Bald Eagle
Haliaeetus leucocephalus
Bald eagles were historically found on all the Channel Islands and on mainland southern California. The southern-coast mainland population disappeared by the 1930s, most likely as a result of habitat loss from encroaching development and harassment. Bald eagles were present on the Channel Islands until the mid-1950s or early 1960s, but no successful nesting activity was known. The reasons for the decline and eventual disappearance of bald eagles on the Channel Islands are not completely understood. Possible causes include shooting, egg collecting, nest destruction, poisoning, removal of young from nests, and nest disturbance (Kiff 1980). The most likely cause of population declines, however, was the production and use of the industrial pesticide DDT (dichloro-diphenyl-trichloro ethane). Between 1947 and 1961 an estimated 37 to 53 million liters of DDT-contaminated acid sludge, containing 348-696 metric tons of DDT, were disposed of in an ocean dump site 16 km northwest of Catalina Island. In addition, it was estimated that another 1800 metric tons of DDT were discharged from the Joint Water Pollution Control Plant outfall, 3.3 km offshore of Palos Verdes Peninsula (Chartrand et al. 1985). The introduction of DDT into the Santa Monica Basin marine ecosystem was implicated in the decline of two other piscivorous bird populations on the Channel Islands, the brown pelican (Pelecanus occidentalis) and the double-crested cormorant (Phalacrocorax auritus) (Risebrough et al. 1971, Gress et al. 1973). These declines coincided with the decline of bald eagles as a breeding species on the Channel Islands.
The use of DDT was banned in the United States in 1972. By the late 1970s other bird species that had been affected by the pesticide, such as pelicans and cormorants, were again successfully breeding.
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These two bald eagle nestlings were the first to be banded in a nest on San Clemente Island. The size of the nest suggests it has been used in prior years and these are likely not the first produced at this location.
A biologist approaches the nest at Trap Canyon on Santa Rosa Island; one of many nests where juvenile bald eagles are given identification bands, wing tags and transmitters, allowing us to monitor their movements.
Literature Cited
Chartrand, A. B., S. Moy, A. N. Safford, T. Yoshimura, and L. A. Schinazi. 1985. Ocean dumping under Los Angeles Regional Water Quality Board permit: A review of past practices, potential adverse impact and recommendations for future action. California Regional Water Quality Control Board, Los Angeles Region, March 1985 47 p.
Gress, F., R. W. Risebrough, D. W. Anderson, L. F. Kiff, and J. R. Jehl, Jr. 1973. Reproductive failures of double-crested cormorants in southern California and Baja California. Wilson Bulletin 85:197-208.
Kiff, L. F. 1980. Historical changes in resident populations of California islands raptors. Pages 651-673 in D. M. Power (ed.), The California islands: Proceedings of a multidisciplinary symposium. Santa Barbara Museum of Natural History, Santa Barbara, CA.
Risebrough, R. W., F. C. Sibley, and M. N. Kirven. 1971. Reproductive failure of the brown pelican on Anacapa Island in 1969. American Birds 25:8-9