Science News: Fire, Owls, and Farallon Gulls
April 30, 2021
The Benefits of Fire for Birds
Fire is a phenomenon that may not be easy to think positively about when it comes to areas where we live, especially in California right now. But the story is more complicated than whether fire is all good or all bad. In the Sierra Nevada our research has revealed essential benefits that moderate to high-severity fire provides for wildlife, and these benefits can last for decades. In a study that we recently published in Forests, we looked at how different types of disturbance–moderate to high-severity fire, low-severity fire, and mechanical forest thinning–affected the abundance of 71 forest bird species in the Sierra Nevada over a 20 year period using data collected from Point Blue’s Sierra study sites. We found the highest bird diversity in areas that had experienced moderate to high-severity fires, and that all disturbances led to higher diversity compared to undisturbed forest. We also found that more than half of all species had higher abundance at some point following moderate to high-severity fire, including 10 species that were more than twice as abundant in these places. These results led us to conclude and recommend that fuels treatments and other forest management, prescribed fire, and especially wildfire, must all be embraced when creating forest restoration management policies and plans to best mitigate future ecological stressors. Our study also underscores the value of long-term datasets in order to better understand key environmental processes.
Photo: Sierra Nevada Group Director Ryan Burnett doing a bird survey in post-fire Sierra habitat. Credit: Ken Etzel.
A Path Forward for Southern California Spotted Owls
When we think about wildlife responding to habitat loss and climate change, we conservationists can help species adapt by helping them find the safest paths to migrate among existing habitat patches. One way we can do this is by restoring or protecting the habitat “corridors” that allow species to migrate from patch to patch, upslope, or any other direction that is more suitable. When habitat patches are connected by corridors, individuals can move to new patches when there are no longer the necessary resources, like nesting sites or food, within their existing patch. As we share in a study recently published in Diversity and Distributions, we created population models for Southern California Spotted Owls that considered key characteristics important to prioritizing where to place corridors. Providing information for future conservation actions, we identified priority corridors for this species. While most connectivity approaches “map” corridors without considering their impact on populations, our models included owl births, deaths, and ability to move or disperse among patches in Southern California. Our models advance connectivity decision making for species of conservation concern by quantifying important criteria for corridor identification and prioritization, namely: a corridor’s irreplaceability, its local versus regional benefit, and its resilience in a changing landscape.
Photo: Spotted owl in Noble Canyon on Laguna Mountain, East San Diego County. Credit: Megan Jennings.
Our Science Shows the Gulls Will Be Ok
As many of you are aware the US Fish and Wildlife Service is leading an effort to restore the Farallon Islands’ ecosystem. The Service proposes eradicating non-native, invasive house mice that are causing critical harm to many species on the island, especially a sensitive seabird species, the Ashy Storm-petrel. The plan to eradicate the mice has been thoroughly planned over the past decade and backed by Point Blue science, but some express concern about the potential accidental death of non-mouse species that ingest the rodenticide targeting the mouse. The Western Gull is the species whose population is most at risk of being exposed to and ingesting the rodenticide, but our assessment, the overall plan, and our science show that any anticipated mortality is not likely to have long-term impacts to the population on the Farallon Islands.
We recently published a study in Ecosphere examining how Western Gull populations on the Farallon Islands might be affected over the long term by a mortality event that decreases their population at one point in time. We highlight the fact that gulls are long lived (up to approximately 25 years) and their populations are stochastic, meaning their numbers strongly fluctuate from year to year, reflecting in part fluctuations in their prey and other aspects of their environment. Taking these fluctuations, or “stochasticity,” into account we performed a first-of-its-kind study to predict the threshold of mortality from a one-time event that would affect the long-term (20yr) trajectory of the overall population. We found that, in a realistic scenario, a novel mortality event would need to exceed 3.3% or 1,050 individuals in the Farallon population to have a discernible, negative effect on their long-term population trend.
The current plan for mouse eradication details steps to be taken to ensure that non‐target mortality of Western Gulls is much less than the levels identified in this study—and could even be as low as zero. These steps include timing the project outside of the gull breeding season and active hazing of gulls to keep them off of the islands during the application of rodenticide (see results of hazing trial here). Additionally, our results indicate that existing environmental and population variability will, after 20 years, swamp the effects of a mortality event of magnitude 3.3% or less of this long-lived species.
Photo: Western Gulls on the Farallon Islands National Wildlife Refuge. Credit: Point Blue photo.
News Bites
Carbon and Rangeland Management. A new 3-year grant from Foundation for Food & Agriculture Research will help us launch a new project assessing how carbon responds to commonly recommended rangeland management practices. Read the full blog post here.
Farms, feathers, and fins share water in California. A recent Grist article highlighted our work with the Migratory Birds Conservation Partnership (Point Blue, Audubon CA, The Nature Conservancy in California, farmers, and government agencies) to create innovative solutions that benefit wildlife and people. Read the article here.
How does a climate scientist celebrate Earth Day? Read a recent article in Sonoma Magazine highlighting Point Blue Climate Adaptation Director Dr. Sam Veloz and how he’s “finding new approaches to combating sea level rise–and raising a family of surfers.”
Understanding Soil Carbon Science. Point Blue’s Dr. Chelsea Carey with partners from Yale University and The Nature Conservancy review research on soil’s ability to sequester carbon from the atmosphere. Read it here.
Recent Conservation Awards! We’re proud and honored to share that Wendell Gilgert, who recently retired from his position as Working Lands Director at Point Blue, received an Individual Partners In Flight Leadership Award for his lifelong work. He integrated PIF bird and habitat conservation into the USDA-Natural Resource Conservation Service (NRCS) programs, ensuring birds and wildlife remained a high priority natural resource. Point Blue is also honored to have received the 2021 Distinguished Landscape Practitioner Award from the North American Chapter of the International Association for Landscape Ecology (IALE-NA) for our efforts in landscape level conservation such as the Migratory Shorebird Project, Our Coast Our Future, and the Rangeland Monitoring Network.
Events
In case you missed them: here is a recording of our nature journaling program with John Muir Laws. Find recordings of all other past programs, including Science Stories from Palomarin and In the Field Live programs, on our events page.
Birds and Climate Change with Peregrine Audubon Society. Tuesday, May 18th, 2021, 7-8pm. We’re excited to be sharing our “Science Stories from Palomarin, Episode 2: Tracking a Changing Climate” program with Ukiah’s Peregrine Audubon Chapter. If you missed it the first time around, want to see it again, and/or want to meet folks in this Mendocino County group of bird lovers, consider joining. Find information here.