Development and Field Evaluation of an Elevated Bait Station for Control of Deer Mice in Almonds

Deer mice (Peromyscus spp.) have been identified as a serious pest in almonds in portions of the San Joaquin Valley of California. Broadcast anticoagulant bait is normally used to control deer mice, but is prohibited in areas where the endangered giant kangaroo rat (Dipodomys ingens) occurs, leaving growers with no practical means of control. The objectives of this study were to design and test in the laboratory a disposable, spill-resistant, bait station for deer mice, and to field test the bait station in almond orchards. We obtained 20 captive-bred deer mice and observed them interact with prototype bait stations in an observation chamber and in simulated almond trees in outdoor pens. Mouse activity was videotaped in the pens and food consumption measured. Field efficacy trials were conducted in July 2002 in 2 almond orchards, Meyers Block 3 and Cantua, both in Fresno County, California. We used an activity index based on sign left in the crotch of almond trees to estimate efficacy. Mice entered and fed in the prototype bait stations in the observation chamber. Review of 315 hr of videotapes from the pens revealed that the mice readily climbed the almond tree stumps and entered the bait stations to feed. The mice were nocturnal and most active from about 2020 hr through 0530 hr, with virtually no activity during the daylight hours. Use of the bait stations averaged up to 39 entries /mouse/night. The average daily consumption of clean grain per mouse for males was 2.6 gm (SE = 0.39, range = 1.1 - 3.6 gm) and for females was 2.2 gm (SE = 0.26, range = 1.4 - 3.0 gm). Feeding behavior appeared normal and food consumption was not inhibited by the bait stations. The field efficacy trial consisted of 1-week pretreatment period, 2 weeks of treatment with 0.005% diphacinone on oat groats, and a 1-week posttreatment period. Each study area included a treated area of ∃1150 trees and a control (nontreated) area of ∃435 trees. We deployed bait stations filled with 100 gm of bait or clean grain in a grid pattern of every 3rd row and 3rd tree within a row, 119 stations for treated plots and 47 or 48 stations on the control plots. Based on activity indices, efficacy was 72% at Meyers Block 3 and 33% at Cantua. Consumption of diphacinone bait on the treated plots averaged 0.6 and 3.2 gm/station for the 2- week treatment period, at Meyers 3 and Cantua, respectively. Consumption of clean grain on the control plots averaged 1.2 and 5.1 gm/station for the 2-week treatment period, or 0.08 and 0.36 gm/day, at Meyers 3 and Cantua, respectively. Consumption of clean grain did not approach levels recorded in our pen tests. These findings suggest poor bait acceptance. We speculate that almonds were preferred over oat groats, and that bait acceptance might improve if the grain bait was offered during the winter or early spring when the supply of almonds would be reduced

Evaluation of a Floating Bird Diverter

Hazing at oil spills can reduce bird mortalities. This study evaluated the effectiveness of the Firefly Pond Diverter™ (Firefly Diverters LLC, Grantsville, UT), a device that floats on the water and is claimed to use motion, reflectivity, and ultraviolet (UV) and visible light emissions to alert and repel birds. The diverter could be useful at a spill, but little is known about how waterbirds would respond. The objectives of this study were to determine if waterbirds were repelled to a greater degree by the diverter compared to a simple novel object (a life ring), to identify the species that responded to the diverter, and determine if birds habituate to the diverter. The study was conducted in December 2007 in a stormwater retention basin in Woodland, California. We divided the study into a 3-day pretreatment period and a 6-day treatment period and counted birds in the morning and afternoon each day. On each day during the treatment period we randomly selected 2 areas of the basin and anchored 2 diverters in one area and 2 life rings in a second area. We moved the diverters and the life rings to new locations daily. During the bird counts we recorded all birds within 15.2 m of each diverter or life ring. For the basin as a whole, we found the temporal pattern of use (fewer birds present in the morning than the afternoon) and number of birds using the basin did not change with the deployment of the diverters and life rings. Species composition was similar during the pretreatment and treatment periods. Gulls, geese, and diving ducks accounted for over 90% of the birds, with gulls most numerous. We observed 7 and 9 species of birds within 15.2 m of the diverters and life rings, respectively. Gulls represented 91% and 81% of the birds near the diverters and the life rings, respectively. There was no difference in the number of birds within 15.2 m of the diverters or the life rings. There also was no difference in the number of birds within 15.2 m of the diverters or \u3e 15.2 m from the diverters. We found the same relationship for the life rings. After field work concluded we were informed that rotation of the flappers on the diverters and an ultraviolet index (UVI) \u3e2 were critical for the diverter to function. During the treatment period there was wind sufficient to spin the flappers during 7 of 12 counts. We observed birds within 15.2 m of the diverters on 6 out of 7 counts with wind. As reported in local newspapers, the UVI was never \u3e2 during the treatment period. If UV radiation has any effect on performance, then December, a month with low UVI values in northern California, was not the optimum time to test. The diverters did not repel birds during this study. It is not known if the diverters will repel birds during conditions of higher UVI. Additional research should be undertaken

GROWER PRACTICES FOR BLACKBIRD CONTROL IN WILD RICE IN CALIFORNIA

We surveyed 29 wild rice growers, representing 96% of the California acreage grown in 1993, to determine current practices for blackbird damage control. Twenty-seven growers (93%) had blackbird damage. The period of greatest damage and most intensive control was July through September. Red-winged blackbirds (Agelaius phoeniceus) most frequently caused damage, but three other species of blackbirds and the European starling (Sturnis vulgaris) were also identified. Most growers (72%) reported 1 to 10% yield loss. Average loss ranged from $121 to$309/ha, and from $14,530 to$32,061/grower. Most growers (97%) attempted to control blackbirds for an average of 3.5 months during the growing season, relying primarily on shotguns, propane cannons, shell-crackers or bird bombs, and patrols. Growers in northeastern California tended to rate these techniques as more effective than growers in the Sacramento Valley, possibly due to the larger field sizes in the Valley. Average effectiveness ratings for all techniques indicated little better than slight control for the techniques used, suggesting grower dissatisfaction with the available techniques. Average cost for control averaged $86.21/ha, which was among the highest costs for any single aspect of wild rice production

A model to predict the likelihood of cliff swallow nesting on highway structures in northern California

Cliff swallows (Petrochelidon pyrrhonota) are colonially breeding migratory birds that frequently nest on highway structures. Under the Migratory Bird Treaty Act of 1918, people cannot harm swallows or their active nests. This restriction causes problems and delays for construction and maintenance divisions of many departments of transportation. In planning future projects, it would be useful for these divisions to have a habitat selection model that can predict the likelihood of cliff swallow nesting on a particular highway structure. We used logistic regression on data collected from 206 highway structures and 2 different land cover data sets to develop habitat selection models for northern California. The models indicated that low urban development and structure undersurfaces with multiple junctures were the 2 most important predictors of cliff swallow occupancy. Both the presence of water under a structure and a large underpass opening were also factors included in the models. The models correctly predicted 59% of sites occupied by cliff swallows and 88% of sites not occupied. The occupancy classification rate may offer departments of transportation useful insight into the nesting behavior of cliff swallows

Evaluation of Damage by Vertebrate Pests in California Vineyards and Control of Wild Turkeys by Bioacoustics

Complaints of agricultural damage by wild turkeys (Meleagris gallopavo), particularly from wine grape growers, have increased in California. We assessed damage by vertebrate pests in vineyards and tested a bioacoustic-aversion technique for turkeys as an alternative to other control techniques (e.g., reflective tape, trapping, bird netting). We selected 12 vineyards in the Napa Valley and Sierra Foothills American Viticultural Areas of California. We conducted damage surveys to assess percentages of missing or damaged grapes (i.e., grapes that had been stripped, pecked, and plucked) for every grape cluster on 20 randomly-selected vines before harvest in 2007 and on 40 vines in 2008. We assumed that all observed damage was caused by vertebrate pests and that most of this damage was caused by birds. Grape damage caused by wild turkeys was identified by contiguous sections of berries plucked from a cluster, which we referred to as stripped damage. We attributed pecked and plucked damage to passerines. In 2008, we randomly selected 3 vineyards in each area for treatment with broadcast calls (wild turkey alarm, domestic turkey alarm, crow distress). We used motion-activated video cameras to document evidence of damage caused by turkeys and other animals. Damage in the vineyard perimeter was greater than in the interior for all damage types in 2008, but only for plucked damage in 2007. In 2008, stripped, pecked, and plucked damage means for treated vineyards were 1.3%, 1.4%, and 1.5%, respectively; stripped, pecked, and plucked damage means for untreated vineyards were 1.3%, 0.7%, and 0.2%, respectively. There was no difference in mean stripped damage between treated and untreated vineyards in 2008, indicating that broadcast calls had no effect. Comparison between treated sites in 2008 with the same untreated sites in 2007 yielded similar results. Turkeys caused damage in several of the study vineyards, but the problem varied among vineyards and was inconsistent between years. Motion-activated video recordings suggested that raccoons (Procyon lotor), gray foxes (Urocyon cinereoargenteus), and other vertebrate pests were to blame for some of the stripped damage

Improved Methods for Deterring Cliff Swallow Nesting on Highway Structures

Cliff swallows (Petrochelidon pyrrhonota) are migratory birds that frequently nest on highway structures, such as bridges. Because cliff swallows are protected by the Migratory Bird Treaty Act of 1918, nesting control methods must not harm cliff swallows or disturb active nests. This can cause delays for maintenance divisions of state departments of transportation, resulting in additional cost. In a multiyear project, we evaluated the effects of bioacoustic deterrents and bridge surface modifications on nesting behavior of cliff swallows. We used cliff swallow alarm and distress calls as bioacoustic deterrents (hereafter, broadcast calls [BC]) because they previously had been shown to delay the onset of nesting. We used low-friction plastic sheeting (PTFE, commonly called by its trade name, Teflon®) and silicone-based paint for bridge surface modification. In 2007, swallows were able to complete nests on silicone paint, but did not successfully complete any nests on PTFE. In 2008, PTFE+BC treatment significantly reduced nesting compared with no treatment, although some nests were completed at PTFE and PTFE+BC sites on the bare concrete next to the sheeting or at locations where sheeting had peeled away. We recommend treatment with PTFE+BC to reduce the likelihood of cliff swallow nesting on bridge surfaces, but this should be supplemented with weekly site visits to check treatment integrity and to remove any partial nests on untreated surfaces

Woodrats

Eight species of woodrats (genus Neotoma) occur in North America. Locally known as pack rats or trade rats, these rodents are about the size of the common Norway rat. They are distinguishable from Norway rats by their hairy rather than scaly tail, soft, fine fur, and large ears. They usually have light-colored feet and bellies.The Key Largo woodrat (Neotoma floridana smalli) was federally listed as endangered in 1991. Exclusion: Woodrats can be permanently excluded from buildings. Cultural Methods: Not generally useful. Trim lower branches of citrus trees. Repellents: None are registered or considered effective at this time. Toxicants: Anticoagulants (registered in some states). Zinc phosphide (registered in some states). Fumigants: Not useful. Trapping: Rat snap trap. Live traps. Burrow-entrance traps. Glue boards. Shooting: Limited usefulness. Other Control Methods: Destruction of dens

THE CLIFF SWALLOW—BIOLOGY AND CONTROL

Cliff swallows (Petrochelidon pyrrhonota) nesting in colonies on man-made structures can cause aesthetic problems and health hazards. Cliff swallows are migratory, wintering in South America and breeding throughout most of North America. Cliff swallows have a homing tendency to old colonies and are attracted to the gourd-shaped mud nests. Egg laying begins before nest construction is finished; clutch size averages 3 or 4 eggs. Re-nesting is common if a nest fails and some pairs may raise 2 broods in 1 nesting season. Cliff swallows may be present at a colony for up to 132 days. Cliff swallows are protected by the Migratory Bird Treaty Act of 1918, and a permit from the United States Fish and Wildlife Service is required for certain control activities. Successful control methods include nest removal by water hose or a pole, and exclusion using netting, poultry wire, or strip doors. Nest substrate modification is successful in some instances. Methods employed with little success or that remain unproven include metal spines, repellents, frightening devices, predator models, taped alarm calls, and a fresh coat of paint. Attention to architectural design may alleviate cliff swallow nesting problems

URBAN CROW ROOSTS IN CALIFORNIA

We reviewed the historical and current status of the American crow (Corvus brachyrhynchos), urban crow roosts and control efforts in California. Crows aggregate in traditional winter roosting areas. In the late 1930s most crows in California roosted in the Sacramento Valley in rural locations. Crow roosts were not a concern except for potential damage to adjacent farmlands. From the 1960s through 1980s crows colonized urban areas for nesting and winter roosting. A phone survey of vertebrate pest management officials indicated all known roosts were in urban areas, with most occurring in the Sacramento Valley. From 1970 to 1989 the winter crow population in the Central Valley of California doubled, with more crows found in the Sacramento Valley than the San Joaquin Valley. In the late 1980s crows in a traditional roost area in Yuba City, Sutter County, increased to 1 million birds. Political pressure prevented attempts at population reduction in 1991 and 1992 and led to examination of non-lethal techniques to disperse crows from urban roosts. Methods and materials tested included mylar tape, strobe lights, netting, monofilament lines, eyespot balloons, pyrotechnic devices, water-misters, sticky repellents, and taped crow and owl vocalizations. Qualitative evaluations by residents and local officials indicated strips of mylar tape tied on branch tips and pyrotechnic devices were relatively effective in dispersing crows

SWALLOWS

Eight members of the swallow family Hirundinidae breed in North America: the tree swallow (Tachycineta bicolor), violet-green swallow (Tachycineta thalassina), purple martin (Progne subis), bank swallow (Riparia riparia), northern rough-winged swallow (Stelgidopteryx serripennis), barn swallow (Hirundo rustica), cave swallow (Hirundo fulva), and the cliff swallow (Hirundo pyrrhonota). Cliff and barn swallows are found throughout most of North America. Four basic conditions are found near most cliff and barn swallow nest sites: (1) an open habitat for foraging, (2) a suitable surface for nest attachment beneath an overhang or ledge, (3) a supply of mud of the proper consistency for nest building, and (4) a body of fresh water for drinking. All swallows are insectivores, catching a variety of insects. Cliff and barn swallows winter in South America. Swallows have a homing tendency toward previous nesting sites. Cliff swallow nests are gourd-shaped, enclosed structures with an entrance tunnel that opens downward. Cliff swallows usually begin laying eggs before the entrance tunnel is completed. Renesting will occur if nests or eggs are destroyed