David G. Decker

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.

Anthraquinone protects rice seed from birds

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

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

Responses of captive fish crows to eggs treated with chemical repellents

Eggs of many bird species are subject to predation by corvids. To evaluate whether predation might be reduced through food avoidance learning, we offered japanese quail (Coturnix japonica) eggs treated with various repellent chemicals to captive fish crows (Corvus ossifragus). Topically applied methyl anthranilate (100 mg/egg), alone and in combination with injected methiocarb (18 mg/egg), effectively reduced (P = 0.015) egg eating by crows. Crows that received topical methyl anthranilate alone, however, lost their avoidance response when untreated eggs were offered. Egg eating was not reduced (P > 0.05) by 18 mg/egg injections of carbachol (carbamylcholine chloride) or methiocarb, or by a combined methiocarb (18 mg/egg) and methyl anthranilate (100 mg/egg) injection

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

Responses of captive blackbirds to a new insecticidal seed treatment

Development of new repellent chemicals specifically to control crop damage by birds may be cost-prohibitive. Instead, the use of compounds developed for other pest control needs may be more practical. Thus, we conducted 2-cup feeding trials with singly caged red-winged blackbirds (Agelaius phoeniceus) and brown-headed cowbirds (Molothrus ater) to test the repellency of a new seed treatment insecticide, imidacloprid (proposed common name for Miles Incorporated NTN33893). Both redwings and cowbirds were strongly deterred (P < 0.05) from feeding on rice seed treated with imidacloprid at 620 and 1,870 ppm. When applied to wheat seed, imidacloprid effectively reduced (P < 0.05) consumption by redwings at rates as low as 165 ppm

Mint plant derivatives as blackbird feeding deterrents

Abstract 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.

Repellency of fungicidal rice seed treatments to red-winged blackbirds

We evaluated the feeding responses of male red-winged blackbirds (Agelaius phoeniceus) to rice seed treated with fungicidal compounds in a series of 2-cup, 1-cup, and flight pen trials. Of the materials tested, Kocide ® SD, a fungicide containing 30% copper hydroxide, was the most effective. Although this chemical caused mortality (due to hemolytic anemia) when applied at relatively high concentrations in the 1-cup test, birds consistently avoided it without ill effects in 2-cup and flight pen trials. Applied at the currently registered label rate, Kocide may safely and effectively repel birds feeding on newly planted rice. Currently registered fungicides and other pesticides may offer new alternatives for bird damage control

Cage and flight pen evaluation of avian repellency and hazard associated with imidacloprid-treated rice seed

Abstract A series of cage and flight pen trials evaluated the responses of male red-winged blackbirds ( Agelaius phoeniceus ) to rice seed treated with imidacloprid, a systemic insecticide. In two-cup trials, when both the treated and untreated seed was either dyed or undyed, individually caged redwings consistently avoided rice seed treated with 833 and 2500 mg kg −1 imidacloprid but not 278 mg kg −1 . When birds had a choice between undyed, untreated rice and dyed imidacloprid-treated rice, consumption of treated seed was suppressed at all levels. In a one-cup trial, rice consumption during the 4-day test phase was reduced relative to that during the 4-day pretest period at 833 and 2500 mg kg −1 of imidacloprid but not at 0 and 278 mg kg −1 . During 4-day trials in a 0.2 ha flight pen, six different ten-bird flocks removed an average of 41.1% of the untreated rice seed on sample quadrats compared with 8.8% lost from plots having 2500 mg kg −1 imidacloprid-treated seed. On the basis of residues from whole seeds and from hulls of rice seed eaten by test birds, it is estimated that redwings ingested 13–16% of the imidacloprid initially present on the seed. Thus, even at 2500 mg kg −1 , red-winged blackbirds feeding at an average rate of six seeds min −1 acquired only a fraction of the imidacloprid calculated to be a lethal dose. Imidacloprid appears to be an effective bird repellent seed treatment with minimal avian hazard.

Repellency of cinnamic acid esters to captive red-winged blackbirds

Each year, blackbirds cause millions of dollars of damage to newly planted rice in the southern United States. Currently, there is no product registered as a bird repellent rice seed treatment, so we conducted 2-cup feeding trials with individually caged male red-winged blackbirds (Agelatus phoeniceus) to test the repellency of methyl cinnamate and ethyl cinnamate, 2 naturally occurring esters of cinnamic acid. While ethyl cinnamate was moderately deterrent, consumption of treated rice was virtually eliminated by a 1.0% (g/g) application of methyl cinnamate. Additional effort should be given to understanding the chemical and physiological bases of repellency of feeding deterrents such as methyl cinnamate as well as to the development of these materials as bird management tools