Population dynamics of the cattle Egret in Texas, 1954-1999

Cattle Egrets probably established the first breeding colonies in the coastal area of Texas between 1954-1959. The first nests were recorded in Galveston Bay on the upper coast in 1959 and probable breeding birds were also seen on the lower coast and in southeast Texas. Between 1959-1968, they had breeding colonies in coastal and southeast and northeast inland areas. From these nuclear areas, they radiated (1969-1975) until most of the coast and eastern area of Texas was colonized (1976-1999). Between 1987-1999, small scattered colonies have been established in west Texas. Range expansion and colonization were uniformly linear. Population growth was logistic with an upper asymptote reached about 1979. Apparently, there is an annual influx of immigrant breeding birds from Mexico or Central America. The limiting factor to population growth appears to be the availability of nest-sites within heronries established by native colonial herons and egrets