2019 Riparian Birds Survey and Nest Monitoring Report

Home , American yellow warbler

Western Riverside County Multiple Species Habitat Conservation Plan Biological Monitoring Program

Yellow-breasted Chat nest in the Temescal Wash Core Area. Photo by Robert Packard.

15 April 2020 2019 Riparian Birds Survey and Nest Monitoring Report

TABLE OF CONTENTS INTRODUCTION ...... 1

GOALS AND OBJECTIVES ...... 3

METHODS ...... 3

SURVEY DESIGN ...... 3

FIELD METHODS ...... 4

RESULTS ...... 4

DETECTIONS OF TARGET SPECIES ...... 4

NESTING OF TARGET SPECIES ...... 7

DISCUSSION ...... 11

DETECTIONS OF TARGET SPECIES ...... 11

NESTING OF TARGET SPECIES ...... 12

RECOMMENDATIONS ...... 14

ACKNOWLEDGEMENTS ...... 14

LITERATURE CITED ...... 15

LIST OF TABLES Table 1. Most recent detections on currently conserved land of the two target species of our 2019 riparian bird surveys...... 5 Table 2. Most recent evidence of successful reproduction on currently conserved land by the two target species of our 2019 riparian bird surveys...... 7 Table 3. Summary of 2019 Yellow Warbler nest counts, and the number of fledglings observed, by Core Area...... 7

LIST OF FIGURES Figure 1. Riparian bird Core Areas and stations surveyed in 2019 ...... 2 Figure 2. Detection of Yellow Warblers within the Plan Area (2005-2019) ...... 6 Figure 3. Detections of Yellow-breasted Chats within the Plan Area (2005-2019) ...... 8 Figure 4. Locations of Yellow Warbler nests and fledglings in 2019 ...... 9 Figure 5. Locations of Yellow-breasted Chat nest and fledglings in 2019 ...... 10

LIST OF APPENDICES Appendix A. Avian species detected during 2019 riparian bird surveys ...... 18

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NOTE TO READER: This report is an account of survey activities conducted by the Biological Monitoring Program for the Western Riverside County Multiple Species Habitat Conservation Plan (MSHCP). The MSHCP was permitted in June 2004. Reserve assembly is ongoing and is expected to take 20 or more years to complete. The Conservation Area includes lands acquired under the terms of the MSHCP and other lands that have conservation value in the Plan Area (called public or quasi-public lands in the MSHCP). In this report, the term “Conservation Area” refers to these lands as they were understood by the Monitoring Program at the time the surveys were conducted. The Monitoring Program monitors the status and distribution of the 146 species covered by the MSHCP within the Conservation Area to provide information to Permittees, land managers, the public, and the Wildlife Agencies [i.e., the California Department of Fish and Wildlife (CDFW, formerly California Department of Fish and Game) and the U.S. Fish and Wildlife Service]. Monitoring Program activities are guided by defined conservation objectives for each Covered Species, other information needs identified in MSHCP Section 5.3 or elsewhere in the document, and the information needs of the Permittees. A list of the lands where data collection activities were conducted in 2019 is included in Section 7.0 of the Western Riverside County Regional Conservation Authority (RCA) Annual Report to the Wildlife Agencies. The primary author of this report was the 2019 Avian Program Lead, Nicholas Peterson. This report should be cited as: Biological Monitoring Program. 2020. Western Riverside County MSHCP Biological Monitoring Program 2019 Riparian Birds Survey and Nest Monitoring Report. Prepared for the Western Riverside County Multiple Species Habitat Conservation Plan. Riverside, CA. Available online: http://wrc-rca.org/about-rca/monitoring/monitoring-surveys/. While we have made every effort to accurately represent our data and results, the reader should recognize that data management and analysis are ongoing activities. Anyone wishing to make further use of the information or data provided in this report should contact the Monitoring Program to ensure that they have access to the best available or most current data. Please contact the Monitoring Program Administrator with questions about the information provided in this report. Questions about the MSHCP should be directed to the Executive Director of the RCA. Further information on the MSHCP and the RCA can be found at www.wrc-rca.org. Contact Information: Executive Director Monitoring Program Administrator Western Riverside County Western Riverside County MSHCP Regional Conservation Authority Biological Monitoring Program Riverside Centre Building 1835 Chicago Ave., Suite C 3403 10th Street, Suite 320 Riverside, CA 92507 Riverside, CA 92501 Ph: (951) 320-2168 Ph: (951) 955-9700

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INTRODUCTION Thirteen bird species covered by the MSHCP inhabit riparian areas, including Cooper’s Hawk (Accipiter cooperii), Downy Woodpecker (Dryobates pubescens), Least Bell’s Vireo (Vireo bellii pusillus), MacGillivray’s Warbler (Geothlypis tolmiei), Nashville Warbler (Leiothlypis ruficapilla), Sharp-shinned Hawk (Accipiter striatus), Southwestern Willow Flycatcher (Empidonax traillii extimus), Tree Swallow (Tachycineta bicolor), Western Yellow-billed Cuckoo (Coccyzus americanus occidentalis), White-tailed Kite (Elanus leucurus), Wilson’s Warbler (Cardellina pusilla), Yellow-breasted Chat (Icteria virens), and Yellow Warbler (Setophaga petechia brewsteri). The Plan Area is part of the present or historical regular breeding range for the following nine of these Covered Species: Cooper’s Hawk, Downy Woodpecker, Least Bell’s Vireo, Southwestern Willow Flycatcher, Tree Swallow, White-tailed Kite, Yellow- billed Cuckoo, Yellow-breasted Chat, and Yellow Warbler. The remaining four species occur within the Plan Area only during migration, except for small, occasional breeding populations, particularly at higher elevations. The species objectives for Yellow Warbler and Yellow-breasted Chat require the demonstration of both use and successful reproduction within 75% of specified Core Areas (Fig. 1) every five years, and we last surveyed for them in 2014. Thus, these two species were the targets of our 2019 riparian bird surveys, but we also collected data on any other covered riparian bird species observed. The statewide population of Yellow Warblers is considered greatly reduced (>40– 80%) since population estimates reported by Grinnell and Miller (1944), with a current estimate of between 100,000 and 1,000,000 birds (Heath 2008). The range size of Yellow Warblers in California is moderately (>20–40%) reduced since the publication of Grinnell and Miller (1944). By 2028, habitat loss, habitat degradation, or other human- induced threats are projected to slightly reduce (>5–10%) the species’ population in California (Heath 2008). Breeding Yellow Warblers generally inhabit wet thickets of deciduous trees, especially those dominated by alders (Alnus spp.), cottonwoods (Populus spp.), or willows (Salix spp.) (Dunn and Garrett 1997; Garrett et al. 2012). Nesting occurs from May through August (Lowther et al. 1999), although the species arrives in western Riverside County in April, so earlier nesting dates are possible. Nests are usually constructed in trees, including willows, and are typically 1–2.5 m above ground, although nest heights up to 15 m have been documented (Trautman 1940; Graber et al. 1983; Peck and James 1987; Knopf and Sedgwick 1992; Briskie 1995; Lowther et al. 1999; Campbell et al. 2001). Clutches usually contain four or five eggs (Lowther et al. 1999) and the incubation period lasts for 11 or 12 days (Bigglestone 1913; Schrantz 1943; Briskie 1995; McMaster and Sealy 1998; Ortega 1998). Young typically fledge 8–10 days post-hatching (Briskie 1995). The statewide population of Yellow-breasted Chats is considered moderately reduced (>20–40%) since population estimates reported by Grinnell and Miller (1944), with a current estimate of between 1,000 and 10,000 birds (Comrack 2008). The range size of Yellow-breasted Chats in California is moderately (>20–40%) reduced since the

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Figure 1. Riparian bird Core Areas and stations surveyed in 2019

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publication of Grinnell and Miller (1944). By 2028, habitat loss, habitat degradation, or other human-induced threats are projected to moderately reduce (>10–15%) the species’ population in California (Comrack 2008). Yellow-breasted Chats breeding in the western U.S. occupy riparian and shrubby habitats with open canopies (Brown and Trosset 1989; Comrack 2008). In areas with too much canopy cover, chat nest survival can be increased by management that includes tree thinning (Reidy and Thompson 2018; Roach et al. 2018). Nesting occurs from May through August and nests are usually constructed in shrubs or dense thickets that commonly contain blackberry (Rubus spp.), wild grape (Vitis spp.), or willow (Grinnell and Miller 1944; Eckerle and Thompson 2001). Nests are low, averaging 0.79–1.0 m above ground (Cheevers 1996; Ricketts 1999; Reidy and Thompson 2018). Clutches usually contain three to five eggs and the incubation period lasts for 11 or 12 days. Fledging occurs eight or nine days post-hatching (Eckerle and Thompson 2001). Goals and Objectives 1. Determine the breeding season distribution of Covered riparian bird species and other co-occurring bird species within riparian habitat. a. Conduct repeat-visit point-transect surveys within accessible riparian habitat in the Plan Area, recording all bird species observed. 2. Determine whether Yellow Warblers and Yellow-breasted Chats are successfully reproducing within their respective Core Areas. a. Conduct nest searches when we observe 2019 target species. When active nests are found, re-visit the nest up to three days per week, and continue to monitor the status of the nest until fledging or failure.

METHODS Survey Design We conducted surveys for Covered riparian bird species by making repeat visits (n = 2 visits) to point-transects (n = 78 transects) within the MSHCP-identified Core Areas. Surveys occurred on conserved lands within riparian habitat, including riparian woodland, forest, and scrub, as defined by our GIS vegetation layer (CDFG et al. 2005). I generated randomly-located transect center points within riparian habitat, separated by a minimum of 250 m, using the Hawth’s Tools extension (Beyer 2004) in ArcGIS (ESRI 2018). Each transect consisted of three survey points: a central “B” point and terminal “A” and “C” points that were exactly 100 m from the “B” point (Fig. 1). We conducted our 2019 surveys from 1 April–26 July. This period generally encompasses the time during which our target species are most likely to be present within the Plan Area. Observers started their first survey approximately 15 min after sunrise and did not start new transects after 1000 h (i.e., transects already being surveyed at 1000 h were completed, regardless of time). We terminated surveys early if precipitation exceeded a light drizzle, the temperature was >35 °C, or maximum wind speeds were >38 km/h.

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Field Methods Observers began by navigating to their survey point using a handheld GPS. They started at either the “A” or “C” point of their transect. After arriving at the survey point, the observer recorded environmental data, including the sky code, ambient noise, and starting temperature (°C). The observer then activated their anemometer to record maximum and average wind speeds throughout the survey. Surveys consisted of 5 min of passive listening during which the observers recorded on their data sheet the first individual of each bird species observed. Observers recorded information for subsequently-observed individuals only if those individuals were a Covered Species. This allowed us to record data on the detectability, abundance, and distribution of non-covered species within the Plan Area without compromising the ability to detect and record Covered Species. For each observation, observers recorded the species, using a four-letter code; the sex of the bird; and the age class of the bird. After five minutes of passive listening observers moved to the central point (B), then to the remaining endpoint (either A or C), repeating the procedure described above at each point. Observers used a separate data sheet for each of the three points along transects. At the end of the survey period, observers recorded on their data sheet the maximum and average wind speeds during the survey period, as well as the ending temperature. At this time observers also attempted to identify any birds that they detected but were unable to identify during the survey period. Additional birds detected during this time were recorded in the “Notes” section of the data sheet. Observers also recorded any birds detected between survey points, or “in-transit,” in the “Notes” section of the data sheet. If any of those individual birds are subsequently detected during a survey period, the observer removed the observation from the “Notes” section and recorded the necessary information on the survey data sheet. Finally, Covered avian species detected outside of survey periods were considered incidental observations, as were all detections of Covered non-avian species, regardless of when that species was detected. If an observer detected one of the target species, they notified a nest searcher upon returning from the field. Nest searchers returned to the site within one week of the observation and attempted to locate an active nest. The survey methods are more completely described in the Western Riverside County MSHCP Biological Monitoring Program 2019 Riparian Bird Survey Protocol.

RESULTS Detections of Target Species We detected Yellow Warblers and Yellow-breasted Chats in 89% and 80% of their Core Areas, respectively, during the current reporting period of 2015–2019, thereby meeting the objective for demonstration of use for both species (Table 1). Overall, we detected 93 avian species during our 2019 surveys, including 18 species covered by the MSHCP (Appendix A).

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Table 1. Most recent detections on currently conserved land of the two target species of our 2019 riparian bird surveys. Shading indicates designated Core Areas for each species. Parenthetical values indicate the number of detections on currently conserved land within the current reporting period (2015–2019). “N. R.” indicates that our Program has no records of the species on conserved land in the Core Area from 2004 onward. Core Area Yellow Warbler Yellow-breasted Chat Murrieta Creek 2015 (1) N. R. Prado Basin/Santa Ana River 2019 (325) 2019 (243) San Bernardino National Forest 2019 (6) N. R. San Timoteo Creek 2019 (24) 2019 (6) Temecula Creek 2019 (8) 2019 (11) Temescal Canyon, including 2019 (45) 2019 (5) Alberhill Creek Vail Lake N. R. N. R. Wasson Canyon 2019 (3) 2015 (1) Wilson Creek 2019 (2) N. R. Percentage of Core Areas in which we have detected the 89 80 species during the current reporting period

Yellow Warbler We detected Yellow Warblers in 89% of their designated Core Areas during the current reporting period (2015–2019), with nearly all Core Area detections occurring most recently during our 2019 survey effort (Table 1). We have detected Yellow Warblers on currently conserved land in the Murrieta Creek Core Area just once, in 2015 (Fig. 2). We have never detected the species in the Vail Lake Core Area because our Program has never been granted permission to conduct surveys on conserved land there. The closest Yellow Warbler detection to the Vail Lake Core Area by our Program biologists occurred 670 m south of the Core Area, along Arroyo Seco (Fig. 2). We have historically detected Yellow Warblers on several occasions within the following locations, any of which should be considered as alternative or additional Core Areas for the species: Lake Mathews/Estelle Mountain (Existing Core C; n = 21 detections from 2006–2019), Lake Perris/Mystic Lake (Existing Core H; n = 85 detections from 2005–2019), and Lake Skinner/Diamond Valley Lake (Existing Core J; n = 81 detections from 2005–2017) (Fig. 2). Yellow-breasted Chat We detected Yellow-breasted Chats in 80% of their designated Core Areas during the current reporting period (2015–2019), with all Core Area detections occurring most recently during our 2019 survey effort (Table 1). As previously referenced, we have never detected the species in the Vail Lake Core Area because our Program has never been granted permission to conduct surveys on conserved land there. We have historically detected Yellow-breasted Chats within the following two locations, either of which should be considered as alternative or additional Core Areas for the species: Lake Mathews/Estelle Mountain (Existing Core C; n = 14 detections from

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Figure 2. Detection of Yellow Warblers within the Plan Area (2005-2019)

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2006–2014) and Lake Skinner/Diamond Valley Lake (Existing Core J; n = 4 detections from 2007–2011) (Fig. 3) Nesting of Target Species We documented successful reproduction by Yellow Warblers in just 56% of their Core Areas, failing to meet their reproductive objective during the current reporting period (Fig. 4 and Table 2). We documented evidence of successful reproduction by Yellow-breasted Chats in 80% of their Core Areas, meeting the reproductive objective for the species (Fig. 5 and Table 2).

Table 2. Most recent evidence of successful reproduction on currently conserved land by the two target species of our 2019 riparian bird surveys. Shading indicates designated Core Areas for each species. The current reporting period is 2015–2019. “N. R.” indicates that our Program has no records of the species nesting successfully on conserved land in the Core Area from 2004 onward. Core Area Yellow Warbler Yellow-breasted Chat Murrieta Creek N. R. N. R. Prado Basin/Santa Ana River 2019 2019 San Bernardino National Forest 2019 N. R. San Timoteo Creek 2019 2019 Temecula Creek 2019 2019 Temescal Canyon, including 2019 2019 Alberhill Creek Vail Lake N. R. N. R. Wasson Canyon N. R. N. R. Wilson Creek N. R. N. R. Percentage of Core Areas in which we documented evidence of successful 56 80 reproduction during the current reporting period

Yellow Warbler We documented the production of Yellow Warbler fledglings in 30% of the 10 nesting attempts we observed (Table 3). Of the seven nesting attempts that failed, we attributed all to undetermined causes due to the height of the nests and our inability to inspect the contents following failure.

Table 3. Summary of 2019 Yellow Warbler nest counts, and the number of fledglings observed, by Core Area. Core Area n nesting attempts n successful attempts (% of total) n fledglingsa Prado Basin/Santa Ana River 1 1 (100%) 6 San Bernardino National Forest 2 1 (50%) 2 San Timoteo Creek 2 0 (0%) 1 Temecula Creek 3 1 (33%) 2 Temescal Canyon, including 2 0 (0%) 6 Alberhill Creek Total 10 3 (30%) 17 a Minimum number of fledglings seen; data include fledglings whose nests we did not locate.

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Figure 3. Detections of Yellow-breasted Chats within the Plan Area (2005-2019)

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Figure 4. Locations of Yellow Warbler nests and fledglings in 2019

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Figure 5. Locations of Yellow-breasted Chat nest and fledglings in 2019

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Yellow Warbler nests found by our Program in 2019 were an average of 10.7 m above ground (range = 7–18 m) and substrates were an average of 15 m tall (range = 10–23 m). The three nesting substrates used by Yellow Warblers in 2019 were cottonwood (Populus spp.; n = 3 nests), California live oak (Quercus agrifolia; n = 1), and willow (Salix spp.; n = 6). The earliest Yellow Warbler nest we found in 2019 was in the construction stage on 16 April. We first observed nestlings on 15 May and fledglings on 21 May. The latest group of fledglings that we observed fledged sometime during the first 10 days of July. Yellow-breasted Chat We found just one Yellow-breasted Chat nest in 2019, within the Temescal Canyon/Alberhill Creek Core Area (Fig. 5). The nest was in the incubation stage when we found it on 14 June, containing three eggs. The nest was empty on our subsequent visit on 21 June, having failed sometime in the interim. The nest did not have any structural damage, so we assumed that depredation occurred, perhaps by an avian or snake predator. The nest was constructed in a tangle of Indian hemp (Apocynum cannabinum) and poison oak (Toxicodendron diversilobum) and was approximately 1.2 m above ground. We found a minimum of seven chat fledglings distributed among the Prado Basin/Santa Ana River (n ≥ 2 fledglings), San Timoteo Creek (n ≥ 2), Temecula Creek (n ≥ 2), and Temescal Canyon/Alberhill Creek (n ≥ 1) Core Areas (Fig. 5). We first detected fledglings on 13 June, in the Temecula Creek Core Area, and detected our latest fledgling on 31 July, in the Temescal Canyon/Alberhill Creek Core Area.

DISCUSSION Detections of Target Species Yellow Warbler We regularly detect Yellow Warblers within the Prado Basin/Santa Ana River, San Bernardino National Forest (NF), San Timoteo Creek, Temecula Creek, and Temescal Canyon/Alberhill Creek Core Areas. All these Core Areas contain conserved riparian habitat that is preferred by the species and can be characterized as wet thickets of deciduous trees that include cottonwoods and willows (Dunn and Garrett 1997; Garrett et al. 2012). We had fewer detections than usual within the San Bernardino NF this year because two of the main routes into the Core Area, State Routes 74 and 243, were damaged during winter rains, which made access to much of the area difficult. As a result, we surveyed for warblers in a relatively small portion of the Core Area. We rarely detected Yellow Warblers within the Murrieta Creek, Wasson Canyon, and Wilson Creek Core Areas within the current reporting period (Table 1). Within Murrieta Creek, none of the currently conserved land is considered suitable for breeding Yellow Warblers based upon the habitat requirements described by Dunn and Garrett (1997) and Garrett et al. (2012). The one record our Program has of a Yellow Warbler on conserved land within this Core Area in the current reporting period was a bird that was primarily using nearby habitat that is not currently conserved.

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Similarly, the Wasson Canyon Core Area contains little conserved riparian habitat, except for an unnamed creek that traverses the northwestern section of the Core Area and provides just 5.3 ha of habitat. This is where two of our three Yellow Warbler detections have occurred within the Core Area during the current reporting period. The two detections occurred on the same day in mid-April 2019, and the birds were not detected during subsequent visits, suggesting that they were using the creek as a migratory route, rather than as a breeding site, in 2019. We have detected Yellow Warblers just three times on conserved land within the Wilson Creek Core Area. All three detections occurred in mid-May, with one occurring in 2011 and two occurring in 2019. The Core Area consists largely of desert transition habitat, with approximately 97 ha of riparian habitat currently in conservation. The creeks within the riparian habitat in the Core Area are generally dry during the Yellow Warbler breeding season, except following particularly wet winters, when water can persist into the summer. Both years we have detected Yellow Warblers within the Wilson Creek Core Area followed winters when the area received more than 100% of the historical average for precipitation, and occurred during the two wettest years in the Plan Area since at least 2007 (NOAA 2019). Despite the above-average rainfall, however, we were unable to find evidence of Yellow Warbler nesting in the Wilson Creek Core Area in 2011 and 2019, suggesting that the area may be used by migratory, rather than breeding, warblers. Yellow-breasted Chat Yellow-breasted Chats generally require at least 0.82–1.2 ha (Brewer 1955; Thompson and Nolan 1973) of early successional riparian habitat with a well-developed shrub layer and an open canopy (Comrack 2008). There should also be dense thickets and tangles of vegetation below 2.5 m (Grinnell and Miller 1944; Ehrlich et al. 1988). These characteristics are present on conserved land in the four Core Areas in which we have detected chats during the current reporting period. This year is the first time in our Program history that we detected chats on currently conserved land within the Temescal Wash/Alberhill Creek Core Area (Fig. 3), although some earlier detections were near the Core Area boundaries. We searched the area previously (Biological Monitoring Program 2015) but were unable to detect the species. Four of our detections in 2019 occurred within the Regional Conservation Authority’s Toscana Donation Phase 1 property, acquired in December 2017. The property contains approximately 10 ha of ideal chat habitat that includes water and dense stands of grape and poison oak. Our fifth chat detection in the Core Area occurred on Riverside County Flood Control property along Alberhill Creek and may have been a migrating bird because we detected it once in April, but not during subsequent visits. Nesting of Target Species Yellow Warbler In 2019 we documented evidence of successful reproduction by Yellow Warblers in the same five (56%) designated Core Areas in which we have typically seen nesting since 2007 (Table 2). Our Program has two records of warblers unsuccessfully nesting in the Wasson Canyon Core Area in 2008, but the nests were not on currently conserved land. As stated previously, none of the conserved land within the Murrieta Creek Core

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Area is suitable for nesting Yellow Warblers, which explains the lack of nesting data for that area. The Wilson Creek Core Area appears to be used only infrequently by the species, perhaps during migration, and this is unlikely to change unless the creeks contain water during the breeding season on a regular basis. Finally, the Vail Lake Core Area likely contains breeding habitat for the species, but our Program biologists have never been granted permission to survey within the area. Yellow Warbler nests in 2019 were an average of 10.7 m above ground, which is similar to what we observed in 2008 (10.3 m; Biological Monitoring Program 2009) and taller than what we observed in 2011 (5.9 m; Biological Monitoring Program 2012). Willows were the most commonly used nesting substrate in 2019, which is also what we observed in 2008 and 2011 (Biological Monitoring Program 2009, 2012). Similarly, Timmer et al. (2011) reported that all Yellow Warbler nests (n = 22) at their study sites in Santa Cruz and Monterey counties, California, were constructed in willows. The preference for constructing nests in willows seems to be a rangewide inclination for the species (Lowther et al. 1999; Heath 2008), and conservation of potential warbler habitat within the Plan Area should focus on this habitat feature. We first observed warbler nests being constructed on 16 April in 2019, which is 2–3 weeks earlier than we observed in 2008 and 2011 (2 and 5 May, respectively; Biological Monitoring Program 2009, 2012). We first observed fledglings on 21 May 2019, which is only slightly earlier in the season than first fledglings seen in 2008 and 2011 (23 May and 1 June, respectively; Biological Monitoring Program 2009, 2012). Within California, Yellow Warblers are known to initiate breeding beginning in April (Heath 2008), so our 2019 initiation dates are not abnormal for the species. Yellow-breasted Chat In 2019 we documented evidence of successful reproduction by Yellow-breasted Chats in 80% of their designated Core Areas (Fig. 5). Prior to 2019, our Program had not documented successful reproduction by chats in more than 60% of Core Areas, but this was the first time we documented successful reproduction in the Temescal Canyon/Alberhill Creek Core Area, bringing the total to 80%. Successful reproduction by chats in that Core Area in 2019 occurred in the aforementioned and recently acquired Toscana Donation Phase 1 property, which contains approximately 10 ha of ideal chat habitat. Chat fledglings in the Temecula Creek Core Area were in a Riverside County Flood Control-managed parcel that was acquired in 2016 and is east of Interstate 15 and south of Pechanga Drive. The parcel is 6.1 ha in size and seems to contain ideal riparian habitat; similar habitat extends to the east of the parcel and should be targeted for future conservation of riparian habitat. We found chat fledglings in the San Timoteo Creek Core Area within RCA-owned Oak Valley Partners property, which is north of San Timoteo Canyon Road. Riparian habitat here is somewhat sparse, but dense grape preferred as nesting substrate by chats is present. Chats are relatively abundant within the Prado Basin/Santa Ana River Core Area, as is their preferred nesting habitat, so we are usually able to find evidence of successful nesting without having to do extensive searches. Finally, the Vail Lake Core Area was the one Core Area in which we were not allowed to survey in 2019, and this is also the only Core Area where we did not document successful reproduction by chats.

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Recommendations Future Surveys We should continue to include in our subsequent survey efforts any recently acquired properties that appear to contain suitable habitat for targeted riparian bird species. Two of our chat nests in 2019 occurred on such properties and helped us to meet the reproductive objective for the species. Beyond this, the methods we used in 2019 allow us to detect focal species within one or two visits to survey sites, so should be continued in future survey efforts. Conservation and Management The Murrieta Creek Core Area does not currently contain any conserved land that is likely to be used by breeding Yellow Warblers, as evidenced by the fact that we have detected warblers here once in the last five years. Suitable breeding habitat exists within the Core Area boundaries, and if this land is acquired for conservation, we would likely be able to add Murrieta Creek to the list of Core Areas in which we regularly detect Yellow Warblers. The parcel in the Temecula Creek Core Area in which we detected Yellow- breasted Chat fledglings contains ideal breeding habitat for the species. Immediately east of this parcel is a continuation of the habitat, and its acquisition for conservation should be considered, if possible. As outlined in the Results section of this report, there are three non-Core Areas where we regularly detect Yellow Warblers, and these should be considered as alternative Core Areas for the species, especially if the Murrieta Creek and Vail Lake Core Areas continue to lack riparian habitat or present access difficulties, respectively. These areas are Lake Mathews/Estelle Mountain (Existing Core C), Lake Perris/Mystic Lake (Existing Core H), and Lake Skinner/Diamond Valley Lake (Existing Core J). Similarly, Lake Mathews/Estelle Mountain and Lake Skinner/Diamond Valley Lake should be considered as alternative Core Areas for Yellow-breasted Chat, especially if our Program will not be granted access to Vail Lake. Finally, continued efforts should be made to acquire access to conduct surveys in the Vail Lake Core Area, specifically within the vicinity of the lake itself. This is a Core Area for Yellow Warblers and Yellow-breasted Chats, and suitable habitat may exist, but we are unable to make this determination without being able to access the site.

ACKNOWLEDGEMENTS We thank the land managers in the MSHCP Plan Area, who in the interest of conservation and stewardship facilitate Monitoring Program activities on the lands for which they are responsible. Funding for the Biological Monitoring Program is provided by the Western Riverside Regional Conservation Authority and the California Department of Fish and Wildlife. Program staff who conducted surveys in 2019 were Masanori Abe, Cristina Juran, Robert Packard, Nicholas Peterson, and Nathan Pinckard.

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LITERATURE CITED Beyer JL. 2004. Hawth’s Analysis Tools for ArcGIS. Available at http://spatialecology.com/htools. Bigglestone HC. 1913. A study of the nesting behavior of the Yellow Warbler (Dendroica aestiva aestiva). Wilson Bulletin 25:49–67. Biological Monitoring Program. 2009. Coastal California Gnatcatcher, Least Bell’s Vireo, Southwestern Willow Flycatcher, Yellow-breasted Chat, and Yellow Warbler Nesting Report, 2008. Prepared for the Western Riverside County Multiple Species Habitat Conservation Plan. Riverside, California. Available from http://wrc-rca.org/about-rca/monitoring/monitoring-surveys (accessed November 2019). Biological Monitoring Program. 2012. Riparian Bird Surveys and Nest Monitoring, 2011. Prepared for the Western Riverside County Multiple Species Habitat Conservation Plan. Riverside, California. Available from http://wrc- rca.org/about-rca/monitoring/monitoring-surveys (accessed November 2019). Biological Monitoring Program. 2015. Western Riverside County MSHCP Biological Monitoring Program 2014 Riparian Bird Survey Report. Prepared for the Western Riverside County Multiple Species Habitat Conservation Plan. Riverside, California. Available from http://wrc-rca.org/about- rca/monitoring/monitoring-surveys (accessed November 2019). Brewer R. 1955. Size and home range in eight bird species in a southern Illinois swamp-thicket. Wilson Bulletin 67:140–141. Briskie JV. 1995. Nesting biology of the Yellow Warbler at the northern limit of its range. Journal of Field Ornithology 66:531–543. Brown BT, Trosset MW. 1989. Nesting-habitat relationships of riparian birds along the Colorado River in Grand Canyon, Arizona. Southwestern Naturalist 34:260–270. [CDFG] California Department of Fish and Game, Aerial Information Systems, California Native Plant Society. 2005. Vegetation – Western Riverside Co. [ds170]. Publication Date: 2005-07-31. Available from https://www.wildlife.ca.gov/Data/BIOS (accessed November 2019). Campbell RW, Dawe NK, McTaggart-Cowan I, Cooper JM, Kaiser GW, McNall MCE, Stewart AC. 2001. The birds of British Columbia, Volume 4: Wood- warblers through Old World Sparrows. Royal British Columbia Museum, Victoria. Cheevers JW. 1996. Yellow-breasted Chat. Pages 372–373 in Robbins CS, Blom EAT, editors. Atlas of the breeding birds of Maryland and the District of Columbia. University of Pittsburgh, Pittsburgh, Pennsylvania.

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Comrack LA. 2008. Yellow-breasted Chat (Icteria virens). Pages 351–358 in Shuford WD, Gardali T, editors. California Bird Species of Special Concern: A ranked assessment of species, subspecies, and distinct populations of birds of immediate conservation concern in California. Studies of Western Birds 1. Western Field Ornithologists, Camarillo, California, and California Department of Fish and Game, Sacramento. Dunn JL, Garrett KL. 1997. A field guide to the warblers of North America. Houghton Mifflin, Boston. Eckerle KP, Thompson CF. 2001. Yellow-breasted Chat (Icteria virens), version 2.0. In Poole AF, Gill FB, editors. The Birds of North America, Cornell Lab of Ornithology, Ithaca, New York. Available from https://doi.org/10.2173/bna.575 (accessed October 2019). Ehrlich PR, Dobkins DS, Wheye D. 1988. The birder’s handbook: A field guide to the natural history of North American birds. Simon & Schuster, New York. Environmental Systems Research Institute (ESRI) ArcGIS: Release 10.1 (2018) [software]. Redlands, California: Environmental Systems Research Institute, 1999–2019. Garrett KL, Dunn JL, Small BE. 2012. Birds of southern California. R. W. Morse, Olympia, Washington. Graber JW, Graber RR, Kirk EL. 1983. Illinois birds: Wood warblers. Illinois Natural History Survey Biological Notes 118. Grinnell J, Miller AH. 1944. The distribution of the birds of California. Pacific Coast Avifauna 27. Heath SK. 2008. Yellow Warbler (Dendroica petechia). Pages 332–339 in Shuford WD, Gardali T, editors. California Bird Species of Special Concern: A ranked assessment of species, subspecies, and distinct populations of birds of immediate conservation concern in California. Studies of Western Birds 1. Western Field Ornithologists, Camarillo, California, and California Department of Fish and Game, Sacramento. Knopf FL, Sedgwick JA. 1992. An experimental study of nest-site selection by Yellow Warblers. Condor 94:734–742. Lowther PE, Celada C, Klein NK, Rimmer CC, Spector DA. 1999. Yellow Warbler (Setophaga petechia), version 2.0. In Poole AF, Gill, FB, editors. The Birds of North America, Cornell Lab of Ornithology, Ithaca, New York. Available from https://doi.org/10.2173/bna.454 (accessed October 2019). McMaster DG, Sealy SG. 1998. Short incubation periods of Brown-headed Cowbirds: How do cowbird eggs hatch before Yellow Warbler eggs? Condor 100:102–111.

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[NOAA] National Oceanic and Atmospheric Administration. 2019. Advanced Hydrologic Prediction Service: Precipitation Analysis. Available from https://water.weather.gov/precip/index.php (accessed November 2019). Ortega CP. 1998. Cowbirds and other brood parasites. University of Arizona Press, Tucson. Peck GK, James RD. 1987. Breeding birds of Ontario: Nidiology and distribution. Volume 2. Passerines. Miscellaneous Publications of the Royal Ontario Museum, Toronto. Reidy JL, Thompson FR, III. 2018. Songbird nest survival in managed oak savannas and woodlands in the Missouri Ozarks. American Midland Naturalist 180:189–206. Ricketts MS. 1999. Possible influence of vegetation structure on the nesting success of Yellow-breasted Chats (Icteria virens). Master’s thesis, Eastern Kentucky University, Richmond. Roach MC, Thompson FR, III, Jones-Farrand T. 2018. Songbird nest success is positively related to restoration of pine-oak savanna and woodland in the Ozark Highlands, Missouri, USA. Condor 120:543–556. Schrantz FG. 1943. Nest life of the Eastern Yellow Warbler. Auk 60:367–387. Thompson CF, Nolan V, Jr. 1973. Population biology of the Yellow-breasted Chat (Icteria virens L.) in southern Indiana. Ecological Monographs 43:145–171. Timmer M, Suddjian DL, Lambrecht S, Bros-Seemann S. 2011. Nesting success of the Yellow Warbler in a disturbed riparian forest in coastal California. Western Birds 42:96–102. Trautman MB. 1940. The birds of Buckeye Lake, Ohio. University of Michigan, Museum of Zoology Miscellaneous Publications 44.

Western Riverside County MSHCP 17 Biological Monitoring Program 2019 Riparian Bird Survey and Nest Monitoring Report

Appendix A. Avian species detected during 2019 riparian bird surveys. Species in bold are covered by the MSHCP.

COMMON NAME SCIENTIFIC NAME Acorn Woodpecker Melanerpes formicivorus American Crow Corvus brachyrhynchos American Goldfinch Spinus tristis American Robin Turdus migratorius American Yellow Warbler Setophaga petechia brewsteri Anna's Hummingbird Calypte anna Ash-throated Flycatcher Myiarchus cinerascens Barn Swallow Hirundo rustica Bell's Sparrow Artemisiospiza belli Belted Kingfisher Megaceryle alcyon Bewick's Wren Thryomanes bewickii Black Phoebe Sayornis nigricans Black-chinned Hummingbird Archilochus alexandri Black-chinned Sparrow Spizella atrogularis Black-headed Grosbeak Pheucticus melanocephalus Blue Grosbeak Passerina caerulea Blue-gray Gnatcatcher Polioptila caerulea Brewer's Sparrow Spizella breweri Brown-headed Cowbird Molothrus ater Bullock's Oriole Icterus bullockii Bushtit Psaltriparus minimus California Gull Larus californicus California Quail Callipepla californica California Scrub-Jay Aphelocoma californica California Thrasher Toxostoma redivivum California Towhee Melozone crissalis Canada Goose Branta canadensis Cassin's Kingbird Tyrannus vociferans Cedar Waxwing Bombycilla cedrorum Cliff Swallow Petrochelidon pyrrhonota Coastal California Gnatcatcher Polioptila californica californica Common Raven Corvus corax Common Yellowthroat Geothlypis trichas Cooper's Hawk Accipiter cooperii Costa's Hummingbird Calypte costae Dark-eyed Junco Junco hyemalis Double-crested Cormorant Phalacrocorax auritus Downy Woodpecker Dryobates pubescens Eurasian Collared-Dove Streptopelia decaocto European Starling Sturnus vulgaris Great Blue Heron Ardea herodias Great Egret Ardea alba Great Horned Owl Bubo virginianus

Western Riverside County MSHCP 18 Biological Monitoring Program 2019 Riparian Bird Survey and Nest Monitoring Report

Appendix. Continued.

COMMON NAME SCIENTIFIC NAME Green Heron Buorides virescens Hermit Thrush Catharus guttatus Hooded Oriole Icterus cucullatus House Finch Haemorhous mexicanus House Sparrow Passer domesticus House Wren Troglodytes aedon Hutton’s Vireo Vireo huttoni Killdeer Charadrius vociferus Lazuli Bunting Passerina amoena Least Bell's Vireo Vireo bellii pusillus Lesser Goldfinch Spinus psaltria Mallard Anas platyrhynchos Mountain Quail Oreortyx pictus Mourning Dove Zenaida macroura Nashville Warbler Leiothlypis ruficapilla Northern Flicker Colaptes auratus Northern Mockingbird Mimus polyglottos Northern Rough-winged Swallow Stelgidopteryx serripennis Nuttall's Woodpecker Dryobates nuttallii Oak Titmouse Baeolophus inornatus Orange-crowned Warbler Leiothlypis celata Osprey Pandion haliaetus Pacific-slope Flycatcher Empidonax difficilis Phainopepla Phainopepla nitens Red-shouldered Hawk Buteo lineatus Red-tailed Hawk Buteo jamaicensis Red-winged Blackbird Agelaius phoeniceus Rock Pigeon Columba livia Rock Wren Salpinctes obsoletus Ruby-crowned Kinglet Regulus calendula Campylorhynchus San Diego Cactus Wren brunneicapillus couesi Say's Phoebe Sayornis saya Song Sparrow Melospiza melodia Southern California Rufous- Aimophila ruficeps canescens crowned Sparrow Spotted Towhee Pipilo maculatus Tree Swallow Tachycineta bicolor Turkey Vulture Cathartes aura Violet-green Swallow Tachycineta thalassina Warbling Vireo Vireo gilvus Western Bluebird Sialia mexicana Western Kingbird Tyrannus verticalis Western Wood-Pewee Contopus sordidulus White-crowned Sparrow Zonotrichia leucophrys White-tailed Kite Elanus leucurus

Western Riverside County MSHCP 19 Biological Monitoring Program 2019 Riparian Bird Survey and Nest Monitoring Report

Appendix. Continued.

COMMON NAME SCIENTIFIC NAME White-throated Swift Aeronautes saxatalis White-winged Dove Zenaida asiatica Wilson's Warbler Cardellina pusilla Wrentit Chamaea fasciata Yellow-breasted Chat Icteria virens Yellow-rumped Warbler Setophaga coronata

Western Riverside County MSHCP 20 Biological Monitoring Program