Paleoindian seafaring, maritime technologies, and coastal foraging on California's Channel Islands.

Three archaeological sites on California's Channel Islands show that Paleoindians relied heavily on marine resources. The Paleocoastal sites, dated between ~12,200 and 11,200 years ago, contain numerous stemmed projectile points and crescents associated with a variety of marine and aquatic faunal remains. At site CA-SRI-512 on Santa Rosa Island, Paleocoastal peoples used such tools to capture geese, cormorants, and other birds, along with marine mammals and finfish. At Cardwell Bluffs on San Miguel Island, Paleocoastal peoples collected local chert cobbles, worked them into bifaces and projectile points, and discarded thousands of marine shells. With bifacial technologies similar to those seen in Western Pluvial Lakes Tradition assemblages of western North America, the sites provide evidence for seafaring and island colonization by Paleoindians with a diversified maritime economy.

Pleistocene to historic shifts in bald eagle diets on the Channel Islands, California.

Studies of current interactions among species, their prey, and environmental factors are essential for mitigating immediate threats to population viability, but the true range of behavioral and ecological flexibility can be determined only through research on deeper timescales. Ecological data spanning centuries to millennia provide important contextual information for long-term management strategies, especially for species that now are living in relict populations. Here we use a variety of methods to reconstruct bald eagle diets and local abundance of their potential prey on the Channel Islands from the late Pleistocene to the time when the last breeding pairs disappeared from the islands in the mid-20th century. Faunal and isotopic analysis of bald eagles shows that seabirds were important prey for immature/adult eagles for millennia before the eagles' local extirpation. In historic times (A.D. 1850-1950), however, isotopic and faunal data show that breeding bald eagles provisioned their chicks with introduced ungulates (e.g., sheep), which were locally present in high densities. Today, bald eagles are the focus of an extensive conservation program designed to restore a stable breeding population to the Channel Islands, but native and nonnative prey sources that were important for bald eagles in the past are either diminished (e.g., seabirds) or have been eradicated (e.g., introduced ungulates). In the absence of sufficient resources, a growing bald eagle population on the Channel Islands could expand its prey base to include carrion from local pinniped colonies, exert predation pressure on a recovering seabird population, and possibly prey on endangered island foxes.