Finding Oregon Vesper Sparrows: A Vital Census in the Cascade-Siskiyou National Monument
Why look for Oregon Vesper Sparrows?
It is estimated that only 3,000 individuals of this declining subspecies remain. The small population size of the Oregon Vesper Sparrow is well-documented, but the causes of its at-risk status are not. As with all migratory birds, population trends may be caused by factors on their breeding grounds, wintering grounds, or migration stopover areas.
Since 2018 Klamath Bird Observatory has been trying to understand the cause of this subspecies’ decline. Getting a snapshot of how many of these birds there are in the Cascade-Siskiyou National Monument – and where they are – is important baseline data. This information will be especially important if the Oregon Vesper Sparrow is listed as federally endangered or threatened – it is currently in review with the U.S. Fish and Wildlife Service for potential listing under the Endangered Species Act.
How many Oregon Vesper Sparrows live in the Cascade-Siskiyou National Monument?
This past summer, it was KBO’s goal to find out. Armed with paper maps, Avenza maps, GPS units, and binoculars, we bumped down endless back roads and completed the most rigorous inventory in the Monument to date. This included >7000 acres of potential montane meadow habitat, including some sizeable meadows that had never before been surveyed for Oregon Vesper Sparrows. We were interested in the bird’s abundance and distribution, and recording which meadows were occupied by this declining, at-risk subspecies. KBO surveyors spent many hours this summer hiking in steep terrain, getting our boots wet in the dewy grass, counting sparrows on transect surveys, and recording their locations on maps.
We surveyed 54 montane meadows in the Monument, mostly on public lands, and counted 140 Oregon Vesper Sparrows in 27 of them. Because this survey method is most likely to detect singing males (and most of those males will have mates), and there are also meadows on private property within the Monument that we could not survey, this number is almost certainly an underestimate. A striking finding was that there were more Oregon Vesper Sparrows than we thought, with many in quite small subpopulations scattered across meadows of varying sizes (some as small as 17 acres) all throughout the Monument. Only five meadows had 10 or more individuals detected; 75% of occupied sites had only 1-5 individuals. This is in addition to the three big meadows with the highest abundance of Oregon Vesper Sparrows just outside of the Monument – Owen’s Meadow, Lower Vesper Meadow, and Lily Glen – which have 30-50 pairs each. We now know that the Monument supports a substantial number of Oregon Vesper Sparrows, probably at least 10% of the global population which is estimated to be about 3,000 individuals.
We enjoyed the opportunity to visit all of these remote corners of our local Monument! It’s a wonderful resource to have in our collective “backyard” with a considerable diversity of habitats, including the montane meadows that support Oregon Vesper Sparrows and other grassland creatures. We are currently writing up a report to share our findings, and their conservation implications, with local BLM staff tasked with managing the Monument.
Editor’s Note: Funding for 2024 research activities was provided by the BLM National Conservation Lands Management Studies Support Program and Oregon Wildlife Foundation. KBO Field Technicians Lin Stern, Elijah Hayes, and Nate Trimble, and staff Sarah Rockwell and Sam Webb conducted surveys in the field.
If you want to support this work, you can use this link to donate: https://klamathbird.org/product/donate/
