Loggerhead Shrike Survey Report 2018

Western Riverside County Multiple Species Habitat Conservation Plan Biological Monitoring Program

2018 Loggerhead Shrike (Lanius ludovicianus) Survey and Nest Monitoring Report

Loggerhead Shrike nestlings in a nest within the Wilson Valley Core Area in 2018. 27 March 2019 2018 Loggerhead Shrike Survey and Nest Monitoring Report

TABLE OF CONTENTS INTRODUCTION ...... 1

GOALS AND OBJECTIVES ...... 3

METHODS ...... 3

SURVEY DESIGN ...... 3

FIELD METHODS ...... 5

DATA ANALYSIS ...... 6

RESULTS ...... 6

DETECTIONS OF LOGGERHEAD SHRIKES ...... 6

DETECTION RATES AND DETECTION PROBABILITY ANALYSIS ...... 8

LOGGERHEAD SHRIKE NESTING ...... 8

DISCUSSION ...... 9

DETECTIONS OF LOGGERHEAD SHRIKES ...... 9

DETECTION RATES AND DETECTION PROBABILITY ANALYSIS ...... 13

LOGGERHEAD SHRIKE NESTING ...... 14

RECOMMENDATIONS ...... 18

ACKNOWLEDGEMENTS ...... 18

LITERATURE CITED ...... 18

LIST OF TABLES Table 1. Model rankings for Loggerhead Shrike surveys in 2018 ...... 8 Table 2. Summary of 2018 Loggerhead Shrike nest counts and the number of fledglings observed, by Core Area...... 8 Table 3. Nesting substrates used by Loggerhead Shrikes in 2018, and frequency of successful nests built within each substrate species ...... 9 Table 4. Summary of apparent nest success (number of successful nests/number of nests monitored) of Loggerhead Shrikes reported throughout the range of the species...... 15 Table 5. Summary of daily survival rates of Loggerhead Shrike nests reported throughout the range of the species ...... 15 Table 6. Summary of presumed Loggerhead Shrike nest failure rates due to depredation, reported throughout the range of the species ...... 16 Table 7. Summary of earliest dates that Loggerhead Shrike nests have contained eggs for investigations occurring between latitudes 30° and 35° north ...... 17

Western Riverside County MSHCP ii Biological Monitoring Program 2018 Loggerhead Shrike Survey and Nest Monitoring Report

LIST OF FIGURES Figure 1. Loggerhead Shrike Core Areas, with detections and nest locations prior to the current reporting period (2005-2010) ...... 2 Figure 2. Loggerhead Shrike Core Areas and 2018 survey station locations ...... 4 Figure 3. Loggerhead Shrike Core Areas, detections within the current reporting period (2011-2018), and 2018 fledgling and nest locations ...... 7 Figure 4. View south through the Potrero Unit of the SJWA in 2018 ...... 10 Figure 5. View east along Temecula Creek ...... 13

LIST OF APPENDICES Appendix. Avian species detected during 2018 Loggerhead Shrike surveys ...... 23

Western Riverside County MSHCP iii Biological Monitoring Program 2018 Loggerhead Shrike Survey and Nest Monitoring Report

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 2018 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 2018 Avian Program Lead, Nicholas Peterson. This report should be cited as: Biological Monitoring Program. 2019. Western Riverside County MSHCP Biological Monitoring Program 2018 Loggerhead Shrike 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, it should be recognized that data management and analysis are ongoing activities. Any reader 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 4500 Glenwood Drive, Bldg. C 3403 10th Street, Suite 320 Riverside, CA 92501 Riverside, CA 92501 Ph: (951) 248-2552 Ph: (951) 955-9700

Western Riverside County MSHCP iv Biological Monitoring Program 2018 Loggerhead Shrike Survey and Nest Monitoring Report

INTRODUCTION The Loggerhead Shrike (Lanius ludovicianus) is one of 45 bird species covered by the Western Riverside County MSHCP (Dudek & Associates 2003), and is designated as a Species of Special Concern by the State of California (Humple 2008). The statewide population is considered greatly reduced (>40–80%) since population estimates reported by Grinnell and Miller (1944), with a current estimated size of 10,000–100,000 birds. By 2028, habitat loss, habitat degradation, or other human-induced threats are projected to moderately reduce (>10– 15%) the species’ population in California (Humple 2008). The indirect effects of climate change may also negatively affect the productivity of the species (Borgman and Wolf 2016). Within California, the species occurs statewide except for the coastal slopes, the Coast Ranges, the Klamath and Siskiyou Mountains in the northwest, the Sierra Nevada and southern Cascades, and high elevations of the Transverse Ranges (Humple 2008). Shrikes are widely distributed throughout the Plan Area, occurring relatively frequently within the central portion of the Plan Area, but with few records in the montane areas (Fig. 1). Shrikes occur in western Riverside County as yearlong residents, both breeding and wintering in the area (Garrett et al. 2012). The Western Riverside County MSHCP identifies three species objectives for Loggerhead Shrikes. The first objective requires the conservation of a minimum of 67,820 ha of suitable nesting and foraging habitat, including agriculture; grassland; cismontane alkali marsh; playa and vernal pools; desert scrubs; Riversidean alluvial fan sage scrub; coastal sage scrub; peninsular juniper woodland and scrub; riparian scrub, woodland and forest; and oak woodlands and forest. The second objective requires the conservation of at least eight breeding and foraging Core Area locations for the species, including the Badlands, Lake Mathews/Estelle Mountain, Lake Perris/Mystic Lake/San Jacinto Wildlife Area (SJWA), Prado Basin/Santa Ana River, Quail Valley, Temecula Creek, Wasson Canyon and Wilson Valley, and (Fig. 1). Finally, the third species objective for Loggerhead Shrikes requires that shrikes use and successfully reproduce in at least 75% of the aforementioned Core Areas once every eight years (Dudek and Associates 2003). Shrikes in California tend to breed in shrublands or open woodlands that contain some grass cover mixed with open ground. They also require tall, isolated perches, such as trees or power lines, from which to hunt (Humple 2008; Becker et al. 2009). Such perches should ideally be located near open areas consisting of short grasses, forbs, or open ground, in which shrikes can locate and capture their prey, which consist of arthropods, reptiles, amphibians, small rodents, and birds (Craig 1978; Yosef 1996). Finally, shrikes require impaling sites from which they can hang their prey, and such sites can either be natural (e.g., thorns) or man-made (e.g., barbed wire fences) (Humple 2008). Loggerhead Shrikes in southern California begin breeding in January and February and may continue through July (Unitt 2004). Nests, built by both males and females, are typically constructed 1–2 m above ground (Yosef 1996; Biological Monitoring Program 2011; Borgman and Wolf 2016), though investigators have reported nest heights exceeding 9 m above ground on nearby San Clemente Island (Sullivan et al. 2005).

Western Riverside County MSHCP 1 Biological Monitoring Program

(! Ä60 Legend

CALIMESA *# Loggerhead Shrike nest (2010) (! (! ¨¦§15 215 (! (! (! ¨¦§ (!(! Loggerhead Shrike detection (2005-2010) EASTVALE (! 10 (! ! ¨¦§ (! ( (! Highways RIVERSIDE Ä60 BEAUMONT BANNING Water Bodies (! MORENO VALLEY NORCO Ä91 (!(!(! Existing Conservation Land (! (! Ä79 (! (!(! !(!(!(!(! (! !( !(! (!(! (!((!(!(!(! (!*#(!(! (! (! (! (!(!(!(! (! (! (! (!*#(!*#(!(!*#(! Cities (!(! ! (!(!(! (! (! (!!(!(!(!*# (! (!(!(!((! *#(! *#(!(!!((! ! #(!*#(! (!(!(! 243 (! ! ((!( *#*#(!*#(!(!*#(!((! (!( (!*(!(!*#(!*#*#(!(! Ä ( ( (! (!(!(! (! (!!(! CORONA (! (! (! (!(! (! (! (!(! *#((! (! (!(!(! (! (! (! (! §15 (! (! (! ¨¦ (! (! 215 (!(!(!*#(!(!(!(! ¨¦§ (!(!*#(!*#(! (! SAN JACINTO (! (! PERRIS (! (! (! (!(! (! (!(! Ä74 (! Ä HEMET (! (! (! (! Ä74 (!Ä (! Ä74 (! (! MENIFEE LAKE ELSINORE (! (! 215 (! ¨¦§ (!(!(! (!(! (!(!(! (!(! (! WILDOMAR (! Ä79 Ä (! ¨¦§15 (! (! (! (!(! MURRIETA (!(! (! (! *#(!#(!(! Loggerhead Shrike Core Areas (!* (! Ä371 (!(! *#(!(!(!(! Badlands (! *#(! (!*#(! (!*#(! (! (!(! (!*#(!(! (!(!(!(! Lake Mathews/Estelle Mountain (! (!(! TEMECULA Ä79 Lake Perris/Mystic Lake/SJWA (!(! (! (! (! (! (! Prado Basin/Santa Ana River (! 15 (! (! Quail Valley ¨¦§ (! Temecula Creek Date: 15 February 2019 Wasson Canyon UTM Nad 83 Zone 11 Wilson Valley km Contact: Nicholas Peterson I 0 2.5 5 10 15 20 MSHCP Biological Monitoring Program

Figure 1. Loggerhead Shrike Core Areas, with detections and nest locations prior to the current reporting period (2005-2010).

2018 Loggerhead Shrike Survey and Nest Monitoring Report

In southern California, shrikes may construct their nests in a variety of substrates, especially mesquite (Prosopis spp.) (Unitt 2004), though thorny or spiny substrates may be preferred if they are available (Humple 2008). Within the Plan Area, shrikes in 2010 most frequently constructed nests in big saltbush (Atriplex lentiformis), California scrub oak (Quercus berberidifolia), chaparral bush mallow (Malacothamnus fasciculatus), and sugar bush (Rhus ovata) (Biological Monitoring Program 2011). Rangewide, shrike nests typically contain five or six eggs (overall range of 1–9 eggs), with nests at higher latitudes or in the western U.S. containing more eggs (Yosef 1996). Incubation is performed solely by females and is initiated prior to completion of the clutch (Sullivan et al. 2005). Hatching occurs approximately 14 days into the incubation period, at which time both parents provide food to the nestlings. Young typically fledge 17 or 18 days post-hatching and may remain with their parents for several weeks, though they are capable of independent foraging at about 40 days post-fledging. In southern California, shrikes may undertake a second nesting attempt following a first attempt (successful or unsuccessful; Sullivan et al. 2005). Goals and Objectives 1. Document the distribution of Loggerhead Shrikes in the MSHCP-identified Core Areas. a. Conduct repeat-visit line transect surveys within accessible Loggerhead Shrike habitat in the Plan Area. 2. Determine whether Loggerhead Shrikes are successfully reproducing in at least 75% of the MSHCP-identified Core Areas. a. Conduct nest searches and monitoring for any nesting shrike pairs detected during the 2018 surveys. Active nests will be monitored weekly until fledging or failure occurs.

METHODS Survey Design We conducted surveys for Loggerhead Shrikes by making repeat visits (n = 7 visits) to line transects (n = 107 transects) within the MSHCP-identified Core Areas (Fig. 2). I developed survey methods using techniques described in Buckland et al. (2001) and Rosenstock et al. (2002). The design I used allows for the calculation of transect-level detection probability and can be used to evaluate correlations between covariates (MacKenzie et al. 2006). I began study site selection by identifying apparently suitable Loggerhead Shrike habitat on Conserved Lands within the MSHCP-identified Core Areas. I selected these habitats from our ArcGIS (ESRI 2006) vegetation layer (CDFG et al. 2005) and they were based upon the habitat types in which our biologists have most often detected shrikes from 2005–2017, namely agricultural land; chaparral; coastal sage scrub; grasslands; playas and vernal pools; and riparian scrub, woodland, and forest. Finally, I generated 107 transects that were 150 m long and separated by at least 300 m, within the patches of apparently suitable shrike habitat. The number of biologists conducting surveys in 2018 was similar to 2010, so I maintained approximately the same number of transects in 2018 that we used in 2010. Additionally, the number of transects in 2018 exceeded the minimum recommended sample size (Equation 6.3, MacKenzie et al. 2006) based upon our 2010 shrike survey data.

Western Riverside County MSHCP 3 Biological Monitoring Program

Ä60 Legend (! CALIMESA 2018 Loggerhead Shrike survey station ¨¦§15 215 (!(! ¨¦§ (! Highways EASTVALE (!(!(! 10 ¨¦§ Water Bodies RIVERSIDE Ä60 BEAUMONT BANNING Existing Conservation Land MORENO VALLEY NORCO Ä91 (!(!(! Cities (!(! (! (!(! (! Ä79 (!(!!(!(!(! (!(! (! (! (!((! (! (! (! ! (!(! (! (!(! (! (! ( (!(! 243 (! (!(! (! (!(! (! (! Ä (!(!! (! ! (! (! (! (!(!( ((! ( CORONA (!(! (!(!(!(! (!(!(!(! (!(!(! (!(! 15 (! ¨¦§ (!(!(! (! (!(! 215 (! (! ¨¦§ (! (! (! SAN JACINTO PERRIS

(! Ä74 (! (!(! HEMET Ä74 Ä74 (! ! (!(!(! MENIFEE LAKE ELSINORE(! ¨¦§215

WILDOMAR Ä79 ¨¦§15

MURRIETA Loggerhead Shrike Core Areas (! 371 (!(! Ä (! Badlands (! (! (! (! (! (! Lake Mathews/Estelle Mountain TEMECULA (! Lake Perris/Mystic Lake/SJWA Ä79 (!(!(! Prado Basin/Santa Ana River Quail Valley ¨¦§15 Temecula Creek Date: 15 February 2019 Wasson Canyon UTM Nad 83 Zone 11 Wilson Valley km Contact: Nicholas Peterson I 0 2.5 5 10 15 20 MSHCP Biological Monitoring Program

Figure 2. Loggerhead Shrike Core Areas and 2018 survey station locations.

2018 Loggerhead Shrike Survey and Nest Monitoring Report

I oriented transects in a north-south direction (Buckland et al. 2015), except where this was not feasible due to the configuration of small parcels of Conserved Land. Field Methods We began our first round of surveys on 8 January 2018 and completed our final round of surveys on 23 July 2018. We conducted surveys from 0.5–4.5 hours following sunrise, which is one of two periods that generally represent daily peak activity for Loggerhead Shrikes (Craig 1978). We terminated surveys during any periods of rain or dense fog, if the ambient temperature exceeded 35 °C, or if maximum wind speed exceeded 38 km h-1. At the beginning of the survey, observers recorded on their datasheet the survey start time, ambient temperature (°C), and sky conditions. Observers surveyed transects beginning at one of the transect termini and navigating to the opposite terminus of the transect, ensuring that they remained along a straight path during the survey. Observers attempted to walk at a constant speed while surveying for shrikes, spending a minimum of 10 min walking the length of the transect. While walking the transect, observers recorded on their data sheet information for all bird species detected. For non-covered species, observers recorded information for only the first individual of that species detected, which provides species richness data for the site. For such species, observers recorded the four-letter species code, age class information, and sex. For Covered Species, observers recorded the four-letter species code, age class, and sex for every individual detected along the transect. If observers were unsure whether they had already recorded data on an individual (i.e., they are double-counting), they erred on the side of caution and recorded information on that individual. If an observer detected a shrike during a survey, they spent as much time as necessary to determine whether the shrike had an active nest nearby. This was done while either standing on the transect and observing the shrike, or following completion of the transect survey. We visited on a weekly basis all active shrike nests found in 2018. Such follow-up visits occurred at a distance from which the observer could determine nest status based upon shrike behavior, but not so close that the shrikes were disturbed. We continued monitoring active nests until fledging or failure occurred. In 2018, I incorporated a removal sampling design for our shrike surveys beginning in the fourth survey round (MacKenzie et al. 2006). If we detected a shrike along a transect during the first three survey rounds, we did not conduct additional surveys along that transect beginning in the fourth round. Similarly, if we detected a shrike along a transect during the fourth through sixth survey rounds, we did not conduct additional surveys along that transect. This design allowed me to calculate detection probabilities for shrikes based upon the first three rounds of data, and provided more precise estimates of occupancy ( ) (MacKenzie et al. 2006). The survey methods are more completely described in the Western Riverside County MSHCP Biological Monitoring Program 2018 Loggerhead Shrike Survey Protocolψ� .

Western Riverside County MSHCP 5 Biological Monitoring Program

2018 Loggerhead Shrike Survey and Nest Monitoring Report

Data Analysis I estimated per-visit (p) and cumulative detection probability (P*) for Loggerhead Shrikes using closed-capture occupancy models (MacKenzie et al. 2006). I considered locations with observations of shrikes to be used rather than occupied because my survey design may not have met the assumption of population closure (i.e., random movement of animals in and out of sample plots across visits). I used Program MARK (White and Burnham 1999) to construct and compare candidate models that examine site and visit effects on p. I then ranked candidate models according to Akaike’s Information Criterion for small samples (AICc), calculated Akaike weights (wi), and derived weighted-average estimates for p across the entire candidate set unless a single model showed clear support (i.e., wi > 0.9) (Burnham and Anderson 2002). I calculated cumulative detection probability across the first three visits using model-averaged estimates of p, and the following formula where pi is the detection probability on a given survey visit:

= 1 3 1 ∗ 𝑃𝑃 − �� − 𝑝𝑝𝑖𝑖� Finally, I calculated variances for P* using𝑖𝑖= the1 delta method (MacKenzie et al. 2006; Powell 2007). I calculated the daily survival rate (DSR) for nests using Program MARK (White and Burnham 1999; Dinsmore et al. 2002; White 2005), assuming a constant DSR because we had relatively infrequent (i.e., weekly) follow-up visits for nests. Finally, DSR values, when raised exponentially to a power that is equal to the length of a nesting cycle, from first egg laid until the first chick fledges, provided me with a period nest survival estimate for Loggerhead Shrikes.

RESULTS Detections of Loggerhead Shrikes We detected Loggerhead Shrikes in seven (87.5%) of their designated Core Areas during the current reporting period (2011–2018), thereby meeting the species objective for demonstration of use. We detected shrikes in five of the Core Areas most recently during our 2018 effort, including the Badlands, Lake Mathews/Estelle Mountain, Lake Perris/Mystic Lake/SJWA, Quail Valley, and Wilson Valley. We have detected shrikes in the Prado Basin/Santa Ana River five times, most recently in 2017, and three times in Wasson Canyon, most recently in 2015. We have never detected shrikes in the Temecula Creek Core Area, with our closest detection occurring approximately 3.3 km outside of the Core Area (Figs 1 and 3). Finally, we detected 130 avian species during our 2018 surveys, including 28 species covered by the MSHCP (Appendix). We have detected Loggerhead Shrikes on several occasions within two additional locations, both of which should be considered as alternative or additional Core Areas for the species. These locations include Lake Skinner/Diamond Valley Lake (Core J plus Proposed Extensions of Existing Cores 6 and 7; n = 128 detections from 2005–2018) and the area encompassing Tule Valley (Proposed Core 6; n = 11 detections from 2005–2016) (Figs 1 and 3).

Western Riverside County MSHCP 6 Biological Monitoring Program

(!(! Ä60 Legend CALIMESA XY 2018 Loggerhead Shrike fledgling (nest not found) 15 215 (! ¨¦§ § (! (! ¨¦ (! (! *# 2018 Loggerhead Shrike nest (successful) EASTVALE (! ¨¦§10 (! ") 2018 Loggerhead Shrike nest (failed) RIVERSIDE Ä60 BEAUMONT ! BANNING (! ( MORENO VALLEY Loggerhead Shrike detection (2011-2018) NORCO (! (! Ä91 (! (! (! (!(! (!(!(!(!(!(!(!(! (! Ä79 Highways !(! !((!(!!(!(!(!(! (!(! (! Ä (!(!(! (!(!(!(!(!(!(!!((!(!(!(!(!(!(! !(! (!(!(! (!")(!(!(!!(!(!(!(!(!(! (! (!(! ((!(!(!(! (! (!((!(!(!(!(! (!(!(!(! (! (! (! (!(!( Water Bodies XY(!(!")(!(!(!(!(! (!(!*#(!(!(!(!(! (! (! (! (!*#(!(! 243 (! ! ")(!")(!(!(!*# (!XY(!(!(!*#(!*#(!(!(!(!(!!(!(!(!(! ")")(! (!")(!(! Ä (! (!( (!*#(!(!(!#(! (!(!(!")*#((! (! (! (!(! (!(!(! CORONA (! ")*#(!(!(!*(!(!(!(! (! ( Existing Conservation Land (!(!(! (! (!(!(!(!(!(!(!(! (! XY (! (!(!(!(! (!(!!( (!(!(! (! (!(! (! (! Cities 15 *#(!(! ¨¦§ (! (!(!(!(!")(! (! (! (!(!(!(!(!(!! 215 (! (! (! ")(!(!(!(!(!(! ¨¦§ (! (! (!(! SAN JACINTO PERRIS ! !(! ( ! (! ( (! (!(!(! Ä74 (! Ä (! HEMET (! (! Ä74 Ä74 (! (! (!

(! MENIFEE LAKE ELSINORE (! (! (! 215 (! (! ¨¦§ (!(!(!(!(!(! (! ! (! ( (!(!(! (! (!(! (! (! WILDOMAR (! (! Ä79 (!(!(! (! (! 15 ! (! ¨¦§ ( ! (! (!( (! (!(!(! (!(!!(!!((!(!(!(!(! (! MURRIETA (!(((!(! (!(!( (! (! (!(!!(!(! (! (! Loggerhead Shrike Core Areas XY(!")(! (! (! (! 371 (! (! Ä (!(! (!(!!(!(! Badlands (!(!(!((!(! (!(! (!(! (! (! (! (! (! (!(!(!(!(! (! (! ")(!(! Lake Mathews/Estelle Mountain (! (! (! (! (! (! (! TEMECULA ")*#(!(! (! Lake Perris/Mystic Lake/SJWA Ä79 (!(!(! (!(! (! (! (! (! ! (! (! Prado Basin/Santa Ana River ( (! ¨¦§15 (! Quail Valley (! Temecula Creek Date: 15 February 2019 Wasson Canyon UTM Nad 83 Zone 11 Wilson Valley km Contact: Nicholas Peterson I 0 2.5 5 10 15 20 MSHCP Biological Monitoring Program

Figure 3. Loggerhead Shrike Core Areas, detections within the current reporting period (2011-2018), and 2018 fledgling and nest locations. 2018 Loggerhead Shrike Survey and Nest Monitoring Report

Detection Rates and Detection Probability Analysis We conducted seven survey rounds in this study, incorporating the previously-mentioned removal sampling design. The percentage of surveyed transects along which we detected shrikes remained relatively consistent during the first three rounds, increasing from 14% in Round 1 to 15% in Round 2, then dropping slightly to 12% in Round 3. We detected shrikes along 38 of our transects in 2018, and most (n = 26, or 68.4%) of these were in the Lake Perris/Mystic Lake/SJWA Core Area. We detected them less frequently along transects in the Badlands (n = 3 transects), Lake Mathews/Estelle Mountain (n = 3), and Wilson Valley (n = 6) Core Areas. I included in my detection probability analysis the p(t) and p(.) models, which consider variations in detection probability by time (t) and a constant detection probability (.) across time and among groups. I eliminated from my analysis the p(g) model, which considers variations in detection probability by group (g), or Core Area, because we had too few Loggerhead Shrike detections outside of the Lake Perris/Mystic Lake/SJWA to justify including the model. I ultimately model-averaged the data because Program MARK did not show strong support for either of these two models (i.e., wi < 0.9 for both models) (Table 1). These data produced an average detection probability (± SE) of 0.28 (± 0.07) for each of the first three survey rounds and an occupancy estimate (ψ) of 0.58. The cumulative detection probability during this same period was 0.63 (± 0.10).

Table 1. Model rankings for Loggerhead Shrike surveys in 2018. I modeled variables for detection probabilities (p) to remain constant (.) and vary by time (t) and I modeled occupancy (ψ) to remain constant. Finally, I used Akaike’s Information Criterion corrected for small sample size (AICC) for model selection. a b Model ∆ AICC wi Model likelihood k p(.) ψ(.)c 0 0.88 1.00 2 p(t) ψ(.) 3.97 0.12 0.14 4 a AICC weight b Number of parameters c AICC = 239.0900 Loggerhead Shrike Nesting We documented evidence of successful nesting by Loggerhead Shrikes at four (50%) Core Areas in 2018 (Fig. 3), which falls below the 75% threshold established in the species objective. We did not document any additional nests from 2011 to 2017. Overall, fledglings were produced in 44% of the 32 nesting attempts we observed (Table 2). Of the 18 nesting attempts that failed, we attributed 15 (83%) to depredation, two (11%) to unknown reasons, and one (6%) to abandonment. None of the nests that apparently failed due to depredation exhibited structural damage, suggesting that avian predators or snakes, rather than mammalian mesopredators, could have been responsible.

Table 2. Summary of 2018 Loggerhead Shrike nest counts and the number of fledglings observed, by Core Area. Core Area n nesting attempts n successful attempts (% of total) n fledglingsa Badlands 6 2 (33%) 4 Lake Mathews / Estelle Mountain 3 1 (33%) 2 Lake Perris / Mystic Lake / SJWA 18 9 (50%) 15 Wilson Valley 5 2 (40%) 3 Total 32 14 (44%) 24 a Minimum number of fledglings seen; data include fledglings whose nests we did not locate.

Western Riverside County MSHCP 8 Biological Monitoring Program

2018 Loggerhead Shrike Survey and Nest Monitoring Report

The 32 nesting attempts we observed in 2018 were represented by 30 unique nests (i.e., two nests were re-used by shrike pairs following the failure of their initial attempt). Nests were an average of 1.47 m (range = 0.58–3.38 m) above ground and substrates were an average of 4.19 m (range = 1.12–9.99 m) tall. There was no significant difference between either of these variables when I compared successful and unsuccessful nests. The most commonly used nesting substrates in 2018 were Atriplex canescens (n = 5 nests, or 16.7% of all nests, all of which were in the Lake Perris/Mystic Lake/SJWA Core Area), Sambucus nigra (n = 5 nests, or 16.7%, which was used in each of the four Core Areas where nesting was confirmed), Schinus molle (n = 4 nests, or 13.3%, all of which were in the Lake Perris/Mystic Lake/SJWA Core Area), and Rhus ovata (n = 3 nests, or 10%, all of which were in the Wilson Valley Core Area). All nests constructed in Atriplex canescens were successful and most (60%) nests constructed in Sambucus nigra were successful (Table 3). Both instances of re- use of a nest, one in a Sambucus nigra and one in a Schinus molle, failed.

Table 3. Nesting substrates used by Loggerhead Shrikes in 2018, and frequency of successful nests built within each substrate species. % of nests constructed in substrate Substrate n nests constructed in substrate that were successful Amaranthus palmeri 1 0 Atriplex canescens 5 100 Atriplex spp. 1 0 Lycium andersonii 2 50 Olea europaea 2 50 Quercus berberidifolia 2 0 Rhamnus crocea 2 0 Rhus ovata 3 33 Salix gooddingii 1 100 Salix lasiolepis 1 100 Salsola tragus 1 100 Sambucus nigra 5a 60 Schinus molle 4a 0 a This number treats the re-use of a nest in the substrate as one unique nest. Both attempts ultimately failed. The earliest nest we found in 2018 was in the incubation stage on 5 February, meaning construction and egg-laying were initiated in January. We first observed nestlings on 27 February and fledglings on 9 March. The latest group of fledglings that we observed fledged sometime during the first week of June. I calculated a daily nest survival rate of 0.956 (95% CI: 0.931–0.972), implying a period nest survival estimate of 0.165 (95% CI: 0.057–0.321), assuming an average of 40 days from the initiation of incubation to fledging (Yosef 1996). We did not have enough nest data from nest revisits to calculate variations in nest survival based upon nest stage.

DISCUSSION Detections of Loggerhead Shrikes Badlands

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2018 Loggerhead Shrike Survey and Nest Monitoring Report

The Badlands Core Area contains approximately 512 hectares of potentially suitable shrike habitat in Conservation. Most (74%) of this habitat occurs within the Potrero Unit of the SJWA, which is where 78% of our Program’s shrike detections in the Core Area have occurred. The two remaining blocks of Conserved shrike habitat occur on the RCA’s Wolfskill-Driscoll property north of Gilman Springs Road, and near the El Casco Substation in San Timoteo Canyon. This Core Area accounted for most of our shrike detections during the 2010 Loggerhead Shrike survey effort (Biological Monitoring Program 2011), with nearly all the detections occurring in Potrero. At the time, I characterized Potrero as ideal shrike habitat because it contained large tracts of relatively flat grassland of short and intermediate height, with isolated trees and shrubs scattered throughout. In 2017, though, the quality of this habitat was severely affected by the Manzanita Fire that burned 2,553 ha of habitat in late June, including more than 60% of the Conserved shrike habitat. Much of the burn area was still recovering during our 2018 survey effort (Fig. 4) and was likely not suitable for shrikes; specifically, potential nest substrates were less dense due to the fire, providing poor nest concealment as a result, and herbaceous cover was still absent in some locations, which may have reduced prey availability for shrikes.

Figure 4. View south through the Potrero Unit of the SJWA in 2018. There is little herbaceous growth following the 2017 Manzanita Fire, and shrubs in the foreground are still defoliated. These conditions made the site less than ideal for Loggerhead Shrikes in 2018.

Conserved land in San Timoteo Canyon contains about 90 ha of apparently suitable shrike habitat, most of which is located south of San Timoteo Canyon Road between the El Casco Substation and Fisherman’s Retreat. We detected a shrike here just once in 2018 and have detected the species 11 times in the vicinity since 2010. There are some flat grasslands in the area that may occasionally support shrikes, but overall the site may be too topographically diverse for the species. Additionally, shrubs that are in the area tend to be in dense stands located on hillsides, which is not particularly conducive to nesting shrikes (Yosef 1996).

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2018 Loggerhead Shrike Survey and Nest Monitoring Report

Lake Mathews/Estelle Mountain This Core Area contains about 1,603 ha of apparently suitable shrike habitat. We have detected shrikes 101 times within the Core Area from 2006–2018, with 15 of those occurrences occurring during our 2018 survey period. Nearly all (93%) of our shrike detections have occurred in two locations within the Core Area, specifically the grasslands northeast of Lake Mathews and the northern portion of the Estelle Mountain Reserve. Both locations are generally characterized as being a mix of grassland, old agricultural land, and low-density coastal sage scrub. Isolated shrubs and small trees that can serve as nest substrates are scattered throughout, including Juniperus californica, Lycium andersonii, and Sambucus nigra. Linear features such as fencelines and utility wires are generally absent from these locations. Such features serve as hunting perches for Loggerhead Shrikes, and their general absence within the Core Area may partially explain why we see fewer shrikes here than within the Lake Perris/Mystic Lake/SJWA Core Area. Lake Perris/Mystic Lake/San Jacinto Wildlife Area The Lake Perris/Mystic Lake/SJWA Core Area contains 7,772 ha of Conserved land, 68% of which is agricultural land, chaparral, coastal sage scrub, or grassland that is potentially suitable for Loggerhead Shrikes. We detected shrikes most frequently along transects within the Lake Perris/Mystic Lake/SJWA Core Area in 2018. This Core Area has also contained more than 36% of our Program’s shrike detections since 2005, more than any other Core Area. The Core Area has more than 3,550 ha of shrike habitat in Conservation, including grassland and converted agricultural land that are scattered with preferred nesting substrates such as Atriplex spp. and Sambucus nigra. Few (11%) of our 2018 shrike detections in the Core Area were near Lake Perris, which is generally consistent with where our Program biologists have detected shrikes in the Core Area since 2005. Apparently suitable habitat within the Lake Perris area consists mostly of former agricultural land that has converted to grassland, but there is an overall lack of perch sites and potential nesting substrates on the landscape. One of the two locations where we detected a shrike at Lake Perris in 2018 was centered on the lone shrub in the vicinity, a Rhus ovata, while the other location was on the periphery of a patch of coastal sage scrub. By contrast, the San Jacinto Wildlife Area portion of the Core Area, including Mystic Lake, contains an abundance of perch sites for Loggerhead Shrikes. These include the nest substrates themselves but also include large snags, fencelines, and utility wires. Whereas potential nesting substrates were sparse at Lake Perris, they are relatively abundant at SJWA, especially where dense stands of Atriplex spp. are found near Mystic Lake. Prado Basin/Santa Ana River This Core Area contains approximately 62 ha of suitable shrike habitat in Conservation, consisting of one site with 39 ha of agricultural land and a second site with 23 ha of developed/disturbed land. We have detected shrikes five times within this Core Area, from 2010–2017, and four of those detections occurred within or near the two aforementioned sites. The fifth detection occurred in 2010 at a location that has since been developed into a campground. Historical data indicate that shrikes were not necessarily abundant in this Core Area prior to the implementation of the MSHCP (i.e., from 1974–1999), when there were just 21

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detections (Dudek & Associates 2001). More recently, CNDDB does not contain any records for shrikes along the Santa Ana River (CDFW 2018), further suggesting that this Core Area is used infrequently by Loggerhead Shrikes. The agricultural land within this Core Area is at the Hidden Valley Wildlife Area. Both shrike detections that occurred here were outside of the breeding season and there does not appear to be much suitable nesting habitat on site. Further, the site is adjacent to riparian habitat, which may be avoided by nesting shrikes due to increased predation risk. The developed/disturbed land is north of the Prado Basin and encompasses the Orange County Water District’s office and the Raahauge’s Shooting Enterprises firing range. Again, both shrike detections that occurred here were outside of the breeding range, and suitable nesting habitat appears to absent; however, there may be suitable habitat immediately to the north of this location, in San Bernardino County, where there is an orchard and an agricultural field. Overall, the majority of this Core Area consists of riparian woodland and scrub habitat that is not ideal for nesting shrikes (Yosef 1996). Management for nesting shrikes within this Core Area, then, would likely require expansion of the small open areas at the cost of riparian habitat, which is an unlikely scenario. Quail Valley and Wasson Canyon Most (89%) of the Conserved habitat within these adjacent Core Areas is coastal sage scrub, and more than one-third of that exceeds 40% density and is thus likely too dense for use by Loggerhead Shrikes. Grassland, which is generally more preferred by shrikes, comprises just 4% of the Conserved habitat within these Core Area. Further, the grassland habitat is fragmented into small pieces that average 1.9 ha in size and do not exceed 7.6 ha. We have detected shrikes seven times within these Core Area from 2006–2018. Prior to the MSHCP, shrikes were detected here six times between 1989 and 1998 (Dudek & Associates 2001). The small, fragmented pieces of grassland habitat within these Core Areas contain few ideal nesting trees or shrubs. Additionally, the paucity of shrikes detections in the area may further reduce the likelihood of the site being occupied by nesting shrikes in the future. For example, Etterson (2003) reported that shrikes tend to select breeding territories based upon the presence of breeding conspecifics. Because the fragmented pieces of habitat in these Core Areas are unlikely to support any nesting shrikes, let alone multiple pairs, management here should focus on conserving larger, contiguous tracts of suitable habitat and planting isolated nesting substrates such as Lycium andersonii, Quercus berberidifolia, or Sambucus nigra, all of which have been used as nesting substrates at the nearby Lake Mathews/Estelle Mountain Core Area. Temecula Creek The Temecula Creek Core Area contains at least 96 ha of potentially suitable shrike habitat, including agricultural land, chaparral, coastal sage scrub, and grassland; however, none of this habitat is Conserved. Rather, most of the 11.5 ha of Conserved land within the Core Area is within riparian scrub habitat (Fig. 5). This type of habitat is occasionally favored by shrikes (Yosef 1996) but accounts for less than 8% of the habitat in which our shrike detections have occurred in western Riverside County.

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Figure 5. View east along Temecula Creek. This is typical of the Conserved riparian scrub habitat within the Core Area, which is not suitable for use by Loggerhead Shrikes.

Our Program biologists have never detected shrikes within Temecula Creek, and the closest detection occurred approximately 3.3 km from the eastern end of the Core Area boundary. Additionally, there was just one historic record of shrikes occurring in the Core Area prior to the MSHCP, in 1995 (Dudek & Associates 2001). To increase the likelihood of detecting shrikes within this Core Area, potentially suitable habitat within Temecula Creek should be conserved. Wilson Valley This Core Area contains 847 ha of Conserved land, 88% of which consists of coastal sage scrub, chaparral, or grassland habitats that are potentially suitable for shrikes. Much of the Conserved land within Wilson Valley also contains scattered, oftentimes isolated, shrubs and small trees that can serve as nest substrates for shrikes, including Rhus ovata and Sambucus nigra. Overall, Conserved habitat in the Core Area appears to be highly suitable for Loggerhead Shrikes and our Program biologists have detected the species 161 times in this area from 2006– 2018. Detection Rates and Detection Probability Analysis The rate at which we detected Loggerhead Shrikes in 2018 was substantially higher than in 2010. We detected shrikes on 38 (35.5%) transects this year, whereas we detected them on just 18.6% of transects in 2010. Additionally, we detected shrikes on 12%–15% of transects during

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each of our first three survey rounds, and we never detected them along more than 7.1% of transects within any survey round in 2010 (Biological Monitoring Program 2011). The most likely cause for the increase in detection rates in 2018 was that we surveyed transects within the Lake Perris/Mystic Lake/SJWA Core Area, which we did not do in 2010. We detected shrikes along more transects within this Core Area than any others, thereby increasing our overall detection rate. Indeed, we only detected shrikes on 20.7% of transects outside of the Lake Perris/Mystic Lake/SJWA Core Area this year, which is similar to our overall detection rate of 18.6% of transects in 2010 (Biological Monitoring Program 2011). Shrikes within this Core Area seem to be more abundant than within other Core Areas, and the relatively flat topography and conspicuous elevated perches from which shrikes hunt likely contribute to the higher detection rates within this Core Area. Our detection probabilities this year remained constant across the first three survey rounds (p = 0.28), which was slightly different from what we saw in 2010, when detection probabilities fluctuated somewhat between survey rounds. Further, our detection probabilities never exceeded 0.17 within a survey round in 2010 (Biological Monitoring Program 2011), which is about 37% lower than in 2018. Our survey methods did not change this year and our biologists were held to the same training standards as in 2010, so I suspect that our increased detection probability values in 2018 were due entirely to the addition of survey efforts within the Lake Perris/Mystic Lake/SJWA Core Area. As stated previously, this Core Area has relatively flat topography within our survey sites and shrikes frequently perched in conspicuous locations, both of which increase the likelihood of our biologists detecting birds that are present. Many of the other Core Areas in which we surveyed were more topographically diverse and had fewer tall perches, especially utility wires, than Lake Perris/Mystic Lake/SJWA. The 2018 detection probability and occupancy data indicate that future surveys for Loggerhead Shrikes should consist of approximately 159 transects if we want to achieve a standard error of 0.05 for our detection probability estimates (Equation 6.3, MacKenzie et al. 2006). If we choose to once again incorporate a removal sampling design, we could survey each transect a maximum of nine times, with no subsequent surveys occurring after a shrike has been detected (Table 6.5, MacKenzie et al. 2006). If, however, we forego using a removal sampling design, the optimum number of surveys for each transect would be approximately six (Table 6.1, MacKenzie et al. 2006). Loggerhead Shrike Nesting We documented successful nesting in the same four (50%) Core Areas in 2018 as we did in 2010, specifically the Badlands, Lake Mathews/Estelle Mountain, Lake Perris/Mystic Lake/SJWA, and Wilson Valley. These four Core Areas generally contain large, contiguous pieces of suitable shrike habitat, including potential perch and nest sites, whereas such habitat is generally less abundant in the remaining four Core Areas. I do not expect shrike nesting to occur with any regularity at those locations unless or until Conserved habitat consists of more contiguous patches of suitable habitat that include potential perch and nest sites. We documented that fledglings were produced in 14 of 32 (44%) nesting attempts in 2018, which is slightly higher than we found in 2010 (39%; Biological Monitoring Program

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2011). This metric, which is oftentimes called apparent nest success, provides a biased estimate of nest success when nests in the study are found at different stages of the nesting cycle (Nur et al. 2004); however, it allows us to compare our data to previous investigations in which apparent nest success data were provided. Our 2018 apparent nest success value is similar to those reported for other populations of Loggerhead Shrikes on the west coast and is generally similar to several others within the range of the species (Table 4).

Table 4. Summary of apparent nest success (number of successful nests/number of nests monitored) of Loggerhead Shrikes reported throughout the range of the species. Apparent nest success (%) Location Source 12.5–61 California Sullivan and Kershner 2005 26–41 Oklahoma Tyler 1992 29 Illinois Walk et al. 2006 31 Florida Yosef 1994 37–52 Alberta, Canada Collister and Wilson 2007 39 New Mexico Borgman and Wolf 2016 39 California Biological Monitoring Program 2011 44 California This study 48 Oregon Nur et al. 2004 50 Kentucky Peterson 2006 54 California Hudgens et al. 2009 55 Florida Yosef 2001 65 South Carolina Gawlik and Bildstein 1990 66 Colorado Porter et al. 1975 74 Minnesota Brooks and Temple 1990 78–89 Ontario, Canada Chabot et al. 2001

Daily survival rate (DSR) is a less biased measure of nest survival that is increasingly incorporated into nesting studies. Our DSR in 2018 was 0.956, which is slightly lower than what we found during our 2010 shrike study (0.960; Biological Monitoring Program 2011). This value is also on the low end of DSR values reported throughout the range of Loggerhead Shrikes (Table 5). The primary way for us to potentially observe increased DSR values is to visit nests more frequently. We were typically able to visit nests just one or two days per week in this study, and it is possible that DSR values were low as a result (e.g., if a nest failed between visits that were several days apart, Program MARK must make a “best guess” as to when failure occurred, which can potentially lead to inaccurately low survival estimates). The benefit of more frequent visits, however, must be balanced against the potential increased risk of attracting nest predators while monitoring nests (Martin and Geupel 1993).

Table 5. Summary of daily survival rates of Loggerhead Shrike nests reported throughout the range of the species. Daily survival rate Location Source 0.956 California This study 0.957–0.973 Illinois Walk et al. 2006 0.960 California Biological Monitoring Program 2011 0.973 Alberta, Canada Collister and Wilson 2007 0.978 Oklahoma Etterson et al. 2007 0.987–0.992 Arizona Boal et al. 2003

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We attributed the majority (83%) of shrike nest failures to depredation, which is similar to what we observed in 2010 (85%; Biological Monitoring Program 2011). These data also fall within the range reported by previous investigations, in which predation is presumed to have accounted for 52–89% of Loggerhead Shrike nest failures (Table 6). DeGeus (1990) suggested that two factors may contribute to high levels of nest predation in shrikes, specifically that shrikes tend to nest along linear habitats, such as fencelines, that also serve as travel corridors for predators, and that populations of some potential nest predators may be increasing within the range of Loggerhead Shrikes. Subsequent investigations appear to support the theory that shrike nests along linear habitats are at increased risk of failure due to depredation (Yosef 1994; Walk et al. 2006), presumably because such habitats are easily searched by predators (Major et al. 1999), especially if nests are at high densities (Crabtree et al. 1989). This explanation, however, does not likely explain cases of nest predation in our study because we had few instances of nests occurring along linear habitats. Rather, nest failures attributed to depredation in our study were perhaps partially due to the presence of known avian nest predators, including Common Ravens (Corvus corax), Red-shouldered Hawks (Buteo lineatus), and Red-tailed Hawks (B. jamaicensis) (Yosef 1996), all of whose populations may be increasing in California according to Breeding Bird Survey data (Sauer et al. 2017). Additionally, the average daily temperature in our region of California during the 2018 nesting season was considered much above the historical average (NOAA 2018), which may have led to increased snake activity, thereby contributing to nest predation (Borgman and Wolf 2016) by species such as red racers (Coluber flagellum piceus) and San Diego gopher snakes (Pituophis catenifer annectens) (Rodríguez-Robles 2002; DeGregorio et al. 2014).

Table 6. Summary of presumed Loggerhead Shrike nest failure rates due to depredation, reported throughout the range of the species. Predation failure rate a (%) Location Source 52 Colorado Porter et al. 1975 53 Oklahoma Tyler 1992 71 Florida Yosef 2001 72 New Mexico Borgman and Wolf 2016 83 California This study 85 Alberta, Canada Collister and Wilson 2007 85 California Biological Monitoring Program 2011 86 Florida Yosef 1994 88 Illinois Walk et al. 2006 89 Kentucky Peterson 2006 a Percentage represents the number of nest failures attributed to depredation/total number of failed nests.

Nest heights in our study (x = 1.47 m) were slightly higher than nests in 2010 (x = 1.21 m; Biological Monitoring Program 2011), but within rangewide averages reported for Loggerhead Shrikes (0.79–4.4 m; �Gawlik and Bildstein 1990; Woods and Cade 1996).� Similarly, substrate heights in our study (x = 4.19 m) were slightly higher than in 2010 (x = 3.80 m; Biological Monitoring Program 2011), but within the rangewide averages for the species (1.62–7.7 m; Gawlik and Bildstein 1990; �Woods and Cade 1996). � The most common nesting substrates used by shrikes in this study differed somewhat from what we found in 2010, when Quercus berberidifolia, Rhus ovata, Atriplex spp., and

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Malacothamnus fasciculatus were the most common substrates used (Biological Monitoring Program 2011). We found just two nests in Quercus berberidifolia and both were within the Potrero Unit of the SJWA, in the Badlands Core Area. This is where all the Q. berberidifolia nests were in 2010, as well, and it is possible that the 2017 Manzanita Fire reduced the availability of this substrate within Potrero. Similarly, all the Malacothamnus fasciculatus nests were in Potrero in 2010, and we did not find any nests in that substrate this year, perhaps owing to the effects of the Manzanita Fire. The inclusion of Sambucus nigra and Schinus molle in 2018 likely reflects the fact that we were surveying in the Lake Perris/Mystic Lake/SJWA Core Area in 2018, in which all the Schinus molle nests and 40% of the Sambucus nigra nests were located, and we did not conduct surveys here in 2010. Rangewide, shrikes are eclectic in their choice of nest substrates, selecting sites based upon degree of cover (Yosef 1996) and presence of thorns for protection from predators (Porter et al. 1975). In San Diego County, Unitt (2004) reported that shrikes most commonly nest in mesquite, whereas shrikes on San Clemente Island tended to use Rhus integrifolia, Artemesia spp., and Baccharis pilularis. Shrikes in our study selected several different substrates as well, many of which appeared to confer some potential degree of protection from predators via foliage density (e.g., Rhus ovata) or thorn-like projections (e.g., A. lentiformis). The primary exception to this was nests built in Schinus molle, which provides neither dense foliage nor thorny features, all of which failed. Conversely, shrike nests in our study that were constructed in the thorniest substrates (i.e., Atriplex and Lycium spp.) were successful 75% of the time (Table 3). Rangewide, Loggerhead Shrikes tend to lay eggs and incubate from mid-March to mid- June. The nestling stage tends to occur from early April to late June (Yosef 1996). During our 2018 study, all of these nesting stages occurred somewhat earlier, and even occurred 2–3 weeks earlier than we observed in 2010 (Biological Monitoring Program 2011). In general, shrikes in the southern part of the species’ range tend to nest earlier than their northerly conspecifics (Yosef 1996); however, the earliest nesting that we observed in 2018 is substantially earlier than what has been reported in previous investigations at similar latitudes (Table 7).

Table 7. Summary of earliest dates that Loggerhead Shrike nests have contained eggs for investigations occurring between latitudes 30° and 35° north. Latitude Earliest date (°N) Location Year(s) of study egg present Source 34 Riverside County, CA 2010 28 February Biological Monitoring Program 2011 Riverside County, CA 2018 5 February This study 35 Albuquerque, NM 2007–2012 7 March Borgman and Wolf 2016 Lawton, OK 1985–1988 13 March Tyler 1992

Recent investigations of shrike populations in the southwestern U.S. have also documented shifts in Loggerhead Shrike nesting phenology. Borgman and Wolf (2016) reported that Loggerhead Shrikes in their Albuquerque, New Mexico population nested an average of 20 days earlier in 2012 than 2007. This shift corresponded with an increased air temperature of 3 °C during the local breeding season (March–July) from 2007–2012. The authors did not specifically examine the effects of precipitation on nest initiation, but they reported that the earliest nests in their study typically occurred in the driest years. Conversely, Hudgens et al. (2009) reported that

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San Clemente Loggerhead Shrikes in their study seemed to delay nesting during particularly dry years, with pairs receiving supplemental food nesting earlier in the season than their counterparts. The 2018 breeding season in western Riverside County was much warmer than average, with average to slightly below average precipitation (NOAA 2018), suggesting that warmer temperatures may have contributed to the earlier nesting dates that we observed. Recommendations Future Surveys Subsequent surveys for Loggerhead Shrikes should employ the same methods we used in 2010 and 2018. An ideal number of transects is approximately 159, based upon our 2018 data, and if a removal sampling design is used, each transect should be surveyed a maximum of nine times. Finally, if staff availability is sufficient, future surveys should incorporate more frequent revisits to nests to get a more accurate measure of daily survival rate. These more frequent visits should be balanced against the potential for increased nest failure that may result from the increased human activity at nest sites. Conservation and Management The portions of the Lake Mathews/Estelle Mountain Core Area in which we have periodically detected shrikes could benefit from the installation of linear habitat features such as fencelines, which could serve as hunting perches for shrikes. Similarly, the Lake Perris area could benefit from the addition of isolated, discrete hunting perches such as shrubs, which could also serve as nesting sites. Within the Prado Basin/Santa Ana River, Quail Valley/Wasson Canyon Core Area, and Temecula Creek Core Areas, future management and conservation should seek to conserve large, contiguous pieces of shrike habitat, along with isolated nesting substrates, both of which are currently absent from these three Core Areas.

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 2018 were Masanori Abe, Jess Burton, Tara Graham, Lynn Miller, and Nicholas Peterson.

LITERATURE CITED Becker ME, Bednekoff PA, Janis MW, Ruthven DC. 2009. Characteristics of foraging perch- sites used by Loggerhead Shrikes. Wilson Journal of Ornithology 121:104–111. Biological Monitoring Program. 2011. Loggerhead Shrike (Lanius ludovicianus) Survey Report, 2010. Prepared for the Western Riverside County Multiple Species Habitat Conservation Plan. Riverside, CA. Available from http://wrc-rca.org/about-rca/monitoring/monitoring- surveys/ (accessed December 2018).

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Boal CW, Estabrook TS, Duerr AE. 2003. Productivity and breeding habitat of Loggerhead Shrikes in a southwestern urban environment. Southwestern Naturalist 48:557–562. Borgman CC, Wolf BO. 2016. The indirect effects of climate variability on the reproductive dynamics and productivity of an avian predator in the arid Southwest. Oecologia 180:279–291. Brooks BL, Temple SA. 1990. Dynamics of a Loggerhead Shrike population in Minnesota. Wilson Bulletin 102:441–450. Buckland ST, Anderson DR, Burnham KP, Laake JL, Borchers DL, Thomas L. 2001. Introduction to distance sampling: Estimating abundance of biological populations. Oxford University Press, Oxford. Buckland ST, Rexstad EA, Marques TA, Oedekoven CS. 2015. Distance sampling: Methods and applications. Springer, Cham, Switzerland. Burnham KP, Anderson DR. 2002. Model selection and multimodel inference: A practical information-theoretic approach. 2nd Edition. Springer, New York. 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 http://bios.dfg.ca.gov/ (accessed October 2017). CDFW (California Department of Fish and Wildlife). 2018. California Natural Diversity Database (CNDDB) – Government version 5.66.18 dated 2 December 2018. Available from https://map.dfg.ca.gov/bios/?bookmark=326 (accessed December 2018). Chabot AA, Bird DM, Titman RD. 2001. Breeding biology and nesting success of Loggerhead Shrikes in Ontario. Wilson Bulletin 113:285–289. Collister DM, Wilson S. 2007. Contributions of weather and predation to reduced breeding success in a threatened Loggerhead Shrike population. Avian Conservation and Ecology – Écologie et conservation des oiseaux 2:11. Available from http://www.ace-eco.org/vol2/iss2/art11/ (accessed December 2018). Crabtree RL, Broome LS, Wolfe ML. 1989. Effects of habitat characteristics on Gadwall nest predation and nest-site selection. Journal of Wildlife Management 53:129–137. Craig RB. 1978. An analysis of the predatory behavior of the Loggerhead Shrike. Auk 95:221– 234. DeGeus DW. 1990. Productivity and habitat preference of Loggerhead Shrikes inhabiting roadsides in a Midwestern agroenvironment. Master’s thesis. Iowa State University, Ames. DeGregorio BA, Chiavacci SJ, Weatherhead PJ, Willson JD, Benson TJ, Sperry JH. 2014. Snake predation on North American bird nests: Culprits, patterns and future directions. Journal of Avian Biology 45:325–333.

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Dinsmore SJ, White GC, Knopf FL. 2002. Advanced techniques for modeling avian nest survival. Ecology 83:3476–3488. Dudek & Associates. 2001. Species 8 Occurrence Point Data. Prepared for County of Riverside Transportation and Lands Management Agency. Prepared by Dudek & Associates, Inc. Created January, 2001. Dudek & Associates. 2003. Western Riverside County Multiple Species Habitat Conservation Plan (MSHCP). Final MSHCP, volumes I and II. Prepared for County of Riverside County Transportation and Lands Management Agency by Dudek & Associates, Inc. Approved June 17, 2003. [ESRI] Environmental Systems Research Institute. 2006. ArcGIS: Release 10.1 [software]. Redlands, California: Environmental Systems Research Institute, 1999–2012. Etterson MA, Nagy LR, Robinson TR. 2007. Partitioning risk among different causes of nest failure. Auk 124:432–443. Garrett KL, Dunn JL, Small BE. 2012. Birds of southern California. R. W. Morse Company, Olympia, Washington. Gawlik DE, Bildstein KL. 1990. Reproductive success and nesting habitat of Loggerhead Shrikes in north-central South Carolina. Wilson Bulletin 102:37–48. Grinnell J, Miller AH. 1944. The distribution of the birds of California. Pacific Coast Avifauna 27. Hudgens BR, Johnston NN, Bradley JE, Bridges AS. 2009. Benefits of supplemental feeding are climate dependent in the San Clemente Loggerhead Shrike. Pages 315–325 in Damiani CC, Garcelon DK, editors. Proceedings of the 7th California Islands Symposium. Institute for Wildlife Studies, Arcata, California. Humple D. 2008. Loggerhead Shrike (Lanius ludovicianus) (mainland populations). 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. MacKenzie DI, Nichols JD, Royle JA, Pollack KH, Bailey LL, Hines JE. 2006. Occupancy estimation and modeling: Inferring patterns and dynamics of species occurrence. Elseiver, London. Major RE, Christie FJ, Gowing G, Iverson TJ. 1999. Elevated rates of predation on artificial nests in linear strips of habitat. Journal of Field Ornithology 70:351–364. Martin TE, Geupel GR. 1993. Nest-monitoring plots: Methods for locating nests and monitoring success. Journal of Field Ornithology 64:507–519. NOAA (National Oceanic and Atmospheric Administration). 2018. National Temperature and Precipitation Maps. Available from https://www.ncdc.noaa.gov/temp-and-precip/us- maps/ (accessed December 2018).

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Nur N, Holmes AL, Geupel GR. 2004. Use of survival time analysis to analyze nesting success in birds: An example using Loggerhead Shrikes. Condor 106:457–471. Peterson NR. 2006. Territory size, habitat use, hunting behavior, and reproductive success of Loggerhead Shrikes in central Kentucky. Master’s thesis. Eastern Kentucky University, Richmond. Porter DK, Strong MA, Giezentanner JB, Ryder RA. 1975. Nest ecology, productivity, and growth of the Loggerhead Shrike on the shortgrass prairie. Southwestern Naturalist 19:429–436. Powell LA. 2007. Approximating variance of demographic parameters using the delta method: A reference for avian biologists. Condor 109:949–954. 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. Rodríguez-Robles JA. 2002. Feeding ecology of North American gopher snakes (pituophis catenifer, Colubridae). Biological Journal of the Linnean Society 77:165–183. Rosenstock SS, Anderson DR, Giesen KM, Leukering T, Carter MF. 2002. Landbird counting techniques: Current practices and an alternative. Auk 119:46–53. Sauer JR, Niven DK, Hines JE, Ziolkowski DJ, Pardieck KL, Fallon JE, Link WA. 2017. The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, Maryland. Available from https://www.mbr-pwrc.usgs.gov/bbs/ (accessed December 2018). Sullivan BL, Kershner EL. 2005. The birds of San Clemente Island. Western Birds 36:158–273. Tyler JD. 1992. Nesting ecology of the Loggerhead Shrike in southwestern Oklahoma. Wilson Bulletin 104:95–104. Unitt P. 2004. San Diego County bird atlas. Proceedings of the San Diego Society of Natural History 39. Walk JW, Kershner EL, Warner RE. 2006. Low nesting success of Loggerhead Shrikes in an agricultural landscape. Wilson Journal of Ornithology 118:70–74. White GC. 2005. Program MARK. Mark and recapture survival rate estimation. Version 7.1. Available from http://www.cnr.colostate.edu/~gwhite/mark/mark.htm (accessed July 2013). White GC, Burnham KP. 1999. Program MARK: Survival estimation form populations of marked animals. Bird Study 46 Supplement: 120–138. Yosef R. 1994. The effects of fencelines on the reproductive success of Loggerhead Shrikes. Conservation Biology 8:281–285. Yosef R. 1996. Loggerhead Shrike (Lanius ludovicianus), 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.231 (accessed October 2018).

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Yosef R. 2001. Nesting ecology of resident Loggerhead Shrikes in southcentral Florida. Wilson Bulletin 113:279–284.

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Appendix. Avian species detected during 2018 Loggerhead Shrike surveys. Species in bold are covered by the MSHCP.

COMMON NAME SCIENTIFIC NAME Acorn Woodpecker Melanerpes formicivorus American Avocet Recurvirostra americana American Coot Fulica americana American Crow Corvus brachyrhynchos American Goldfinch Spinus tristis American Kestrel Falco sparverius American Peregrine Falcon Falco peregrinus anatum American Pipit Anthus rubescens American White Pelican Pelecanus erythrorhynchos American Wigeon Mareca americana American Yellow Warbler Setophaga aestiva brewsteri Anna's Hummingbird Calypte anna Ash-throated Flycatcher Myiarchus cinerascens Bald Eagle Haliaeetus leucocephalus Barn Swallow Hirundo rustica Bell's Sparrow Artemisiospiza belli Bewick's Wren Thryomanes bewickii Black Phoebe Sayornis nigricans Black-crowned Night-heron Nycticorax nycticorax Black-necked Stilt Himantopus himantopus Black-throated Sparrow Amphispiza bilineata Blue Grosbeak Passerina caerulea Blue-gray Gnatcatcher Polioptila caerulea Bonaparte's Gull Chroicocephalus philadelphia Brewer's Blackbird Euphagus cyanocephalus Brewer's Sparrow Spizella breweri Brown-headed Cowbird Molothrus ater Bufflehead Bucephala albeola Bullock's Oriole Icterus bullockii Burrowing Owl Athene cunicularia Bushtit Psaltriparus minimus Campylorhynchus Cactus Wren brunneicapillus California Gull Larus californicus California Horned Lark Eremophila alpestris actia California Quail Callipepla californica California Scrub-Jay Aphelocoma californica California Thrasher Toxostoma redivivum California Towhee Melozone crissalis Canada Goose Branta canadensis Canyon Wren Catherpes mexicanus Cassin's Kingbird Tyrannus vociferans Cattle Egret Bubulcus ibis

Western Riverside County MSHCP 23 Biological Monitoring Program 2018 Loggerhead Shrike Survey and Nest Monitoring Report

Appendix. Continued.

COMMON NAME SCIENTIFIC NAME Cinnamon Teal Spatula cyanoptera 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 Ferruginous Hawk Buteo regalis Gadwall Mareca strepera Golden-crowned Sparrow Zonotrichia atricapilla Great Blue Heron Ardea herodias Great Egret Ardea alba Greater Roadrunner Geococcyx californianus Greater Yellowlegs Tringa melanoleuca Great-tailed Grackle Quiscalus mexicanus Green-winged Teal Anas crecca Hermit Thrush Catharus guttatus Hooded Oriole Icterus cucullatus House Finch Haemorhous mexicanus House Sparrow Passer domesticus House Wren Troglodytes aedon Killdeer Charadrius vociferus Lark Sparrow Chondestes grammacus Lawrence's Goldfinch Spinus lawrencei Least Bell's Vireo Vireo bellii pusillus Least Sandpiper Calidris minutilla Lesser Goldfinch Spinus psaltria Lincoln's Sparrow Melospiza lincolnii Loggerhead Shrike Lanius ludovicianus Long-billed Curlew Numenius americanus Mallard Anas platyrhynchos Marsh Wren Cistothorus palustris Merlin Falco columbarius Mountain Bluebird Sialia currucoides Mourning Dove Zenaida macroura Northern Flicker Colaptes auratus Northern Harrier Circus hudsonius Northern Mockingbird Mimus polyglottos Northern Pintail Anas acuta Northern Rough-winged Swallow Stelgidopteryx serripennis Northern Shoveler Spatula clypeata

Western Riverside County MSHCP 24 Biological Monitoring Program 2018 Loggerhead Shrike Survey and Nest Monitoring Report

Appendix. Continued.

COMMON NAME SCIENTIFIC NAME Nuttall's Woodpecker Dryobates nuttallii Orange-crowned Warbler Oreothlypis celata Phainopepla Phainopepla nitens Pied-billed Grebe Podilymbus podiceps Prairie Falcon Falco mexicanus Red-shouldered Hawk Buteo lineatus Red-tailed Hawk Buteo jamaicensis Red-winged Blackbird Agelaius phoeniceus Ring-billed Gull Larus delawarensis Rock pigeon Columba livia Rock Wren Salpinctes obsoletus Ruby-crowned Kinglet Regulus calendula Ruddy Duck Oxyura jamaicensis Sage Thrasher Oreoscoptes montanus Savannah Sparrow Passerculus sandwichensis Say's Phoebe Sayornis saya Short-eared Owl Asio flammeus Snow Goose Anser caerulescens Snowy Egret Egretta thula Song Sparrow Melospiza melodia Sora Porzana carolina Southern California Rufous- Aimophila ruficeps canescens crowned Sparrow Spotted Towhee Pipilo maculatus Swainson's Hawk Buteo swainsoni Tree Swallow Tachycineta bicolor Tricolored Blackbird Agelaius tricolor Turkey Vulture Cathartes aura Vesper Sparrow Pooecetes gramineus Violet-green Swallow Tachycineta thalassina Western Bluebird Sialia mexicana Western Grebe Aechmophorus occidentalis Western Kingbird Tyrannus verticalis Western Meadowlark Sturnella neglecta White-crowned Sparrow Zonotrichia leucophrys White-faced Ibis Plegadis chihi White-tailed Kite Elanus leucurus White-throated Swift Aeronautes saxatalis Wilson's Snipe Gallinago delicata Wilson's Warbler Cardellina pusilla Wrentit Chamaea fasciata Yellow-breasted Chat Icteria virens Yellow-rumped Warbler Setophaga coronata

Western Riverside County MSHCP 25 Biological Monitoring Program