|(Editor's note: This is the first in what will be an occasional series of brief essays providing background information on phenomena CoastWatchers and other beach visitors may observe out on the shore. This debut "Sightings” article was contributed by Bonnie Henderson, adopter of Mile 157 and author of Strand: An Odyssey of Pacific Ocean Debris.) |
Recent news about dead or emaciated and apparently starving brown pelicans has brought new attention to a species that has made a spectacular comeback on the West Coast. The species is typically a spring, summer and fall visitor, migrating north to Oregon after breeding in southern California and Mexico. But widespread use of organochlorine pesticides (DDT and its relatives) in the 1950s and ‘60s wrecked havoc on brown pelican, bald eagle, peregrine falcon and other bird populations. DDT alters birds' calcium metabolism, thinning their eggshells to the point where the shells are not able to support the weight of the adult bird, which inadvertently crushes the shell during incubation. By the time the problem was identified and DDT was widely banned in the U.S. in 1972, the number of nesting pairs in southern California and northern Baja California had fallen to fewer than 1,000 pairs (with virtually no reproductive success), and in 1973 the brown pelican was listed as an endangered species.
Brown pelicans were slower to recover from the DDT scourge than were bald eagles, but rebound they have; in 2006, the population of southern California-northern Baja birds had risen to an estimated 11,695 breeding pairs. They're visiting the Oregon coast in much larger numbers now, skimming the waves in their characteristic formations. As a result, the West Coast populations of brown pelicans were “delisted”—removed from the federal Endangered Species List—on Dec. 17, 2009, making the brown pelican one of only nine endangered bird species ever to recover enough to be delisted. Non-breeding subadult pelicans usually start arriving in April, joined later by post-breeding adults and juveniles; their population peaks in August and September, and most birds head south again in November. Historically, a few have lingered into December or even stayed all winter long.
But overwintering pelicans (especially immature birds) are vulnerable to storms and wind, which challenge the birds’ ability to survive. Both the increasing population and the winter vulnerability of pelicans is reflected in recent statistics from COASST (Coastal Observation and Seabird Survey Team), the citizen science project that tracks numbers of dead birds on Northwest beaches. In 2005-06, a total of only two dead pelicans were found by COASST volunteers on beaches monitored in Oregon and Washington. The next year seven were found, and in 2007-08 they found 22. Last year (the year ending in May 2009) COASST volunteers found 70 dead pelicans—a huge jump from the previous year.
Most years, pelican deposition peaks right about now, in January. This year (2009-10), COASST saw an early spike, last December, when 24 brown pelicans were found by CoastWatcher Robert "Olli" Ollikainen on Mile 286. COASST staff attribute it to a “wreck”—their term for a single, anomalous incident, or what they call “wrong place, wrong time” for the birds. Lots of pelicans hang out on Cape Meares Lake; the deaths were an apparent result of a single big storm. CoastWatch volunteers can expect to see evidence of more wrecks like this one, now and then, as the brown pelican population is reinvigorated and returns to historic levels.
Contact: Bonnie Henderson