Michael L. Avery

Behavioral flexibility and species invasions: the adaptive flexibility hypothesis

Behavioral flexibility is an important adaptive response to changing environments for many animal species. Such plasticity may also promote the invasion of novel habitats by introduced species by providing them with the ability to expand or change their ecological niche, a longstanding idea with recent empirical support. At the individual level, flexibility may arise through innovation, in which an individual invents a new behavior, or through social learning, in which an individual adopts a behavior used by others. There is increasing evidence that the adaptive value of these two modes of learning, and the overall expression of behavioral flexibility, may vary with social and environmental context. In this paper, we propose that invasive species may change the degree to which they express behavioral flexibility in an adaptive manner during the different stages of invasion. Specifically, the “adaptive flexibility hypothesis” predicts that the expression of behavioral flexibility, and thus the diversity of behaviors observed in a population, will be high during the initial stage of introduction into a novel environment due to innovation, followed by a decline in behavioral diversity during the establishment and growth of a founding population due to social learning of successful behavioral variants. We discuss several alternatives to this hypothesis and suggest empirical and theoretical tests of these hypotheses. This “adaptive flexibility hypothesis” suggests that a more nuanced approach to the study of the behaviors employed by individuals in populations at different invasion stages could generate new insight into the importance of such flexibility during species invasions, and the evolution of behavioral plasticity in general

Detecting an elusive invasive species: a diagnostic PCR to detect Burmese python in Florida waters and an assessment of persistence of environmental DNA.

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.

An Estimate of Avian Mortality at Communication Towers in the United States and Canada

Avian mortality at communication towers in the continental United States and Canada is an issue of pressing conservation concern. Previous estimates of this mortality have been based on limited data and have not included Canada. We compiled a database of communication towers in the continental United States and Canada and estimated avian mortality by tower with a regression relating avian mortality to tower height. This equation was derived from 38 tower studies for which mortality data were available and corrected for sampling effort, search efficiency, and scavenging where appropriate. Although most studies document mortality at guyed towers with steady-burning lights, we accounted for lower mortality at towers without guy wires or steady-burning lights by adjusting estimates based on published studies. The resulting estimate of mortality at towers is 6.8 million birds per year in the United States and Canada. Bootstrapped subsampling indicated that the regression was robust to the choice of studies included and a comparison of multiple regression models showed that incorporating sampling, scavenging, and search efficiency adjustments improved model fit. Estimating total avian mortality is only a first step in developing an assessment of the biological significance of mortality at communication towers for individual species or groups of species. Nevertheless, our estimate can be used to evaluate this source of mortality, develop subsequent per-species mortality estimates, and motivate policy action.

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.

Assessing Allowable Take of Migratory Birds

Abstract Legal removal of migratory birds from the wild occurs for several reasons, including subsistence, sport harvest, damage control, and the pet trade. We argue that harvest theory provides the basis for assessing the impact of authorized take, advance a simplified rendering of harvest theory known as potential biological removal as a useful starting point for assessing take, and demonstrate this approach with a case study of depredation control of black vultures (Coragyps atratus) in Virginia, USA. Based on data from the North American Breeding Bird Survey and other sources, we estimated that the black vulture population in Virginia was 91,190 (95% credible interval = 44,520–212,100) in 2006. Using a simple population model and available estimates of life-history parameters, we estimated the intrinsic rate of growth (rmax) to be in the range 7–14%, with 10.6% a plausible point estimate. For a take program to seek an equilibrium population size on the conservative side of the yield curve, the rate of take needs to be less than that which achieves a maximum sustained yield (0.5 × rmax). Based on the point estimate for rmax and using the lower 60% credible interval for population size to account for uncertainty, these conditions would be met if the take of black vultures in Virginia in 2006 was <3,533 birds. Based on regular monitoring data, allowable harvest should be adjusted annually to reflect changes in population size. To initiate discussion about how this assessment framework could be related to the laws and regulations that govern authorization of such take, we suggest that the Migratory Bird Treaty Act requires only that take of native migratory birds be sustainable in the long-term, that is, sustained harvest rate should be

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

Evaluation of Bird Shield as a blackbird repellent in ripening rice and sunflower fields

Abstract Chemical repellents sometimes can provide a nonlethal alternative for reducing wildlife impacts to agricultural production. In late summer and autumn 2002, we evaluated Bird Shield™ (active ingredient: methyl anthranilate, Bird Shield Repellent Corporation, Spokane, Wash.) as a blackbird (Icteridae) repellent in Missouri rice fields and North Dakota sunflower fields. We selected 5 pairs of ripening rice fields in southeastern Missouri and randomly allocated treatments (treated and control) within pairs. The repellent was aerially applied by fixed-winged aircraft at the recommended label rate and volume (1.17 L Bird Shield/ha and 46.7 L/ha, respectively); 1 field received 2X the label rate. We observed no difference in average bird activity (birds/minute) between treated and control fields over the 3-day post-treatment period (P = 0.503). We used reversed-phase liquid chromatography to quantify methyl anthranilate residues in treated fields. The maximum concentration of methyl anthranilate in rice samples was 4.71 µg/g. This concentration was below reported threshold values that irritate birds. In North Dakota we selected 6 pairs of sunflower fields used by foraging blackbirds. We randomly selected 1 field from each pair for 2 aerial applications of Bird Shield at the label-recommended rate ∼1 week apart. The remaining 6 fields served as controls. Daily bird counts, starting the first day of application and continuing for 5–7 days after the second application, showed similar numbers of blackbirds within treated and control fields (P = 0.964). We observed no difference in sunflower damage within treated and control fields (P = 0.172) prior and subsequent to the treatment. Bird Shield was not effective for repelling blackbirds from ripening rice and sunflower fields.

Evaluation of Methyl Anthranilate and Starch-Plated Dimethyl Anthranilate as Bird Repellent Feed Additives

We conducted 3 experiments to evaluate the effectiveness of methyl anthranilate (MA) as a bird repellent. In Experiment 1, we examined the repellency of several technical MA concentrations in 6-hour tests―a time period similar to the duration of exposure of livestock feed in feedbunks. In Experiment 2, we determined the lowest concentration of technical MA that was as effective as 1.0% dimethyl anthranilate starch (DMA; our field-tested standard). Finally, in Experiment 3, we explored the repellency of starch-encapsulated MA to grouped red-winged blackbirds (Agelaius phoeniceus) and European starlings (Sturnus vulgaris) in an outdoor aviary. Experiments 1 and 2 indicated that 0.4-0.5% MA was as repellent as 1.0% DMA-starch. Experiment 3 showed that although 1.0% MA reduced consumption by grouped starlings and red-wings in 2-choice tests, only starlings avoided treated food in 1-choice tests. Red-wings habituated to the substance, and consumption returned to baseline levels by treatment Day 3. We conclude that MA is an economical alternative to DMA, although species and/or social factors may influence repellency

Genetic evidence links invasive monk parakeet populations in the United States to the international pet trade

BackgroundSevere ecological and economic impacts caused by some invasive species make it imperative to understand the attributes that permit them to spread. A notorious crop pest across its native range in South America, the monk parakeet (Myiopsitta monachus) has become established on four other continents, including growing populations in the United States. As a critical first step to studying mechanisms of invasion success in this species, here we elucidated the geographical and taxonomic history of the North American invasions of the monk parakeet. Specifically, we conducted a genetic assessment of current monk parakeet taxonomy based on mitochondrial DNA control region sequences from 73 museum specimens. These data supported comparative analyses of mtDNA lineage diversity in the native and naturalized ranges of the monk parakeet and allowed for identification of putative source populations.ResultsThere was no molecular character support for the M. m. calita, M. m. cotorra, and M. m. monachus subspecies, while the Bolivian M. m. luchsi was monophyletic and diagnosably distinct. Three haplotypes sampled in the native range were detected within invasive populations in Florida, Connecticut, New Jersey and Rhode Island, the two most common of which were unique to M. m. monachus samples from eastern Argentina and bordering areas in Brazil and Uruguay.ConclusionThe lack of discrete morphological character differences in tandem with the results presented here suggest that M. m. calita, M. m. cotorra and M. m. monachus are in need of formal taxonomic revision. The genetic distinctiveness of M. m. luchsi is consistent with previous recommendations of allospecies status for this taxon. The geographic origins of haplotypes sampled in the four U.S. populations are concordant with trapping records from the mid-20th century and suggest that propagule pressure exerted by the international pet bird trade contributed to the establishment of invasive populations in the United States.

An analytical framework for quantifying and testing patterns of temporal dynamics in social networks

Change is fundamental to all social systems. Temporal dynamics are critical in understanding how relationships form and change over time but rarely are studied explicitly in animal groups. Social network approaches are useful in describing association patterns and provide promising tools for investigating the dynamics of change in social structure but have rarely been used to quantify how animal associations change over time. In this study, we describe and test a framework for temporal analysis of social structure. We propose an analytical framework of methods that integrates across social scales and comparatively analyses change in social structure across multiple types of social association. These methods enable comparisons in groups that differ in size and are flexible to allow application to weighted and unweighted networks, where ties can be directed or undirected, and relationships can be symmetric or asymmetric. We apply this analytical framework to temporal social network data from experimentally formed captive groups of monk parakeets, Myiopsitta monachus, to both evaluate our analysis methods and characterize the social structure of this species. We compared dynamics of dyadic network formation, ego network formation and global network stabilization patterns across neutral, affiliative and agonistic associations. We found that social structure of captive monk parakeets formed and stabilized over a short period, but patterns differed by social association type. We also found evidence for consistency in the temporal dynamics of formation and stabilization of social structure between replicate social groups. Our analysis methods successfully identified change in social structure that corresponded well with qualitative observations. This framework is likely to be useful in characterizing patterns of temporal dynamics in social structure in longitudinal data in wide variety of social systems and species. 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.