Staff of Orange County Nature Reserve
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(See reports below)

Current Projects

Monitoring Cactus Wren Reproduction, Dispersal and Survival (2009 to present)

Cactus Wren (Campylorhyncus brunneicapillus) inhabiting cactus scrub habitats in coastal southern California have declined over the last few decades. The Cactus Wren is a Target Species in Orange County’s Central and Coastal Natural Community Conservation Plan/Habitat Conservation Plan (NCCP/HCP). NROC is responsible for monitoring Target Species within the NCCP/HCP and has invested considerable effort into determining the distribution and abundance of wrens across the 37,000 acre Reserve System. It is estimated that since 1993 Cactus Wren populations have been reduced by over 80%, largely as a result of catastrophic wildfires in 1993 and 2007. Even in unburned areas wren populations have declined. NROC began a study in 2009 to identify and better understand the factors contributing to this decreasing population trend. The study monitors Cactus Wren reproduction, dispersal and survival. NROC biologists find and follow nests over time to determine nest success, the number of offspring produced, and to identify causes of nest failure. NROC biologists also capture adult, nestling, and juvenile wrens in order to band them with unique combinations of color bands so individual dispersal and survival can be documented. Volunteers from Sea and Sage Audubon, California State Parks, Orange County Parks, and the Nature Conservancy have helped survey for banded individuals and gather data on nesting wrens. NROC is also collaborating with the United States Geological Survey (USGS) to collect blood samples containing DNA. USGS scientists are using these samples to analyze genetic structure and evaluate connectivity of Cactus Wren populations in coastal southern California. Information gathered from this research is being used to guide management of Cactus Wren populations in the NCCP/HCP Reserve System.

California Gnatcatcher Surveys

The California Gnatcatcher (Polioptila californica) is listed as a federally-threatened species by the United States Fish and Wildlife Service (USFWS). The gnatcatcher is also a focus of the California Department of Fish and Game’s Natural Community Conservation Planning Act, and is a Target Species in Orange County’s Central and Coastal NCCP/HCP. The USFWS and NROC collaborated in 2009 to evaluate California Gnatcatcher monitoring methods. USFWS employees surveyed for California Gnatcatchers in San Diego County, employing repeated point count and walking survey methodologies at 100 sampling points. Comparisons were made of the efficiency of point counts compared with walking surveys and to evaluate how well the two methods estimated detection probabilities and habitat occupancy. Both methods performed well and NROC selected the walking survey methodology. During spring 2011 a team of experienced biologists conducted three rounds of surveys at 150 randomly selected locations across the Coastal and Central Reserves. Data are being entered and analyzed and will provide a baseline to compare the results of future surveys.

Tecate Cypress Management Plan (2009)

NROC and the California Department of Fish and Game funded a research project by Dr. Suding and Post-Doctoral Fellow Susana Rodriguez-Buriticá from the University of California system to study Tecate cypress (Cupressus forbesii) in the Santa Ana Mountains. Tecate cypress is a rare and endemic tree species occurring only in the Santa Ana Mountains, Guatay Mountain, Otay Mountain and Tecate Peak in southern California and in isolated areas of northern Baja California, Mexico. An important component of the study was field studies to document the current status of Tecate cypress in the Santa Ana Mountains, where recent fires have had considerable impact on the population. The research team developed predictive models providing the basis for management recommendations on NCCP/HCP lands. Models were developed to evaluate fire risk, predict habitat suitability, and assess the effects of different fire regimes on population demographics. The results of this research were used by the research team and NROC to prepare a Tecate Cypress Management Plan in consultation with the Tecate Cypress Management Committee.

Improving Statistical Sampling and Vegetation Monitoring (2007-2011)

Monitoring to detect ecological change is an important component of conservation programs. The Nature Conservancy, NROC, and San Diego Multiple Species Conservation Program have identified vegetation communities as targets for long term monitoring. Dr. Deutschman’s research team from San Diego State University is sampling conserved lands in southern California to improve the power of the analysis and to integrate vegetation monitoring across the region. The objective of this project is to evaluate the precision and accuracy of different sampling designs and field protocols for monitoring vegetation communities. Coastal sage scrub, chaparral, and grassland vegetation are being sampled in Orange County’s Central (2007-2011) and Coastal (2008-2010) SubregionsSampling was designed to focus on three sources of variation: temporal, spatial and methodological. Spatial variation consists of three nested levels: vegetation community, site, and plot. Methodological variation includes two levels: method and team. Semi-arid shrublands in southern California are found to be highly variable spatially, so that allocating a significant amount of effort to spatial coverage is appropriate for most response variables. Some species and functional groups are also dramatically affected by rainfall, showing high temporal variation. Team to team variability is small in shrublands and grasslands and could be minimized with appropriate training. Transects are providing the most accurate and precise estimates for cover of individual species and functional groups in shrublands and grasslands. Quadrats provide more information on richness and presence of uncommon small species, but systematically underestimate cover.

In 2009, Dr. Deutschmann and his team began developing methods and metrics for long term monitoring of the status of oak woodlands. Data sampling initiated in 2009 was expanded to additional sites in 2010 and 2011.

Past Projects

Cactus Wren Status in the Central Subregion (2008)

Following the 2007 Windy Ridge and Santiago wildfires, NROC mapped cactus scrub habitat and Cactus Wren locations in the Central Subregion during spring 2008. The methodology was consistent with 2006 and 2007 Coastal Subregion surveys so that a reserve-wide assessment could be made of cactus resources and Cactus Wren distributions. Burned cactus scrub was mapped and categorized as to the severity of fire damage. A total of 1,855 acres of cactus scrub were mapped in the Central Reserve. Of that total, 1,420 acres sustained Low, Moderate or High levels of fire damage, 75% of which was severely burned and evaluated as unsuitable for supporting nesting Cactus Wrens. Six hundred eighty three acres were judged suitable for occupancy by Cactus Wrens and surveyed. Surveys of potentially suitable habitat identified 58 occupied sites in the first round of surveys and 56 sites in the second round. These occupied sites represent a preliminary estimate of 67 territories, a decline of 82.1% since approximately 374 territories were estimated in 2004.

Cactus Wren Telemetry Project (2007)

NROC conducted a radio telemetry project in 2007 to document the dispersal of juvenile Cactus Wrens. Banded Cactus Wrens translocated to Upper Newport Bay in 2006 were also monitored. Radio transmitters could only be attached to 7 juveniles as production of young was very low in 2007, a year of extreme drought. Juveniles with radio transmitters were tracked for 3 to 48 days. Two hatch-year wrens were tracked for more than 45 days. One remained on the natal territory and the other moved away from the natal territory but did not leave the study site. Three juvenile wrens were tracked for 14-24 days and another lost the transmitter after 10 days. None of these wrens were relocated again. One young wren’s partially eaten remains were found after three days of tracking. A banded male relocated to Upper Newport Bay in 2006 made a 0.7 km breeding dispersal and mated with a relocated female to produce a single fledgling in 2007.

Cactus Wren Status in the Coastal Subregion (2006)

In 1993 the Laguna Fire burned 75% of the coastal reserve of the Nature Reserve of Orange County (NROC). From 1999 to 2004, annual monitoring efforts showed the Cactus Wren population in the coastal reserve declined from an estimated 132 (±93) to 55 (±40) territories, a 58% decline during the six years. In the same period, the estimated decline in the central reserve was only 26%, a figure consistent with short-term declines documented for other CSS birds, including the California gnatcatcher, during the same period. In 2006, we completed two rounds of focused Cactus Wren surveys in the coastal reserve, including existing use, special linkages, and non-NROC open space areas. We mapped and classified all cactus-containing habitats within 20 management areas. These surveys found 65 occupied territories within the coastal reserve. Using site occupancy models we estimate 71.4 (±6) territories were present in the surveyed area. Out of 2,323 acres of cactus scrub mapped in 2006, 1,336 acres, or 58%, mostly within the Laguna Fire perimeter appeared to be insufficiently developed for occupancy by Cactus Wrens. Only 187 acres were found to be occupied, whereas our estimates based on historic data indicate approximately 1,473 acres were occupied in 1992, an 87% decline. Out of eight management areas that held at least 8 territories in 1992, only two areas, Sand Canyon and Turtle Rock, did not show significant declines between 1992 and 2006. Portions of the coastal reserve experiencing significant losses included the Sycamore Hills and Aliso & Woods management areas, both of which did not burn in 1993. Declines in unburned areas may reflect differences in biological productivity, edge effects, and an inability of wrens to disperse large distances. Given the small size of the Cactus Wren population in the coastal reserve, slow recovery of burned cactus scrub habitat, and significant population declines in unburned areas, this population warrants further focused study and development of a management program that aims toward stabilizing the population in the short-term.

Cactus Wren Translocation Project (2006)

Effective management of coastal populations of the Cactus Wren is considered one of the great challenges in bird conservation for southern California. Loss and fragmentation of habitat due to development, agricultural displacement, and high frequency wildfire, have led to major declines in this species throughout large portions of the region. Even on protected conservation lands populations are vulnerable to local extinction, and the need for active management of this species is becoming increasingly obvious. Between 17 June and 23 September 2006 we captured, color-banded, and relocated ten Cactus Wrens in order to study the biological and behavioral response of adult and juvenile wrens to translocation. Following release, the wrens were monitored for a minimum of 60 days and information concerning their behavior and survivorship was obtained. One adult and all five juveniles disappeared during the monitoring period (due to dispersal or mortality), but four adults persisted near the release sites and showed the capacity to adapt quickly and successfully to their new surroundings. The relative success of this experiment, at least in the short term, suggests that translocation could prove to be an effective management tool for the reestablishment and bolstering of isolated populations of Cactus Wrens in coastal southern California.

Cactus Wren Video (2006)

In 2006, the Nature Reserve of Orange County successfully relocated the Cactus Wrens observed in this video to protected lands in the coastal reserve. The effort was funded as part of a study to evaluate translocation as an effective tool for management of isolated populations of Cactus Wrens in southern California. Video shot by Dana Kamada (2006). See Video

Western Spadefoot Toad Habitat Map (2006)

In partnership with the US Geological Survey, The Nature Conservancy, and County of Orange, the Nature Reserve of Orange County developed a predicative map in 2006 of spadefoot toad habitat within Orange County, California. The purpose of developing the map was to identify existing habitat and potential restoration sites for the spadefoot toad throughout the county. The map was constructed using GIS and based on observed relationships between historic and recent county spadefoot toad locations and available environmental data, specifically, information on area topography (slope), soils, vegetation, and land cover. Based on these relationships, existing GIS data layers were queried and habitat potential categories defined and ranked. Mapped areas, defined as being of high, medium, and low potential, account for less than 15% of the total area in the county, but >95% of all identified spadefoot locations. In the future, the map will be validated via field surveys and become an important contribution to an aquatics wildlife management plan that is being developed for the region.

Ants of Southern California (2006)

Ants are considered important ecological components of most terrestrial communities and valuable indicators of ecosystem health. Recent field studies have revealed the invasive argentine ant (Linepithema humile) represents a major threat to native ant communities in areas of co-occurrence. We describe native ant community structure and the spatial distribution of argentine ants in coastal southern California. We investigate the relationship between argentine ants and distance to urban/agricultural edges and watercourses, and measure changes in the native ant community when in the presence of argentine ants. We sampled 172 sites across 20 geographic areas in coastal southern California from 1999 through 2003. We identified 54 native ant species (in 24 genera) and 2 exotic ant species. Argentine ants were most likely encountered within 200 meters of urban and agricultural edges and the native ant community richness was substantially reduced when argentine ants were present. Calculations of total reserve area within 200m of urban/agricultural areas for the 37,000 acre Nature Reserve of Orange County indicated 24% of the reserve in 1992 and 44% of the reserve following complete build-out was and will be vulnerable to argentine ant invasion. It is within these areas that the native ant community experiences the greatest threat of being displaced and many basic ecological processes will likely be disrupted.

Biological Research and Monitoring Program Review for Central/Coastal Natural Community Conservation Plan/HCP (2006)

In 2006, the Nature Reserve of Orange County completed a written review of the Reserve’s Biological Research and Monitoring Program. In the report, NROC (1) reviews NCCP/HCP guidelines as they pertain to research and monitoring activities within the reserve system, (2) provides a comprehensive overview of the research objectives and results of the individual research projects conducted under the Reserve’s Umbrella Monitoring Program (1997 – 2004), and (3) makes program recommendations to facilitate development and implementation of a new research and monitoring program for NROC.

(See reports below)

Weed Control Program (1994-2011)

Since 1994 NROC has conducted an Invasive Plant Control Program on NCCP Reserve lands in the Coastal Reserve. NROC in coordination with the Nature Conservancy and more recently with the Irvine Ranch Conservancy has also provided invasive plant control for several sites in the Central Reserve. Historically, much of NROC was grazed by cattle and sheep with overgrazing resulting in disturbed soils and with impacts to native grassland and coastal sage scrub plant communities. This overgrazing promoted establishment of invasive plant species which changes the composition and structure of native plant communities. The primary target of this program was Artichoke thistle (Cynara cardunculus) which had invaded over 4,000 acres of the 38,000 acre reserve system. Weed control efforts have been successful reducing artichoke thistle to less than 4% cover in treated areas which encompass approximately 3,000 acres of reserve lands. The weed control program also treats other weed species emerging as threats to native habitats. These species include garland chrysanthemum (Chrysanthemum coronarium), veldt grass (Ehrharta calycina), tree tobacco (Nicotiana glauca), castor bean (Ricinus communis), and pampas grass (Cortaderia selloana). A Geographic Information Systems layer was developed to show artichoke thistle treatment history from 1997-2006 in the Coastal Subregion. This map shows the spatial extent of treatment and the number of years of treatment.

Artichoke Thistle Sustainability Project (2007-2009)

Artichoke thistle is an extremely problematic invader of disturbed grasslands in southern California. It invaded over 4,000 acres of NROC reserve lands. NROC and the Nature Conservancy established a control program for artichoke thistle involving direct application of herbicide to individual plants. Thousands of acres have been treated annually since 1994. Beginning in 2007, Dr. Suding’s research team has conducted a study of the sustainability of artichoke thistle treatment efforts. Their first objective is to resurvey areas initially surveyed in 1998 to assess changes in the plant community in areas treated by the weed control program. The focus is on assessing changes in artichoke thistle cover and on identifying what replaces artichoke thistle in treated areas. The second objective of the project is to evaluate how treated areas respond to the cessation of weed control over the long-term. The third objective is to investigate the response of native plant communities to active restoration in areas where weed control was applied but in which native plant diversity and cover remained low.

Brown-headed Cowbird (1999-2011)

NROC is responsible for conducting a Brown-headed Cowbird (Molothrus ater) trapping program within the Reserve System to reduce incidental parasitism of nests of sensitive bird species. Of particular concern is minimizing cowbird impacts to California Gnatcatcher (Polioptila californica californica) and Least Bell’s Vireo (Vireo, bellii pusillus), two federally listed species. Annual cowbird trapping began in 1993 in the San Joaquin Hills and is now conducted at a wider range of sites on reserve lands. The location of traps is determined annually based upon on an assessment of trapping history and the status of cowbird populations in areas with sensitive bird species.

Habitat Restoration Plan (2003)

This plan was designed to:

  • Maintain biological values within the NROC Reserve System
  • Enhance degraded habitat to support native biodiversity
  • Restore non-wildland areas to native habitats
  • Improve the ability of the Reserve System to support identified species of particular sensitivity through targeted restoration and enhancement actions
  • Promote development of state-of-the-art restoration and enhancement methods by using monitoring to track success of various methods and to inform restoration decisions
  • Minimize disturbances to resist invasion and establish an early warning system of infestations
  • Develop Geographic Information Systems for documenting restoration activities

This plan identifies the range of conditions existing in potential restoration areas and provides information on the most effective methods and costs of enhancement/restoration and targets and prioritizes areas for weed management within the Reserve System.

Coastal Subregion Cactus Scrub Restoration Project (2009)

The California Department of Fish and Game and NROC are funding restoration of cactus scrub habitat in the Coastal Subregion. This project will re-establish a linkage between Cactus Wren populations in the Shady Canyon area with suitable cactus scrub habitat to the southeast in James Dilley Reserve. The 1993 Laguna Fire destroyed cactus scrub in this area resulting in increasing isolation of wren populations. This project implements a management recommendation resulting from the 2006-2007 Coastal Subregion Cactus Wren surveys. The Irvine Ranch Conservancy is also conducting a cactus scrub restoration project in burned areas of the Central Subregion. NROC and the Irvine Ranch Conservancy are working together to develop similar monitoring and restoration methods so that the results of the two projects are comparable. Cactus salvaging and planting will begin this fall/early winter.


Monitoring Projects

2000 Ant Pitfall Trapping Report.pdf
2000 Mammalian Carnivore Study Report.pdf
2000 Mapping Avian Productivity & Survival Report.pdf
2000 Reptile Monitoring Report.pdf
2001 Ant Pitfall Trapping Report.pdf
2001 Mapping Avian Productivity & Survival Annual Report.pdf
2002 Reptile Monitoring Report.pdf
2003 Target Bird 1999-2001 Survey Report.pdf
2006 Ant Community Report.pdf
2006 Cactus Wren Status Report.pdf

2006 Cactus Wren Translocation Report.pdf

2006-2007 Cactus Wren Methods.pdf
2007 CACW Telemetry & Translocation Final Report.pdf
2007 Vegetation Monitoring Final Report.pdf

2007-2010 Vegetation Monitoring Final Report.pdf

2008 Vegetation Monitoring Final Report.pdf
2008 Central Region Cactus Wren Survey Final Report.pdf
2009-11 CACW Monitoring Final Report.pdf
2009 Cactus Wren Monitoring Report.pdf
2010 Cactus Wren Monitoring Interim Report.pdf

2010 Oak Tree Monitoring Final Report.pdf
2010 Tecate Cypress Management Plan.pdf
2011 Pacific Pocket Mouse Canine Survey Report.pdf
2011 USFWS NROC Pacific Pocket Mouse Trapping Report.pdf

Predictive Map of Western Spadefoot Toad

NROC Monitoring Program Review.pdf
Cactus Wren Video


Restoration Projects

1997-2006 Exotic Plant Control History
1999 Veldt Grass Monitoring Program.pdf
1999-2000 Native Plant Salvage Report.pdf

2000 Weed Control Report.pdf
2001 Weed Control Report.pdf
2002 Weed Control Report.pdf
2003 Habitat Restoration Plan.pdf

2005 Weed Control Final Report.pdf
2005 Brown-headed Cowbird Final Report.pdf
2006 Brown-headed Cowbird Final Report.pdf

2006 Weed Control Final Report.pdf

2007 Weed Control Final Report.pdf
2007 Artichoke Thistle Final Report.pdf
2007 Brown-headed Cowbird Final Report.pdf
2008 Brown-headed Cowbird Final Report.pdf

2008 Artichoke Thistle Final Report.pdf

2008 Weed Control Final Report.pdf

2009 Brown-headed Cowbird Final Report.pdf

2009 Laguna Canyon Cactus Wren Linkage Restoration Plan.pdf
2009 Weed Control Report.pdf
2009 Brown-headed Cowbird Final Report.pdf
2010 Brown-headed Cowbird Final Report.pdf

2010 EEMP Coastal Reserve Cactus Scrub Linkage Restoration Plan.pdf
2010 Laguna Canyon Cactus Wren Linkage Restoration Report.pdf
2010-11 EEMP Cactus Scrub Restoration Report.pdf
2010 Laguna Canyon Cactus Wren Linkage Restoration Report.pdf
2010 Invasive Control for Santiago Burn Areas.pdf

2010 Weed Control Report.pdf
2011 Weed Control Report.pdf
2011 LFSP Cactus Salvage & Restoration Plan.pdf


*Some pdf files are larger than others and may require more time to download. Please contact us if you have problems viewing any of these reports.