; however, concern over the brown pelican's nesting effort and success prompted a return
to annual nesting surveys in 1991.
Data Limitations
The data are reliable and consistently collected over time and should provide an excellent measure of the health of the coastal environment. There are several data limitations, however. The number of nests must be estimated due to the inherent limitatio
ns of an aerial survey. And, because the survey is conducted one time per year, an underestimation of nests may occur, as the “nesting peak” may vary between areas.
Data Analysis
Between 1968 and 1989 brown pelican nesting populations followed a generally increasing trend. This may be attributed to increases in nesting populations, increased survey efforts, or both. Nesting population declined from 12,310 in 1989 to 8,866 in 199
3. This decline in nesting effort may be a result of the mangrove-destroying freezes of the 1980s. Pelicans have been forced to use alternative types of vegetation or nest on the ground due to the degradation of the nesting substrate. In 1994 the brown
pelican nesting population was 9,278.
Year Nesting Population Year Nesting Population 1968 6,936 1982 8,666 1969 6,133 1983 6,980 1970 7,690 1984 n/a 1971 5,923 1985 9,078 1972 7,990 1986 n/a 1973 6,010 1987 10,882 1974 6,090 1988 n/a 1975 5,950 1989 12,310 1976 5,491 1990 n/a 1977 6,532 1991 10,208 1978 7,780 1992 9,335 1979 8,942 1993 8,866 1980 8,095 1994 9,278 1981 8,125