Artificial habitat supplementation is a valuable management tool for species facing population declines due to habitat loss, as in the case of the federally endangered light-footed Ridgway's rail (Rallus obsoletus levipes). The majority of this rail's endemic coastal salt marsh habitat has been developed, and remaining habitat is threatened by degradation, fragmentation, and sea-level rise. Currently, artificial rafts in several southern California marshes provide supplemental habitat for nesting and high tide refugia; however, factors impacting the use of these rafts by rails have not yet been examined. Racoons (Procyon lotor), a rail predator, have also been documented using rafts, potentially precluding safe use by rails. To elucidate this, we placed camera traps on artificial rafts and recorded frequency of use of both rails and raccoons and collected data on abiotic conditions, surrounding habitat characteristics and landscape features for each raft. Our preliminary results indicate that rails use rafts more frequently that are placed in habitat with a lower percentage of open, unvegetated  area and a higher diversity of prey species. Conversely, raccoon raft use may be more opportunistic. The insights from this study will help determine how to most effectively allocate management resources and bolster the light-footed Ridgway's rail population.

The Swainson's hawk (Buteo swainsoni) is a medium-sized buteo. It was listed as threatened in 1983 by the California Fish and Game Commission due to habitat loss and decreased numbers across the state. It breeds in the western United States, often nesting within agricultural areas or along roadways. Caltrans works with CDFW on adaptive management to avoid and minimize adverse effects to Swainson’s hawk when incidental take is authorized. Observations of nesting from several projects constructed from 2018-2023 show this species can be tolerant of disturbance when nesting. In Solano County, Swainson’s hawk nested and successfully fledged near both the Midway Rd. and McCune Creek bridges along Interstate Route 80 within 60 and 140 ft of each construction site, respectively. In Napa County, a large intersection improvement project adjacent to two active nests delayed starting, then worked through the subsequent nesting season where a nest 35 ft from the roadway and 100 ft from active construction was successful, but another nest 700 ft away on private property was harassed by red-tail hawk and did not produce offspring. Ongoing efforts seek to understand disturbance thresholds and behavior patterns of Swainson’s hawk breeding pairs nesting adjacent to transportation infrastructure.

Acoustic monitoring is an increasingly common technique for surveying avian species in the field. Low-cost autonomous recording units (ARUs) are driving this increase in acoustic field surveys, which allows for occupancy and abundance data to be collected without a human observer present. Coupled with software that can detect avian species by their call, this method of passive observation allows for large amounts of recorded audio to be analyzed with less manual processing and validation effort required. During 2023, we completed a pilot study deploying 40 ARUs across northern California public hunting areas (n = 8) to monitor ring-necked pheasants. Units recorded 2.5 hours per day for 45 days and were subsequently recovered from the field. The recordings were uploaded to an avian species detection software program (BirdNET Analyzer) that processes sound data and outputs a list of detections with time stamps and confidence estimates. A subset of the total detections was validated (87 percent total accuracy above 0.1 confidence threshold), and we created distributional maps of relative pheasant abundance using an inverse distance weighting function. Using ARUs can facilitate an increase in the capacity to monitor managed game and non-game species of concern over larger areas and in remote regions.

The combined effects of over a century of post-colonial forest management, resource extraction and fire suppression, and climate change in the Sierra Nevada are manifesting in larger, more severe fires, a change with dire implications for biodiversity. For decades, Spotted Owl conservation has shaped forest management, with most other species receiving scant attention – if any. The recent establishment of an ecosystem-scale passive acoustic monitoring program across the Sierra Nevada (>1,600 recording sites across ~25,000km2) and machine learning tools capable of identifying most bird species means that comprehensive assessments of the actual umbrella effects of priority species can now be assessed. We used multi-species occupancy models to estimate the probability of co-occurrence of 70 species of Sierra Nevada birds, including the Spotted Owl and other priority species. Preliminary results suggest that 15 of 69 species (22% of the community) are positively associated with Spotted Owl occurrence, a similar number of non-overlapping species are positively associated with Fox Sparrows, and very few species are associated with the relatively scarce Black-backed Woodpecker. Quantifying the umbrella effects of what have been assumed to be complementary indicator species can help inform urgently needed forest restoration to maximize short-term biodiversity conservation before the presumed long-term benefits of such interventions accrue.

A pair of Black Oystercatchers (Haematopus bachmani) established a nest in June 2022 at “Tern Town”, an island located in Hayward, California along the eastern side of the San Francisco Bay. This is the first documented occurrence of oystercatchers successfully nesting and fledgling young in association with California Least Terns. The island provides nesting habitat for three special status species. Since 2015, and for a total of six breeding seasons, the endangered California Least Tern (Sternula antillarum browni), the threatened Western Snowy Plover (Charadrius alexandrinus nivosus) and species-of-special-concern Black Skimmer (Rynchops niger), have nested successfully, in association with American Avocet (Recurvirostra americana) and Black-necked Stilt (Himantopus mexicanus). We collected shells near the oystercatcher nest to assess their diet. Diet data showed the oystercatchers foraged on, in decreasing order of abundance, Japanese Little-necked Clams (Ruditapes philippinarum), Ribbed Mussels (Geukensia demissa), Bent-nose Clams (Macoma nasuta), Limpets (Patellogastropoda sp.) and Bay Mussels (Mytilus edulis). This new report on breeding Black Oystercatchers indicates that managing habitat for California Least Tern, Western Snowy Plover, and Black Skimmer can also benefit Black Oystercatcher. This site-specific information on breeding Black Oystercatchers supports recovery plan tasks that are consistent with managing habitat for California Least Tern, Western Snowy Plover and Black Skimmer.