John S. Humphrey

Feeding deterrence of anthraquinone, anthracene, and anthrone to rice-eating birds

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.

Methyl anthranilate as a rice seed treatment to deter birds

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

COLOR, SIZE, AND LOCATION OF ARTIFICIAL FRUITS AFFECT SUCROSE AVOIDANCE BY CEDAR WAXWINGS AND EUROPEAN STARLINGS

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

Cold weather and the potential range of invasive Burmese pythons

The Burmese python (Python molurus bivittatus) is established in Everglades National Park and neighboring areas in south Florida. Beyond its substantial ecological impacts to native fauna in south Florida, concerns have been raised as to its potential to occupy other parts of the USA, even as far north as Washington, DC. During a recent period of cold weather, seven of nine captive Burmese pythons held in outdoor pens at our facility in north-central Florida died, or would have died absent our intervention. This cold-induced mortality occurred despite the presence of refugia with heat sources. Our findings cast doubt on the ability of free-ranging Burmese pythons to establish and persist beyond the subtropical environment of south Florida.

Field evaluation of methyl anthranilate for deterring birds eating blueberries

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 <4 ppm 6 days postspray. At 3 of the 5 study sites, extensive leaf discoloration followed ReJeX-iT AG-36 applications. Innovative application technologies will need to be developed if formulated MA is to be effective as a bird deterrent in blueberries.

SEED COLOR AVOIDANCE BY CAPTIVE RED-WINGED BLACKBIRDS AND BOAT-TAILED GRACKLES

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

Potential risk to ring-necked pheasants from application of toxic bait for blackbird control in south Dakota

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.

Evaluating Trap Alternatives for Removal of Salvator merianae (Black and White Tegu)

Abstract 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 we recommend well-designed field trials as a next step.

Improved Satellite Transmitter Harness Attachment Technique

TÉCNICA MEJORADA DE SUJECIÓN DEL ARNÉS DE UN TRANSMISOR SATELITAL La telemetría satelital a menudo requiere de la sujeción de un transmisor en el ave utilizando un arnés de configuración tipo mochila. El calce apropiado del arnés sobre el ave es esencial para un despliegue efectivo y para el bienestar de las aves. Presentamos una técnica mejorada de sujeción del arnés que emplea un remache barato y disponible de forma inmediata. Este método reduce el tiempo de manipulación y permite a los investigadores ajustar las guías del arnés de forma rápida y luego asegurarlas eficientemente sin coser, enroscar o pegar con plástico caliente.