June 20, 2006
Preliminary results of the California Department of Fish and
Game’s (DFG) investigation into central coast California brown
pelican deaths indicate causes may be starvation and malnutrition.
The large number of recently fledged birds competing with adults
for the existing food supply might be the reason for unusually
high mortality rates.
DFG veterinary pathologists from the Marine Wildlife Care and
Research Center have been investigating the mystery since early
May, when the endangered birds first started stranding in the
Ventura area. They will continue to examine affected pelicans and
issue a report once significant findings and summary information
have been collected.
Several dozen adult and immature pelicans, either very sick or
dead were found on Ventura County beaches in May. Initially, the
birds’ symptoms suggested possible domoic acid intoxication, but
laboratory test results have so far been inconclusive. By June 1,
investigators had found as many as 100 more pelicans with similar
symptoms, first in the Pismo Beach and Morro Bay areas, and then
in the Monterey Bay area. These pelicans were almost exclusively
juveniles in poor body condition. In the last few days,
investigators sent 31 dead pelicans to DFG’s wildlife care and
research center in Santa Cruz, where biologists and veterinary
pathologists are examining them. Starvation and malnutrition are
the most common findings, but one bird had a broken wing and one
was heavily oiled.
California brown pelicans breed and lay their eggs in winter, with
the majority nesting in Mexico and smaller numbers on California’s
Channel Islands. The eggs hatch in early spring and chicks usually
begin to fledge in May and June. Nesting was very successful this
year, with the first breeding on Prince Island in recent history.
Both state and federal agencies have listed the brown pelican as
an endangered species since the 1970s, due to severe reproductive
failure caused by DDT pollution. Recovery efforts over the last
three decades have resulted in the seabird again becoming a common
sight along the West Coast. In light of the rebound success, the
U.S. Fish and Wildlife Service is considering delisting the
species in the near future.
The DFG has been working with the UC Davis Wildlife Health Center
and the International Bird Rescue Research Center throughout this
investigation.
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