Ferruginous Hawks, Burrowing Owls, and the Value of Citizen Science
As a birder, many of us have no doubt used eBird and participated in events like the Christmas Bird Count. Collectively, this data, called Citizen Science by biologists can provide very important information for scientists to document bird distribution and abundance. A 2024 paper in the Journal of Raptor Research by Ed Pandolfino, Lilly Douglas, and Chris Raye on Ferruginous Hawks wintering in California (https://www.researchgate.net/publication/381305123_Population_Trends_of_the_Ferruginous_Hawk_Buteo_regalis_Wintering_in_California ) shows just how valuable this type of data can be.
Using Christmas Bird Count data for a 25-yr period from 22 California Christmas Bird Count circles in the core winter range of Ferruginous Hawks, they found a significant positive trend. California’s wintering population of Ferruginous Hawks is increasing. This is surprising given the ongoing declines of this species’ preferred winter habitat in California during this same time period and with the continent-wide negative trends observed for most grassland bird species.
Figure 1. Year-round migration patterns of adult Ferruginous Hawks breeding in the Pacific Northwest, USA, and tracked for up to 6 yr (n ¼ 30). Solid lines are tracks from birds outfitted with GPS transmitters; dotted lines are tracks from birds outfitted with ARGOS platform transmitter terminals (https://www.argos-system.org/products/transmitters/). Reprinted with permission from Watson et al. (2018) (from Pandolfino et al 2024).
It is not entirely clear why California’s wintering Ferruginous Hawk populations are increasing. It’s thought that most of our wintering Ferruginous Hawks come from Washington and Oregon (Figure 1) however other regions of the West are poorly studied. Some possible explanations include: California’s wintering habitats may have an abundance of food for the species, the loss of wintering habitats in California may concentrate the hawks in areas where they are more likely to be observed, or wintering habitats outside of California could be decreasing causing more hawks to come to California. Whatever the case the fact that wintering population are increasing despite generally decreasing breeding populations and loss of habitats will no doubt prompt more research and highlights how important Citizen Science data can be for conservation. Though not used here, eBird data can be just as valuable.
Speaking of raptors, California’s conservation community got a victory on October 10th when the California Fish and Game Commission voted unanimously to support a petition by The Center for Biological Diversity, Defenders of Wildlife, Burrowing Owl Preservation Society, Santa Clara Valley Audubon Society, Urban Bird Foundation, Central Valley Bird Club, and San Bernardino Valley Audubon Society to list western Burrowing Owl as threatened or endangered pursuant to the California Endangered Species Act (https://fgc.ca.gov/CESA#wbo). Chris Conard, who sits on the Central Valley Bird Club Conservation Committee as well as Sacramento Audubon’s Conservation Committee played a large role in providing the biological information for the petition and testified in person at the meeting. In fact, this petition brought together the Central Valley Bird Club and Sacramento Audubon and presented the opportunity for the Central Valley Bird Club’s Conservation Committee and Sacramento Audubon’s Conservation Committee to collaborate. It has helped lay the ground work for us to work more closely on conservation issues moving forward as three of the Sacramento Audubon Conservation Committee members also sit on the CVBC Conservation Committee (myself, Chris Conard, and Dan Airola).
I hope you are all enjoying the change of season and the arrival of our wintering birds!