Point Reyes Light - August 1, 2002
Pt. Reyes study predicts more birds here
By Ivan Gale
In the fall of 2003, when birds from the pacific northwest descend upon Point Reyes as part of their annual migration to wintering grounds in Western Mexico, birders may be surprised to see more flycatchers, thrushes and warblers because of the predicted El Niño winter.
Report released
So says the Institute for Bird Populations (IBP), of Point Reyes Station. The institute released the results of a new study this week.
The report stated following El Niño winters, when the weather in western Mexico is cooler and wetter than normal, birds in the Pacific Northwest raise more young.
The report suggested more insects and fruits are available as food for birds, allowing them to maintain good physical condition before and after their migration northwards and to produce more young.
Though most of these birds spend their summers in Oregon and Washington, the birds stop over in Point Reyes during their annual southern migration. "Point Reyes is a hotbed for lots of migrants passing through," said Nicole Michel, a biologist for IBP.
Next fall, when the birds born after El Niño once again fly down to Mexico, there should be a much greater number of neotropical wintering birds stopping through Point Reyes, and birders can expect to see increased sightings of Swainson’s thrush, Townsend’s Warbler, Wilson’s warbler, Warbling vireo, the Hammond’s, Dusky, and "Western" flycatchers, Common yellowthroat, and Western tanager, among other species.
El Niño
Populations of swallows that nest in the eaves of West Marin barns every summer may also be increased by El Niño, said report lead author Phil Nott, though he noted swallows were not included in the study.
Nott said bird populations are affected by La Niña weather conditions as well. La Niña is a weather phenomenon that, like El Niño, is affected by the intricate relationship between ocean and atmosphere. La Niña, however, results in a hotter and dryer winter in western Mexico.
These conditions, though, adversely affect bird productivity. "In the two big El Niño years of 1992 and 1997, the reproductive success of neotropical migrants in the Pacific Northwest was two to three times greater than it was in the extreme La Niña year of 1999," Nott said.
Nott explained that while the El Niño weather pattern is generally believed to be a cyclical event that occurs around every four years, it is happening with increased frequency, as 1993 and 1998 also experienced El Niño-type conditions. "We’ve seen some extreme El Niño and La Niña events in the last two decades compared with the rest of the century," he said.
La Niña
Dr. David DeSante, executive director of the institute and creator of the Monitoring Avian Productivity and Survivorship (MAPS) program that collected the data for the institute’s report added an additional perspective: "Of course, the El Niño/Southern oscillation may affect birds’ condition through other factors in addition to food, such as wind directions over migration routes. Tailwinds during El Niño years may help push the birds northward," he said. "During La Niña years, the birds face more headwinds during migration. In those years, they may arrive on their nesting grounds later and be less physically able to lay eggs and raise young."
Scientists obtained results for the report by analyzing data from nine years of operating 36 MAPS stations on six national forests in Washington and Oregon.
MAPS consists of a nationwide network of over 500 bird-banding stations that monitor the birth and death rates of birds. Though none are in West Marin, the institute calls Point Reyes Station its administrative home because it is where its executive director Dr. DeSante resides. DeSante is also the former program director for the Point Reyes Bird Observatory.