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Kus and Whitfield OM pub.pdf events

Lead author: Barbara Kus
A  .—Cowbird (Molothrus spp.) control is a major focus of recovery-oriented management of two endangered riparian bird species, the Least Bell's Vireo (Vireo bellii pusillus) and Southwestern Willow Flycatcher (Empidonax traillii extimus). During the past 20 years, annual trapping of cowbirds at Least Bell's Vireo and Southwestern Willow Flycatcher breeding sites has eliminated or reduced parasitism in comparison with pretrapping rates and, thereby, signifi cantly increased seasonal productivity of nesting pairs. Enhanced productivity, in turn, has resulted in an 8-fold increase in numbers of Least Bell's Vireos; Southwestern Willow Flycatcher abundance, however, has changed li le, and at some sites has declined despite cowbird control. Although generally successful by these short-term measures of host population response, cowbird control poses potential negative consequences for long-term recovery of endangered species. As currently employed, cowbird control lacks predetermined biological criteria to trigger an end to the control, making these species' dependence on human intervention open-ended. Prolonged reliance on cowbird control to manage endangered species can shi a ention from identifying and managing other factors that limit populations—in particular, habitat availability. On the basis of our analysis of these long-term programs, we suggest that cowbird control be reserved for short-term crisis management and be replaced, when appropriate, by practice

2006 Factors Influencing the Incidence of Cowbird Parasitism of Least Bell's Vireos fact sheet

Lead author: Barbara Kus

Figure 3 Superior Ready Mix Mission Gorge Quarry Site LBVI Survey Areas other


2020 Recording - July 2020 SDMMP Management and Monitoring Coordination Meeting other


2001 Least Bell's Vireo Survey Guidelines protocol

The following suggested guidelines are provided to facilitate accurate assessments of the presence/absence of the State and federally endangered least Bell's vireo (Vireo bellii pusillus, vireo) to provide the Fish and Wildlife Service with sufficient information to adequately respond to requests for applicable Federal permits and licenses, and to fulfill our mandate to conserve and recover the species.

2020 Recording - July 2020 SDMMP Management and Monitoring Coordination Meeting recording

Lead author: Kris Preston
Recording for the July 22, 2020 SDMMP Mgmt. and Mon. Coordination Meeting. Least Bell's Habitat Suitability Model for California– Kris Preston (USGS/ SDMMP). Old-growth Chaparral Stores More Carbon than Younger Burnt Stands – Breahna Gillespie (UC Davis/ SDSU)

2008 Least Bell's Vireo Surveys on the San Luis Rey River, College Boulevard in Oceanside to Interstate 15 in Fallbrook, San Diego County, California report

Lead author: Barbara Kus
We surveyed for Least Bell's Vireo (Vireo bellii pusillus) along the San Luis Rey River, between College Boulevard in Oceanside and Interstate 15 in Fallbrook, California in 2008. We found 102 vireo territories, at least 48 of which were occupied by pairs. Four other vireos were transients. Vireos were concentrated in three clusters within the survey area. Only one vireo territory was found in the stretch of the river where giant reed (Arundo donax) was recently removed. Fourteen banded vireos were detected within the survey area. All positively identified banded vireos were originally banded along the San Luis Rey River.

2008 Least Bell's Vireos and Southwestern Willow Flycatchers at the San Luis Rey Flood Risk Management Pr report

Lead author: Kimberly Ferree
Surveys for the endangered least Bell's vireo (Vireo bellii pusillus) were conducted at the San Luis Rey Flood Control Project Area (Project Area) in the city of Oceanside, San Diego County, California, between 1 April and 15 July 2008. Three protocol surveys were conducted during the breeding season and supplemented by weekly territory monitoring visits. A total of 130 least Bell's vireo territorial males were identified; 117 were confirmed as paired, four were confirmed as single males, and nine were not confirmed as paired. Six transient vireos were detected during surveys. The least Bell's vireo population at the San Luis Rey Flood Risk Management Project Area increased by 20% (22 territories) from 2007, to achieve the highest number of territories ever detected at this site. We evaluated the impact of ongoing channel vegetation clearing and giant reed (Arundo donax) eradication that has occurred in the river channel since 2005 on the Project Area vireo population by comparing vireos in the river channel (Channel), where vegetation treatment has occurred, with sites outside of the river channel (Untreated), where vegetation treatment has not occurred. While the total number of territories in 2008 at Untreated sites outside of the river channel rebounded to the same number as in 2006, the number of territories in the Channel, increased by 11 territories since 2006. Therefore, despite major habitat changes between 2005 and 2008 within the Channel, vegetation removal did not appear to have a negative impact on the abundance of vireos in 2008. The majority of vireo territories (64%) occurred in habitat characterized as willow riparian. Sixteen percent of birds occupied habitat co-dominated by willows (Salix spp.) and cottonwoods (Populus fremontii), and 20% of territories were found in riparian scrub, dominated by mule fat (Baccharis salicifolia) and/or sandbar willow (S. exigua). Most vireo territories (61%) were established in habitat where 50 to 95% of the vegetation cover was native species, 38% of the territories were in habitat vegetated almost entirely (>95%) by native species, and one territory was placed in habitat where 5 to 50% of the vegetation cover was native. The most common exotic species within territories was A. donax followed by black mustard (Brassica nigra), poison hemlock (Conium maculatum) and tamarisk (Tamarix ramosissima). Nesting activity was monitored in 102 territories. Pair success was slightly higher fo

2008 Least Bell's Vireos and Southwestern Willow Flycatchers at the San Luis Rey River Flood Control Proj report

Lead author: Barbara Kus
Surveys for the endangered least Bell's vireo (Vireo bellii pusillus) were conducted at the San Luis Rey River Flood Control Project area in the city of Oceanside, San Diego County, California, between 1 April and 15 July 2007. Three protocol surveys were conducted during the breeding season and supplemented by weekly territory monitoring visits. One hundred and eight least Bell's vireo territorial males were identified; all but three males were paired. The vireo population in the project area declined by 9% (11 territories) from 2006, the largest drop observed in five years. Overall there was a net increase of five territories in the channel where exotic and native vegetation removal has occurred (Treated) and a net loss of 16 territories in the Untreated sites where vegetation removal will not occur (Untreated), suggesting that factors other than vegetation removal may have contributed to the 2007 decline. Factors contributing to the vireo decline may include drier conditions, reduced habitat quality, and human disturbance. The majority of vireo territories (70%) occurred in habitat characterized as Willow Riparian. Ten percent of birds occupied habitat co-dominated by willows (Salix spp.) and cottonwoods (Populus fremontii), and 20% of territories were found in Riparian Scrub, dominated by mule fat (Baccharis salicifolia) and/or sandbar willow (S. exigua). Most vireo territories (63%) were established in habitat where 50 to 95% of the vegetation cover was native species while 37% of the territories were in habitat vegetated almost entirely (>95%) by native species. Giant reed (Arundo donax) was the most common exotic species within territories followed by black mustard (Brassica nigra), poison hemlock (Conium maculatum) and tamarisk (Tamarix ramosissima). Nesting activity was monitored in 97 territories. Pair success from both treatments was comparable; 82% (50/61) of Treated pairs vs. 87% (27/31) of Untreated pairs were successful in fledging young from at least one nest. Nest success (number of nests fledging at least one young/total number of nests found) of pairs breeding in the channel (Treated) did not differ statistically from that of pairs breeding in the Untreated sites (49%; 60/122 vs. 59%; 32/54). Successful and failed nests within Treated and Untreated sites did not differ statistically in average nest height, height of the host plant, or the distance the nest was placed from the edge of the host plant. Eighty to ninet

2006 Least Bell's Vireo (Vireo bellii pusillus) 5-Year Review Summary and Evaluation report

Dr. Donald McGraw was contracted by the U. S. Fish and Wildlife Service to gather and synthesize information regarding the status of the Least Bell?s Vireo (Vireo Bellii pusillus). This review was subsequently compiled by Peter Back of the Carlsbad Fish and Wildlife Office and considered Dr. McGraw?s final report, office files, available literature, new survey information, and interviews of individuals involved with surveying, research, and management of this species. Least Bell?s Vireo survey reports submitted to the Ventura Fish and Wildlife Office were supplied to the Carlsbad Fish and Wildlife office by Chris Dellith of the Ventura Fish and Wildlife Office

2018 Least Bell's Vireo Response to Kuroshio Shot Hole Borer/Fusarium Dieback at the Tijuana River, California - 2017 Data Summary report

Lead author: Scarlett L. Howell

2001 Least Bell's Vireo Surveys and Nest Monitoring at Anza Borrego Desert State Park in 2000 report

Lead author: Barbara Kus

2008 Least Bell's Vireo Surveys at Selected Drainages in San Diego County, California report

Lead author: Barbara Kus

2007 Distribution and Breeding Activities of the Least Bell's Vireo and Southwestern Willow Flycatcher at the San Luis Rey River, San Diego County, California report

Lead author: James W. Rourke
Surveys and monitoring for least Bell's vireos (Vireo bellii pusillus) and southwestern willow flycatchers (Empidonax traillii extimus) were conducted on the San Luis Rey River, San Diego County CA, between 1 April and 21 August 2006. Vireo surveys were conducted from Interstate 15 west approximately 6.5 km to Mission Road. Southwestern willow flycatchers were surveyed in the same area, as well as downstream between Sante Fe Road and a point approximately 1 km upstream on the San Luis Rey River (Guajome Regional Park). Fifty-three territorial male least Bell's vireos were observed within the study area, 50 of which (94 percent) were confirmed as paired. Nine transient male vireos were also detected. Within the section of river consistently monitored since 2003, vireo numbers declined from 46 territories in 2005 to 31 in 2006. For the three years prior to 2006 the number of resident territorial males had remained relatively constant, varying from 40 to 46 territorial males. Nesting activity at 99 nests within 43 vireo territories was monitored. Thirty-six percent of nests were successful, fledging at least one vireo young, while 64 percent failed. Sixty percent of vireo nests whose contents were observed were parasitized by brown-headed cowbirds (Molothrus ater). Nest predation and cowbird parasitism accounted for 66 and 21 percent of failures, respectively. However, biologists "rescued" parasitized nests by removing cowbird eggs shortly after they were laid, allowing some to fledge young. Without "rescuing" it is likely that nest success would have been only 15 percent. In total, 86 vireo young fledged from 35 nests, and pairs fledged on average 2.2 young by the end of the breeding season. Thirteen least Bell's vireos banded prior to the 2006 breeding season were resighted within the study area. All had been banded as nestlings on the San Luis Rey River. Eight of the thirteen possessed a unique combination of color bands or were recaptured during the 2006 season and therefore could be identified to individual. Two of the eight were banded as nestlings outside of the study area and dispersed 14 and 4.9 km into the study area. All other uniquely color banded vireos fledged from and dispersed within the study area. The extent of their dispersal ranged from 0.8 to 4.4 km. Five other adult vireos that had been banded as nestlings with a single federal band were target netted, but attempts to recapture them were unsuccessful. Two additional adult vireos w

2008 Distribution, Abundance, and Breeding Activities of the Least Bell's Vireo at Marine Corps Base Ca report

Lead author: James W. Rourke
Surveys for the endangered least Bell's vireo (Vireo bellii pusillus) were conducted at Marine Corps Base Camp Pendleton, California, between 2 April and 11 July 2007. Drainages containing riparian habitat suitable for vireos were surveyed three to seven times. Because of difficulties in maintaining radio contact with Range Control the upper Santa Margarita River was surveyed once for vireos. Seven hundred and seven territorial male vireos were detected on 19 out of the 23 drainages/sites surveyed. Ninety-one percent of all vireo territories occurred on the seven most populated drainages, with the Santa Margarita River containing 58% of all territories on Base. Eighty percent of male vireos were confirmed as paired. In 2007, the overall size of the vireo population was similar to the 2006 population, differing by only 11 territories, and was within the range of approximately 700-1000 territories observed on Marine Corps Base Camp Pendleton for the past 13 years. The number of territories on 87% (20/23) of drainages surveyed differed by fewer than four territories compared to 2006, while 65% (15/23) of drainages differed by one or fewer territories. Six drainages increased in vireo numbers, 10 decreased, and 7 showed no change. Overall, the vireo population on Base decreased by 2% in 2007 compared to 2006. The majority of vireo territories occurred in habitat characterized as Willow Riparian, with 74% of males in the study area found in this habitat. An additional 6% of birds occupied willow habitat co-dominated by cottonwoods or sycamores. Thirteen percent of territories were found in Riparian Scrub, dominated by Baccharis salicifolia and/or Salix exigua. Six percent of the vireos used drier habitats including areas dominated by a mix of sycamores and oaks (1% of total) or upland vegetation (5%). Fewer than 1% of vireo territories were placed in habitat dominated by solely non-native vegetation. Nesting activity was monitored in 48 territories within the A. donax Removal and Reference monitoring areas. A total of 108 nests were monitored during the breeding season; however, 10 of these were not completed and were excluded from calculations of nest success and productivity. Nest success of pairs breeding in Reference and Removal sites did not differ significantly. Forty-seven percent (25/53) of Reference nests and 49% (22/45) of Removal nests successfully fledged young. Predation was believed to be the primary source of nest failu

2009 Distribution, Abundance, and Breeding Activities of the Least Bell's Vireo along the San Diego River, California report

Lead author: Suellen Lynn
Surveys for the endangered Least Bell's Vireo (Vireo bellii pusillus) were conducted along the San Diego River between 31 March and 23 June 2008. Riparian habitat suitable for vireos from Interstate 5 to the El Capitan Reservoir was surveyed three times. Eighty-two territorial male vireos were detected, forty-five of which were confirmed as paired. One transient vireo was also detected. Most (96%) vireo territories occurred in four of six sections surveyed: Santee (37%), Park (28%), Lakeside (17%), and Gorge (15%). The Valley survey section contained two vireo territories and no vireos were detected in the El Capitan survey section. The number of territorial Least Bell's Vireos detected in 2009 increased 30% from 2008. Vireo numbers increased in four of the six survey sections, with the largest increase in the Santee area (50%). The majority of vireo territories occurred in habitat characterized as mixed willow (Salix spp.) riparian, with 72% of territories in the study area found in this habitat. Twenty-four percent of territories occurred in willow habitat co-dominated by cottonwoods (Populus fremontii), and one territory each occurred in willow habitat co-dominated by sycamores (Platanus racemosa), riparian scrub, and non-native vegetation. A total of 84 banded Least Bell's Vireos were observed during the 2009 season. These included 40 adult vireos (26 banded prior to 2009 and 14 banded in 2009) and 44 nestlings that were banded for the first time in 2009. Of the 40 adult vireos, 39 were banded with unique color combinations and 1 was observed with a single metal light blue service band, indicating it had been banded as a nestling in 2008. The nestlings were banded with a single light blue numbered federal band on the right leg. Seventy-two percent (80% of males and 50% of females) of adult vireos banded prior to 2009 returned to the San Diego River in 2009. All returning adults occupied the same territory that they had occupied in 2008. One additional adult vireo that was not detected in 2008 was captured and banded in 2009. This vireo fledged from a nest on the San Luis Rey River in 2007, 55 km from his 2009 breeding site. Twenty-six percent (40% of males and 13% of females) of vireos banded as nestlings in 2008 were resighted in 2009, one of which was captured and banded on Marine Corps Base Camp Pendleton (61.3 km from his natal territory). The average distance first-year vireos dispersed from the San Diego River to all sites was 10.2 ± 22

2009 Distribution, Abundance, and Breeding Activities of the Least Bell's Vireo along the San Diego River, California report

Lead author: Mike J. Wellik
Surveys for the endangered least Bell's vireo (Vireo bellii pusillus) were conducted along the San Diego River between 31 March and 23 June 2008. Riparian habitat suitable for vireos from Interstate 5 to the El Capitan Reservoir was surveyed three times. Fifty-nine territorial male vireos were detected, 43 of which were confirmed as paired. Nine transient vireos were also detected. Most (98%) vireo territories occurred in four of six sections surveyed: Santee (34%), Park (31%), Lakeside (19%), and Gorge (15%). The Valley and El Capitan survey sections contained one or no territories. The number of territorial least Bell's vireos detected in 2008 was similar to the number detected in 1997 and approximately double the number detected in 1987. The distribution of vireos in 2008 shifted relative to that in previous years: more vireos were detected in the Park and Lakeside survey sections and fewer vireos were detected in the Valley, Gorge, Santee, and El Capitan survey sections than in 1997. The majority of vireo territories occurred in habitat characterized as mixed willow (Salix spp.) riparian, with 68% of males in the study area found in this habitat. The remaining 32% of males occupied willow habitat co-dominated by cottonwoods (Populus fremontii). Only one territory was dominated by exotic vegetation (salt-cedar; Tamarix ramosissima). A total of 74 least Bell's vireos were banded during the 2008 season. These included 21 adult vireos and 53 nestlings that were banded for the first time in 2008. The 21 adult vireos were banded with unique color combinations. The nestlings were banded with a single light blue numbered federal band (49 on the left leg and four on the right leg). Three other vireos that had been banded prior to 2008 were resighted along the San Diego River in 2008. One was banded as an adult in 2006 near its 2008 territory. Two others were banded as nestlings in 2007, one on the Santa Margarita River on Marine Corps Base Camp Pendleton and one on the Sweetwater River. These two birds moved 39.0 + 32.5 km from their natal sites to their 2008 breeding territories. Nesting activity was monitored in 30 territories within two Treatment sites (one giant reed (Arundo donax) removal site and one cowbird control site) and two Reference sites. Treatments had not occurred by the 2008 breeding season, so these results represent a pretreatment baseline. A total of 68 nests were monitored during the breeding season; howeve

2006 Distribution, Abundance, and Breeding Activities of the Least Bell's Vireo at Marine Corps Base Camp report

Lead author: Barbara Kus
Surveys for the endangered least Bell's vireo (Vireo bellii pusillus) were conducted at Marine Corps Base Camp Pendleton, California, between 1 April and 15 July 2005. All drainages containing riparian habitat suitable for vireos were surveyed three to seven times. A small number of other sites containing more marginal habitat were periodically checked throughout the season for vireos. Eight hundred and twenty-seven territorial male vireos were detected over 23 drainages. Ninety-two percent of all vireo territories occurred on the nine most populated drainages, with the Santa Margarita River containing 56 percent of all territories on Base. Seventy percent of all male vireos were confirmed as paired. The majority of vireo territories (62 percent) occurred in habitat characterized as Willow Riparian. The second most commonly used habitat type, Riparian Scrub (dominated by Baccharis salicifolia and/or Salix exigua), was occupied by 19 percent of the population. An additional eight percent of birds occupied willow habitat co-dominated by cottonwoods (Populus fremontii) or sycamores (Platanus racemosa). Habitat characterized by upland vegetation was used by 10 percent of vireos, with the remaining 1 percent occupying territories composed entirely of non-native vegetation. However, exotic plants were found to be dominant or co-dominant in approximately 20 percent of all vireo territories. The primary exotic plants found in vireo territories were poison hemlock (Conium maculatum), black mustard (Brassica nigra), giant reed (Arundo donax), and tamarisk (Tamarix spp.). Nesting activity was monitored in 62 territories within two Giant Reed Removal and two Reference monitoring areas. Nest success and productivity estimates of pairs breeding in Reference sites did not differ appreciably from those at Removal sites. Although nesting vireos at Removal sites exhibited a higher hatching rate (67% vs. 58%; percent of all eggs that hatched) and had higher hatching success (70 % vs. 59%, percent of nests with one or more hatchlings), average clutch size, average brood size, and the average number of young fledged per pair were not statistically different from the reference sites. A large proportion of vireos at both sites were successful in fledgling young from at least one nest as 93 percent (14/15) of Reference pairs and 85 percent (17/20) of Removal pairs, within fully monitored territories, fledged young. Successful and unsuccessful nests within Reference and Removal

2002 Surveys for the Least Bell's Vireo and Southwestern Willow Flycatcher at the San Luis Rey River report

Lead author: Barbara Kus
This report summarizes the results of least Bell's vireo (Vireo bellii pusillus) and southwestern willow flycatcher (Empidonax traillii extimus) surveys conducted in 2002 along the San Luis Rey River in San Diego County, California. The primary objectives of this study were to determine the number and location of least Bells' vireo and southwestern willow flycatchers within the survey areas, and document reproductive status of the southwestern willow flycatcher.

2003 Report of 2003 Brown-headed Cowbird Trapping Program For Mission Trails Regional Park - Year 3 report

INTRODUCTION The City of San Diego (City) is required to implement a brown-headed cowbird ( Molothrus ater, Cowbird) trapping program at Kumeyaay Lake as requi red by the Biological Opinion issued for construction of the Kumeyaay Campground . The focus trapping area for the program in 2003 was Kumeyaay Lake. Santee, San Diego County, California. Varanus Biological Services (Varanus) placed traps adjacent to nati ve riparian habitats (Southern Willow Riparian Forest and Southern Cottonwood-willow Riparian Forest) in the vicinity of the lake. Since the early 1980's, Cowbird trapping has been an important component of recovery measures in suppo1t ofrecovery of the federally endangered least Bell's vireo (see Morrison et al. 1999), which is a small. insectivorous migratory songbird. The breeding range of the least Bell's vireo is southern California including portions of the California deserts. Least Bell's vireos winter in Baja California. Mex ico and typically migrate northward to their breeding grounds in southern Cal ifornia between mid-March and mid-April and occasionally as late as early May. During the breeding season the least Bell's vireo inhabits an assortment of riparian habitats. Dense low growing thickets of willows (Salix spp.), mule fat (Baccharis salicif olia) , California blackberry ( Rubus ursinus), Douglas' mugwort (Artemisia douglasiana) or other similar species are essential components of the habitat. An overstory composed of willows. cottonwoods (Pop11!11s fi'emo ntii), and/or sycamores ( Platanus racemosa) is often present . Other nesting habitats are dense patches of herbaceous understory in Coast Live Oak Riparian Forest and Coast Live Oak Woodland (W. Haas pers. obs), and occasionally patches of non-native habitat (P. Famolaro pers. com.) that now commonly form intricate mosaics with native habitats throughout the current breeding range of this species. Once widespread through much of California. the breedi ng range of the Least Bell 's Vireo extended from the northern edge of the Sacramento Valley of California to no1ihern Baja California. Least Bell's vireo population numbers declined dramatically between the l 940's and mid-1980's (Franzreb 1989). Two factors are primarily responsible for the decline and hence the endangered status of the Least Bell 's Vireo: habitat loss resulting from eradication, fragmentation, and degradation of riparian habitats; and brood parasit ism by Cowbird s (U. S. Fish and Wildlife Ser

2001 2001 Upper San Luis Rey River and PAMO Valley Brown-headed Cowbird Control Program report

Lead author: Jane C. Griffith
A trapping program was implemented along the upper San Luis Rey River (uslr) and Pamo Valley (pv) in San Diego County, California, to protect nesting southwestern willow flycatchers (Empidonax trail/ii extimus, flycatcher, swfl), least Bell's vireos ( Vireo bellii pusillus, vireo, lbvi), and riparian cohabitants from brood parasitism by the brown-headed cowbird (Molothrus ater). Four traps were operated in each location (8 total) from 1 April to 30 June 2001. We removed 284 cowbirds (68 males, 42 females, and 1j 11veniles at 11slr; 103 males, 60 females, and 10juveniles at pv). In addition, 290 individuals of 8 non-target species were captured (47 at uslr, 243 at pv), of which all but 2 (0.7%) were released unharmed. Topical protection from cowbird parasitism allows targeted populations of host species to increase annual productivity and to grow, but does not affect the regional cowbird population (Griffith and Griffith 2000).

2009 2008 Species Survey Annual Report report

Lead author: Pete Famolaro
This report describes species monitoring and management efforts for the 2008 calendar year and is intended to fulfill annual reporting requirements pursuant U.S. Fish and Wildlife Service (USFWS) Recovery Permit TE813431-4 and California Department of Fish and Game (CDFG) Memorandum of Understanding (MOU) (2005). Sweetwater Authority's biologist, Peter Famolaro, is the principal investigator for these respective federal and state authorizations. In 2008, work under these permits included surveys for least Bell's vireo (Vireo bellii pusillus) and willow flycatcher (Empidonax traillii), as well as brown-headed cowbird trapping (Molothrus ater). All work was performed within the Sweetwater River watershed in southern San Diego County, California (Exhibit 1). 2008 Species Survey Report 2 In 2008, the Sweetwater Authority contracted the U.S. Geological Survey Western Ecological Research Center (USGS WERC) to assist in least Bell's vireo and willow flycatcher surveys. As such, USGS's work is also described in this annual report. All work by USGS WERC was performed pursuant to authorizations held by Barbara Kus PhD (USFWS Recovery Permit TE- 829554, CDFG 2006).

2003 2003 Upper San Luis Rey River and PAMO Valley Brown-headed Cowbird Control Program report

A trapping program was implemented along the upper San Luis Rey River (uslr) and Pamo Valley (pv) in,San Diego County, California, to protect nesting southwestern willow flycatcher (Empidonax traillii extimus, flycatcher, swfl), least Bell's vireo ( Vireo bellii pusillus, vireo, lbvi), and their riparian cohabitants from brood parasitism by the brown-headed cowbird (Molothrus ater). Four traps were operated in each location (8 total) from 1 April to 30 June 2003. We removed 207 cowbirds (54 males, 38 females, and 0 juveniles at uslr; 61 males, 48 females, and 6 juveniles at pv). In addition, 330 individuals of 8 non-target species were captured (79 at uslr, 251 at pv), of which all but 6 (l.8%) were released unharmed. Topical protection from cowbird parasitism allows targeted populations of host species to increase annual productivity and to grow between years, but does not affect the regional cowbird population (Griffith and Griffith 2000).

1998 1998 USFS Upper San Luis Rey River Brown-headed Cowbird Trapping Program report

Lead author: J. Turnbull
Introduction In an effort to both protect nesting Southwestern Willow Flycatchers as well as mitigate for potential indirect impacts from off-site grazing on Forest Service lands, the U.S. Forest Service has funded a yeai-ly Brown-headed Cowbird trapping program along the upper San Luis Rey River since 1992. The purpose of this trapping program is to reduce the threat and impact of brood parasitism to the endangered Southwestern Willow Flycatcher (Empidona:x trailli extimus). The Brown-headed Cowbird (Molothrus ater) is an obligate brood parasite which lays its eggs in the nests of other bird species and is dependent upon the host to incubate their eggs and rear their young. Averaging 6"-7" in length, the Brown-headed Cowbird is a medium sized songbird with sexually dimorphic plumage. Adult males are dark brown to gloss black with a brown head and neck. Females are slightly smaller than males and dull tan to light brown with indistinct streaking on the breast. Originally restricted to the midwest region of North America, the Brown-headed Cowbird expanded in both range and abundance following the settlement and alteration of natural habitats, particularly with the increase in agriculture and livestock production. Reaching California in the late 1800's, this species was first documented breeding in San Diego County in 1915 (Unit 1984), and had become well established within southern California by the 1930's (Rothstein 1994, Willett 1933). Songbird species or populations which had not evolved with the cowbird and have no experience with parasitism may be subject to significantly reduced reproductive success. Brood parasitism combined with other impacts, such as habitat loss and fragmentation can lead to declines in songbird species, especially those with an already limited population and distribution. Cowbird trapping has proven to be an effective method in the conservation efforts of sensitive- . songbird populations throughout the United States, and was initially utilized in the recovery efforts of the Kirtland's Warbler in Michigan (Mayfield 1977). Subsequently, cowbird trapping has become an important tool in the management of several other sensitive songbird species, including the Black-capped Vireo, Least Bell's Vireo, and Southwestern Willow Flycatcher.

2015 Riparian Bird Surveys for South and East Tecolote Canyon report

Riparian bird surveys were conducted in the southern and eastern portions of Tecolote Canyon in order to determine presence or absence of sensitive riparian species, focusing primarily on detection of least Bell's vireo (Vireo bellii pusillus).The purpose of the riparian bird surveys was 1) to determine the current status of least Bell's vireo where the bird had been documented previously, and 2) to expand the survey area to East Tecolote Canyon where additional potentially suitable habitat occurs. The results from the surveys will provide updated information on the status of sensitive riparian bird species within the southern and eastern portions of Tecolote Canyon to guide management as detailed in the Draft Natural Resources Management Plan for Tecolote Canyon Natural Park.

1998 1997 Sensitive Species Survey Results for Pine Creek and Hauser Canyon Wilderness Areas, Descanso Ranger District, Cleveland National Forest, San Diego County, California. report

Lead author: Jeffery M. Wells
The following report summarizes the results of sensitive species surveys conducted for the Southwestern Willow Flycatcher (Empidonax traillii extimus), Least Bell's Vireo (Vireo bellii pusillus), Southwestern Arroyo Toad (Bufo microscaphus califomicus), and Southwestern Pond Turtle ( Clemmys marmorata pallida). Surveys were performed on the Pine Creek, Bauser Creek, and Cottonwood Creek drainages within the Pine Creek and Bauser Canyon Wilderness areas of the Cleveland National Forest. The purpose of these surveys was to determine both species presence, population number, and breeding status, as well as habitat conditions within the survey areas.

2010 Encinas Creek Habitat Conservation Area (Formerly known as the North County Habitat Bank) Annual Work Plan October 2010 - September 2011 report

Introduction This annual work plan has been developed from the guidelines for goals and objectives set forth in the North County Habitat Bank Long-Term Management Plan (HMP) (Helix 2007) The HMP includes management requirements set forth by the City of Carlsbad (City), the United States Fish and Wildlife (USFWS) and California Department of Fish and Game (CDFG). CNLM holds title to the North County Habitat Bank Habitat Conservation Area (HCA or Preserve), and has changed its name to Encinas Creek Habitat Conservation Area. The Preserve is located about ½ mile east of Interstate 5 along the south side Palomar Airport Road, east of Costco and west of Hidden Valley Road. CNLM has managed the HCA since May of 2007 at which time we received the entire endowment to fund the long-term management of the HCA. The HCA is currently being used by Westmark Development Corporation (Westmark) as a wetlands mitigation bank. Westmark is the Bank Owner and handles all credit sales and accounting. Westmark restored several acres of disturbed wetland pursuant to a restoration plan (Helix 2007b) and received regulatory signoff for final success criteria in December of 2007 (ACOE, 2007). The purpose of this work plan is to identify the tasks and budget required to complete the management activities for the upcoming fiscal year that will begin on October 1, 2010 and end on September 30, 2011. Unless otherwise stated, all tasks will be performed by CNLM's Preserve Manager Patrick McConnell and Ranger, Justin Trujillo. Summary of Tasks and Goals for the Fiscal Year: - Install signs as necessary - Monitor large and medium sized mammal use of the site using wildlife cameras - Note all animal species observed and map locations of any sensitive species - Remove nonnative plant species - Conduct brown-headed cowbird trapping (Molothrus ater) - Patrol and conduct site enforcement on a regular basis - Conduct surveys for least Bell's vireo and coastal California gnatcatcher - Report and describe data collected and management actions taken on the Preserves to the wildlife agencies - Install and mend fencing as necessary Appendix 1 (Task Schedule) identifies the approximate schedule of field work throughout the fiscal year and Appendix 2 depicts the location of the Preserve.

2001 Report of 2001 Brown-headed Cowbird Trapping Program For Mission Trails Regional Park report

INTRODUCTION The City of San Diego (City) is required to implement a brown-headed cowbird (Molothrus ater, BHCO) trapping program at Kumeyaay Lake as required by the Biological Opinion issued for construction of the Kumeyaay Campground. The focus trapping area for the program in 2001 was Kumeyaay Lake, Santee, San Diego County, California. Varanus Biological Services (Varanus) placed traps adjacent to native riparian habitats (Southern Willow Riparian Forest and Southern Cottonwood-willow Riparian Forest) adjacent to the lake. Cowbird trapping is conducted in support of recovery of the federally listed endangered least Bell's vireo ( Vireo bellii p usillus). Least Bell's vireos are small, insectivorous migratory songbirds of extremely limited range. Wintering in Baja California, Mexico, least Bell's vireos typically migrate northward to their breeding grounds in southern California between mid-March and mid-April. They breed almost exclusively in early succession willow-riparian habitats characterized by the presence of dense understory vegetation. Other nesting habitat includes dense patches of herbaceous understory in Coast Live Oak Riparian Forest and Coast Live Oak Woodland, and occasionally in patches of non-native habitat that now commonly form intricate mosaics with native habitats throughout the coastal range of this species. Once widespread in low-elevation riverine valleys as far north as Tehama County in northern California, least Bell's vireo population numbers declined dramatically between the 1940's and mid-l 980's. Two factors are primarily responsible for this species' demise and hence have contributed to its status as an endangered species: habitat loss resulting from eradication, fragmentation and degradation of southern California riparian corridors, and brood parasitism by BHCO. The explosive increase in BHCO population outside its historic range has accompanied the decline of riparian habitat. In southern California, the increase in BHCO has paralleled the decline in numerous other songbird populations including yellow warbler (Dendroica petechia ) and warbling vireo ( Vireo gilvus) in San Diego County (Unitt 1984). Brown-headed cowbirds were historically associated with buffalo and possibly antelope herds, and subsequently livestock in the Great Plains of the United States. It is hypothesized that brood parasitism in BHCO evolved to accommodate the species' reliance on benefits gained foraging among

2009 Pilgrim Creek Restoration Project: Bird Community and Vegetation Structure report

Lead author: Barbara Kus

2021 Modeling Least Bell’s Vireo Habitat Suitability in Current and Historic Ranges in California report

Lead author: Kris Preston
We developed a habitat suitability model for the federally endangered Least Bell’s Vireo (Vireo bellii pusillus) across its current and historic range in California. The vireo disappeared from most of its range by the 1980s, remaining only in southern California and northern Baja California, Mexico. This decline was due to habitat loss and introduction of brood parasitic brown-headed cowbirds (Molothrus ater) into California in the late 1800s. Habitat protection and management since the mid-1980s increased southern California vireo populations with small numbers of birds recently expanding back into the historic range. The vireo habitat model will help meet the U.S. Fish and Wildlife Service recovery objectives by distinguishing specific areas to survey for new occurrences; characterizing important vireo-habitat relationships; and identifying areas for habitat management. We constructed models based on the vireo’s current range to predict suitable habitat in the historic range, which differs substantially in environmental conditions. We used the partitioned Mahalanobis D2 modeling technique designed to predict habitat suitability in areas not included in a sample of species locations and under novel conditions. We constructed alternative models with different combinations of environmental variables hypothesized to be important components of vireo habitat. We selected a set of best performing models to predict suitable habitat for a riparian vegetation grid buffered 500 meters across California. Most models for southern California did not predict suitable habitat in the historic range. The top performing model has an area under the curve value of 0.93. It is a simple model and discriminated among riparian habitats, with only 6 percent predicted as suitable. On average, suitable vireo habitat had more than 60-percent riparian vegetation and flat land at the 150-meter scale, little-to-no slope, and was within 130 meters of water.

2021 Modeling Least Bell’s Vireo Habitat Suitability in Current and Historic Ranges in California report

Lead author: Kris Preston
We developed a habitat suitability model for the federally endangered Least Bell’s Vireo (Vireo bellii pusillus) across its current and historic range in California. The vireo disappeared from most of its range by the 1980s, remaining only in southern California and northern Baja California, Mexico. This decline was due to habitat loss and introduction of brood parasitic brown-headed cowbirds (Molothrus ater) into California in the late 1800s. Habitat protection and management since the mid-1980s increased southern California vireo populations with small numbers of birds recently expanding back into the historic range. The vireo habitat model will help meet the U.S. Fish and Wildlife Service recovery objectives by distinguishing specific areas to survey for new occurrences; characterizing important vireo-habitat relationships; and identifying areas for habitat management. We constructed models based on the vireo’s current range to predict suitable habitat in the historic range, which differs substantially in environmental conditions. We used the partitioned Mahalanobis D2 modeling technique designed to predict habitat suitability in areas not included in a sample of species locations and under novel conditions. We constructed alternative models with different combinations of environmental variables hypothesized to be important components of vireo habitat. We selected a set of best performing models to predict suitable habitat for a riparian vegetation grid buffered 500 meters across California. Most models for southern California did not predict suitable habitat in the historic range. The top performing model has an area under the curve value of 0.93. It is a simple model and discriminated among riparian habitats, with only 6 percent predicted as suitable. On average, suitable vireo habitat had more than 60-percent riparian vegetation and flat land at the 150-meter scale, little-to-no slope, and was within 130 meters of water.