Masters Thesis

The reintroduction of bald eagles on Santa Catalina Island, California

In 1980 a program was initiated to reintroduce bald eagles (Haliaeetus leucocephalus) to the California Channel Islands. Bald eagles were historically found on all of the islands, and were numerous on the larger islands. From 1980 through 1984, 20 eagles were translocated to Santa Catalina Island and reared on hacking platforms until released. All released birds returned to the platforms to feed. Early flights by the birds were comparable to other reintroduction programs and to wild reared eagles. The eagles subsisted on food provided by the investigators for up to seven weeks of age. There were seven known cases of mortality. Causes of mortality included shooting, electrocution on high power lines, and intraspecific aggression. Birds in the first, second, and third year age classes, all used available habitats significantly different than expected from random (P 0.05). Birds in their first year used only the chaparral differently than expected between seasons. Habitats used differently than expected between seasons for second and third year birds were relict coastal sage, oak woodland and relict oak woodland (second year birds); relict oak woodland and grassland (third year birds). Availability of carrion during the fall and winter hunting seasons may effect the distribution of the eagles on the island. Female eagles were significantly more successful (P = 0.001) in supplanting male eagles from carcasses and perches. Females were 100 percent successful in supplanting same aged males. Males of the same age only attempted to supplant females in 21 percent of the interactions (n = 58) and were successful in 42 percent of their attempts. Age does not appear to play as important of a role as sex in determining the outcome of supplanting attempts.

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