California Black Rails (Laterallus jamaicensis coturniculus) have a disjunct and poorly understood distribution. After a new population was discovered in Yuba County in 1994, we conducted call playback surveys from 1994 to 2006 in the Sierra foothills and Sacramento Valley region to determine the distribution and residency of Black Rails, estimate densities, and obtain estimates of site occupancy and detection probability. We found Black Rails in 164 small, widely scattered marshes distributed along the lower western slopes of the Sierra Nevada foothills from just northeast of Chico (Butte County) to Rocklin (Placer County). Marshes were surrounded by unsuitable habitat, creating a patchy or metapopulation structure. We observed Black Rails nesting and found that they are year‐round residents. Assuming perfect detectability, we estimated a mean density of 1.78 rails/ha. Assuming a detection probability of 0.5, this estimate increases to a mean density of 3.55 rails/ha. The probability of detecting occupancy with a single call playback survey at a marsh was high (= 0.84), and the estimated proportion of marshes occupied (across all years) was 0.58. Irrigation ditches were the primary water source for 75% of the marshes with Black Rails. Our results indicate that Black Rails are more widespread in the Sierra foothills than previously known, and the foothills distribution appears to be discontinuous with populations in the San Francisco Bay‐Delta Estuary. Occupancy surveys may be an improved method for monitoring population trends of this secretive marsh bird where habitat patches are highly fragmented.
Impacts of livestock grazing in arid and semiarid environments are often concentrated in and around wetlands where animals congregate for water, cooler temperatures, and green forage. We assessed the impacts of winter-spring (November-May) cattle grazing on marsh vegetation cover and occupancy of a highly secretive marsh bird that relies on dense vegetation cover, the California Black Rail (Laterallus jamaicensis coturniculus), in the northern Sierra Nevada foothills of California, U.S.A. Using detection-nondetection data collected during repeated call playback surveys at grazed vs. ungrazed marshes and a "random changes in occupancy" parameterization of a multi-season occupancy model, we examined relationships between occupancy and habitat covariates, while accounting for imperfect detection. Marsh vegetation cover was significantly lower at grazed marshes than at ungrazed marshes during the grazing season in 2007 but not in 2008. Winter-spring grazing had little effect on Black Rail occupancy at irrigated marshes. However, at nonirrigated marshes fed by natural springs and streams, grazed sites had lower occupancy than ungrazed sites. Black Rail occupancy was positively associated with marsh area, irrigation as a water source, and summer vegetation cover, and negatively associated with marsh isolation. Residual dry matter (RDM), a commonly used metric of grazing intensity, was significantly associated with summer marsh vegetation cover at grazed sites but not spring cover. Direct monitoring of marsh vegetation cover, particularly at natural spring- or stream-fed marshes, is recommended to prevent negative impacts to rails from overgrazing.
Tree shelters have been used effectively in many locations to establish a wide range of tree species including oaks. However, their efficacy in Mediterranean climates like the hardwood rangelands of California has not been thoroughly tested. This study evaluated the field performance of blue oak (Quercus douglasii)—a species that is reported to be regenerating poorly in many locations in the state—protected by several sizes of tree shelters and compared response of directly sown acorns to that of 4-month-old transplants. After five growing seasons, seedlings in all sizes of tree shelters are larger than their unprotected counterparts. Tree shelters have been especially effective in promoting rapid height growth. However, regardless of tree shelter size, when seedlings grew above the tops of the shelters, average height growth diminished and diameter growth increased. Differences among stock types were relatively small, although transplants tended to perform better than directly sown acorns. These results suggest that tree shelters can greatly reduce the time required by seedlings to grow to a size where they are less vulnerable to browsing. As such, they appear to be a promising tool in efforts to regenerate blue oak in California. West. J. Appl. For. 16(4):153-158.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.