Nesting Populations Of Brown Pelicans In Florida

Aerial searches and mail questionnaires revealed 22 active nesting colonies of brown pelicans (Pelecanus occidentalis) on small islands close to shore off the Florida peninsula and a number of additional colonies in Florida Bay and the Florida Keys between 1968 and 1970. The same nesting islands were occupied in most years. Nesting took place during late winter and spring in Florida Bay and during late spring and summer in colonies off the peninsula. The maximum numbers of nests counted during 1968, 1969, and 1970 was 6,926,6,100, and 7,690 respectively. This represents a conservative estimate of 12,200 to 15,380 brown pelicans nesting during the period of the census. Prebreeding age classes were not counted. Most colonies were in trees on small natural islands. One colony on a spoil island in Anclote Sound was on the ground. At least three other colonies were on w~olly or partially filled islands. Trees used for nesting had strong outer branches which offered unimpeded access to and from nests. Black mangrove (Avicennia nitida) was the principal tree used on the east coast and red mangrove (Rhizophora mangle) was the species most often used for nesting on the Gulf coast, although black mangrove was important on the Gulf coast also. The number of colonies and variety of nesting cover used were greater in the Gulf. The adult population has apparently remained stable in Florida duriI}g the past three years. The census techniques used in this survey are not sensitive enough to reveal small changes in population size; therefore, this survey gives no indication whether reproduction has been sufficient to sustain this population size over a long period of time.

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