IN ANCIENT ROME “bird seers” were priests, or augurs, who delivered prophecies based on their observations of birds. The right combination of bird behaviors augured favorable conditions, but the wrong patterns spelled trouble.
Today, spanning nearly 60 years, in partnership with the Point Reyes National Seashore within its southern border, generations of modern-day bird seers have been banding birds, collecting an extensive dataset to track changes in bird populations as an indicator of environmental health. Near the northern California hamlet of Bolinas, avian ecologists at the Palomarin Field Station, run by Point Blue Conservation Science, are studying the interrelationship of birds and their habitats, and training early-career scientists in the practice of bird banding and other field techniques.
“Palomarin is California’s longest-running bird-banding field station with a songbird nest-monitoring and territory-mapping program that spans four decades,” explains Diana Humple, senior avian ecologist who leads the field station’s programs for Point Blue, based in Petaluma. “Our primary objective is to track bird populations, looking at environmental fluctuations like habitat and climate change, and how these may impact birds.”
Long-term shifts in temperatures and weather patterns can be natural, due to changes in the sun’s activity or large volcanic eruptions. Since the 1800s, however, human activities have been the main driver of climate change, primarily due to the burning of fossil fuels like coal, oil and gas, and the subsequent production of greenhouse gases — especially carbon dioxide — released to the atmosphere and causing the earth to warm over time.
On the front lines of habitat conservation
Avian biologists are often among the first to see the impact of environmental changes and habitat loss by studying bird numbers and their species diversity. A 2019 study in the journal Science by a consortium of scientists and conservation organizations, revealed the cumulative loss of nearly 3 billion birds across most North American flora and fauna communities since 1970. This decline signals a pervasive and ongoing avifaunal crisis due to habitat loss and climate change. Forests alone have lost 1 billion birds, while grassland bird populations have declined by 53%, or another 720 million birds.
Ecologists at Palomarin band birds to understand their migration patterns, populations and survival rate, and assess the impacts of environmental changes and contaminants. In addition to providing insights into the effects of climate change and human development on bird populations, bird banding provides a wealth of data to support species recovery programs for endangered birds and informs conservation and land management decisions. Moreover, the practice helps to address bird diseases such as H5N1 bird flu that may threaten human health.
Studies at Palomarin help to differentiate normal environmental impacts from those that may be attributable to climate change. Many changes in bird diversity are driven by changes in vegetation, while others are influenced by temperature and precipitation. White-crowned Sparrows and California Towhees, for example, are not as numerous as coastal scrub vegetation is replaced by forest. “Douglas-firs are encroaching on the coastal prairie system. It’s happening here, but it’s also happening up and down the California coast,” Humple noted.
A recent review published by Point Blue indicates changes in climate are influencing when various species of migratory birds arrive at their wintering habitats. “One thing we look at is the seasonal arrival timing of migratory birds. Bird arrival times are often changing year to year relative to weather conditions — we’re seeing a lot of variability in when various species arrive.”
Palomarin is also a community resource where people observe science in action. Every year, approximately 1,500 students and community members learn how decades of data on bird populations inform their ongoing studies. “There’s an immense power of seeing a wild animal up close, learning about it, and making the connection between the creature and the action that people take with conservation management,” Humple added.
One of the world’s premier facilities for training field biologists in avian ecology, Palomarin has welcomed more than 700 interns and apprentices from 23 countries since 1966. Data collected on songbirds and their habitat, and the impact of environmental change, have been the basis for more than 100 scientific papers.
Natalia Ocampo-Peñuela, born in Colombia, received training in mist netting and bird banding at Palomarin in the fall of 2009 as an undergraduate via an internship from the Park Flight Migratory Bird Program, National Park Service, U.S. Department of the Interior. “I never had a rigorous, structured experience in bird banding,” she said. “This was a tool I wanted to use in my Ph.D. research. I applied to Point Blue, and I was incredibly lucky to be able to join Palomarin. I had some of the best times of my life, and I felt like I was getting the highest quality training I have ever seen in bird banding.”
Ocampo-Peñuela also enjoyed conducting bird-banding demonstrations for Palomarin visitors. “I loved seeing the kids from schools come in and we would take them on walks to check the mist nets and show them how we band birds. Seeing the look in their eyes, their smiles, was really something that I always enjoyed.”
Now assistant professor of field conservation ecology at the University of California, Santa Cruz, Ocampo-Peñuela teaches and continues her research, including a 15-year program that began in Colombia on bird-window collisions which are responsible for more than a billion bird deaths per year worldwide. “It’s one of the direct causes of human-caused mortality in birds and a pretty big issue, especially for migratory birds.”
Net proceeds
Mark Dettling, Point Blue avian ecologist, studies birds in the riparian ecosystems of coastal California, coordinating Point Blue’s Pacific Flyway Shorebird Survey, and helps to train the next generation of field biologists at Palomarin. On a brisk, sunny morning he monitored several black finely meshed nets for captured birds to band.
About 40 feet long and 8-to-10 feet high, each “mist net” is hung between two poles at a location not far from the field station where birds are apt to fly. In a loose pocket of the net, he spots a local inhabitant flittering its wings — a black and yellow Townsend’s Warbler common to Douglas-fir forests. After safely dislodging the bird from the net, he carefully places it in a small cloth bag for data collection and banding at the field station.
“On average 10 birds per day are captured in the mist nets,” said Dettling, walking back to the field station. He joined Point Blue communications manager Lishka Arata and apprentice Jacqueline Quinones, who are collecting data on several birds caught that morning.
“After we identify a bird, the first thing we want to do is get a band on the bird’s leg. The U.S. Geological Survey is the permitting agency for the U.S. Band numbers don’t overlap. There’s a unique identifier, a nine-digit number for each bird that’s kept in a central database.”
Holding a metal template for estimating a bird’s leg diameter, Dettling explained there’s a different sized band for each bird, so it fits snugly on the bird’s leg and doesn’t fall off. “They’re very light. Our scales, which go down to a tenth of a gram, wouldn’t register the band.”
Recaptures of banded birds from Palomarin provide key information about their seasonal behavior. “We often capture the same bird multiple times. On those rare occasions when it’s not clear where a bird was banded, we’ll submit its band information to the USGS Bird Banding Lab, and they can look in the main database and tell us where it was banded,” Dettling said.
It takes about 10 minutes to measure and record data on each bird before it is released. “We note species, sex, individual marks, age, weight, whether it’s got fat, take wing measurements, and examine if it’s growing other feathers.”
Dettling explained how a young bird’s age can be determined by examining patterns of skull development visible through the skin of a bird’s head. “We look at skull development by parting the feathers on the head to examine layers of bone. It takes 3-to-6 months for a bird’s skull to fully develop. They only have one layer when they’ve recently hatched. The second layer grows in during the subsequent months.”
After all the required measurements and data are collected, Dettling releases the fragile feathered passerine back to the wild. “What we do can be boiled down to understanding birds and how they’re interacting with their environment … when we see population changes, we’ll have a much better idea of why that may be happening.”
Palomarin Field Station offers bird-banding demonstrations to drop-in visitors of 1-to-5 people, and by-appointment-only for classes, larger groups, or smaller groups with special requests. More information can be found on the Point Blue website.
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