Monitoring Least Bell’s (Vireo bellii pusillus) and comparing breeding landbird populations at the Dos Rios Ranch restoration site and San Joaquin River National Wildlife Refuge 2015-2016

Report prepared for River Partners, in support of habitat restoration work funded by the Central Valley Project Conservation Program. Final Report in fulfillment of grant agreement R12AP20047.

November 2016 Kristen E. Dybala, Robert G. Walsh, and Nathaniel E. Seavy

Monitoring Least Bell’s Vireo (Vireo bellii pusillus) and comparing breeding landbird populations at the Dos Rios Ranch restoration site and San Joaquin River National Wildlife Refuge 2015-2016

November 2016

Point Blue Conservation Science

Kristen E. Dybala, Robert G. Walsh, and Nathaniel E. Seavy

Acknowledgements This project was made possible by funding from the Central Valley Project Conservation Program.

Suggested Citation Dybala KE, Walsh RG, Seavy NE. 2016. Monitoring Least Bell’s Vireo (Vireo bellii pusillus) and comparing breeding landbird populations at the Dos Rios Ranch restoration site and San Joaquin River National Wildlife Refuge 2015-2016. Point Blue Conservation Science, Petaluma, CA. This is Point Blue Contribution No. 2101.

Point Blue Conservation Science – Point Blue’s 140 staff and seasonal scientists conserve , other wildlife and their ecosystems through scientific research and outreach. At the core of our work is ecosystem science, studying birds and other indicators of nature’s health. Visit Point Blue on the web www.pointblue.org.

Cover photo credit: Robert G. Walsh

Table of Contents

EXECUTIVE SUMMARY ...... 1 INTRODUCTION ...... 2 MONITORING OBJECTIVES ...... 3 METHODS AND RESULTS ...... 4 Study areas and sampling design ...... 5 surveys and vegetation monitoring at point count stations ...... 5 Riparian landbird response to restoration ...... 6 Least Bell’s Vireo monitoring ...... 11 RECOMMENDATIONS ...... 15 PROJECT DATA ...... 17 Data management ...... 17 Other products ...... 17 REFERENCES ...... 18 APPENDICES ...... 22 Appendix A. Point count coordinates ...... 22 Appendix B. Vegetation data and metadata ...... 22 Appendix C. Least Bell’s Vireo media and coordinates ...... 22 Appendix D. PowerPoint slides of key results ...... 22 Appendix E. Annotated bird list, 2016 ...... 23

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EXECUTIVE SUMMARY This report describes the results of our 2015-2016 efforts to (1) document any evidence of colonization by Least Bell’s Vireo on Phase 1 of the Dos Rios Ranch restoration or recolonization on the adjacent San Joaquin River National Wildlife Refuge (SJRNWR), Stanislaus County, California, and (2) assess the response of the overall breeding landbird community to the Dos Rios Ranch restoration phase 1 and how it compares to the breeding bird community using the older restored riparian habitat in the SJRNWR. During spring of 2015 and 2016, we surveyed birds at 39 point count stations distributed across restoration sites at Dos Rios Ranch and SJRNWR, including 2 visits per year to each station for a total of 156 point count surveys. Vegetation was surveyed at each point count station in each year, and an additional 107 hours were spent on targeted searches for, and monitoring of, Least Bell’s . A single territorial male Least Bell’s Vireo was observed at the SJRNWR for two weeks in June of 2016. To our knowledge, this was the only record of the from the entire Central Valley for the 2016 breeding season. A search for all Bell’s Vireo records from all of Central and Northern California produced an estimated average of just 1.3 individual vireos detected per year over the past several decades. Thus, in addition to requiring suitable riparian habitat, successful colonization of Dos Rios Ranch and SJRNWR by Least Bell’s Vireo will depend on whether more birds disperse out of southern California. We compared the species richness and breeding densities of landbirds at the Dos Rios Ranch restoration Phase 1 (1-2 years old) to restoration sites at SJRNWR, grouped into sites that were 3-6 years old and 9-12 years old. Species richness and the breeding densities of six Central Valley Join Venture (CVJV) riparian focal species at Dos Rios Ranch were already similar to that of the 3-6 year old SJRNWR sites. Further, Dos Rios Ranch has already achieved the CVJV breeding density objective for Song Sparrows. Using the data from SJRNWR and Dos Rios together, we found that bird species richness was correlated with tree, shrub, and ground cover, as well as canopy height, suggesting that species richness will continue to increase as restoration plantings mature. Finally, we make several recommendations: (1) Continue to evaluate restoration success using a broad suite of riparian species, which can provide broad insights into changes in the overall condition of riparian habitat. (2) Maximize the chances of vireo colonization by ensuring that restored sites are maturing into the vegetation structure most suitable for Least Bell’s Vireo. (3) Develop a plan for monitoring any future vireo nest attempts, including obtaining and maintaining permits. (4) Consider providing habitat for Tricolored Blackbirds at Dos Rios Ranch. (5) Consider monitoring black rats, Brown-headed cowbirds, or other species that could have negative impacts on riparian restoration success. (6) Evaluate whether current restoration designs are climate-smart and capable of adapting to projected climate conditions. (7) Continued to restore riparian vegetation and improve floodplain connectivity to provide important habitat for riparian-dependent species, as well as to provide the many other benefits of improved riparian ecosystem function, such as reducing flood risk, sequestering carbon, and contributing to local economies.

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INTRODUCTION Riparian ecosystems are hotspots of avian diversity in the western United States (Knopf et al. 1988; Knopf and Samson 1994). The Central Valley of California in particular provides essential breeding and wintering habitat, migration stopover areas, and corridors of dispersal for riparian- associated birds (Humple and Geupel 2002; Latta et al. 2012; Cormier et al. 2013; Dybala et al. 2015). Sixty-two species of landbirds have regularly bred in Central Valley riparian forests over the last two decades (Point Blue Conservation Science unpublished data) and many others use riparian areas during portions of their life cycle. Loss of riparian habitat may be the most important cause of population declines among landbird species in western North America (DeSante and George 1994), including the decline and extirpation of many riparian species once common in the Central Valley (RHJV 2004; CVJV 2006; Dybala et al. In press). While the populations of many riparian have declined in the Central Valley, the extirpation of the Least Bell’s Vireo (Vireo bellii pusillus) is one of the most dramatic examples (Howell et al. 2010). The Least Bell’s Vireo was once common in riparian habitat of coastal Southern California and the Central Valley (Goldman 1908; Grinnell and Miller 1944). However, by the late 1970s, the species had declined dramatically; extensive surveys in the Central Valley failed to detect a single individual (Goldwasser et al. 1980). As a result, the Least Bell’s Vireo was listed as state endangered in 1980 and federally endangered in 1986. In 1986, only 300 pairs remained with the majority in San Diego, Riverside, and Santa Barbara counties and eight or fewer pairs or territorial males within each of San Bernardino, Riverside, Orange, Los Angeles, Ventura, Inyo, and Monterey counties (USFWS 1998). More recently, the outlook for the Least Bell’s Vireo has been improved by extensive efforts to restore habitat and boost reproductive success. As a result of these efforts, the southern California population has increased to an estimated 3000 pairs as of 2008 (Kus et al. 2008), and the species has recolonized the Santa Clara and Mojave rivers in that region (B. Kus, pers. comm.). In the Central Valley, project-scale monitoring of riparian restoration sites has shown that restored habitat is rapidly colonized by riparian birds, and after as few as 10 years can provide habitat for a suite of birds similar to those that occur in mature riparian forest (Gardali et al. 2006). Additionally, there is evidence that the Least Bell’s Vireo may recolonize the San Joaquin Valley. Several breeding attempts by at least one pair of the Least Bell’s Vireo occurred in 2005- 2007 on the San Joaquin River National Wildlife Refuge (SJRNWR) in restored riparian habitat (Howell et al. 2010). The 850 ha (2100 ac) Dos Rios Ranch restoration project sits at the confluence of the Tuolumne and San Joaquin rivers, adjacent to the SJRNWR (Figure 1). Phase 1 of the Dos Rios Ranch restoration project comprised approximately 80 ha (198 ac), with goals of increasing and improving riparian habitat for numerous federal- and state-listed endangered and threatened species, including the riparian brush rabbit (Sylvilagus bachmani riparius), San Joaquin riparian woodrat (Neotoma fuscipes riparia), valley elderberry longhorn beetle (Desmocerus californicus dimorphus), Least Bell’s Vireo, Western Yellow-billed Cuckoo (Coccycus americanus occidentalis), Swainson’s Hawk (Buteo swainsoni), Bank Swallow (Riparia riparia), Tricolored Blackbird (Agelaius tricolor), and Little Willow Flycatcher (Empidonax traillii brewsteri), as well as other Neotropical migrant songbirds, year-round resident and wintering migrant P a g e | 3 songbirds, shorebirds, waterfowl, and California Quail (Callipepla californica; River Partners 2014). This report describes the results of our 2015-2016 efforts to (1) document any evidence of colonization by Least Bell’s Vireo on Phase 1 of the Dos Rios Ranch restoration site or the adjacent SJRNWR and (2) assess the response of the overall breeding landbird community to the Dos Rios Phase 1 restoration and how it compares to the breeding bird community using the older restored riparian habitat in the SJRNWR.

MONITORING OBJECTIVES Our work has been designed to meet the following objectives:

1. Phase 1 Dos Rios Ranch restoration monitoring a. Document any evidence of colonization by Least Bell’s Vireo on the Phase 1 of the Dos Rios Ranch restoration site. b. Describe the post-restoration riparian landbird community on Phase 1 of the Dos Rios Ranch restoration site.

2. Historical restoration site monitoring a. Survey a sample of historical restoration sites on the SJRNWR that are 3-6 and 9-12 years old to document any evidence of recolonization by Least Bell’s Vireo. b. Compare the riparian landbird communities of restoration sites that are 3-6 and 9-12 years old. The information will be used evaluate the success of these restoration sites and further refine performance criteria for Phase 1 site, as well as future restoration phases at Dos Rios Ranch.

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Figure 1. Map of San Joaquin River NWR and Dos Rios Ranch Phase 1 point count stations, Stanislaus County, California. 4

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METHODS AND RESULTS

Study areas and sampling design Because Least Bell’s Vireos are likely to occur at low densities, previous efforts have explored a variety of methods to survey for them (Dettling et al. 2012). Following this precedent, we used a combination of point count surveys and Least Bell’s Vireo specific searches to ensure that all potential Vireo habitat on the Phase 1 project site was fully covered. The 80 ha (198 ac) in Phase 1 include relatively large areas of mixed riparian forest, mixed shrub thicket, and willow riparian forest in which we established 12 point count stations. We complemented these point count stations with surveys in areas of the SJRNWR that had been restored between 2004 and 2012. We grouped these areas into two restoration age groups: those that were 3-6 years old at the time of the surveys in 2015-2016 (restored between 2009 and 2012), and those that were 9-12 years old (restored between 2004 and 2007). The 3-6 year old sites are the most recent restorations on the SJRNWR, providing a useful comparison to the Dos Rios Ranch restoration, and are the most likely to provide suitable habitat for Least Bell’s Vireo, which prefers relatively early successional riparian vegetation. The 9-12 year old sites provide a perspective on the potential longer-term trajectory of these restorations as they mature and the richness of the landbird community they support. We used previously-established SJRNWR point count stations and incorporated new ones for a total of 11 point count stations in 3-6 year old restorations and 16 in 9-12 year old restorations. In total, we surveyed 39 point count stations in the Dos Rios Ranch and SJRNWR restoration areas (Figure 1; Appendix A). All point count stations were located at least 200 meters apart from each other and at least 25 meters from the edge of the restoration unit to give broad, representative coverage of the study area.

Bird surveys and vegetation monitoring at point count stations We used a five-minute point count method (Ralph et al. 1993), surveying each of the point count stations twice during the peak breeding season for the Central Valley (once in May and once in June) in each year, for a total of 156 surveys. Surveys were conducted on mornings without strong wind or rain, and within the first 3-4 hours after local sunrise. Survey occasions were separated by at least ten days. All observers had expertise in bird identification and were trained on the survey methods. We recorded the method of detection (song, visual, or call) and any observed breeding behavior (e.g., copulation, nest material, or food carry), and estimated the distance to all birds detected. Distances to detected birds were estimated in 10 m bands outward to 50 m, followed by three larger bands extending from 50 to 75 m, 75 m to 100 m and beyond 100 m. In 2015, Trevor Watts and Mark Dettling surveyed all points between 14 May and 16 June, and in 2016, Bobby Walsh surveyed all points between 12 May and 30 June (Table 1). At all point count stations, we also captured the key components of the riparian vegetation structure and composition within 50 m of the station using a simplified relevé survey (based on Ralph et al. 1993). Vegetation data included visual estimates of canopy height (the average height of trees in the overstory to the nearest m) and the percent cover of vegetation in 3 separate layers: tree cover (woody plants >5 m tall), shrub cover (woody and non-woody plants within the height range of 0.5 – 5 m), and ground cover (including separate estimates for grass and

P a g e | 6 herbaceous cover; Appendix B). In 2015, Trevor Watts conducted vegetation surveys at the point count stations during 11-16 June. In 2016, Bobby Walsh conducted vegetation surveys at the point count stations during 27-30 June. On Dos Rios ranch, all 12 point count locations were co- located with River Partners long-term vegetation monitoring plots. On the refuge, 22 of the 27 point count locations were co-located with long-term vegetation monitoring sites. Although we did not analyze the River Partners vegetation data, these data could be used with the bird data for further analysis in the future.

Table 1. Dates of point count surveys conducted at the Dos Rios Ranch Restoration Phase 1 and SJRNWR 3-6 and 9-12 year old restoration areas. All sites were surveyed once in May and once in June in each year.

Dos Rios Phase 1 SJRNWR restoration sites Visit Year (1-2 years old) (3-6 years old) (9-12 years old) 2015 1 14 May 20-21 May 19-20 May 2 11 June 15-16 June 12-15 June 2016 1 19 May 26-27 May 12, 27 May 2 27 June 29-30 June 28-29 June

Riparian landbird response to restoration Species densities We first analyzed the point count data to compare the densities of breeding riparian landbirds using the Dos Rios Ranch restoration Phase 1 to densities in the older SJRNWR restoration sites as well as to the Central Valley Joint Venture riparian landbird density objectives for the San Joaquin region (Dybala et al. In press). We focused on a suite of nine focal species selected by the Central Valley Joint Venture to capture a broad range of life histories and specific vegetation associations (Table 2; Dybala et al. In press). Eight of these nine species were detected on our point count surveys, suggesting they are breeding in the Dos Rios Ranch and SJRNWR region. We conducted distance sampling analyses (Buckland et al. 2001; Thomas et al. 2010) of the point count data, using the R packages “Distance” and “mrds” (Laake et al. 2016; Miller 2016; R Core Team 2016) to fit detection functions and estimate species densities with a 95% confidence interval while correcting for differences in detection probability. We estimated the densities of the six focal species with a sufficient number of detections to analyze (Table 2), including three species associated with dense understory (, Spotted , and Common Yellowthroat) and three species associated with more mature riparian woodland or forest (Black- headed Grosbeak, Ash-throated Flycatcher, and Nuttall’s Woodpecker). For Common Yellowthroat and Nuttall’s Woodpecker, we supplemented detections with additional point count data collected from the San Joaquin region of the Central Valley, solely to aid in fitting detection functions.

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Table 2. Central Valley Joint Venture riparian focal species, nest substrates, and vegetation associations (Dybala et al. In press), shown with the total number of 2015-2016 detections within 100 m of point count stations at Dos Rios Ranch and SJRNWR, Stanislaus County, California. Special status focal species not shown (and not detected on point count surveys) include: Least Bell’s Vireo, Western Yellow-billed Cuckoo (Coccyzus americanus occidentalis), and Bank Swallow (Riparia riparia).

Species common name Nest Vegetation Total (Scientific name) substrate associations detections

A. Species associated with dense understory Song Sparrow Herb, Dense understory 138 (Melospiza melodia) Shrub Spotted Towhee Ground Dense understory and ground 222 (Pipilo maculatus) cover Common Yellowthroat Herb, Dense understory and ground 19 (Geothlypis trichas) Shrub cover, esp. near river edges and wetlands

B. Species associated with dense, shrubby riparian thickets Lazuli Bunting Herb, Open scrubby and early- 2 (Passerina amoena) Shrub successional riparian, edges Yellow Warbler Shrub Riparian thickets, esp. willows 3 (Setophaga petechia) Yellow-breasted Chat Shrub Dense, shrubby riparian thickets 0 (Icteria virens)

C. Species associated with large trees and mature riparian woodland Black-headed Grosbeak Tree Complex habitat with large trees 37 (Pheucticus melanocephalus) and dense understory Ash-throated Flycatcher Tree, Mature, open riparian woodland 34 (Myiarchus cinerascens) 2° cavity Nuttall’s Woodpecker Tree, Mature riparian woodland 11 (Picoides nuttallii) 1° cavity

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Overall, the densities of the 6 riparian focal species were remarkably similar across the restoration sites, despite the differences in their ages and the different vegetation associations of the focal species (Figure 2). We noted a general pattern of a slight, though not statistically significant, increase in densities with restoration age, even among species more associated with dense understory. A notable exception was Song Sparrow, which was abundant at Dos Rios, already surpassing the CVJV density objective. This species takes readily to open areas with dense understory like those currently available at Dos Rios Ranch, and densities could decline as the vegetation matures. In contrast, we would expect the densities of the focal species that require more mature riparian trees to increase with restoration age. For example, Nuttall’s Woodpeckers must have trees large enough for excavating nest cavities, and Ash-throated Flycatchers use nest cavities abandoned by woodpeckers or created by rot in larger, older trees. The densities of these focal species were low relative to CVJV density objectives, even among the 9-12 year old SJRNWR restoration sites, suggesting a lack of the large trees and tree cover that would attract higher densities of these species.

Figure 2. Densities of CVJV focal riparian species with 95% confidence intervals at the 1-2 year old Dos Rios restoration Phase 1, 3-6 year old restoration sites at SJRNWR, and 9-12 year old restoration sites at SJRNWR. Dashed lines represent Central Valley Joint Venture density objectives (Dybala et al. in press). Note the different ranges on the y-axis for the top row of species (associated with dense understory) and the bottom row of species (associated with mature riparian forest).

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The three focal species with the fewest detections were Yellow Warbler, Lazuli Bunting, and Yellow-breasted Chat, which was undetected (Table 2). These three species are all associated with dense, especially early successional riparian thickets, and are also among the least common of the focal species, having relatively low breeding densities in the San Joaquin region compared to the other focal species (Dybala et al. In press). Similarly, Common Yellowthroat also had relatively few detections compared with Song Sparrow and Spotted Towhee even though all 3 are associated with dense understory, but this species also has far lower breeding densities in the San Joaquin region (Dybala et al. In press). Thus, for these less common species, there are fewer individuals available to respond to restoration at this time.

Species richness We also examined patterns of species richness in relation to restoration age and vegetation characteristics. Over both years of monitoring at Dos Rios Ranch and SJRNWR, we detected a total of 26 species within 100 m of one of our point count stations (not including species only detected flying over). Within each restoration age group, the median number of species detected from point count stations in the Dos Rios Ranch restoration phase 1 (n = 14) was the same as the 3-6 year old SJRNWR restoration sites, and slightly lower than the 9-12 year old SJRNWR restoration sites (n = 17; Figure 3). However, we detected 25 of the 26 species at a single point count station in the Dos Rios Ranch restoration Phase 1 (point DORI-09), the greatest number of species detected from any single point count station over the two years of monitoring.

Figure 3. Total number of species detected within 100 m of point count stations in the Dos Rios Ranch restoration Phase 1 (1-2 years old) in comparison to 3-6 year old and 9-12 year old restoration sites in the SJRNWR. Each boxplot shows the median (horizontal line), 25th-75th percentiles (box), and range (whiskers) of the number of species detected from point count stations in each age group. The single dot for Dos Rios represents an outlier (station DORI-09), with more species detected than any other station.

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Species richness at each point count station was positively associated with the percent of tree, shrub, and ground cover (herbaceous plants and grass), as well as canopy height within 50m of each point count station (Figure 4). The relationships between species richness and tree, shrub, and ground cover were all statistically significant (p < 0.05) and canopy height approached significance (p = 0.11). Point DORI-09, which had the highest species richness of any point, is notable in that it had greater tree cover than any of the other Dos Rios Ranch points (Figure 4A). However, we estimated that no point count stations in restoration sites of any age had more than 30% tree cover within 50 m. We presume that the relatively large number of species detected from point DORI-09 is due to a combination of the densely planted vegetation, the presence of nearby surface water due to irrigation at Dos Rios and in the nearby orchard, and the presence of electrical wires which provided perches for some species.

Figure 4. Relationship between species richness and vegetation characteristics: (A) tree cover (%), (B) shrub cover (%), (C) tree canopy height (m), and (D) ground cover (%), including both herbaceous plants and grass. A p-value < 0.05 indicates a significant correlation between species richness and the vegetation characteristics.

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Least Bell’s Vireo monitoring We listened and watched for Least Bell’s Vireos during all point count surveys, including during travel between point count stations, and during additional visits to the study area for targeted vireo searches. We spent a total of 107 hours searching for Least Bell’s Vireos, and an estimated additional 50 hours including the point count surveys. Despite extensive searches, no Least Bell’s Vireos were located in 2015. However, on 14 June 2016, a Least Bell’s Vireo was detected by Eric Hopson, SJRNWR Manager, and he requested a follow-up confirmation of the observation. Bobby Walsh visited the refuge the next morning, met with Hopson, and the two were able to relocate the bird in the same spot where it had been seen initially. The bird was identified as Bell’s Vireo by appearance and song, and it was identified as the “Least” subspecies (Vireo bellii pusillus) on the basis of its overall gray plumage (Figure 5). The eastern subspecies are much more saturated olive, and the Arizona subspecies tends toward browner-gray plumage, though differences are slight (Kus et al. 2010). Walsh passively observed the bird from a distance so as not to interfere with its normal behavior, and recorded field marks including plumage, vocalizations, and behavior, as well as GPS coordinates, audio, and video (Appendix C). Observations were conducted over many consecutive hours to identify any evidence of a mate or breeding behavior, such as carrying food or nest material. At no time were playback devices used or were attempts to capture the bird made.

Figure 5. Least Bell’s Vireo male from June 2016.

Over several mornings of observation, the vireo was observed moving methodically throughout the adjacent areas of the refuge, covering a total of approximately 2.95 hectares (Figure 6). It was not strictly restricted to restored areas but moved readily across a dirt road, approached an almond orchard to the west, and used areas of the refuge both accessible to and off-limits to the public.

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Figure 6. Map of Least Bell’s Vireo male territory from June 2016. The territory was approximately 2.95 hectares.

The bird’s preferred location remained the spot where it had been initially seen. This consisted of a clump of mature black willows (Salix goodingii) and a few cottonwoods (Populus fremontii) with an understory dominated primarily by mugwort (Artemisia douglasiana) with some Sonoma hedgenettle (Stahcys stricta) in shadier patches. There was open water nearby. The other areas used by the vireo were more varied, but it was never far from tall, mature black willows or water. The most abundant birds in its immediate vicinity were Common Yellowthroats, three pairs of which nested nearby. Other common neighbors were Western Kingbird, House Wren, Tree Swallow, American Robin, Yellow Warbler, Song Sparrow, Spotted Towhee, Black-headed Grosbeak, and Bullock’s Oriole. The vireo could be detected from at least 50 m due to its frequent vocalizations – an average of 9.3 songs per minute in the early morning diminishing somewhat as the day progressed. The bird was classified as a territorial but unmated male; it stayed in one area but there was no evidence that it was actively breeding. It was never observed in the presence of another vireo, and all observed prey captures (mainly Lepidoptera larvae) were consumed by the bird itself rather than carried to nestlings or fledglings. Further, no lapse in singing or movement was detected that would suggest incubation, a duty shared by both sexes in this species (Kus et al. 2010). After the initial discovery, the bird was observed again on subsequent dates by Hopson and Walsh as well as by Stanislaus Audubon President Sal Salerno and two other Audubon members. The last confirmed sighting was late in the morning of 27 June by Walsh. The following morning, he returned to the refuge for point counts in another area and could not locate the vireo before or after, or during any of several subsequent trips and broader searches of the area.

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Estimating Least Bell’s Vireo Numbers in Central and Northern California Recent modelling of habitat suitability suggests that parts of the Central Valley are highly suitable for Bell’s Vireos (Klicka et al. 2016; Figure 7), yet there was only one male observed in the past two years of survey efforts. Why the mismatch? The modelling was based on climate suitability, not habitat, so a lack of suitable riparian vegetation may provide an explanation for much of the Central Valley. However, an equally important consideration is how many Bell’s Vireos actually disperse into Central and Northern California, especially for sites like Dos Rios Ranch and the SJRNWR that have suitable habitat for a wide range of riparian songbirds.

Figure 7. Maps showing the contemporary occurrence of Bell’s Vireos (left) and modeled niche suitability (right), reproduced from Klicka et al. (2016). The red areas are the most suitable, blue least. Suitability was based on climate, not vegetation.

One of the most comprehensive sources of contemporary bird observations is the Cornell Lab of Ornithology’s eBird database. Thousands of checklists are submitted to the database website each month by California birders, so it is a useful barometer of general bird abundance and distribution. We queried the database for all Bell’s Vireo observations (i.e., not strictly limited to Least Bell’s Vireos, as it may not be possible to determine subspecies in the field). We then focused on records from Central and Northern California, defined here as north of Fresno to determine the number of birds at a particular location and their duration there. In all, 28-30 Bell’s vireos were reported between 1993 and 2016, an estimated average of 1.3 Bell’s Vireos observed per year. This estimate corresponds well with data compiled by Howell et al. (2010). The authors of that effort gathered Bell’s Vireo sightings in Northern California from 1983-2007 using reports in North American Birds, Central Valley Bird Club Bulletin, and unpublished PRBO data. They found 30 records in 24 years, which also produces an estimated average of 1.3 Bell’s vireo observations in Central and Northern California per year. While some vireos almost certainly go undetected or unreported, the annual rate of observations remains low almost a decade after Howell et al.’s (2010) compilation of Bell’s Vireo observations despite additional restoration of riparian habitat in Central and Northern California. Further, the vast majority of eBird records were of single birds, and occurrences were spread out across many counties and across all months of the year except for February and March (Table 3). Thus, Bell’s Vireos in Central and Northern California remain rare and widely scattered in both time and

P a g e | 14 space, and recolonization of suitable habitat in the Central Valley will depend on whether more birds disperse north of their stronghold in Southern California. More active management strategies, such as the translocation of birds from Southern California, have been suggested (Franzreb 1990) but never been pursued.

Table 3. Summary of records of Bell’s Vireos on Central and Northern California based on eBird data queried through July of 2016. Note that not all detected birds are reported to this database. For example, the 2005-6 breeding pair at SJRNWR was not reported by eBird users.

County Year Count Months Present Notes

Inyo 1993 1 May Inyo 1994 1 May Santa Cruz 1996 1 May Inyo 2002 1 December Mono 2002 1 May Contra Costa 2005 1 May San Francisco 2005 1 November Sacramento 2006 1 August Fresno 2006 1 January Stanislaus 2007 1 May SJRNWR Inyo 2009 2 May San Francisco 2009 1 June Southeast Farallon Island Inyo 2010 1 May Merced 2010 1-2 May, July San Mateo 2010 1-2 May – June Yolo 2010 2 April – August Santa Cruz 2011 1 September Merced 2012 2 May – July Stanislaus 2012 1 May – July SJRNWR Yolo 2012 1 May Sacramento 2013 1 April Inyo 2014 1 April Inyo 2015 1 January Sonoma 2015 1 October Santa Clara 2016 1 May

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RECOMMENDATIONS (1) Continue to evaluate restoration success using a broad suite of riparian species. Restoration objectives for a broad suite of riparian species provide multiple metrics of restoration success that reflect different aspects of the riparian habitat. For example, the CVJV density objectives for riparian landbird focal species (Dybala et al. In press) provide a way to evaluate the responses of species with a broad range of habitat requirements and will collectively provide better insights into changes in overall riparian habitat condition than the response of a single species. While the recolonization of rare and endangered species like the Least Bell’s Vireo is a major goal, a lack of response thus far may only be indicative of their continued rarity in central and northern California. We recommend continuing to monitor the Dos Rios Ranch site for colonization by Least Bell’s Vireo over the next 3-5 years, during which we expect the vegetation to mature into the structure they prefer. We also recommend surveying the landbird community again once it is 8-10 years old to evaluate the response of the full suite of riparian landbird focal species and the contributions of the Dos Rios Ranch restoration to the CVJV objectives.

(2) Maximize habitat suitability for Least Bell’s Vireos by ensuring that restored sites are maturing into the required vegetation structure. Because vireo dispersal into central and northern California is rare, maximizing habitat suitability may increase the likelihood that dispersing vireos stop in the Dos Rios Ranch and SJRNWR area. A habitat suitability model has identified that nesting vireos use riparian vegetation with dense and layered canopy over 8 m tall, with highest foliage density within 1-2 m of the ground where they place their nests (Kus 1998). In evaluating riparian restoration sites in southern California, Kus (1998) found that many restoration sites only partially matched the habitat suitability model, for example with patches that were suitably dense but failed to meet the canopy height requirement or were suitably tall but lacked sufficient understory. We estimated average canopy heights < 8 m at many of our point count stations, and vegetation cover in all layers was highly variable (Figure 4). Thus, as the Dos Rios Ranch site matures, we recommend comparing the vegetation structure against the recommendations from this habitat suitability model.

(3) Develop a plan for monitoring vireo nest attempts. The Least Bell’s Vireo we discovered did not find a mate and nest, but if it had, we would have needed a plan in place for monitoring nest success. To prepare for future vireo nest attempts in the Dos Rios Ranch and SJRNWR area, we recommend developing a monitoring plan that meets State and Federal guidelines for approaching nests, as well as any desired interventions to prevent brood parasitism by Brown- headed Cowbirds (e.g., addling or removing eggs). We also recommend identifying who will obtain and maintain the necessary permits to conduct monitoring, and that the appropriate permitting processes are initiated well before they become necessary.

(4) Consider providing habitat for Tricolored Blackbirds at Dos Rios Ranch. In 1914, John Mailliard reported a colony of thousands of nesting Tricolored Blackbirds in a marsh at a site described as “Ranchos Dos Rios” in Stanislaus County (Mailliard 1914). Although we did not formally survey for breeding Tricolored Blackbirds, we did encounter a flock flying across the Dos Rios Ranch study area in 2016 (Appendix E). The historical and present-day occurrence of Tricolored Blackbirds at Dos Rios Ranch raises the potential for this area to host a colony today. If land managers decide that providing habitat for Tricolored Blackbirds is a priority, we encourage them to contact the Tricolored Blackbird Working Group

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(http://tricolor.ice.ucdavis.edu/tbwg) to identify the best strategies for enhancing habitat conditions and employing conspecific attraction techniques (Schlossberg and Ward 2004).

(5) Consider monitoring black rats, cowbirds, or other species that may have negative impacts. A growing concern among restoration ecologists is that restored sites can inadvertently become ecological traps if they attract wildlife that ultimately experience reduced fitness (Battin 2004), such as an attractive breeding site that also attracts unusually high densities of nest predators and parasites, such as black rats (Rattus rattus) or Brown-headed Cowbirds (Molothrus ater). The risk of Central Valley riparian restoration creating an ecological trap through cowbird parasitism is low, because population-level impacts of cowbird parasitism are low for most species, cowbird densities in the Central Valley did not increase with restoration age, and parasitism rates are generally not higher in restored riparian habitat than remnant riparian habitat (Dybala et al. 2014). In comparison, black rats did increase in abundance with riparian restoration age on the Sacramento River (Golet et al. 2008), and they can be an important nest predator (Small 2005; Hammond 2008), yet their population-level impacts remain unclear. Recommendations for minimizing the risk of cowbird parasitism are well-established and include managing for a dense shrub layer, eliminating grazing and mowing near riparian areas, and minimizing the availability of nearby cowbird food sources, such as those provided by dairies and feedlots (Dybala et al. 2014). Yet, the most common recommendation for minimizing cowbird risk is simply to restore habitat, specifically to improve the continuity of large tracts of habitat, widen narrow corridors, and minimize edges, all of which may have the added benefit of reducing access to many nest predators (Dybala et al. 2014), possibly including black rats. It is not yet clear how best to limit habitat suitability for black rats, although they appear to be strongly associated with areas of dense vine cover, particularly Himalayan blackberry (Rubus discolor; Whisson et al. 2007). Trapping and removal efforts for either species are likely to be expensive and require ongoing annual effort since they may rapidly disperse into areas where individuals have been removed (Rothstein and Peer 2005), and it is unclear whether a sufficient number of black rats can be removed to have a significant impact on nest success rates (Hammond 2008). Because these species remain a concern for riparian restoration in the Central Valley, and because more research and monitoring may help identify best management practices, we recommend considering whether black rats, cowbirds, or other species that may have a negative impact on restoration success, may be worth monitoring in future efforts.

(6) Evaluate whether current restoration designs are climate-smart. We recommend incorporating climate change projections into riparian restoration planning and design (Perry et al. 2015; Gardali et al. In prep). For example, consider whether current designs use plant species and varietals that will continue to thrive under projected climate conditions, including changes in temperature and precipitation, more extreme weather patterns, and changes in hydrology and groundwater availability. The long-term success of current riparian restoration efforts will depend on whether species being planted now will survive for decades.

(7) Continue efforts to restore riparian vegetation and improve floodplain connectivity. Riparian ecosystems are important hotspots of biodiversity, and efforts to restore riparian vegetation and improve river processes are essential to supporting large, resilient populations of riparian- dependent bird species in the Central Valley (Dybala et al. In press). Further, riparian restoration can provide many additional benefits to local communities, including: reducing downstream

P a g e | 17 flood risk, improving water quality, and recharging groundwater (Naiman et al. 2010); sequestering large amounts of carbon (Matzek et al. 2015); supporting pollinators and organisms that help control agricultural pests (Kremen et al. 2002; Buddle et al. 2004); as well as increasing property values, providing recreational opportunities, and attracting wildlife watchers who help support local economies (Carver 2013; Carver and Caudill 2013; Liu et al. 2013).

PROJECT DATA

Data management For all point count data collected as part of this monitoring program, the field crew have proofed the data and entered it into the California Avian Data Center (CADC; www.prbo.org/cadc). CADC is a secure, well-tested platform for managing, analyzing, and visualizing avian monitoring data (Ballard et al. 2008). It is a node of the Avian Knowledge Network (www.avianknowledge.net), which represents several interconnected bird data repositories. CADC data are available for viewing and downloading to outside researchers with an account. The vegetation data have been entered into an Access database that is backed up on Point Blue servers, and these data are available upon request. All hard copies of data forms have been scanned and stored at Point Blue headquarters in Petaluma, California, and the scanned digital copies have been stored on regularly backed-up Point Blue servers.

Other products In addition to the field work and data analysis described in this final report, Point Blue staff have worked on several additional products, including two presentations that discussed the Dos Rios Ranch restoration as an example of how the Central Valley Joint Venture objectives can be used to measure riparian restoration success and a newsletter article: Dybala KE, Rayburn A, Rentner J, Seavy NE, Gardali T (2015) Measuring restoration success: Applying the Central Valley Joint Venture population objectives for riparian birds. San Joaquin River Restoration Program workshop, June, Los Banos CA. Dybala KE, Seavy NE, Gardali T (2016) Measuring riparian restoration success using Central Valley Joint Venture objectives. California Society for Ecological Restoration (SERCAL), May 11-12, North Lake Tahoe CA. Rayburn A, Dybala K. 2015. Bird Response to Climate-smart Restoration in the San Joaquin Valley. River Partners JOURNAL 12:7.

We also created PowerPoint slides of the main findings in this final report for use in future presentations (Appendix D), and an annotated bird list describing field observations in 2016 (Appendix E).

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REFERENCES Ballard G, Herzog M, Fitzgibbon M, Moody D, Jongsomjit D, Stralberg D. 2008. The California Avian Data Center [web application]. Available from: www.prbo.org/cadc Battin J. 2004. When good love bad habitats: Ecological traps and the conservation of populations. Conservation Biology 18:1482–1491. doi: http://dx.doi.org/10.1111/j.1523-1739.2004.00417.x 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, UK. Buddle CM, Higgins S, Rypstra AL. 2004. Ground-dwelling assemblages inhabiting riparian forests and hedgerows in an agricultural landscape. American Midland Naturalist 151:15–26. doi: http://dx.doi.org/10.1674/0003-0031(2004)151[0015:GSAIRF]2.0.CO;2 Carver E. 2013. Birding in the United States: a demographic and economic analysis. Arlington, Virginia: U.S. Fish and Wildlife Service, Division of Economics, Arlington, VA. Available from: https://www.fws.gov/southeast/economicimpact/pdf/2011-birdingreport--final.pdf Carver E, Caudill J. 2013. Banking on nature: The economic benefits to local communities of National Wildlife Refuge visitation. U.S. Fish and Wildlife Service, Division of Economics, Washington, D.C. Available from: http://digitalmedia.fws.gov/cdm/singleitem/collection/document/id/1832/rec/1 Cormier RL, Gardali T, Wood JK. 2013. Assessing migratory stopover site quality for birds during fall migration along two California rivers. Western North American Naturalist 73:72– 79. doi: http://dx.doi.org/10.3398/064.073.0107 [CVJV] Central Valley Joint Venture. 2006. Central Valley Joint Venture implementation plan: Conserving bird habitat. U.S. Fish and Wildlife Service, Sacramento, CA. Available from: http://centralvalleyjointventure.org DeSante DF, George TL. 1994. Population trends in the landbirds of western North America. Studies in Avian Biology 15:173–190. Available from: http://www.birdpop.org/docs/pubs/DeSante_and_George_1994_Population_Trends_in_the_ Landbirds_of_Western_NA.pdf Dettling MD, Howell CA, Seavy NE. 2012. Least Bell’s Vireo and other songbird monitoring and threat assessment at the San Joaquin River National Wildlife Refuge, 2007-2009. Report to US Bureau of Reclamation, Grant R10AP20573. Point Blue Conservation Science, Petaluma CA. Available from: http://www.prbo.org/refs/files/12173_MarkDettling2012.pdf Dybala KE, Seavy NE, Dettling MD, Gilbert MM, Melcer R. 2014. Does restored riparian habitat create ecological traps for riparian birds through increased Brown-headed Cowbird nest parasitism? Ecological Restoration 32:239–248. doi: http://dx.doi.org/10.3368/er.32.3.239

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Dybala KE, Truan ML, Engilis A. 2015. Summer vs. winter: Examining the temporal distribution of avian biodiversity to inform conservation. Condor 117:560–576. doi: http://dx.doi.org/10.1650/CONDOR-15-41.1 Dybala KE, Clipperton N, Gardali T, Golet GH, Kelsey R, Lorenzato S, Melcer R, Seavy NE, Silveira JG, Yarris GS. In press. Population and habitat objectives for avian conservation in California’s Central Valley riparian ecosystems. San Francisco Estuary and Watershed Science. Franzreb KE. 1990. An analysis of options for reintroducing a migratory, native , the endangered Least Bell’s Vireo Vireo bellii pusillus in the Central Valley, California. Biological Conservation 53:105–123. doi: http://dx.doi.org/10.1016/0006-3207(90)90003-8 Gardali T, Campos B, Dybala KE, Herrera AD, Parodi JJ, McCreedy C, Seavy NE, Thalmayer I, Giambastiani L, and Warzybok P. In prep. A framework for making ecological restoration climate-smart. Gardali T, Holmes AL, Small SL, Nur N, Geupel GR, Golet GH. 2006. Abundance patterns of landbirds in restored and remnant riparian forests on the Sacramento River, California, U.S.A. Restoration Ecology 14:391–403. doi: http://dx.doi.org/10.1111/j.1526- 100X.2006.00147.x Gardali T, Seavy NE, DiGaudio RT, Comrack LA. 2012. A climate change vulnerability assessment of California’s at-risk birds. PLOS One 7:e29507. doi: http://dx.doi.org/10.1371/journal.pone.0029507 Goldman EA. 1908. Summer birds of the Tulare Lake region. Condor 10:200–205. Available from: https://sora.unm.edu/sites/default/files/journals/condor/v010n05/p0200-p0205.pdf Goldwasser S, Gaines D, Wilbur SR. 1980. The Least Bill’s Vireo in California: a de facto endangered race. American Birds 34:742–745. Available from: https://sora.unm.edu/sites/default/files/journals/nab/v034n05/p00742-p00745.pdf Golet GH, Gardali T, Howell CA, Hunt J, Luster RA, Rainey W, Roberts MD, Silveira JG, Swagerty H, Williams N. 2008. Wildlife response to riparian restoration on the Sacramento River. San Francisco Estuary and Watershed Science 6:jmie_sfews_10998. doi: http://dx.doi.org/10.5811/westjem.2011.5.6700 Grinnell J, Miller AH. 1944. The distribution of the birds of California. Pacific Coast Avifauna 27:1–608. doi: http://dx.doi.org/10.1038/156034b0 Hammond JL. 2008. Identification of nest predators and reproductive response of the Modesto Song Sparrow, Melospiza melodia mailliardi, to experimental predator removal [thesis]. Humboldt State University. Available from: http://hdl.handle.net/2148/406 Howell CA, Wood JK, Dettling MD, Griggs K, Otte CC, Lina L, Gardali T. 2010. Least Bell’s Vireo breeding records in the Central Valley following decades of extirpation. Western North American Naturalist 70:105–113. doi: http://dx.doi.org/10.3398/064.070.0111

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Humple DL, Geupel GR. 2002. Autumn populations of birds in riparian habitat of California’s Central Valley. Western Bird Bander 33:34–50. Available from: https://sora.unm.edu/sites/default/files/journals/wb/v33n01/p0034-p0050.pdf Klicka LB, Kus BE, Title PO, Burns KJ. 2016. Conservation genomics reveals multiple evolutionary units within Bell’s Vireo (Vireo bellii). Conservation Genetics 17:455–471. doi: http://dx.doi.org/10.1007/s10592-015-0796-z Knopf FL, Johnson RR, Rich TD, Samson FB, Szaro RC. 1988. Conservation of riparian ecosystems in the United States. Wilson Bulletin 100:272–284. doi: http://dx.doi.org/10.1097/00005176-200406001-00396 Knopf FL, Samson FB. 1994. Scale perspectives on avian diversity in western riparian ecosystems. Conservation Biology 8:669–676. doi: http://dx.doi.org/10.1046/j.1523- 1739.1994.08030669.x Kremen C, Bugg RL, Nicola N, Smith SA, Thorp RW, Williams NM. 2002. Native bees, native plants, and crop pollination in California. Fremontia 30:41–49. Available from: http://www.cnps.org/cnps/publications/fremontia/Fremontia_Vol30-No3and4.pdf#page=41 Kus BE. 1998. Use of restored riparian habitat by the endangered Least Bell’s Vireo (Vireo bellii pusillus). Restoration Ecology 6:75–82. doi: http://dx.doi.org/10.1046/j.1526- 100x.1998.06110.x Kus B, Hopp SL, Johnson RR, Brown BT. 2010. Bell’s Vireo (Vireo bellii). In: Rodewald PG, editor. The Birds of North America Online. Cornell Lab of Ornithology, Ithaca, NY. doi: http://dx.doi.org/10.2173/bna.35 Kus BE, Peterson BL, Deutschman DH. 2008. A multiscale analysis of nest predation on Least Bell’s Vireos (Vireo bellii pusillus). Auk 125:277–284. doi: http://dx.doi.org/10.1525/auk.2008.06038 Laake JL, Borchers DL, Thomas L, Miller D, Bishop J. 2016. mrds: Mark-Recapture Distance Sampling. Available from: http://cran.r-project.org/package=mrds Latta SC, Howell CA, Dettling MD, Cormier RL. 2012. Use of data on avian demographics and site persistence during overwintering to assess quality of restored riparian habitat. Conservation Biology 26:482–92. doi: http://dx.doi.org/10.1111/j.1523-1739.2012.01828.x Liu X, Taylor LO, Hamilton TL, Grigelis PE. 2013. Amenity values of proximity to National Wildlife Refuges: An analysis of urban residential property values. Ecological Economics 94:37–43. doi: http://dx.doi.org/10.1016/j.ecolecon.2013.06.011 Mailliard J. 1914. Notes on a colony of tri-colored redwings. Condor 16:204–207. Available from: https://sora.unm.edu/sites/default/files/journals/condor/v016n05/p0204-p0207.pdf Matzek V, Puleston C, Gunn J. 2015. Can carbon credits fund riparian forest restoration? Restoration Ecology 23:7–14. doi: http://dx.doi.org/10.1111/rec.12153

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Miller DL. 2016. Distance: distance sampling detection function and abundance estimation. Available from: http://cran.r-project.org/package=Distance Naiman RJ, Decamps H, McClain ME. 2010. Riparia: ecology, conservation, and management of streamside communities. Academic Press, Burlington, Massachusetts. Perry LG, Reynolds LV, Beechie TJ, Collins MJ, Shafroth PB. 2015. Incorporating climate change projections into riparian restoration planning and design. Ecohydrology 8:863–879. doi: http://dx.doi.org/10.1002/eco.1645 R Core Team. 2016. R: A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing. Available from: http://www.r-project.org Ralph CJ, Geupel GR, Pyle P, Martin TE, DeSante DF. 1993. Handbook of Field Methods for Monitoring Landbirds. General Technical Report PSW-GTR-144-www. Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture, Albany, CA. Available from: http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1104&context=usdafsfacpub [RHJV] Riparian Habitat Joint Venture. 2004. The riparian bird conservation plan: A strategy for reversing the decline of riparian associated birds in California. Version 2.0. California Partners in Flight. Available from: http://www.rhjv.org River Partners. 2014. Floodplain Expansion and Ecosystem Restoration at Dos Rios Ranch, Stanislaus County, California. Modesto, California. Rothstein SI, Peer BD. 2005. Conservation solutions for threatened and endangered cowbird (Molothrus spp.) hosts: separating fact from fiction. Ornithological Monographs 57:98–114. doi: http://dx.doi.org/10.2307/40166817 Schlossberg S, Ward MP. 2004. Using conspecific attraction to conserve endangered birds. Endangered Species Update 21:132-138. Available from: http://www.umich.edu/~esupdate/wholeissueoctdec2004/schlossberg.pdf Small SL. 2005. Mortality factors and predators of Spotted Towhee nests in the Sacramento Valley, California. Journal of Field Ornithology 76:252–258. doi: http://dx.doi.org/10.1648/0273-8570-76.3.252 Thomas L, Buckland ST, Rexstad EA, Laake JL, Strindberg S, Hedley SL, Bishop JRB, Marques TA, Burnham KP. 2010. Distance software: Design and analysis of distance sampling surveys for estimating population size. Journal of Applied Ecology 47:5–14. doi: http://dx.doi.org/10.1111/j.1365-2664.2009.01737.x [USFWS] U.S. Fish and Wildlife Service. 1998. Draft Recovery Plan for the least Bell’s vireo (Vireo bellii pusillus). Portland, OR: U.S. Fish and Wildlife Service. Available from: https://ecos.fws.gov/tess_public/profile/speciesProfile.action?spcode=B067 Whisson DA, Quinn JH, Collins KC. 2007. Home range and movements of roof rats (Rattus rattus) in an old-growth riparian forest, California. Journal of Mammalogy 88:589–594. doi: http://dx.doi.org/10.1644/06-MAMM-A-239R1.1

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APPENDICES

Appendix A. Point count coordinates Coordinates of the Dos Rios and SJRNWR point count stations in decimal degrees are included in the attachment sent with this report. File name: METADATA_pointcount_DORI-SAJO_2015- 16_coordinates.csv

Appendix B. Vegetation data and metadata Vegetation data and metadata are included in the attachment sent with this report. File names: DATA_vegetation_DORI-SAJO_2015-16.csv, METADATA_vegetation_DORI-SAJO_2015- 16.csv

Appendix C. Least Bell’s Vireo media and coordinates Video and audio recordings of the 2016 SJRNWR Least Bell’s Vireo is included in the attachment sent with this report. File names: LBVI_VIDEO_2016.mp4, LBVI_AUDIO_20160615_1.wav, and LBVI_AUDIO_20160615_2.wav. Coordinates outlining the territory of the Least Bell’s Vireo (as shown in Figure 6) are also included in the attachment sent with this report. File name: LBVI_coordinates_2016.csv

Appendix D. PowerPoint slides of key results PowerPoint slides of the key results from monitoring efforts are included in the attachment sent with this report. File name: RESULTS_DORI-SAJO_2015-16.pptx

Appendix E. Annotated bird list, 2016 This list is based on daily notes of birds made on most visits to SJRNWR and Dos Rios Ranch during 2016. It is important to note that not all areas were visited with equal frequency, so higher average counts do not necessarily mean a species is more common—simply that it was more common and/or conspicuous along survey and point count routes. Special status codes are federally endangered (FE), state threatened/endangered (ST, SE), and state species of special concern (SSC). Climate change vulnerable species (CCV) are those for which there is evidence that climate change will have a negative impact, due to intrinsic traits of the species that make it more sensitive to climate change (such as physiological tolerances) and/or the magnitude of climate change expected within the species’ range (Gardali et al. 2012). Central Valley Joint Venture species (CVJV) are riparian landbird focal species that have been selected because they collectively represent a broad range of life histories and specific vegetation associations and are expected to reflect the condition of riparian ecosystems (Dybala et al. In press).

Special Avg count High count, Detected at Species Notes Status per visit single visit Dos Rios Rarely seen with black-necked stilts American Avocet 0.1 1 in shallow water Few, mostly associated with edges American Crow 1.5 7 X near orchards American Goldfinch Abundant and widespread 8.2 21 X

American Kestrel Nested successfully at Dos Rios 0.3 2 X Several pairs associated with American Robin 1.8 4 X wooded areas Small groups soaring along river American White Pelican SSC, CCV 1.2 11 course Seen more frequently than Black- e g a P Anna's Hummingbird 0.9 5 X chinned hummingbirds

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Ash-throated Flycatcher CVJV Common and vocal 3.4 7 X 23

Special Avg count High count, Detected at Species Notes Status per visit single visit Dos Rios Barn Owl Flushed on point counts at SJRNWR 0.2 1

Barn Swallow Generally high overhead 0.2 2 FE, SE, CCV, Solitary male near SJRNWR main Bell's Vireo 0.1 1 CVJV parking area Belted Kingfisher Few but vocal, conspicuous 0.3 1 Very common in younger, shrubby Bewick's Wren 7.9 18 X restorations Black Phoebe Mostly found near water/structures 1.8 8

Black-chinned Hummingbird Seen collecting nesting material 0.2 1 In flight at dawn or flushed from Black-crowned Night-Heron 0.5 5 willows near water Commonly heard, seen feeding on Black-headed Grosbeak CVJV 4.3 9 X elderberries Vocal and conspicuous in shallow Black-necked Stilt 5.3 50 water Few males on territory in weedy Blue Grosbeak 0.3 3 areas of SJRNWR Usually detected calling on flights Brewer's Blackbird 0.7 7 overhead

Brown-headed Cowbird Very common in small groups 7.1 13 X e g a P Typically associated with older

Bullock's Oriole 3.2 7 X | restorations 24

Special Avg count High count, Detected at Species Notes Status per visit single visit Dos Rios Bushtit Small groups widely spread 7.5 21 X Extremely abundant at all sites, California Quail 71.4 200 X often large coveys Often heard in areas with mature California Thrasher 1.6 4 but open plantings California Towhee Common in dense vegetation 3.6 8 X

Cedar Waxwing Detected well into May 0.8 7 X Commonly seen foraging high Cliff Swallow 4.3 22 overhead in loose flocks Common Raven A couple soared overhead 0.2 2 Common in areas with water, dense Common Yellowthroat CVJV 3.6 11 X vegetation Tended to hunt along wooded Cooper's Hawk 0.3 1 X corridors Double-crested Cormorant Flyover 0.2 1 Readily used twigs, young plantings Downy Woodpecker 1.2 4 X for foraging Seen especially in/near agricultural Eurasian Collared-Dove 1.0 6 X settings

Common and often in groups on e g a P European Starling 11.1 28 X utility lines Routinely seen flying along river

Great Blue Heron 1.0 3 | course 25

Special Avg count High count, Detected at Species Notes Status per visit single visit Dos Rios Routinely seen flying along river Great Egret 5.4 33 X course Great Horned Owl Flushed on point counts at SJRNWR 0.3 1 Flushed at both Dos Rios and Green Heron 0.3 1 X SJRNWR on point counts House Common, fond of elderberries 10.9 38 X The occasional few seen, usually House Sparrow 0.5 3 X not far from structures Very vocal early in season, kept to House Wren 1.7 5 X wooded areas Killdeer Seen on gravel roads, levee banks 1.5 9 X

Lark Sparrow Prefer open country 0.2 2 Observed calling overhead in late Lawrence's Goldfinch 0.3 3 June, SJRNWR Calling and singing during Lazuli Bunting CVJV 0.6 4 migration, nesting uncertain Fairly common in open areas with Lesser Goldfinch 4.3 18 scattered trees Loggerhead SSC A pair or two at Dos Rios 0.7 3 X

Nesting in grassy areas and foraging e g a P Mallard 11.0 40 in flooded spots

Marsh Wren Very vocal in reed beds 4.6 17 X |

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Special Avg count High count, Detected at Species Notes Status per visit single visit Dos Rios Mourning Dove Very common and widespread 16.1 34 X Often heard calling, pairs widely Northern Flicker 1.7 6 X scattered Occasionally seen coursing over Northern Harrier SSC 0.4 2 X fields and marshes Thrive in restored areas with Northern Mockingbird 7.1 20 X mature shrubs Nesting along river and moving to Northern Rough-winged Swallow 2.0 12 grasslands to forage Stayed in woodlands with Nuttall's Woodpecker CVJV occasional movements into 1.7 6 X restored patches Found in dense shrubby areas with Oak Titmouse 0.7 3 X mature trees nearby A pair in young restored area of Dos Phainopepla 0.3 1 X Rios, ate golden currants Heard calling from shallow marshy Pied-billed Grebe 0.2 2 area at SJRNWR Common and conspicuous, Red-tailed Hawk 3.8 10 X juveniles present Large, noisy groups clumped across Red-winged Blackbird 30.5 82 X many areas Ring-necked Pheasant Males heard in open areas 0.2 2

e g a P

Rock Pigeon Flyover 0.1 1

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Special Avg count High count, Detected at Species Notes Status per visit single visit Dos Rios SSC, CCV, Very common, especially in dense, Song Sparrow 13.8 38 X CVJV well-established restorations Very common, most consistently Spotted Towhee CVJV 15.1 29 X vocal bird across seasons Noisy and conspicuous, many Swainson's Hawk ST, CCV juveniles, especially Dos Rios (high 3.8 9 X vole population, a preferred food) Associated with mature snags and Tree Swallow 4.8 20 X fields nearby Tricolored Blackbird SE, SSC Flock seen moving through SJRNWR 1.9 21 X A couple of males sang late into 0.3 2 spring, but no nesting detected Near powerline corridor at Western Bluebird 0.7 3 X SJRNWR, near orchard at Dos Rios Vocal, conspicuous breeding Western Kingbird 6.4 25 X residents of most open areas Few singing as shrubland Western Meadowlark 0.3 2 transitioned to grassland Western Scrub-Jay Usually seen in pairs 4.1 10 X

Western Tanager Migrant male singing 0.1 1 Several pairs in mature Western Wood-Pewee 2.0 7

cottonwoods at SJRNWR e g a P White-breasted Nuthatch In large oak among willows 0.1 1

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Special Avg count High count, Detected at Species Notes Status per visit single visit Dos Rios White-face Ibis Tight flocks often seen overhead 9.2 53 X Pair in the older restoration area at White-tailed Kite 0.3 1 X SJRNWR Largest group was hen with many Wood Duck 1.8 15 attendant ducklings Restricted to densely planted levee Wrentit 0.8 4 banks Heavily associated with mature Yellow Warbler CVJV, SSC black willows and cottonwoods 3.6 13 near water

e g a P Breeding birds observed at Dos Rios and SJRNWR, left to right:

Western Wood-Pewee, Bullock’s Oriole, Loggerhead Shrike, Swainson’s Hawk.

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