western riverside county · 2020. 5. 7. · prado basin, santa rosa plateau/tenaja, steele peak,...

Western Riverside County Multiple Species Habitat Conservation Plan

(MSHCP) Biological Monitoring Program

2015 Grasshopper Sparrow (Ammodramus savannarum)

Survey Report

Grasshopper Sparrow on a perch at Johnson Ranch.

31 May 2016

Revised 21 September 2017

2015 Grasshopper Sparrow Survey Report

Western Riverside County MSHCP Biological Monitoring Program

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TABLE OF CONTENTS

INTRODUCTION ................................................................................................ 1

GOALS AND OBJECTIVES ............................................................................................................... 5

METHODS ........................................................................................................ 5

SURVEY DESIGN ........................................................................................................................... 5

FIELD METHODS ........................................................................................................................... 5

DETECTION PROBABILITY ANALYSIS ............................................................................................ 6

RESULTS .......................................................................................................... 6

GRASSHOPPER SPARROW DETECTIONS ......................................................................................... 6

DETECTION PROBABILITY ANALYSIS ............................................................................................ 7

DISCUSSION ..................................................................................................... 8

GRASSHOPPER SPARROW DETECTIONS ......................................................................................... 8

DETECTION PROBABILITY ANALYSIS .......................................................................................... 11

RECOMMENDATIONS FOR FUTURE SURVEYS .............................................................................. 12

ACKNOWLEDGEMENTS .................................................................................. 12

LITERATURE CITED....................................................................................... 13

LIST OF FIGURES

Figure 1. Grasshopper Sparrow Core Areas and 2015 survey locations. .......................... 2 Figure 2. Grasshopper Sparrow Core Areas and 2005-2015 detections. ........................... 4 Figure 3. Typical vegetation structure near Lake Mathews in 2015.. ................................ 9

LIST OF TABLES

Table 1. Total area (ha) of grassland habitat, and area (ha) of conserved grassland habitat, within Grasshopper Sparrow Core Areas. .............................................................. 3 Table 2. The most recent detection of Grasshopper Sparrows within each of the designated Core Areas. ....................................................................................................... 7 Table 3. Model rankings for Grasshopper Sparrow surveys in 2015. ................................ 8

LIST OF APPENDICES

Appendix A. 2015 Grasshopper Sparrow survey data sheet ............................................ 16 Appendix B. Avian species detected during 2015 Grasshopper Sparrow surveys. ......... 17



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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 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 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 2015 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 2015 Avian Program Lead, Nicholas Peterson. This report should be cited as:

Biological Monitoring Program. 2016. Western Riverside County MSHCP Biological Monitoring Program 2015 Grasshopper Sparrow (Ammodramus savannarum) Survey 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. Readers 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 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 4080 Lemon Street, 12th Floor 4500 Glenwood Drive, Bldg. C P.O. Box 1667 Riverside, CA 92501 Riverside, CA 92502-1667 Ph: (951) 248-2552 Ph: (951) 955-9700

http://www.wrc-rca.org/



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INTRODUCTION The Grasshopper Sparrow (Ammodramus savannarum) is one of 45 bird species

covered by the Western Riverside County MSHCP (Dudek & Associates 2003) and is also a Species of Special Concern in the State of California (Unitt 2008). Two species objectives are identified for this species. Objective 1 requires the conservation of at least 38,690 ac (15,657 ha) of suitable non-native, valley, and foothill grassland habitats. Objective 2 requires that the species maintain occupancy in three designated large (i.e., ≥809 ha of conserved grassland habitat) Core Areas and at least three (75%) of four designated smaller (≥202 ha) Core Areas in at least one year out of any five-consecutive-year period. The species account identifies 11 potential Core Areas including Badlands, Box Springs, Kabian Park, Lake Mathews-Estelle Mountain, Lake Skinner/Diamond Valley Lake/Johnson Ranch, Mystic Lake/San Jacinto Wildlife Area (WA), Potrero, Prado Basin, Santa Rosa Plateau/Tenaja, Steele Peak, and Sycamore Canyon (Fig. 1). The Badlands and Potrero are both part of the Plan Area’s Core 3, so they will be combined into a single Core Area for the purposes of this study. We defined the Mystic Lake/San Jacinto WA Core Area in 2015 as Subunit 4 of the Reche Canyon/Badlands Area Plan because this is how the same Core Area is defined for American Bittern (Botaurus lentiginosus), Black-crowned Night-Heron (Nycticorax nycticorax), California Horned Lark (Eremophila alpestris actia), and White-faced Ibis (Plegadis chihi). This definition does not include the entirety of Mystic Lake or San Jacinto WA.

Based upon our definition of 2015 Core Area boundaries, three currently contain at least 809 ha of conserved grassland habitat and can therefore be considered large; these include Lake Mathews-Estelle Mountain, Lake Skinner/Diamond Valley Lake/Johnson Ranch, and Santa Rosa Plateau/Tenaja (Table 1). Two Core Areas, Badlands/Potrero and Sycamore Canyon, qualify as small Core Areas because they contain at least 202 ha of conserved grassland habitat but not the 809 ha that would qualify them as a large Core Area. The remaining Core Areas have less than 202 ha of grassland habitat in conservation and do not officially qualify as small Core Areas; however, we still conducted Grasshopper Sparrow surveys within these Core Areas in 2015. Finally, Objective 2 also requires that five of seven designated Core Areas support at least 20 Grasshopper Sparrow pairs with evidence of successful reproduction within the first five years after permit issuance. This five-year period has already passed and the objective was not met when our program conducted Grasshopper Sparrow surveys in 2005. As a result, our 2015 surveys did not have a nest-searching and monitoring component. We have subsequently reinterpreted this objective and future Grasshopper Sparrow survey efforts will include a nest-searching and monitoring component.

The winter range of Grasshopper Sparrows in North America extends from portions of the southeastern U.S. south through much of Mexico. The species breeds in southern New England west to Montana, and south into northern Texas, Arkansas, Tennessee, and North Carolina, with a patchy distribution west of the Rocky Mountains (Vickery 1996). Grasshopper Sparrows in California occur west of the Sierra Nevada mountain range and are primarily summer residents (McCaskie et al. 1979; Garrett and Dunn 1981) from Mendocino, Tehama, and Trinity counties in the north, to western Riverside and San Diego counties in the south (Grinnell and Miller 1944).

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Figure 1. Grasshopper Sparrow Core Areas and 2015 survey locations.

Date: 11 April 2016UTM Nad 83 Zone 11Contact: Nicholas PetersonMSHCP Biological Monitoring Program

Legend!( GRSP Survey Locations

HighwaysWater BodiesExisting Conservation LandCities

I 0 5 10 15 202.5km

Core AreasBadlands & PotreroBox SpringsKabian ParkLake Mathews/Estelle MountainLake Skinner/Diamond Valley Lake/Johnson RanchMystic Lake/SJWAPrado BasinSanta Rosa Plateau/TenajaSteele PeakSycamore Canyon



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Within western Riverside County, the species is found in suitable habitat in the Riverside Lowlands, San Jacinto Foothills, and Santa Ana Mountains Bioregions (Garrett and Dunn 1981), but predominantly within the central and south-central portions of the Plan Area (Dudek & Associates 2003). Our biologists have detected Grasshopper Sparrows 567 times on Conserved Land in the Plan Area since 2005 (Fig. 2).

Table 1. Total area (ha) of grassland habitat, and area (ha) of conserved grassland habitat, within Grasshopper Sparrow Core Areas.

Core Area Area (ha) of

grassland habitat

Area (ha) of conserved grassland habitat

(% of total available) Designation1

Badlands/Potrero 1254 797 (64) Small

Box Springs 68 50 (74) n/a

Kabian Park 76 30 (39) n/a

Lake Mathews – Estelle Mountain

1433 1090 (76) Large

Lake Skinner / Diamond Valley Lake

1151 836 (73) Large

Mystic Lake / San Jacinto WA

167 150 (90) n/a

Prado Basin 0 0 (n/a) n/a

Santa Rosa Plateau / Tenaja 1168 1160 (99) Large

Steele Peak 227 96 (42) n/a

Sycamore Canyon 229 229 (100) Small

Overall 5773 4438 (77) 1Large = ≥809 ha of conserved grassland habitat, small = ≥202 but <809 ha of conserved grassland habitat, and n/a = <202 ha of conserved grassland habitat.

Throughout their range, Grasshopper Sparrows occupy sites with moderately open grasslands containing patches of bare ground (Vickery 1996). Such grasslands may consist of native or non-native grasses 12–23 cm tall (Jobin and Falardeau 2010; Bogard and Davis 2014) and may contain scattered shrubs that do not form contiguous thickets (Cooper 2000; Unitt 2008). The absence of trees at sites is also an important predictor of use by the species (Collier 1994). Grasshopper Sparrows prefer territories with at least 24% bare ground (Whitmore 1979) but rarely occupy sites with >35% bare ground (Bock and Webb 1984). Finally, the presence of a shallow layer of litter is preferred by breeding Grasshopper Sparrows because it provides concealment for nests (Frey et al. 2008; Stauffer et al. 2011).

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Figure 2. Grasshopper Sparrow Core Areas and 2005-2015 detections.

Date: 11 April 2016UTM Nad 83 Zone 11Contact: Nicholas PetersonMSHCP Biological Monitoring Program

Legend!( GRSP Detection (2011-2015)!( GRSP Detection (2005-2010)

HighwaysWater BodiesExisting Conservation LandCities

I 0 5 10 15 202.5km

Core AreasBadlands & PotreroBox SpringsKabian ParkLake Mathews/Estelle MountainLake Skinner/Diamond Valley Lake/Johnson RanchMystic Lake/SJWAPrado BasinSanta Rosa Plateau/TenajaSteele PeakSycamore Canyon

Oak Mountain



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Goals and Objectives 1. Document the distribution of Grasshopper Sparrows in the MSHCP-identified

Core Areas. a. Conduct repeat-visit transect surveys within accessible Grasshopper

Sparrow foraging and nesting habitat in the Plan Area, recording all bird species observed.

METHODS Survey Design

We conducted surveys for Grasshopper Sparrows by making repeat visits to 100-m-long line transects (Herkert 1994; Best et al. 1997; Reynolds and Krausman 1998; Rahmig et al. 2009; George et al. 2013). I developed survey methods using techniques described in Rosenstock et al. (2002). The design I used allows for the calculation of transect-level detection probability (p) and can also be used to evaluate correlations between covariates (MacKenzie et al. 2006).

I began study site selection by first selecting habitats within our ArcGIS (ESRI 2006) vegetation layer (CDFG et al. 2005) that were identified by the MSHCP (Dudek & Associates 2003) as suitable for Grasshopper Sparrows, specifically non-native, valley, and foothill grasslands. After I identified appropriate sparrow habitat in GIS, I clipped that layer to a separate GIS layer consisting of conserved lands within the Grasshopper Sparrow Core Areas designated by the MSHCP. Next, I generated 94 randomly-located transect center points (Fig. 1), separated by at least 200 m, within those Core Areas. I then generated termini for each transect, with each transect being exactly 100 m long and oriented in a random direction. I chose transect lengths of 100 m because it allowed me to place an adequate number of transects within smaller core areas to allow for data analysis.

Field Methods Surveys in 2015 began on 9 March and ended on 17 June. Round 1 ended on 3

April, Round 2 lasted from 7 April to 11 May, and Round 3 began on 12 May. We conducted surveys during the first four hours following sunrise (Johnson and Sandercock 2010; McLaughlin et al. 2014) and I instructed surveyors to terminate surveys when the temperature exceeded 35 °C, during heavy precipitation or fog, or when maximum wind speeds exceeded 20 km/h (Earnst et al. 2009; Jobin and Falardeau 2010; Graves et al. 2010; George et al. 2013; Bogard and Davis 2014; Henderson and Davis 2014; McLaughlin et al. 2014).

At the beginning of the survey (i.e., at one of the transect termini), observers recorded the transect start time, temperature, and sky conditions. Observers surveyed transects beginning at one of the transect termini and navigating to the central point, and then 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 visually and aurally surveying for Grasshopper Sparrows, spending a minimum of 5 min walking the length of the transect. Observers recorded on their data sheet (Appendix A)



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information for all bird species detected while walking each transect. For non-covered species, observers recorded information for only the first individual of that species detected, which provided 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 were double-counting), they erred on the side of caution and recorded information on that individual.

All field personnel demonstrated proficiency at visual and aural identification of Grasshopper Sparrows prior to conducting surveys. All personnel also demonstrated proficiency with survey techniques, including identification of at least 65 avian species associated with Grasshopper Sparrow habitat, before field surveys commenced.

Detection Probability Analysis I estimated cumulative detection probability (P*) for Grasshopper Sparrows using

closed-capture occupancy models (MacKenzie et al. 2006). I considered locations with Grasshopper Sparrow observations used rather than occupied because the survey design likely did not meet 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 examined the full combination of site and visit effects on transect-level detection probability (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 (P*) across three visits using model-averaged estimates of p and the following formula where pi is the detection probability on a given survey visit:

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3

𝑖𝑖=1

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Finally, I calculated variances for P* using the delta method (MacKenzie et al. 2006; Powell 2007).

RESULTS Grasshopper Sparrow Detections

We detected 96 avian species during our 2015 surveys, 20 of which are covered by the MSHCP (Appendix B). We detected Grasshopper Sparrows in 2 (67%) of the 3 large Core Areas and 1 (50%) of the 2 small Core Areas. Additionally, we have detected the species within the Lake Mathews-Estelle Mountain Core Area during the current reporting period (2011–2015; Table 2). Finally, we did not detect Grasshopper Sparrows within the Box Springs, Kabian Park, Mystic Lake/San Jacinto WA, Prado Basin, Steele Peak, or Sycamore Canyon Core Areas in 2015.



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Table 2. The most recent detection of Grasshopper Sparrows within each of the designated Core Areas. The current reporting period is 2011–2015; parenthetical values indicate years preceding the current reporting period.

Core Area Most recent Grasshopper Sparrow detection

Large Core Areas

Lake Mathews – Estelle Mountain 2014

Lake Skinner / Diamond Valley Lake 2015

Santa Rosa Plateau / Tenaja 2015

Overall within current reporting period 3 (100%) of Large Core Areas

Small Core Areas

Badlands / Potrero 2015

Sycamore Canyon (2005)

Overall within current reporting period 1 (50%) of Small Core Areas

Additional Core Areas

Box Springs Never

Kabian Park (2005)

Mystic Lake / San Jacinto WA Never

Prado Basin Never

Steele Peak Never

We detected Grasshopper Sparrows at 8 (8.5%) of 94 transects in Round 1, 22 (23.4%) of 94 in Round 2, and 10 (11.8%) of 85 in Round 3. Overall, we detected Grasshopper Sparrows at 29 (30.9%) of the 94 transects. We did not survey 8 of the transects in Round 3 because they were within a prescribed burn area and we eliminated a ninth transect after we discovered it was not entirely within Conserved Land.

We have detected Grasshopper Sparrows 567 times on Conserved Land within the Plan Area from 2005 to 2015. Our detections are generally clustered within the Lake Mathews-Estelle Mountain (n = 97 detections), Lake Skinner/Diamond Valley Lake (n = 199), and Santa Rosa Plateau (n = 204) Core Areas. We have detected the species 16 times within the Lake Perris State Recreation Area/San Jacinto WA, but never within the Core Area boundaries. Finally, we have a cluster of 11 detections at Oak Mountain, north of Vail Lake (Fig. 2).

Detection Probability Analysis Program MARK identified the p(t) model (AICC weight = 0.98) as the best-fit

model (Table 3). This model indicated that detection probability (± SE) varied by time (t), or more specifically, during each survey round: 0.23 ± 0.08 in Round 1, increased to 0.64 ± 0.12 in Round 2, and then decreased to 0.35 ± 0.10 in Round 3. The cumulative detection probability (± SE) over three survey rounds was 0.82 ± 0.11. I eliminated the



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p(g) model, which considers variations in detection probability by group (g), from analysis because we had just 40 Grasshopper Sparrow detections overall and not enough in any one Core Area (i.e., group) to justify including the model. Finally, Program MARK provided an overall site occupancy (ψ ± SE) of 0.37 ± 0.07.

Table 3. Model rankings for Grasshopper Sparrow surveys in 2015. Variables for detection probabilities (p) were modeled to remain constant (.) and vary by time (t). Occupancy (ψ) was modeled to remain constant. For model selection, I used Akaike’s Information Criterion corrected for small sample size (AICC). wi = AICC weight and k = number of parameters.

Model Δ AICC wi Model likelihood k

p(t) ψ(.)a 0.00 0.98 1.00 4

p(.) ψ(.) 7.96 0.02 0.02 2 aAICC = 209.49

DISCUSSION Grasshopper Sparrow Detections

We have a combined 500 detections of Grasshopper Sparrows at the 3 large Core Areas from 2005 to 2015, which account for 88% of all of our Grasshopper Sparrow detections on Conserved Land. Many occurred within the Santa Rosa Plateau/Tenaja Core Area, which was identified by Unitt (2008) as being the location in western Riverside County in which the species most consistently occurs. Lake Mathews and Lake Skinner, which are located within our 2 additional large Core Areas, are also identified as sites at which Grasshopper Sparrows occur, albeit irregularly, within western Riverside County (Unitt 2008).

In the Santa Rosa Plateau/Tenaja Core Area, our Grasshopper Sparrow detections are scattered throughout the Core Area rather than occurring in clumped groups (Fig. 2). This is likely a reflection of the fact that the tall, dense grassland habitat preferred by Grasshopper Sparrows is relatively well-distributed within the Core Area.

In the Lake Mathews-Estelle Mountain Core Area, most (91%) of our Grasshopper Sparrow detections are south of Cajalco Road (Fig. 2), where patches of tall and dense grassland are abundant. Grassland habitat at our survey sites within the Lake Mathews portion of the Core Area, which is north of Cajalco Road, was generally too short and sparse to support Grasshopper Sparrows (Fig. 3); however, this was not always true because we detected sparrows within that area 9 times from 2005 to 2011, when grasses were noticeably taller.

More than half (56%) of our Grasshopper Sparrow detections within the Lake Skinner/Diamond Valley Lake Core Area are south of Borel Road, specifically within French Valley Wildlife Area and Johnson Ranch. Grasses here tend to be tall and dense, with patches averaging 3 ha in size. Contrasting this, we have never detected Grasshopper Sparrows at the adjacent El Sol property in which grasses are kept short for the benefit of species such as Burrowing Owls (Athene cunicularia). Our remaining detections within the Core Area north of Borel Road (i.e., within the Southwestern



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Riverside County Multi-Species Reserve) are generally south and southeast of Lake Skinner, but we have detected Grasshopper Sparrows as far north as Crown Valley, south of Diamond Valley Lake.

Figure 3. Typical vegetation structure near Lake Mathews in 2015. For reference, the blue clipboard is about 24 cm tall as positioned in the photo. Grasshopper Sparrows tend to prefer sites with vegetation 12–23 cm tall (Jobin and Falardeau 2010; Bogard and Davis 2014).

We have detected Grasshopper Sparrows in just one of the small Core Areas within the current reporting period, most recently in 2011 and 2015 in the Badlands/Potrero Core Area in grasslands south of San Timoteo Canyon Road and in the northeastern corner of the Potrero Unit of the San Jacinto WA (Fig. 2). Much of the rest of the Conserved Land within that Core Area consists of rugged and hilly terrain that is unsuitable for use by the species. Finally, we have detected Grasshopper Sparrows twice in the Sycamore Canyon Core Area, which is the second small Core Area for the species. The detections occurred on the same day in 2005 and were 53 m apart (Fig. 2), perhaps representing the same individual bird. The northeastern part of the Core Area in which these detections occurred periodically has tall and dense grasses, but much of the rest of the Core Area is periodically grazed by sheep, so the habitat is not conducive to Grasshopper Sparrows.

Within the remaining Core Areas, we have detected Grasshopper Sparrows just once, in 2005, in the Kabian Park Core Area (Fig. 2). This Core Area has just 30 ha of conserved grassland habitat and this is scattered among small patches that average 1.6 ha (range = 0.02–7.6 ha) in size. Patches of this size are generally too small to support Grasshopper Sparrows, which may require patches that are a minimum of 12–100 ha in size (Herkert 1994; Vickery et al. 1994; Walk and Warner 1999).

We have never detected Grasshopper Sparrows within the Box Springs, Mystic Lake/San Jacinto WA, Prado Basin, or Steele Peak Core Areas, as defined in 2015. The Prado Basin Core Area does not currently contain any conserved grassland habitat and the Box Springs and Steele Peak Core Areas contain relatively small amounts of conserved grassland habitat (50 ha and 96 ha, respectively). Grassland habitat within



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these Core Areas is patchily distributed, but even 100-ha patches of grassland habitat may only have a 50% incidence of Grasshopper Sparrow occupancy based upon previous investigations (Vickery et al. 1994). The Mystic Lake/San Jacinto WA Core Area has a larger amount of grassland habitat (150 ha, with an average patch size of 30 ha), but the configuration of the Core Area as defined in 2015 does not currently encompass any of our sparrow detections (Fig. 1). Redefining the Core Area as generally being the eastern portion of existing Core H would include nearly all of Mystic Lake and the Davis Unit of the San Jacinto WA, thereby enabling us to more accurately report that the species is in fact using the Core Area. Thus, the Mystic Lake/San Jacinto WA Core Area will henceforth be defined in this way.

In addition to the designated Core Areas, we have consistently detected Grasshopper Sparrows from 2005 to 2015 in the Oak Mountain area north of Vail Lake (Fig. 2), which is within Proposed Core 7. Because of this, we recommend that this location be considered as an additional or replacement Core Area. Regardless of whether this happens, we should establish survey transects within this area during future Grasshopper Sparrow survey efforts to continue monitoring the status of the population.

Prescribed burns, grazing, mowing, or some combination thereof are common management techniques at sites that contain Grasshopper Sparrows. Such techniques should ideally occur early in the year to avoid causing decreases in Grasshopper Sparrow abundance or return rates (Ingold et al. 2010; Johnson and Sandercock 2010). Because Grasshopper Sparrows prefer a shallow litter layer for nest concealment (Frey et al. 2008; Stauffer et al. 2011), any management technique for sparrows should retain this habitat feature as much as possible, especially during the breeding season. When the litter layer is removed, Grasshopper Sparrows tend to abandon the site. For example, Grasshopper Sparrows avoided burned plots in a southeastern Arizona study site for 2 years following prescribed burns, largely due to the loss of the litter layer (Bock and Bock 1992). Similarly, Grasshopper Sparrow abundance decreased following a wildfire in Washington, but increased in the third and fourth years following the fire (Earnst et al. 2009). These trends were also reported from a site in Texas, where the relative abundance of Grasshopper Sparrows decreased following a prescribed fire, but eventually increased as vegetative regrowth progressed (Reynolds and Krausman 1998).

Grazing and prescribed burns can be used by managers to create similar conditions that are preferred by Grasshopper Sparrows. For example, Grasshopper Sparrows seem to prefer light to moderately grazed sites, which is comparable to entire sites being burned annually. The conditions created by such treatments are preferred by the species over the more extreme conditions created by patch-burn treatments in which litter and vegetation are allowed to accumulate before being completely removed by fire (Coppedge et al. 2008). Grazing and prescribed fire do not always benefit Grasshopper Sparrows in the same way, however. Grasshopper Sparrow abundance and density may be higher in grazed sites, whereas nest success tends to be highest in burned hayfields (Rahmig et al. 2008; Powell and Busby 2013).

Finally, any management technique for improving Grasshopper Sparrow habitat should seek to create a diverse grassland ecosystem that contains a patchwork of bare ground, litter, shrubs, and dense grasses and forbs. This kind of patchwork may



11

encourage use by adult Grasshopper Sparrows but may also be critically important for juvenile Grasshopper Sparrows. Dependent juvenile Grasshopper Sparrows tend to benefit from patches containing high levels of vegetative cover, in which they can hide from predators, whereas independent juveniles must feed themselves and thus benefit from areas that contain bare ground in which they can forage (Small et al. 2015).

Detection Probability Analysis Our methodology in 2015 resulted in per-visit detection probabilities of 0.23–0.64

and a cumulative detection probability of 0.82 over the course of three survey rounds. These numbers are substantially lower than those reported by other investigators. For example, the detection probability of Grasshopper Sparrows within 100 m of point-count stations in Washington was 0.92 (Earnst and Holmes 2012), and the average cumulative detection probability of the species at roadside point-count stations in Delaware was 0.99 (Irvin et al. 2013). Both of these investigations used point-counts rather than line transects. Surveying from points may have allowed their biologists better opportunities to detect singing Grasshopper Sparrows while not having to navigate through dense, dry vegetation, which can easily obscure the sound of a Grasshopper Sparrow singing at a distance.

Another interesting aspect of our data is that we saw a significant increase in detection probability during Round 2, which occurred from 7 April to 11 May. One potential explanation for this increase is that Grasshopper Sparrows were still migrating to the Plan Area during Round 1, meaning that sites that were occupied in Rounds 2 and 3 were not yet occupied in Round 1. We started our surveys in early March with the assumption that Grasshopper Sparrows in southern California are usually territorial by then (Collier 1994); however, some territorial movement can occur through April and May in southern California (Garrett and Dunn 1981). A second explanation is that singing rate fluctuated throughout the breeding season. Audial detections were almost the exclusive way by which we detected Grasshopper Sparrows, and other investigators have reported that song rate varies throughout the breeding season. For example, the sustained song of the males is used more frequently 2 to 3 weeks following territory establishment than it is early in territory establishment (Smith 1959). This would generally occur in mid- to late March in southern California, assuming territory establishment occurs by early March (Collier 1994), and would have continued through Round 2 of our surveys. Finally, song rates in New England have been documented to diminish in mid-morning beginning in the middle of June (Vickery 1996), which could perhaps explain the relative decrease in detection probabilities we saw during Round 3 of our surveys.

Site occupancy in our study was 0.37 and the lowest detection probability was 0.23. Using these data and Table 6.1 in MacKenzie et al. (2006), we can conclude that eight is the optimal number of visits to survey sites in future Grasshopper Sparrow surveys, assuming we use the same methodology as in 2015. We can also conclude that future survey efforts should consist of 31–124 transects, assuming we want to accept a 5–10% coefficient of variation for the occupancy estimate (Equation 6.3 in MacKenzie et al. 2006).



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Recommendations for Future Surveys We recommend defining the San Jacinto Wildlife Area/Mystic Lake Core Area as

generally being the eastern portion of existing Core H. This would encompass nearly all of Mystic Lake and the Davis Unit of the San Jacinto WA, thereby enabling us to more accurately report that the species is in fact using the Core Area.

Following the 2015 survey effort, we have reinterpreted Objective 2 for the species. Objective 2 requires demonstration that five of seven designated Core Areas support at least 20 Grasshopper Sparrow pairs with evidence of successful reproduction within the first five years after permit issuance. This five-year period has passed but future Grasshopper Sparrow survey efforts will include a nest-searching and monitoring component.

We may want to consider conducting future Grasshopper Sparrow surveys using point-counts rather than line transects. This generally contradicts the notion that line transects are more efficient in open habitats such as grasslands, but investigators have achieved high detection probabilities using this method (Earnst and Holmes 2012; Irvin et al. 2013). Surveying from a point means that our biologists will not have to try to detect the insect-like song of the Grasshopper Sparrow over the sound of vegetation being trampled while walking line transects.

Future Grasshopper Sparrow surveys should consist of eight survey rounds and 31–124 survey stations. We may be able to increase our survey efficiency, specifically being able to survey a higher number of stations, if we incorporate a removal design in future surveys. Such a design would mean no additional surveys would be conducted at a site after Grasshopper Sparrows are detected, which would then allow us time to survey at additional sites (MacKenzie et al. 2006).

Finally, we advocate collecting habitat data as part of future Grasshopper Sparrow projects. With the exception of Collier (1994), there are few data available on habitat use by Grasshopper Sparrows in southern California. This information would be useful to land managers wanting to improve or maintain Grasshopper Sparrow habitat at their reserves. The information would also be useful at a broader statewide scale, because while Grasshopper Sparrow habitat use has been studied elsewhere within its range, it has received little attention in California (Unitt 2008), where it is designated as a Species of Special Concern.

ACKNOWLEDGEMENTS Funding for the Biological Monitoring Program is provided by the Western

Riverside Regional Conservation Authority (RCA) and the California Department of Fish and Wildlife (DFW). Program employees who conducted surveys were Nicholas Peterson (Avian Program Lead, DFW), Tara Graham (RCA), Lynn Miller (RCA), Robert Packard (RCA), and David Tafoya (RCA). 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.



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Appendix A. 2015 Grasshopper Sparrow survey data sheet.

Transect ID: Visit #:

Max wind:

Date:

Avg. wind:

Observer:

Sky code:

Start time: Ambient noise:

End time: Start temp.: End temp.:

Species code

Sex

(M, F, U)

Age

(Ad, Ju, Fl, U)

Sky Condition Codes: 0 = clear or few clouds; 1 = partly cloudy; 2 = overcast; 3 = fog or smoke; 4 = light drizzle; 5 = constant snow; 6 = constant rain.

Noise Codes: 0 = no noise; 1 = noise, but not affecting bird detection; 2 = moderate noise, may be affecting detection; 3 = loud noise, reducing ability to

detect birds; 4 = very loud noise, difficult to hear anything at all.

Notes, species observed in transit, etc.

MSHCP Grasshopper Sparrow Survey Data Sheet, 2015

km h-1

Site conditions

km h-1

Notes

Western Riverside County MSHCP

Biological Monitoring Program 16



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Appendix B. Avian species detected during 2015 Grasshopper Sparrow 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 Pipit Anthus rubescens American Wigeon Anas americana Anna's Hummingbird Calypte anna Ash-throated Flycatcher Myiarchus cinerascens Barn Swallow Hirundo rustica Bewick's Wren Thryomanes bewickii Black-headed Grosbeak Pheucticus melanocephalus Black-necked Stilt Himantopus mexicanus Blue Grosbeak Passerina caerulea Blue-gray Gnatcatcher Polioptila caerulea Brewer's Blackbird Euphagus cyanocephalus Brewer's Sparrow Spizella breweri Brown-headed Cowbird Molothrus ater Bullock's Oriole Icterus bullockii Bushtit Psaltriparus minimus California Gnatcatcher Polioptila californica California Gull Larus californicus California Quail Callipepla californica California Thrasher Toxostoma redivivum California Towhee Melozone crissalis Cassin's Kingbird Tyrannus vociferans Cedar Waxwing Bombycilla cedrorum Cliff Swallow Petrochelidon pyrrhonota Common Ground-Dove Columbina passerina Common Raven Corvus corax Common Yellowthroat Geothlypis trichas Cooper's Hawk Accipiter cooperii Costa's Hummingbird Calypte costae Double-crested Cormorant Phalacrocorax auritus Downy Woodpecker Picoides pubescens Eurasian Collared-Dove Streptopelia decaocto European Starling Sturnus vulgaris Ferruginous Hawk Buteo regalis Gadwall Anas strepera Grasshopper Sparrow Ammodramus savannarum Great Blue Heron Ardea herodias Great Egret Ardea alba Greater Roadrunner Geococcyx californianus Great-tailed Grackle Quiscalus mexicanus Hooded Oriole Icterus cucullatus Horned Lark Eremophila alpestris House Finch Haemorhous mexicanus House Wren Troglodytes aedon



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Appendix B. Continued. COMMON NAME SCIENTIFIC NAME Killdeer Charadrius vociferus Lark Sparrow Chondestes grammacus Lazuli Bunting Passerina amoena Least Bell's Vireo Vireo bellii pusillus Lesser Goldfinch Spinus psaltria Loggerhead Shrike Lanius ludovicianus Mallard Anas platyrhynchos Mourning Dove Zenaida macroura Northern Flicker Colaptes auratus Northern Harrier Circus cyaneus Northern Mockingbird Mimus polyglottos Northern Rough-winged Swallow Stelgidopteryx serripennis Nuttall's Woodpecker Picoides nuttallii Oak Titmouse Baeolophus inornatus Orange-crowned Warbler Oreothlypis celata Peregrine Falcon Falco peregrinus 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 Ruddy Duck Oxyura jamaicensis Rufous-crowned Sparrow Aimophila ruficeps Savannah Sparrow Passerculus sandwichensis Say's Phoebe Sayornis saya Song Sparrow Melospiza melodia Spotted Towhee Pipilo maculatus Swamp Sparrow Melospiza georgiana Tree Swallow Tachycineta bicolor Tricolored Blackbird Agelaius tricolor Turkey Vulture Cathartes aura Unidentified gull Family Laridae Unidentified hummingbird Family Trochilidae Unidentified sparrow Family Emberizidae Unidentified warbler Family Parulidae Unidentified woodpecker Family Picidae Unknown blackbird Family Icteridae Vaux's Swift Chaetura vauxi Violet-green Swallow Tachycineta thalassina Western Bluebird Sialia mexicana Western Kingbird Tyrannus verticalis Western Meadowlark Sturnella neglecta Western Scrub-Jay Aphelocoma californica Whimbrel Numenius phaeopus White-crowned Sparrow Zonotrichia leucophrys White-tailed Kite Elanus leucurus White-throated Swift Aeronautes saxatalis Wilson's Warbler Cardellina pusilla Wrentit Chamaea fasciata



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Appendix B. Continued. COMMON NAME SCIENTIFIC NAME Yellow Warbler Setophaga petechia Yellow-breasted Chat Icteria virens Yellow-rumped Warbler Setophaga coronata

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