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Expert Insights “Yosemite Songbirds: How Are Yosemite Songbirds Responding to Climate Change?�

Autumn . Winter 2010 Issue 1


YOSEMITE YOSEMITE SONGBIRDS SONGBIRDS HOW ARE YOSEMITE’S BIRDS RESPONDING TO CLIMATE CHANGE? BY SARAH STOCK AND RODNEY B. SIEGEL Yosemite’s much celebrated birdlife is changing. A recent UC Berkeley study has found that during the past century many bird species have shifted their ranges within the Sierra, likely in response to changes in temperature and precipitation patterns. tions (IBP) and the National Park Service (NPS), discovered that Willow Flycatcher, a diminutive, gray-green songbird that brightens the soundscape of Sierra meadows with its infectiously the early 20th Century, and though it declined throughout the following decades, was apparently still breeding at isolated locations in the park until at least the late 1990s. ABOVE Western Tanager’s spread wing.

Yet these changes likely pale in comparison to changes that will result from accelerating climate change in the coming decades. Climate change models suggest that by late in the 21st Century, average annual temperature in the Sierra Nevada could increase by as much as 3.8º C. More precipitation will fall as rain rather than snow, and the Sierra spring snowpack may decline by as which has already increased during the past several decades, may increase as much as 90% in northern California. Plant community composition throughout the Sierra will change substantially, with losses of up to 80% of subalpine and shifting plant communities—will likely alter the ranges of Sierra bird species and restructure entire bird communities.



Assessing the effects of annual weather variation on birds, predicting the effects of future climate change, and identifying any management actions that might help cushion species from these effects are critical steps for safeguarding Yosemite’s bird populations, and thanks to an enduring partnership between Yosemite NP and IBP, we now have the tools to do all three.


Since 1990 we have operated summer bird banding stations at meadows spanning a large elevation gradient in Yosemite. The stations are part of the continent-wide Monitoring Avian Productivity and Survivorship (MAPS) Program, coordinated by IBP, and our Hodgdon Meadow station was the first MAPS station nation-wide operated by IBP biologists and the NPS. Capturing, banding, and releasing birds throughout the summer every year enables us to track changes in avian community composition, to produce annual indices of adult population size and reproductive success, to estimate annual survival rates, and most importantly, to assess changes in Yosemite’s bird populations over time. Banding birds at MAPS stations requires technical training, and a great deal of dedication. Each year we provide our crews with state-of-the-art training in bird monitoring – teaching them not just the basics of removing birds from nets without harming them, but also more nuanced skills, like determining the age of songbirds from subtle clues in their molt patterns and plumage. Crew members are typically young biologists just launching their careers in conservation science – for professional training and the satisfaction of contributing to bird conservation they are willing to volunteer full-time for an entire summer, a commitment that requires braving 4 a.m. alarm settings, chilly mornings, searing late-summer sunshine, clouds of mosquitoes, and sleeping on the ground for three months.

ABOVE Stock leading a bird banding demonstration.

“The joy of holding a living thrush, warbler, tanager, or other songbird in the hand – to feel its heartbeat, sense the warmth of its body, and really see it up close – inspires a career-long commitment to environmental conservation.” -Sarah Stock Wildlife Biologist

For many volunteers, the joy of holding a living thrush, warbler, tanager, or other songbird in the hand – to feel its heartbeat, sense the warmth of its body, and really see it up close – inspires a career-long commitment to environmental conservation. YOSEMITECONSERVANCY.ORG :: AUTUMN . WINTER 2010 02


More casual visitors and interested NPS staff to Yosemite’s MAPS stations are also able to share in this experience, through education and outreach efforts conducted in association with the monitoring. From teen-age Youth Conservation Corps to regional Audubon Society Chapters, songbirds connect young and old alike to the natural world. NPS Interpreter Naturalists leave the MAPS stations inspired to deepen these connections with other visitors through their bird walks and self-designed interpretive programs - widening the circle of bird conservation even further. This winter we will conduct a comprehensive analysis of 20 years of Yosemite MAPS data - using cutting edge analytical techniques to reveal relationships between annual weather variation and the population dynamics of Yosemite’s birds, and to make predictions about longer-term changes in bird populations likely to result from climate change. Preliminary results indicate that substantial changes in the populations of common bird species at our monitoring stations are already happening – we see significant increases in some species (e.g., American Robin, MacGillivray’s Warbler, and Mountain Chickadee), troubling decreases in several others (e.g., Chipping Sparrow, Dusky Flycatcher, Warbling Vireo, and Yellow Warbler), and evidence of upslope population shifts in several species of flycatchers.


ABOVE Researcher measuring wing chord BELOW Green Tailed Towhee


Our knowledge of songbirds in Yosemite has soared in the last decade – accomplishments include the completion of an extensive field-based inventory of park birds, updating Yosemite’s bird checklist for park visitors, conclusion of the Grinnell Resurveys, initiating and/or completing intensive single-species studies of Northern Goshawk, Peregrine Falcon, Spotted Owl, Great Gray Owl, Willow Flycatcher, and continued annual demographic monitoring of songbird populations at five of Yosemite’s meadows. Our upcoming analysis of 20 years of demographic data from the MAPS Program promises to yield great advances in our understanding of the effects of climate change on Yosemite’s birds, and to help formulate strategies for safeguarding those avian populations that are thriving in the park, and helping to recover those populations that are declining.


SARAH STOCK is a Wildlife Biologist at Yosemite National Park where she studies wildlife ranging from songbird population dynamics to bat ecology. Prior to joining the National Park Service, Sarah was a migratory field biologist working with endangered species in Hawaii and the Marianas Islands, breeding birds in Alaska, spring migrating birds in Louisiana, and conducting bird monitoring programs at Idaho Bird Observatory (six seasons) and Ventana Wildlife Society’s Big Sur Ornithology Lab (four years). She earned her Master’s degree at the University of Idaho in 2001. Sarah has authored many technical reports and peer-reviewed publications on western landbird status, ecology, and management; and serves on California Partners in Flight Executive Steering Committee. Now living in Yosemite Valley, Sarah’s favorite past-time is building her six-year-old daughter’s life list. YOSEMITE CONSERVANCY has provided a grant to Yosemite National Park to help fund the Yosemite MAPS stations; this research enables park biologists and managers to better understand Yosemite songbird populations today and predict longer-term changes in the future. Experience Yosemite’s songbirds up-close and personal with a knowlegeable park naturalist. Yosemite Conservancy offers a variety of birding courses that will focus on locating and observing birds, as well as learning to identify their songs and environments. Learn more at our website: YOSEMITECONSERVANCY.ORG :: AUTUMN . WINTER 2010 04

2010 Autumn Winter Expert Insights-Yosemite Songbirds  

Wildlife biologist, Sarah Stock, talks about songbirds in Yosemite and how they're responding to climate change.