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Recent increases in turkey vulture (Cathartes aura) and black vulture (Coragyps atratus) populations in North America have been attributed in part to their success adapting to human-modified landscapes. However, the capacity for such landscapes to generate favorable roosting conditions for these species has not been thoroughly investigated. We assessed the role of anthropogenic and natural landscape elements on roosting habitat selection of 11 black and 7 turkey vultures in coastal South Carolina, USA using a GPS satellite transmitter dataset derived from previous research. Our dataset spanned 2006–2012 and contained data from 7916 nights of roosting. Landscape fragmentation, as measured by land cover richness, influenced roosting probability for both species in all seasons, showing either a positive relationship or peaking at intermediate values. Roosting probability of turkey vultures was maximized at intermediate road densities in three of four seasons, and black vultures showed a positive relationship with roads in fall, but no relationship throughout the rest of the year. Roosting probability of both species declined with increasing high density urban cover throughout most of the year. We suggest that landscape transformations lead to favorable roosting conditions for turkey vultures and black vultures, which has likely contributed to their recent proliferations across much of the Western Hemisphere.

Squamate reptiles (snakes and lizards) rely on chemical cues from conspecifics to search the environment for potential mates. How such cues are used by invasive species to facilitate reproduction, especially seasonally, is a key question that can inform management practices. The Argentine black and white tegu (Salvator merianae) is an invasive reptile species in south Florida threatening native fauna in biodiverse regions such as Everglades National Park. While some information exists on the reproductive ecology of this species in its native range in South America, the chemical ecology of S. merianae is unclear especially in its invasive range. By testing both male (n = 7) and female (n = 7) tegus in a Y-maze apparatus, we assessed if either sex follows chemical trails left by conspecifics and if behaviors were sex- or season-specific. We conducted three types of trials where conspecifics created odor trails: Male-only (male scent only in base and one arm of Y), Female-only, and Male vs. female. Males did not preferentially follow scent trails from either sex, but they did differentially investigate conspecific scent from both sexes. Seasonally, males showed increased rates of chemosensory sampling (rates of tongue-flicking) during the spring (breeding season; March-May) compared to fall (non-breeding season; September-November). Males also had reduced turning and pausing behavior while trailing in the spring. Female tegus exhibited stronger conspecific trailing abilities than males, following both male and female scent trails, and they explored the maze less before making an arm choice. Females also investigated the scent trails intensely compared to males (more passes in scented arms, more time with scent trails). Our results demonstrate for the first time that females of an invasive reptile species can follow conspecific scent trails. Given the strong female responses to odor, sex-specific targeting of tegus via application of a conspecific chemical cue in traps could enhance removal rates of females during the breeding season.

Salvator merianae (Argentine Black and White Tegu, hereafter, Tegu) is an omnivorous, burrowing lizard native to South America. Tegus were introduced through the pet trade, and free-ranging populations now threaten many native species in Florida. As Tegu control programs expand and more traps are deployed, the need for a simple, inexpensive trap increases. To date, there has been no experimental effort to compare types of traps or alternative lures. In this study, we evaluated responses of 12 captive Tegus to several alternative trap/bait combinations. We video-recorded each of the trials and scored the outcomes based on the trap the Tegu entered first. Our results suggest that alternative trap/lure combinations, such as traps made of PVC pipe baited with commercial mouse-based trap lure, might be just as effective at capturing Tegus, and thus could be less expensive options for Tegu control programs. Trials with captive animals do not necessarily predict outcomes with free-ranging animals, and w...

Animals communicate with potential mates using species-specific signals, and pheromones are powerful sexual signals that modify conspecific behavior to facilitate mate location. Among the vertebrates, snakes are especially adept in mate searching via chemical trailing, which is particularly relevant given that many snake species are invasive outside their native ranges. Chemical signals used in mate choice are, thus, potentially valuable tools for management of invasive snake species. The Burmese python (Python bivittatus) is an invasive snake in the Florida Everglades where it is negatively impacting native fauna. In this study, we sought to: (i) determine if males can follow conspecific chemical trails in a Y-maze; and (ii) describe the mate searching behaviors exhibited by males while trailing. All males consistently followed a single female scent trail in the maze, but when only a male scent trail was present they did not discriminate between the male and blank arms. Rate of tongue-flicking, a proxy for chemosensory sampling, was also marginally higher when males were following female versus male scent trails. However, when both female and male scent trails were simultaneously present in the Y-maze, males did not show a preference for the female arm, although the tongue-flick rate was higher in the female-only trial compared to female versus male. Analyses of multiple male behaviors individually and using an ethogram revealed that behaviors were more frequent and complex in the female-only trials compared to male-only trials. Additional behavioral trials are needed to determine if an effective pheromonal approach to Burmese python management is possible.

Recent studies have demonstrated that detection of environmental DNA (eDNA) from aquatic vertebrates in water bodies is possible. The Burmese python, Python bivittatus, is a semi-aquatic, invasive species in Florida where its elusive nature and cryptic coloration make its detection difficult. Our goal was to develop a diagnostic PCR to detect P. bivittatus from water-borne eDNA, which could assist managers in monitoring this invasive species. First, we used captive P. bivittatus to determine whether reptilian DNA could be isolated and amplified from water samples. We also evaluated the efficacy of two DNA isolation methods and two DNA extraction kits commonly used in eDNA preparation. A fragment of the mitochondrial cytochrome b gene from P. bivittatus was detected in all water samples isolated with the sodium acetate precipitate and the QIAamp DNA Micro Kit. Next, we designed P. bivittatus-specific primers and assessed the degradation rate of eDNA in water. Our primers did not amplify DNA from closely related species, and we found that P. bivittatus DNA was consistently detectable up to 96 h. Finally, we sampled water from six field sites in south Florida. Samples from five sites, where P. bivittatus has been observed, tested positive for eDNA. The final site was negative and had no prior documented evidence of P. bivittatus. This study shows P. bivittatus eDNA can be isolated from water samples; thus, this method is a new and promising technique for the management of invasive reptiles.

In the United States, black vulture (Coragyps atratus) and turkey vulture (Cathartes aura) pose significant birdstrike risks to aircraft. Understanding flight behaviors of vultures in and around military and civilian airfields is necessary to alleviate these risks. Using satellite telemetry data collected from 11 black vultures and 7 turkey vultures equipped with Global Positioning System backpack harness technology, we collected data on location and altitude near the Marine Corps Air Station (MCAS) in Beaufort, South Carolina from September 2006 to September 2008. We used military aircraft flight landing patterns to visualize a new concept, a flight altitude cone of depression (FACOD), which models a three-dimensional flight pattern over the airfield. We then identified areas in and around MCAS where vulture flight paths penetrated the FACOD and locations of vultures were proximate to flight approach routes that posed potential risk to aircraft for a birdstrike. Combining altitude of in-flight locations of vultures or other species with three-dimensional flight patterns of aircraft provides a novel method for managers of military and domestic airfields to assess birdstrike risk and to focus corrective actions.

Growing vulture populations represent increasing hazards to civil and military aircraft. To assess vulture flight behavior and activity patterns at the Marine Corps Air Station in Beaufort, South Carolina, we equipped 11 black vultures (Coragyps atratus) and 11 turkey vultures (Cathartes aura) with solar- powered Global Positioning System (GPS) satellite transmitters during a 2-year study (1 Oct 2006-30 Sep 2008). Turkey vultures had larger seasonal home ranges than did black vultures, and 2 turkey vultures made round-trips to Florida. Black vultures consistently spent less time in flight (8.4%) than did turkey vultures (18.9%), and black vultures flew at higher altitudes than did turkey vultures in all seasons except summer when altitudinal distributions (above ground level) did not differ. Although we recorded maximum altitudes of 1,578 m for black vultures and 1,378 for turkey vultures, most flights were low altitude. A matrix of vulture flight altitude versus time of day revealed that >60% of vulture flight activity occurred from 4 hr to 9 hr after sunrise at altitudes below 200 m. Continuation of aggressive harassment coupled with flexible training schedules to avoid times and altitudes of high vulture activity will decrease hazards to aircraft posed by these birds. 2011 The Wildlife Society.

TECNICA MEJORADA DE SUJECION DEL ARNES DE UN TRANSMISOR SATELITAL La telemetria satelital a menudo requiere de la sujecion de un transmisor en el ave utilizando un arnes de configuracion tipo mochila. El calce apropiado del arnes sobre el ave es esencial para un despliegue efectivo y para el bienestar de las aves. Presentamos una tecnica mejorada de sujecion del arnes que emplea un remache barato y disponible de forma inmediata. Este metodo reduce el tiempo de manipulacion y permite a los investigadores ajustar las guias del arnes de forma rapida y luego asegurarlas eficientemente sin coser, enroscar o pegar con plastico caliente.

Radar and satellite global positioning system-platform transmitter terminal (GPSPTT) transmitters provide complementary information on the movements and behaviors of individual birds. The GPS-PTT tag provides a snapshot of altitude and location of a specific individual of an identified species at predefined intervals. The history of the individual is known because each transmitter has a unique identification code. The radar cannot identify individuals or even species but it provides continuous position reports (altitude and location) of birds within its detection range. By integrating data from the two sources, the behavior and movements of identified individuals (not possible with radar) can be continuously monitored (not possible with satellite tags). In this study the radar detected 40% of the locations of vultures carrying GPS-PTT tags that were within 5 km of the radar. Most (75%) of the locations that were not detected were calculated to be above or below the radar’s antenna beam. Speed and direction values recorded by the GPS-PTT tags and the radar were poorly correlated because the vultures were soaring and circling, which produced rapid changes in both azimuth and ground speed of the targets. Nevertheless, our findings show that combining these two techniques can allow monitoring of species that are of conservation concern where it is otherwise difficult to follow identified individual birds.

The economic impact of blackbirds can be severe to rice producers in the United States. One approach to managing this damage is the application of bird-deterrent chemical to the crop. Previous pilot trials suggested that caffeine offered potential as a safe, economical bird repellent. In this study, cage feeding trials with female red-winged blackbirds and male brown-headed cowbirds confirmed that a treatment rate of 2500 ppm caffeine on rice seed reduced consumption as much as 76%. Trials with mixed species blackbird flocks in a 0.2-ha flight pen resulted in just 4% loss of caffeine-treated rice compared to 43% loss of untreated rice. Field trials of a 10,000 ppm caffeine treatment in Louisiana revealed >90% of caffeine-treated rice seed remained unconsumed on days 2 and 3 of the study whereas blackbirds consumed >80% of the untreated seed. As a rice seed treatment to deter blackbirds, caffeine appears to be effective, economical and environmentally safe, although additional aquatic toxicity testing is desirable. Improvements in formulation will be needed to make the compound practical for general agricultural spray applications and to extend the adherence of caffeine to rice seeds in field conditions.

Author(s): Avery, Michael L.; Humphrey, John S.; Keacher, Kandy L.; Bruce, W. Eddie | Abstract: The invasive Burmese python is a large constrictor snake that is now well established in south Florida. This invasive predator could have major detrimental impacts to native wildlife populations and is a perceived threat to human health and safety. Finding and removing this elusive predator in vast Everglades habitats of wet sawgrass prairies with interspersed hardwood hammocks poses many challenges for biologists and land managers in south Florida, and no single solution is likely to prevail. In ongoing research, we are exploring opportunities to improve detection of this cryptic species using such diverse approaches as environmental DNA, trained detector dogs, and thermal infrared imagery. In this paper we update the status of these efforts. Other research, using captive pythons in outdoor pens at our facility in Gainesville, has resulted in the development of a newly-patented live trap that is specific to large snakes. We are currently testing and evaluating techniques to complement this new trap design for effective python removal in concert with improved detection tools.

Anthraquinone is a promising candidate as a repellent to protect newly planted rice from blackbird depredation. Current technology for applying chemicals to rice seed prior to planting might be incompatible with the relatively large volume of bird repellent material needed on rice seeds. Therefore, an alternate method of application, overspraying the field after the seed is planted, could prove more efficient and practical. We examined this approach in pen and field trials. In group pen tests, red-winged blackbirds (Agelaius phoeniceus) consistently avoided Flight Control (50% anthraquinone) applications equivalent to 23.3 and 37.2 l/ha, but were not deterred by 9.3 l/ha. Several test birds vomited after they fed on treated seeds. In a 0.2 ha flight pen, blackbird flocks removed 58% of rice seed from untreated plots compared to 6% taken from plots sprayed with Flight Control at a rate of 18.6 l/ha. In southwestern Louisiana, plots of newly planted rice were sprayed with Flight Control at either 9.3 or 18.6 l/ha. We did not observe blackbird repellency at any of the treated sites. Anthraquinone residues on rice from the test plots indicated that there was insufficient repellent on the seeds in the fields to deter depredating blackbirds. For overspraying to be practical and effective, methods must be devised to deliver the chemical more efficiently to the planted seeds.

In 1995 and 1996, fish loss due to bird predation was documented at 18 ponds at seven aquaculture facilities in central Florida. Losses in ponds from which birds were excluded with netting averaged 11.1%, whereas losses in unnetted ponds averaged 37.6%. Populations of wading birds varied among facilities, but the snowy egret Egretta thula, green-backed heron Butorides striatus, tricolored heron E. tricolor, and little blue heron E. caerulea were the principal depredating species. Field observations revealed feeding rates by little blue herons as high as 4 fish/min. Estimated monetary losses at unnetted study ponds averaged US$1,360/pond compared with average losses of $589 at netted ponds. Currently, exclusion is the only technique that is consistently reliable, and it appears that netting ponds to control bird depredations is economically feasible, particularly with high-value fish.

Application of bird-repellent chemicals to seed prior to planting is one possible approach to reducing bird damage to rice. Anthraquinone is a promising seed treatment compound, and in this paper we describe a sequence of tests evaluating a formulated commercial anthraquinone product. In l-cup cage tests, rice consumption by individual male red-winged blackbirds (Age&w phoeniceus) and female boat-tailed grackles (Quiscalus major) was reduced 64-93% by 0.5 and 1.0% (g/g) anthraquinone treatments. Daily rice consumption by single male boat-tailed grackles tested in large enclosures was reduced from > 14 g in pretreatment to < 1 g by a 1.0% treatment. One of five test birds ate nothing during a 1 day post-treatment session. In a 7 day trial within a 0.2 ha flight pen, a group of four male grackles consumed 1.3% of anthraquinone-treated rice seed compared to 84.1% of sorghum, a nonpreferred alternate food. At two study sites in southwestern Louisiana, loss of rice sprouts in 2 ha plots sown with anthraquinone-treated seed was 0 and 12% compared to losses of 33% and 98% in nearby untreated plots. The formulation performed well at every stage of testing, and further development of anthraquinone products for bird-damage management is warranted. Published by Elsevier Science Ltd

Fipronil is an insecticide developed for use on rice seed and other crops. In a series of cage and pen trials, we evaluated the responses to dyed, fipronil-treated rice seed of three bird species likely to encounter it in the field. Individually caged red-winged blackbirds (Agelaius phoeniceus), brown-headed cowbirds (Molothrus ater), and boat-tailed grackles (Quiscalus major) displayed no evidence of adverse reaction to treated seed. Chemical analyses of hulls from treated seeds eaten by captive birds revealed that 10-20% of the fipronil originally present was removed during feeding. In group enclosures, male red-winged blackbirds ate as much fipronil-treated rice as they did dyed, untreated seed. In four-day tests within a 0.2-ha flight pen, 10-bird blackbird flocks removed 11.4% of fipronil-treated seed from a test plot compared to 12.5% of dyed, untreated seed removed from the alternate plot. When the alternate plot contained undyed rice, however, seed removal from the treated plot averaged 2.4% compared to 28.9% from the alternative plot, suggesting that the groups of test birds avoided treated seed based on its appearance. We conclude that 325 and 500 mg kg -1 fipronil applications alone do not affect avian feeding activity.

Naturally occurring plant constituents are potentially useful as avian feeding deterrents. In a series of cage trials, pulegone, a compound found in various species of mint, suppressed consumption of rice seed by red-winged blackbirds (Agelaius phoeniceus) more effectively than methyl anthranilate. Furthermore, pennyroyal oil, from which pulegone is obtained, was nearly as effective as pulegone itself. Brown-headed cowbirds (Molothrus ater) were more sensitive to pulegone than were redwings, but female boat-tailed grackles (Quiscalus major) were less sensitive. Because pulegone produces both sensory irritation and post-ingestive distress, it has potential for seed treatment and other bird deterrent applications.

Fruit choice by birds is affected by many factors, but the interactions between sensory and postingestive cues has received little experimental study. To evaluate how post- ingestive responses to fruit sugars relate to color and other visual cues, we offered individually caged Cedar Waxwings (Bombycilla cedrorum) and European Starlings (Sturnus vulgaris) artificial red and green fruits containing 12.8% (g/g) sucrose or hexose (1:1, glucose: fructose) sugars. In 1-h trials with 6-mm-diameter fruits, waxwings preferred hexose to sucrose fruits, re- gardless of color. Birds given only sucrose fruits ate more than other groups. With 11-mm fruits, patterns of consumption were the same, but clear preferences for hexose over sucrose showed only in 3-h trials. Waxwings given red-hexose and red-sucrose fruits or green-hexose and green-sucrose fruits in two-cup tests learned to prefer the hexose fruits from positional cues. Starlings that initially preferred green learned to prefer red-hexose over green-sucrose fruits after two 3-h trials. Similarly, starlings that initially preferred red learned to prefer green-hexose fruits when paired with red-sucrose fruits. These preferences persisted through three posttreatment trials when both red and green fruits had only hexose sugars. In contrast to Cedar Waxwings, starlings given all-sucrose fruits ate the least, and two of four birds in the all-sucrose group stopped eating fruits altogether. At the level tested, sucrose was a strong associative repellent for starlings, probably because of induced postingestional distress due to their inability to digest sucrose. In contrast, waxwings can digest sucrose, but appear unable to maintain positive energy balance feeding solely on high-sucrose fruits. Development of high-sucrose cultivars may alleviate depredation to fruit crops by sucrose-deficient species

We conducted two-cup feeding trials to assess the responses of cedar waxwings (Bombycilla cedrorum (Vieillet)), American robins (Turdus migratorius (L.)), and European starlings (Sturnus vulgaris L.) to food adulterated with phosmet 500 g kg−1 WP (‘Imidan’®). All species avoided phosmet concentrations ⩾ 100 mg kg−1.Robins avoided food containing 60 mg kg−1 phosmet, while food consumption by starlings was reduced by a 30 mg kg−1 treatment. All species were indifferent to phosmet at 10 mg kg−1. These findings suggest that fruit-eating birds will safely avoid ingesting harmful levels of phosmet when the insecticide is applied to small fruit such as blueberries and cherries. Feeding deterrence associated with phosmet might be exploited in management strategies to protect small fruit crops from damage by birds.

Author(s): Avery, Michael L.; Tillman, Eric A.; Humphrey, John S. | Abstract: The use of real and artificial effigies has proven to be an effective alternative to pyrotechnics and other traditional methods for the dispersal of nuisance vulture roosts. During the winters of 2005-2006 and 2006-2007, we applied the same principles of effigy use to a large urban crow roost in the Lancaster, PA area. The initial deployment of effigies occurred in November 2005 in a wooded area where approximately 10,000 birds had already congregated to the detriment of nearby businesses. By December, as the roost grew to approximately 40,000 birds, we successively moved the birds to a series of alternate sites along a wooded creek. In January, the crows split into smaller roosting aggregations and began to disperse. In October 2006, before wintering crows arrived, we installed effigies in wooded areas where the crows had settled the previous year. Although preferred roost habitat in 2005-2006, these areas were used only sparingly by crows throughout the second winter. Instead, crow roosting activity was focused in downtown Lancaster. At wooded sites where 5,000-10,000 birds did settle, we installed additional effigies and the birds responded by leaving. During November-December 2007, we provided technical assistance to a citizen-based crow management effort that successfully incorporated the use of artificial crow effigies with other harassment to move the roost (30,000 to 40,000 birds) to a site acceptable to the community. We conclude that crow effigies (carcasses, taxidermic mounts, or artificial models) are useful components of roost dispersal efforts and can possibly be used in other applications, such as crop damage management.

Depredations to livestock by black vultures are a concern for many producers, and there is an increasing need for effective means to alleviate conflicts between livestock and vultures. One approach to this problem is to identify the roost site that is the source of the offending birds and then disperse that roost. We evaluated this approach in southwestern Virginia, where sheep and cattle operations in the New River Valley have historically experienced depredations by black vultures. During February 2004, we trapped and tagged 200 vultures and equipped 20 of them with radio transmitters. We established data-logger receiving stations at the main roost site in Radford, VA and at 4 nearby livestock operations. We monitored vulture use of the roost and the livestock sites for 2 weeks and then we dispersed the Radford roost using vulture effigies and hand-held lasers. We continued to monitor vulture activity at the livestock study sites for 8 weeks. Our findings showed that although the roost in Radford was dispersed, vulture use of the livestock operations after roost dispersal did not differ from pre-dispersal activity. Vultures in the area apparently shifted to alternate roost sites with no noticeable disruption to their foraging activities. For roost management to be effective against livestock depredations, dispersal activity must include the ancillary roosts as well as the main roost. Furthermore, prompt removal and proper disposal of livestock carcasses should greatly reduce the attractiveness of cattle and sheep operations for foraging black vultures.

Author(s): Tillman, Eric A.; Humphrey, John S.; Avery, Michael L. | Abstract: As land-use patterns change and urban populations surge into previously undeveloped areas, wildlife conflicts inevitably increase. Of increasing concern are problems associated with black (Coragyps atratus) and turkey vultures (Cathartes aura), two species that have shown the capacity to adapt readily to human activities. Previously, we demonstrated that roosting vultures can be successfully dispersed from communication and broadcast towers by hanging a vulture carcass or taxidermic effigy in the structure. Here, we extend that method to situations where vultures are affecting residential property and agricultural resources. At 4 of 8 study sites where vulture damage to property was a concern, damage was eliminated by hanging a carcass or effigy in trees where the vultures roosted. At the other 4 sites, where the roost was inaccessible, vulture damage ceased after carcasses or effigies were hung on or near the property directly affected by the birds. After vulture activity had been reduced, the effigies or carcasses at 4 of the 8 sites were replaced by Canada goose (Branta canadensis) decoys painted to resemble vultures. Vulture activity continued to be suppressed at those locations. At 1 of 2 study sites where depredation to livestock was a concern, vulture activity at a pig breeding facility was reduced 90% after a taxidermic effigy was installed overhead. At the other site, where depredation of cattle and calves by vultures was a concern, a nearby roost of 800 birds was dispersed using effigies; the effect upon depredation has yet to be determined. Our investigation to date has found the hanging of vulture carcasses, taxidermic effigies, and decoy effigies to be effective for the management of vulture problems in a variety of situations. This nonlethal vulture management approach will not be appropriate or effective in every case, but its use should be considered, particularly where roost dispersal is desired.

Author(s): Humphrey, John S.; Avery, Michael L.; McGrane, Arlene P. | Abstract: As distributional patterns of black vultures (Coragyps atratus) and turkey vultures (Cathartes aura) change, and as woodland habitat declines, vultures increasingly come in contact with human activity. Relocation of problem birds is one potential management approach for resolving conflicts. Relocation involves trapping and moving the vultures some distance away where their subsequent behavior is not expected to conflict with human activity. To evaluate vulture responses to relocation, we trapped and patagial-tagged 114 vultures at two roosting areas over a period of ten months and equipped ten of them with satellite transmitters. Of 9,101 locations, 18.6% had a measure of accuracy of 1000 m to l150 m. The remainder had an accuracy of g1000 m of accuracy (n=3149), no estimate of location accuracy (n=2024), or invalid location (n= 1117). Two transmitters were recovered due to removal or illness of the bird, were reset, and deployed on different vultures. Sixteen tagged birds were sighted after their release. Half of the sighted birds were observed at their unmodified trap site, and four of eight birds with transmitters were tracked to within 16 km of their trap site. No birds have been tracked to or seen at the modified trap site. One bird was tracked to within 32 km of its modified trap site. Birds took an average of eight months to return to the trap site. Relocation appears to be effective in the short term, but habitat modification and harassment to render the location unattractive is necessary for successful long-term removal of problem vultures.

Author(s): Avery, Michael L.; Decker, David; Humphrey, John S. | Abstract: Bird repellents to protect seeds are a potentially important aspect of integrated vertebrate pest management strategies. Yet, there currently are no repellents registered for seed treatment uses. This is due not to lack of effective candidate compounds, but to monetary and regulatory constraints that inhibit commercialization of promising compounds. Two examples of this dilemma are methiocarb and anthraquinone, each of which has considerable potential for bird repellent uses and each of which faces considerable registration hurdles as prospective seed treatment compounds. A concerted, coordinated effort among private industry, producer groups, and state and federal agencies may be the best strategy to bring potentially useful repellents to commercial reality.

Offensive visual stimuli represent a potentially important component of avian crop damage reduc- tion strategies. Color perception by diurnal birds is highly developed, but the responses of the red-winged blackbird (Agelaius phoeniceus) to different-colored food have never been investigated. Red-winged blackbirds and boat-tailed grackles (Quiscalus major) cause substantial damage to newly seeded rice in the southern United States, and the examination of color avoidance by these species should contribute to the development of nonlethal methods to reduce depredations. We used rice seed of various colors to conduct a series of feeding trials with captive blackbirds and grackles. Despite variation among individuals and groups of test birds, blue was the least preferred color overall. Differences among species and among background color might affect responses of birds to a given seed color, but, in general, we suggest that blue should be incorporated into strategies for discouraging unwanted feeding by granivorous birds. In particular, further development of visual deterrents should exploit the ability of blackbirds and other species to detect wavelengths in the near ultraviolet. JOURNAL OF WILDLIFE MANAGEMENT 63(3):1003-1008

Blackbird (Icterinae) damage to sunflowers in the northern Great Plains can be locally severe. One approach to alleviating depredation pressure is to reduce blackbird populations through application of brown rice bait treated with the avicide DRC-1339. Because such baiting can potentially affect nontarget species, we conducted pen and field trials to evaluate the potential risk from avicide baiting to ring-necked pheasants (Phasianus colchicus). Although most female pheasants in pen tests preferred cracked corn and sorghum, 2 of 12 birds preferred brown rice. In 4-day trials within a 0.2-ha flight pen, pheasant consumption of brown rice from bait swaths simulating field bait applications was not affected by the presence of an alternate bait swath of cracked corn. Pen trials to evaluate possible avoidance responses following a sublethal dose of DRC-1339 showed that 2 of 7 birds shifted from their previously preferred feeding sites following exposure to the avicide. During March and April 1995, we recorded pheasant numbers in 6 pairs of 0.8-ha plots in corn stubble fields that were either baited with brown rice or were designated as reference plots. Overall, use of test plots was low, but at the most heavily used sites, pheasants visited reference plots more than baited plots (P = 0.004). We conclude that (1) pheasants will eat brown rice treated with DRC-1339; and (2) although chances of exposure to an acute lethal dose can be reduced by increasing the dilution, harmful repeated doses could be obtained because avoidance of feeding sites, following sublethal exposure, cannot be assumed.

Safe, effective bird repellents are needed as seed treatments and for many other agricultural uses. Quinones are distributed widely in nature and many have predator defense and antiherbivory functions. One compound, 9,10-anthraquinone, was identified as a bird repellent in the 1940s, but is not registered for use in the United States. We evaluated it and 2 structurally related compounds, anthrone and anthracene, for repellency to rice-eating birds. In choice tests with individually caged red-winged blackbirds (Agelaius phoeniceus) anthraquinone and anthrone produced comparable reductions in consumption of treated rice at rates of 0.05, 0.10, and 0.25% (g/g). At 0.50%, however, only anthraquinone suppressed consumption of untreated rice as well as treated rice. Anthracene was least effective of the 3 compounds and was tested only at 0.50%. In 1-cup tests, consumption of anthraquinone-treated rice by individual blackbirds was suppressed at 0.10, 0.25, and 0.50%. Rice consumption by individually caged female boat-tailed grackles (Quiscalus major) exposed to the 0.50% treatment was similar to that of redwings at the 0.10% treatment. In choice tests of 3-bird groups in large flight enclosures, red-winged blackbirds discriminated strongly against 0.25% anthraqunione-treated rice. Observations of videotaped birds revealed no evidence of contact irritation or unpleasant taste; rather post-ingestive illness, as evidenced by one vomiting bird, suggests that anthraquinone repellency is due to learned behavior.

In many parts of North America, bird depredation is a major problem for growers of blueberry and other small fruit. Methyl anthranilate (MA) is an effective avian feeding deterrent in some situations, and we conducted a 3-state field trial to evaluate the efficacy of a formulated product, ReJeX-iT AG-36. On 5 0.4-ha plots in Oregon, Washington, and Michigan, we applied 56.8 L of ReJeX-iT (17.2 kg MA/ha) at weekly intervals for 21 days. Numbers of blueberries lost from tagged branches in treated plots did not differ from those lost from paired control plots. Furthermore, yields from treated and control plots did not differ. Residues of MA on fruit immediately after spraying were unexpectedly low (≤115 ppm) and declined rapidly to

Red-winged blackbirds (Agelaius phoeniceus) and related species cause millions of dollars of damage annually to sprouting rice in Louisiana and Texas. Seed treatments that deter birds offer an approach to managing this problem, so we evaluated a formulation (ReJeX-iT AG-36) of methyl anthranilate (MA) in aviary and field tests to assess its potential as an avian feeding deterrent for rice seed. In a feeding trial with an untreated commercial ration as the alternative food, MA suppressed (P < 0.05) rice consumption at 2.5% (g/g) but not at lower rates. With untreated rice as the alternative food, however, repellency occurred at 1.0% MA (P < 0.05). Controlled field trials showed that seed loss from plots having a 1.7% MA treatment averaged 27 and 34% compared with control plot losses of 52 and 73%. We conclude that MA has potential in the management of blackbird damage to rice, particularly if MA residues on rice seed can be prolonged