Basic Information
Common Name: Coastal California Gnatcatcher
Scientific Name: Polioptila californica californica
Species Code: POLPOL
Management Category: VF (species with limited distribution in the MSPA or needing specific vegetation characteristics requiring management)
Occurrence Map
Table of Occurrences
Loading...

Goals and Objectives

Goal: Maintain, enhance and restore coastal sage scrub on Conserved Lands in the MSPA that supports or has the potential to support VF species (i.e., cliff spurge, Palmer's goldenbush, San Diego barrel cactus, snake cholla, Blaineville's horned lizard, California gnatcatcher, San Diego black-tailed jackrabbit) and to incidentally benefit a diverse array of other species (e.g., San Diego thornmint, willowy monardella, Hermes copper, Quino checkerspot, coastal cactus wren) so that the vegetation community has high ecological integrity, and these species are resilient to environmental stochasticity, catastrophic disturbances and threats, such as very large wildfires, invasive plants and prolonged drought, and will be likely to persist over the long term (>100 years).

regional NFO 2020 VF
MON-IMP-MONPL POLPOL-1

Management units: 1, 2, 3, 4, 5, 6, 7, 8

In 2020, implement regional and subregional California gnatcatcher monitoring initiated in 2016 to determine the percent area occupied (PAO) by California gnatcatcher in modeled high and very high suitability habitat on Conserved Lands and military lands in the MSPA as part of a larger monitoring program for southern California. Over the next 15 years, determine trends in California gnatcatcher PAO and in their colonization and extinction rates and be able to detect at least 30% change in PAO. Identify associations between habitat and threat correlates with gnatcatcher PAO and with extinction and colonization rates and develop biologically meaningful thresholds for management and to specify management criteria and recommendations.

Action Statement Action status Projects
IMP-1 When the results of the 2016 California gnatcatcher surveys become available, coordinate with the regional California gnatcatcher survey group made up of wildlife agencies, land managers and scientists, to determine when the next round of regional surveys should be implemented. It is anticipated that the surveys are likely to be held in 2020. Based on the monitoring results and group recommendations, adjust the habitat model and sampling frame as necessary to better predict suitable habitat in the northern extent of the range. on hold
IMP-2 Submit project metadata, monitoring datasets, analyses and reports to the MSP Web Portal. on hold
Criteria Deadline year
Regional and Subregional California Gnatcatcher Surveys completed and report submitted by 2021 2021
Code Obj. code Statement
POLPOL-2 MON-RES-SPEC In 2020, implement California gnatcatcher postfire monitoring conducted in 2015 and 2015 to: determine whether there has been further recovery of California gnatcatchers in areas burned in 2003, 2007 and 2014 (i.e., PAO>10%); evaluate if there is a difference in PAO between areas burned in 2003, 2007 and 2014; investigate the relationship between gnatcatcher PAO and vegetation composition, cover and structure; and evaluate the composition, cover and structure of coastal sage scrub in areas with different fire frequencies and patterns of vegetation recovery based upon time since fire, spatial distribution, previous land use, and environmental conditions. Use the regional gnatcatcher and vegetation monitoring protocols to monitor postfire recovery of gnatcatchers and vegetation at sampling points surveyed in 2016. Analyze gnatcatcher and vegetation data to develop overall and site specific vegetation management recommendations for postfire recovery of coastal sage scrub vegetation to support California gnatcatchers.
regional POST 2020 VF
MON-RES-SPEC POLPOL-2

Management units: 1, 2, 3, 4, 5, 6, 7, 8

In 2020, implement California gnatcatcher postfire monitoring conducted in 2015 and 2015 to: determine whether there has been further recovery of California gnatcatchers in areas burned in 2003, 2007 and 2014 (i.e., PAO>10%); evaluate if there is a difference in PAO between areas burned in 2003, 2007 and 2014; investigate the relationship between gnatcatcher PAO and vegetation composition, cover and structure; and evaluate the composition, cover and structure of coastal sage scrub in areas with different fire frequencies and patterns of vegetation recovery based upon time since fire, spatial distribution, previous land use, and environmental conditions. Use the regional gnatcatcher and vegetation monitoring protocols to monitor postfire recovery of gnatcatchers and vegetation at sampling points surveyed in 2016. Analyze gnatcatcher and vegetation data to develop overall and site specific vegetation management recommendations for postfire recovery of coastal sage scrub vegetation to support California gnatcatchers.

Action Statement Action status Projects
RES-1 Submit project metadata, monitoring datasets, analyses and reports to the MSP Web Portal. On hold
Criteria Deadline year
Postfire California Gnatcatcher Surveys completed and report submitted by 2021 2021
Code Obj. code Statement
POLPOL-1 MON-IMP-MONPL In 2020, implement regional and subregional California gnatcatcher monitoring initiated in 2016 to determine the percent area occupied (PAO) by California gnatcatcher in modeled high and very high suitability habitat on Conserved Lands and military lands in the MSPA as part of a larger monitoring program for southern California. Over the next 15 years, determine trends in California gnatcatcher PAO and in their colonization and extinction rates and be able to detect at least 30% change in PAO. Identify associations between habitat and threat correlates with gnatcatcher PAO and with extinction and colonization rates and develop biologically meaningful thresholds for management and to specify management criteria and recommendations.

Concern

Overall Condition

Improving

Overall Trend

High

Overall Confidence
Metric Condition Trend Confidence
1. Proportion Area Occupied

Proportion Area Occupied (PAO) of conserved lands in San Diego County


Concern

Unknown

High
2. Recovery from Fire

Increase in Proportion Area Occupied (PAO) of burned habitat


Concern

Improving

High
Current Status
The current overall condition status of the Coastal California Gnatcatcher Species Indicator is Concern based on the two metric condition assessments of Concern. The Percent Area Occupied (PAO) in San Diego County is low (Metric 1) with wildfires reducing PAO relative to unburned areas (Metric 2). There are insufficient data to determine a trend in (PAO) for subregional monitoring of gnatcatchers in San Diego County, whereas post-fire recovery is progressing overall. Additional metrics on habitat quality and management will be added to future reports as more information becomes available.
Metrics Dashboard
Full metric information for this species is available on our Dashboard.
Metrics Dashboard
Artesian Creek Restoration
Approximately 300 acres along Artesian Creek, a tributary of the San Dieguito River, was restored to coastal sage or native riparian. The majority of restored land was previously used for grazing, with an additional two miles of riparian habitat. The project is located between Camino Del Sur and Del Dios Highway, just south and southwest of Lake Hodges. The restoration has been completed, but annual treatment of invasive species remains including ongoing treatment of eucalyptus, tamarix and palms. The focal invasive species included: mustard, French broom, Scotch broom, Spanish Fleabane, arundo, Austrailian salt bush, Brazilian Pepper, caster bean, lapidium latifolia, garland chrysanthemum, bridal creeper, Italian thistle, fountain grass, dittrichia graveolens, artichoke, eucalyptus, tree tobacco, acacia, palms, pampas grass, pride of Maderia, tamarix, and fennel.
Bernardo Mountain Post-Fire Habitat Recovery Project
Bernardo Mountain is located north of Lake Hodges, west of I-15. The primary goal of this habitat conservation project is to protect the habitat of the federally listed coastal California gnatcatcher, as well as other listed and sensitive animal species such as coastal cactus wren and sensitive plant and wildlife species that are covered under the Multiple Habitat Conservation Plan ("MHCP").
Calavera Preserve Planning Area Access Control and Habitat Restoration Project
The Restoration Project was implemented in accordance with the Diegan Coastal Sage Scrub Restoration Plan, TransNet EMP Grant Project: Calavera Preserve Planning Area (Restoration Plan), which was prepared by Technology Associates, Inc. (TAIC) (Aug. 24, 2009). The goal of the project was to restore 5 acres of non-native grassland habitat to Diegan coastal sage scrub that is (a) self-sustaining, (b) suitable habitat for the California gnatcatcher, and (3) free of non-native invasive species that could invade adjacent native habitat. In addition to habitat restoration, the City of Carlsbad had an active public outreach program highlighting the benefits of natural open spaces throughout the city.
California Gnatcatcher Genetic Study - FundSource 1 and 2
We examined individual relatedness patterns and population genetic structure among gnatcatcher aggregations throughout coastal southern California from Ventura to San Diego Counties. To accomplish this goal, we developed a set of highly polymorphic microsatellite loci and sampled 268 individuals throughout the range. With genetic analyses we addressed the following questions:1) How many genetically distinguishable populations exist across the U.S. species range?2) Is genetic relatedness among individuals explained by the amount and distribution of suitable habitat?3) What is the range of dispersal distances between presumptive siblings and parents/offspring?4) What are the patterns of genetic diversity within aggregations across the U.S. range and what is the effective population size?5) How do these results impact future management and monitoring efforts aimed at species recovery?
California Gnatcatcher Post-Fire Study
This is a planned 5-year study. The purpose of this study is to: 1) Determine whether there has been further recovery of CAGN in areas burned in 2003 (i.e., occupancy greater than 10%). 2) Determine if there is a difference in CAGN occupancy between areas burned in 2003, 2007, and 2014. 3) Determine the relationship between CAGN occupancy and vegetation composition, cover and structure. 4) Determine the composition, cover, and structure of CSS vegetation in areas with different fire histories and evaluate patterns of vegetation recovery based upon lime since fire, spatial distribution, previous land use, and environmental conditions.
California Gnatcatcher South Coast Regional Monitoring Program
The USGS, USFWS, SDMMP, and the Nature Reserve of Orange County have joined together to develop a long-term coordinated regional monitoring program for the federally-threatened Coastal California Gnatcatcher (Polioptila californica californica) in the United States portion of the species range. Other participants include CDFW, The Nature Conservancy, Western Riverside RCA, Rancho Mission Viejo Conservancy, Naval Weapons Station Fallbrook, Marine Corp Base Camp Pendleton, Marine Corp Air Station Miramar. The goals of this program are to: 1) determine the population status of California Gnatcatchers in southern California on conserved and military lands; 2) track trends in California Gnatcatcher habitat occupancy over time in southern California to identify when thresholds have been met that trigger management actions; and 3) identify habitat attributes and threats associated with gnatcatcher occupancy in order to develop specific habitat-based management criteria and recommendations. To date, there have been no systematic surveys for this species across southern California. Surveys have been conducted periodically in portions of the gnatcatcher's range, particularly on conserved and military lands. However, these surveys have been conducted in different years and with a variety of methods providing different population metrics and as a result do not provide a region-wide estimate. In addition, during the last 15 years, there have been extremely large wildfires in southern California across a substantial portion of suitable habitat for gnatcatchers and there is little information on their status in these burned areas. The first regional Coastal California Gnatcatcher survey is scheduled for 2016. This survey is planned for conserved lands and those military lands in southern California that choose to participate. The objectives of the regional monitoring program are: 1. In 2016, determine the percent area occupied (PAO) by California Gnatcatchers in modeled high and very high suitability habitat on conserved lands and on participating military lands in southern California. 2. Over the next 15 years, determine long-term trends in California Gnatcatcher PAO and in their colonization and extinction rates in modeled high and very high suitability habitat on conserved lands and participating military lands in southern California and be able to detect at least 30% change in California Gnatcatcher PAO. 3. Beginning in 2016, identify associations between habitat and threat correlates with California Gnatcatcher PAO and with colonization and extinction rates in order to develop biologically meaningful thresholds for management and to specify management criteria and recommendations.
Coastal California Gnatcatcher Habitat Suitability Model for Southern California
This habitat model was developed to delineate a sampling frame for regional monitoring of coastal California gnatcatchers (Polioptila californica californica) to determine: 1) percent area occupied (PAO) in high and very high suitability habitat across conserved lands and participating military lands in the U.S. range in southern California; 2) changes in PAO over time; and 3) extinction and colonization rates. One purpose of the model is to identify areas recovering from disturbance, such as wildfire, that may not currently support coastal sage scrub vegetation used by coastal California gnatcatchers, but are otherwise highly suitable. In this way, we can monitor gnatcatcher occupancy associated with habitat changes over time. We used the Partitioned Mahalanobis D2 modeling technique to construct alternative models with different combinations of environmental variables. Variables were calculated at each point in the center of a 150 m x 150 m cell in a grid of points across the southern California landscape. Variables reflect various aspects of topography, climate, land use (percent vegetation and urbanization at 150 m and 1 km scales), Normalized Difference Vegetation Index, and modeled California sagebrush (Artemisia californica) habitat suitability. Due to spatial unevenness in gnatcatcher location data, we divided southern California into five sampling regions and randomly subsampled 50 locations from each region. We repeated this process 1,000 times using a total of 1,063 spatially precise and non-redundant gnatcatcher locations as a calibration dataset. We model-averaged the results from sampling iterations to create a calibration model and partitions for each set of variables. We compared among calibration model-partitions using a validation dataset of 3,205 presence records independently collected from the calibration dataset and an equivalent number of pseudo-absence points randomly selected from the study area grid. For every model-partition, we calculated Habitat Similarity Index (HSI) predictions for presence and pseudo absence points ranging from Very High (0.75 - 1.00); High (0.50 - 0.74); Low (0.25 - 0.49); and Very Low (0 - 0.24). Suitable habitat is identified as grid cells with HSI greater than or equal to 0.5. We calculated Area Under the Curve (AUC) values from a Receiver Operating Curve (ROC) to determine how well models distinguish between presence and pseudo-absence points. We selected a best performing calibration model and partition based upon median HSI calibration and validation values and AUC results. The top performing model-partition Run 18 Partition 1 of 19 alternative models has an AUC of 0.96 and a median calibration and validation HSI of 0.73 and 0.69, respec
Fairbanks Ranch/Rancho Santa Fe Invasive Removal and Stream Enhancement
The long-term goal of this project is to restore and enhance wetland/riparian habitat along 3 miles, 200 acres, of the San Dieguito River and reduce fire risk to the surrounding community. Key actions include non-native, invasive plant removal, revegetation with native species, volunteer training, community workshops and education of local residents on how to improve habitat and create Fire-Safe landscapes around their homes. A secondary goal of this project is to highlight the importance of diverse partnerships in conserving habitat along the San Dieguito River. For more information, go to: http://www.ranchosantafereview.com/news/local-news/sd-cm-rsf-restorationproject-20171101-story.html.
Lusardi Creek Restoration and Invasive Plant Removal
This project is working to eradicate invasive species and support native plants along Lusardi Creek. Many areas have already been treated and are recruiting natives naturally. Other areas are being planted with natives after invasive plant removal. The current goals include: 1) treat artichoke in several upland areas, 2) continue removing tamarix in the creek, 3) treat any regrowing Peruvian pepper, 4) treat any remaining pampas grass or tree tobacco, 5) work on an overall restoration plan. See the map link below for detailed treatment information.
USFWS California Gnatcatcher Monitoring 2004-2009
California gnatcatcher occupancy study across San Diego County.
File name Lead Author Year Type
1.05. Response of California gnatcatchers to wildfires Winchell, Clark 2013 recording
2008 Surveys Cactus Wren and California Gnatcatchers San Dieguito River Valley, San Diego County Hamilton, Robert 2009 report
2009-2010 Annual Report for Otay Ranch Preserve - Salt Creek and San Ysidro Parcels Bennett, Anna; Dodero, Mark 2011 report
2010-11 Baseline Survey Report for the Northern San Ysidro, McMillin, and Little Cedar Canyon Parcels of the the Otay Ranch Preserve O'Meara, Cailin; Sundberg, J.R.; Bennett, Anna; Dodero, Mark 2012 report
A Habitat-Based Metapopulation Model of the California Gnatcatcher Akcakaya, H. Resit; Atwood, Jonathan 1997 journal article
Annual Report City of Carlsbad Habitat Management Plan Year 5, Novermber 2008 - October 2009 2010 report
Barnett Ranch Open Space Preserve Biological Resources Report 2004 report
BASELINE BIOLOGICAL RESOURCES EVALUATION LAKESIDE LINKAGE OPEN SPACE PRESERVE 2008 report
Bernardo Mountain Management Area California Gnatcatcher Habitat Enhancement Summary August 2007-February 2008 San Dieguito River Park 2007 report
Bernardo Mountain Management Area California Gnatcatcher Habitat Enhancement Summary March 2006-July 2007 Lopez, Jason; San Dieguito River Park 2006 report
Biological Monitoring Report for the Tijuana River Valley Regional Park (Monitoring Year 2009) 2010 report
CAGN Regional Monitoring Sample Design Preston, Kris; Kus, Barbara 2015 protocol supplement
CAGN Regional Survey Quadrats Blank Form 2016 field notes/data sheets
CAGN Regional Survey Sampling Protocol for 2016 2016 report
CAGN Regional Survey Veg Sampling Plant Guide 2016 report
CAGN Regional Survey Vegetation Assessment Blank Form 2016 field notes/data sheets
CAGN Regional Survey Vegetation Assessment Protocol for 2016 2016 report
CAGN Vegetation Sampling Protocol 2016 protocol
Calavera Hills Phase II Final Habitat Management Plan 2002 report
Coastal Cactus Wren & California Gnatcatcher Habitat Restoration Project, Phase III Year 1 Report 2014 report
Coastal Cactus Wren & California Gnatcatcher Habitat Restoration Project, Phase III Year 2 Report 2015 report
County of San Diego MSCP Monitoring Summary Report January 1998 - June 2007 County of San Diego 2007 report
Diegan Coastal Sage Scrub Restoration Plan: Calavera Preserve Planning Area 2009 report
Distinguishing recent dispersal from historic genetic connectivity in the coastal Caliofrnia gnatcatcher Vandergast, Amy; Kus, Barbara; Preston, Kris; Barr, Kelly 2019 journal article
Economic Analysis of Critical Habitat Designation for the California Gnatcatcher 2007 report
Effects of Fire, Elevation, and Habitat Quality on the Occupancy, Extinction, and Colonization of Coastal California Gnatcatcher Winchell, Clark; Doherty, Paul 2012 other
Effects of habitat quality and wildfire on occupancy dynamics of Coastal California Gnatcatcher (Polioptila californica californica) Winchell, Clark; Doherty, Paul 2014 journal article
Encinas Creek Habitat Conservation Area (Formerly known as the North County Habitat Bank) Annual Work Plan October 2010 - September 2011 2010 report
Estimation of San Diego County California Gnatcatcher Population Size and Recovery Following the 2003 October Wildfires 2009 report
FINAL Baseline Biodiversity Survey for the San Luis Rey River Park 2011 report
FINAL HABITAT MANAGEMENT PLAN for Starwood - Santa Fe Valley SECOND AMENDMENT 2000 report
Final Report - Riparian Habitat Restoration Phase 1, Lawrence and Barbara Daley Preserve 2012 report
Final Report 2021-2021 Winter Home Range Assessment of Coastal California Gnatcatcher in Recently Burned Habitat Aboard Marine Corps Base Camp Pendleton, California Vernadero Group Inc. 2022 report
Final report for Post-Fire Coastal Sage and Cactus Scrub Restoration Projects Lopez, Jason 2010 report
Final Report for the Rice Canyon Sensitive Plant Species Management Project (SANDAG Grant Number 5005508; RECON Number 9429) Dodero, Mark 2021 report
Genetic Structure in the California gnatcatcher in Coastal Southern California and Implications for Monitoring and Management 2014 report
GREENHILLS RANCH PRESERVE HABITAT MANAGEMENT PLAN ANNUAL REPORT 2013 2004 report
Habitat Management Plan for the Kelly Ranch Habitat Conservation Area 2002 report
Habitat Management Plan for the Kelly Ranch Habitat Conservation Area (2008 -2013) McConnell, Patrick; Vinje, Jessie; Spiegelberg, Markus 2008 report
Habitat Management Plan for the Rancho La Costa Habitat Conservation Area 2005 report
Habitat Restoration Summary 2010 2010 report
La Costa Collection Townhomes Preserve Preserve Management Plan 2012 report
Lakeside Linkage Bird Survey appendices A-K 2008 report
Monitoring California Gnatcatchers in Southern California 2004/2007/2009 2010 powerpoint presentation
Poinsettia Place Preserve Management Plan 2011 report
Preserve Management Plan for the Cantarini Ranch Preserve, Carlsbad, California Loeffler, Wendy 2011 report
Quarry Creek Preserve Management Plan 2011 report
Recording - Rescheduled June 2022 SDMMP Management and Monitoring Coordination Meeting Vandergast, Amy 2022 recording
Regional Occupancy and Post-Fire Recovery of California Gnatcatcher in Southern California Kus, Barbara; Preston, Kris; Houston, Alexandra 2017 powerpoint presentation
Report of Coastal California Gnatcatcher Juvenile Dispersal across Interstate-8 at the MSCP Southe 2003 report
Research Spotlight: Genetics studies in California gnatcatchers Kus, Barbara; Vandergast, Amy; Preston, Kris 2019 fact sheet
ROBERTSON RANCH EAST VILLAGE OPEN SPACE LAND MANAGEMENT PLAN Prepared 2006 report
SDRVC Cactus Scrub Restoration Projects - Summary 2008 workshop summary
State of the Regional Preserve System in Western San Diego County Preston, Kris; Perkins, Emily; Brown, Chris; McCutcheon, Sarah; Bernabe, Annabelle; Luciani, Emilie; Kus, Barbara; Wynn, Susan 2022 report
Subspecies Differentiation and Range‐wide Genetic Structure are Driven by Climate in the California Gnatcatcher, a Flagship Species for Coastal Sage Scrub Conservation Vandergast, Amy; Kus, Barbara; Wood, Dustin; Milano, Elizabeth; Preston, Kris 2022 powerpoint presentation
Trends in California Gnatcatcher Occupancy: Preliminary Results of 2020 Rangewide Surveys Kus, Barbara; Preston, Kris; Houston, Alexandra 2020 powerpoint presentation
Using California Gnatcatcher to Test Underlying Models in Habitat Conservation Plans Doherty, Paul; Winchell, Clark 2010 journal article
Using GIS to Develop a Regional Survey Design for the Coastal California Gnatcatcher Perkins, Emily; Preston, Kris; Kus, Barbara 2016 other

Current Distribution Rangewide

Occurs on coastal slopes of S. Calif., ranging from S. Ventura southward through Palos Verdes Peninsula in Los Angeles Co. through Orange, Riverside, San Bernardino and San Diego Cos. into Baja Calif. to El Rosario, Mexico [1].

List Status

FT/ CSC

Habitat Affinities

Typically occurs in or near coastal sage scrub habitat; plants of this community include California sagebrush (Artemisia californica), various species of sage (Salvia sp.), California buckwheat (Eriogonum fasciculatum), lemonadeberry (Rhus integrifolia), California encelia (Encelia californica), and Opuntia spp. Ninety-nine percent of all gnatcatcher locality records occur at or below an elevation of 984 feet [1].

Taxonomy and Genetics

Mitochondrial DNA sequencing confirmed the species-level recognition of the Coastal Calif. gnatcatcher, which was calculated to differ from the black-tailed gnatcatcher (P. melanura) by 4.0 percent, similar to differences calculated in the black-capped gnatcatcher (P. nigriceps) and white-lored gnatcatcher (P. albiloris) [10]. A recent genetic study casts doubt on the subspecies status for the northern coastal population that occurs in CSS [11].

Seasonal Activity

Most active and vocal during the morning; a lull in activity usually occurs during mid-day and activity increases again late in the day [2].

Life History/Reproduction

Breeding season extends from mid February through mid-August, with the peak of nesting activity occurring from mid-March through mid-May; nest is a small, cup-shaped basket usually found one to three feet above the ground in a small shrub or cactus; clutch sizes range between 3 and 5 eggs, with the average being 4; Juvenile birds associate with their parents for several weeks (sometimes months) after fledging.1 Gnatcatchers typically live for two to three years, although ages of up to five years have been recorded for some banded birds [3].

Diet and Foraging

Diet is primarily leaf- and plant hoppers and spiders; also included in smaller amounts are true bugs, wasps, bees, and ants [4].

Dispersal

Year-round resident [2]. The home range size of the gnatcatcher varies seasonally and geographically, with winter season home ranges being larger than breeding season ranges[7] and inland populations having larger home ranges than coastal [8]. The mean dispersal distance of gnatcatchers banded as nestlings for males was 2.85 km and for females was 3.33 km [9].

Threats

Habitat destruction, fragmentation, adverse modification, nest parasitism, agricultural use, such as grazing and field crops, urbanization, air pollution, increases in fire frequency and the introduction of exotics; high fire frequencies and the lag period associated with recovery of the vegetation may significantly reduce the viability of affected subpopulations of the gnatcatcher [5,6].

Literature Sources

[1] Subspecies limits and geographic patterns of morphological variation in California gnatcatchers (Polioptila californica). Bulletin Southern California Academy of Sciences 90 (3):118-133.

[2] Mock, P.J., B. L. Jones, and J. Konecny. 1990. California Gnatcatcher Survey Guidelines. ERC Environmental and Energy Services Co.

[3] Braden, G.T., McKernan, R.L., Powell, S.M. 1995. Life History of Polioptila californica californica in western Riverside County, CA. Paper delivered at the Symposium on the Biology of the California Gnatcatcher held 15-16 September 1995, University of California, Riverside.

[4] Burger, J. C., M. A. Patten, J. T. Rotenberry, and R. A. Redak. 1999. Foraging ecology of the California gnatcatcher deduced from fecal samples. Oecologia (Berlin) 120: 304-310.

[5] USFWS. 2010. Coastal California gnatcatcher (Polioptila californica californica) 5-year Review: Summary and Evaluation. Carlsbad. September 29.

[6] USFWS 1993. Threatened coastal California gnatcatcher; final rule and proposed special rule. Federal Register 58, number 59.

[7] Bontrager, D.R. 1991. Habitat requirements, home range and breeding biology of the California gnatcatcher (Polioptila californica) in south Orange County, California. Unpublished technical report prepared for the Santa Margarita Company, Rancho Santa Margarita, CA. 19 pp.

[8] Atwood, J.L., and D.R. Bontrager. 2001. California gnatcatcher (Polioptila californica). In Poole, A., and F. Gill (eds.). The birds of North America, No. 574. 32 pp.

[9] Atwood, J. L., S. H. Tsai, and A. M. L. Miller. 1996. California gnatcatchers, cactus wrens, and conservation of coastal sage scrub on the Palos Verdes Peninsula. Progress Report No. 4. Unpublished technical report, Manomet Observatory for Conservation Sciences, Manomet, Massachusetts. 15 pp. + appendices.

[10] Zink, R. M., and R. C. Blackwell. 1998. Molecular systematics and biogeography of arid land gnatcatchers (Genus Polioptila) and evidence supporting species status of the California gnatcatcher (Polioptila californica). Molecular Phylogenetics and Evolution 9: 26-32.

[11] Zink, R.M., J.G. Groth, H. Vazquez-Miranda, and G.F. Barrowclough. 2013. Phylogeography of the California gnatcatcher (Polioptila californica) using multilocus DNA sequences and ecological niche modeling: implications for conservation. The Auk, Vol. 130, No. 3, pp. 449-458.