The Future of Blackbird Management Research

Human society values birds for their intrinsic and aesthetic value as well as the ecosystem services they provide as pollinators, consumers of pests, and distributors of nutrients and seeds (Wenny et al. 2011). At the same time, conflict between birds and humans is an age-old phenomenon that has persisted as society has transformed and the scale of agriculture has expanded (Conover 2002). Managing conflict between birds and agriculture is challenging for many reasons. Foremost, the need to consider both human welfare and conservation of protected bird species is paramount, with nonlethal management methods preferred to lethal measures from societal, economical, and ecological standpoints (Miller 2007; Linz et al. 2015). Second, methods must be effective, practical, and economical for agricultural implementation. Finally, management methods must overcome characteristics that make birds difficult to manage including uncertainty in population estimates, fecundity, mobility, and adaptive behaviors. All challenges are compounded when attempting to establish management methods that fit within modern agricultural practices, while simultaneously supporting conservation efforts to protect wildlife. Labor-saving devices and methodologies resulting from agricultural advances in mechanical, chemical, genetic, and information technologies have facilitated a shift to larger crop fields, a broader range of suitable habitat for a variety of crops, and consolidated farms in North America (MacDonald et al. 20(3). This shift to large. less labor-intensive farms has supported the ability to feed an ever-increasing human population but has complicated the relationship between humans and wildlife. Modern agriculture directly impacts wildlife by altering natural habitat. resulting in the increase of species able to thrive in agricultural landscapes and the decline of species unable to adapt. Thus. agriculture often provides increased carrying capacity for species responsible for agricultural damage (Van Vuren and Smallwood 1996). However, changes in harvest efficiency have resulted in less crop waste and reduced availability of high-energy foods available to birds postharvest, potentially placing common farmland birds at risk of decline (Krapu et al. 2004; Galle et al. 2009). Nevertheless, vertebrate species able to adapt to the agricultural landscape often reach pest levels, resulting in producers seeking tools to reduce damage, tools that have not necessarily advanced in concert with modern agriculture. Red-winged blackbirds (150 million; Agelaius phoeniceus), brown-headed cowbirds (120 million; Molothrus ater), common grackles (69 million; Quiscalus quiscula), and yellowheaded blackbirds (15 million; Xanthocephalus xanthocephalus) are among the most numerous birds in North America (Rosenberg et al. 2016). This book has identified conflicts between blackbirds and agricultural commodity groups including livestock, rice, corn, sunflower, and numerous specialty crops (Dolbeer 1990; Cummings et al. 2005; Anderson et al. 2013; Klosterman et al. 2013; Figure 13.1). Continued progress in development of blackbird management methods and acquisition of baseline knowledge as to its impacts on blackbird populations are needed at local, regional, and national scales. In this chapter, I evaluate gaps in knowledge and potential research directions. I address the following topics: (I) blackbird biology at the species, population, and community levels; (2) the influence of changing landscapes on blackbirds and agricultural damage in terms of agricultural practices, habitat, and climate change; (3) the limitations of lethal and nonlethal management tools (i.e., repellents, frightening devices, and evading strategies) and how research can optimize techniques or facilitate new tool discovery; and (4) economic evaluation of management and human dimensions

Movement Behavior of Radio-Tagged European Starlings in Urban, Rural, and Exurban Landscapes

Since their intentional introduction into the United States in the 1800s, European starlings (Sturnus vulgaris) have become the fourth most common bird species and a nuisance bird pest in both urban and rural areas. Managers require better information about starling movement and habit-use patterns to effectively manage starling populations and the damage they cause. Thus, we revisited 6 radio-telemetry studies conducted during fall or winter between 2005 and 2010 to compare starling movements (n = 63 birds) and habitat use in 3 landscapes. Switching of roosting and foraging sites in habitat-sparse rural landscapes caused daytime (0900–1500 hours) radio fixes to be on average 2.6 to 6.3 times further from capture sites than either urban or exurban landscapes (P \u3c 0.001). Roosts in urban city centers were smaller (100,000 birds) 6–13 km away in industrial zones. Radio-tagged birds from city-center roosts occasionally switched to the outlying major roosts. A multitrack railroad overpass and a treed buffer zone were used as major roosts in urban landscapes. Birds traveling to roosts from primary foraging sites in exurban and rural landscapes would often pass over closer-lying minor roosts to reach major roosts in stands of emergent vegetation in large wetlands. Daytime minimum convex polygons ranged from 101–229 km2 (x̄ = 154 km2). Anthropogenic food resources (e.g., concentrated animal feeding operations, shipping yards, landfills, and abattoirs) were primary foraging sites. Wildlife resource managers can use this information to predict potential roosting and foraging sites and average areas to monitor when implementing programs in different landscapes. In addition to tracking roosting flights, we recommend viewing high-resolution aerial images to identify potential roosting and foraging habitats before implementing lethal culls (e.g., toxicant baiting)

Evaluation of two unmanned aircraft systems as tools for protecting crops from blackbird damage

In response to a need for mitigating blackbird damage to crops, we evaluated the effectiveness of two unmanned aircraft systems (UAS or drones) to protect crops from blackbird damage. UAS are known to elicit behavioral and physiological responses in wildlife and have been proposed as a means to protect row crop agriculture from avian pest depredation. We evaluated the behavioral responses of captive and free-ranging red-winged blackbirds to a fixed-wing and a rotary-wing (multi-rotor, quadcopter) UAS by comparing preflight behaviors to behaviors during UAS approach. Due to the flight limitations of the respective UAS, the fixed-wing and rotarywing were evaluated at different altitudes. Behavioral responses of captive and free-ranging blackbirds to approaching UAS were categorized as no response, alertness, or attempted escape/flight. Neither captive nor freeranging flocks of red-winged blackbirds displayed behavioral responses to approaches by the fixed-wing UAS when flown at or above 52m above ground level (AGL). However, both captive and free-ranging flocks exhibited behavioral responses to the rotary-wing UAS when flown within 30m AGL. Behavioral responses of blackbirds to the rotary-wing UAS were more pronounced with lower altitude approaches. Our findings suggest that UAS have the potential to modify blackbird behavior in a way that may reduce sunflower crop depredation

Foraging Behavior of Red-Winged Blackbirds (Agelaius phoeniceus) on Sunflower (Helianthus annuus) with Varying Coverage of Anthraquinone-Based Repellent

Animals attempt to maximize foraging efforts by making strategic foraging decisions. Foraging efforts can be influenced by chemically defended food. Food resources that are chemically defended force foragers to balance the nutritional gain with the toxic costs of foraging on a defended food resource. Chemical defense, in this case sunflower treated with chemical repellent, may be capable of deterring birds from foraging on treated crops. Blackbirds (Icteridae) cause significant damage to sunflower (Helianthus annuus) with damage estimates of $3.5 million annually in the Prairie Pothole Region of North Dakota, the largest sunflower producing state. Chemical repellents may be a cost-effective method for reducing bird damage if application strategies can be optimized for sunflowers. Anthraquinone-based repellents have been shown to reduce feeding on sunflower achenes by more than 80% in lab studies, but results in the field are inconclusive due to application issues where floral components of sunflower result in low repellent contact with achenes. Ground rigs equipped with drop-nozzles have shown promise in depositing repellent directly on the sunflower face but coverage is variable. We propose to evaluate the feeding behavior of red-winged blackbirds (Agelaius phoeniceus) and the efficacy of an anthraquinone-based avian repellent when applied directly to the sunflower face in a lab-based experiment. Our main objectives are to 1) evaluate the coverage needed on the face of the sunflower to establish repellency, 2) evaluate achene removal rates over time to understand time to aversion at varying repellent coverages, and 3) evaluate the feeding behavior and activity budgets of red-winged blackbirds on treated and untreated sunflower. The results of this study will inform repellent coverage needed at the scale of the sunflower plant to deter feeding or alter time budgets of foraging red-winged blackbirds to ultimately reduce sunflower damage

Foraging behavior of red-winged blackbirds (\u3ci\u3eAgelaius phoeniceus\u3c/i\u3e) on sunflower (\u3ci\u3eHelianthus annuus\u3c/i\u3e) with varying coverage of anthraquinone-based repellent

Animals attempt to maximize foraging efforts by making strategic foraging decisions. Foraging efforts can be influenced by chemically defended food. Food resources that are chemically defended force foragers to balance the nutritional gain with the toxic costs of foraging on a defended food resource. Chemical defense, in this case sunflower treated with chemical repellent, may be capable of deterring birds from foraging on treated crops. Blackbirds (Icteridae) cause significant damage to sunflower (Helianthus annuus) with damage estimates of $3.5 million annually in the Prairie Pothole Region of North Dakota, the largest sunflower producing state. Chemical repellents may be a cost-effective method for reducing bird damage if application strategies can be optimized for sunflowers. Anthraquinone-based repellents have been shown to reduce feeding on sunflower achenes by more than 80% in lab studies, but results in the field are inconclusive due to application issues where floral components of sunflower result in low repellent contact with achenes. Ground rigs equipped with drop-nozzles have shown promise in depositing repellent directly on the sunflower face but coverage is variable. We propose to evaluate the feeding behavior of red-winged blackbirds (Agelaius phoeniceus) and the efficacy of an anthraquinone-based avian repellent when applied directly to the sunflower face in a lab-based experiment. Our main objectives are to 1) evaluate the coverage needed on the face of the sunflower to establish repellency, 2) evaluate achene removal rates over time to understand time to aversion at varying repellent coverages, and 3) evaluate the feeding behavior and activity budgets of red-winged blackbirds on treated and untreated sunflower. The results of this study will inform repellent coverage needed at the scale of the sunflower plant to deter feeding or alter time budgets of foraging red-winged blackbirds to ultimately reduce sunflower damage

Efficacy of an Avian Repellent Applied Using Drop Nozzle-Equipped Ground Rigs in Reducing Blackbird Damage to Sunflower

In North Dakota large flocks of blackbirds feed on ripening crops, after breeding and prior to migration, resulting in an annual damage estimate averaging $3.5 million for sunflower. Since the repellent needs to be ingested to be effective, one obstacle is applying sufficient repellent directly to the sunflower face. Thus, we tested efficacy of an anthraquinone-based repellent when applied via drop-nozzle to sunflower using enclosed blackbirds in a semi-natural field setting. We used a ground-rig equipped with 360 Undercover® drop nozzle sprayers to apply 20 gal/ac of solution to sunflower plots with a product application rate of 1.0 gal/ac (13% AQ). To test efficacy, we installed bird enclosures (12 x 13 x 10 ft) to house 10 captive, male red-winged blackbirds (Agelaius phoeniceus) for 23 days on 10 treated and 10 untreated plots. The repellent did not cause birds to consume more alternative diet (i.e., red milo). Sunflower yield did not differ between treated and untreated enclosures as a result of blackbird damage. Variation in the amount of repellent reaching the face of the sunflower and subsequent residues was a limitation of the application method. Efficacy may be improved by increasing the application rate or repellent in the tank mixture, but sprayer technology and economic limitations related to repellent costs need to be considered. Future studies should aim to optimize the amount of product in tank mixtures and the repellent formulation as designed for specific pests and crops

An assessment of the US endangered species act recovery plans: using physiology to support conservation

Applying physiology to help solve conservation problems has become increasingly prominent. It is unclear, however, if the increased integration into the scientific community has translated into the application of physiological tools in conservation planning. We completed a review of the use of animal physiology in the US Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS) Endangered Species Act (ESA) recovery plans released between 2005 and 2016. Over those 11 years, 135 of the 146 recovery plans mentioned physiology, with 56% including it as background information on the natural history of the species and not as part of the recovery process. Fish and bird species had the lowest proportion of recovery plans to include physiology beyond the description of the natural history. When considering multiple sub-disciplines of physiology, immunology and epidemiology were incorporated as part of the recovery process most often. Our review suggests a disconnect between available physiological tools and the potential role of physiology in developing conservation plans. We provide three suggestions to further guide conservation scientists, managers and physiologists to work synergistically to solve conservation problems: (1) the breadth of knowledge within a recovery plan writing team should be increased, for example, through increased training of federal scientists in new physiology methodologies and tools or the inclusion of authors in academia that have a background in physiology; (2) physiologists should make their research more available to conservation scientists and federal agencies by clearly linking their research to conservation and (3) communication should be enhanced between government conservation scientists and physiologists

Ecology and Management of Red-Winged Blackbirds

The red-winged blackbird (Agelaius phoeniceus) is one of the most abundant bird species in North America, with an estimated spring breeding population of 150 million individuals that nest in emergent wetland vegetation and upland habitats throughout the continent (Yasukawa and Searcy 1995; Forcey et al. 2015; Rosenberg et al. 2016). During the nonbreeding season, red-winged blackbirds are often found in flocks numbering from a few birds to many thousands, sometimes in association with other blackbird species and European starlings (Sturnus vulgaris). In winter, red-winged blackbirds and these associated species gather in roosts occasionally numbering over 10 million birds (Meanley and Royal 1976; White et al. 1985). Migratory male red-winged blackbirds typically arrive at their nesting grounds in early March, a month before the females arrive. At this time, casual bird watchers are apt to notice the robinsized, male red-winged blackbirds with black feathers and highly conspicuous red and yellow epaulets (definitive plumage), prominently displayed while aggressively confronting intruders approaching their nesting territories (Figure 2.1). Loud singing (o-ka-leeee, konk-a-ree) by these males from high perches in their chosen territories adds to their aesthetic value. Second-year males returning to their natal area following their hatching year do not have the definitive plumage of adults. Rather, they have a duller black body and light red or orange epaulets (Yasukawa and Searcy 1995). The female, at least 20% smaller and far less noticeable with brownish feathers, is often misidentified as a large streaked sparrow (Figure 2.2) (Yasukawa and Searcy 1995; Jaramillo and Burke 1999)

Testing a key assumption of using drones as frightening devices: Do birds perceive drones as risky?

Wildlife managers have recently suggested the use of unmanned aircraft systems or drones as nonlethal hazing tools to deter birds from areas of human-wildlife conflict. However, it remains unclear if birds perceive common drone platforms as threatening. Based on field studies assessing behavioral and physiological responses, it is generally assumed that birds perceive less risk from drones than from predators. However, studies controlling for multiple confounding effects have not been conducted. Our goal was to establish the degree to which the perception of risk by birds would vary between common drone platforms relative to a predator model when flown at different approach types. We evaluated the behavioral responses of individual Red-winged Blackbirds (Agelaius phoeniceus) to 3 drone platforms: a predator model, a fixed-wing resembling an airplane, and a multirotor, approaching either head-on or overhead. Blackbirds became alert earlier (by 13.7 s), alarm-called more frequently (by a factor of 12), returned to forage later (by a factor of 4.7), and increased vigilance (by a factor of 1.3) in response to the predator model compared with the multirotor. Blackbirds also perceived the fixed-wing as riskier than the multirotor, but less risky than the predator model. Overhead approaches mostly failed to elicit flight in blackbirds across all platform types, and no blackbirds took flight in response to the multirotor at either overhead or head-on approaches. Our findings demonstrate that birds perceived drones with predatory characteristics as riskier than common drone models (i.e. fixed-wing and multirotor platforms). We recommend that drones be modified with additional stimuli to increase perceived risk when used as frightening devices, but avoided if used for wildlife monitoring. RESUMEN Los gestores de vida silvestre han sugerido recientemente el uso de sistemas aéreos no tripulados o drones como herramientas no letales de atosigamiento para disuadir a las aves de áreas de conflicto entre humanos y vida silvestre. Sin embargo, aún no está claro si las aves perciben a los drones comunes como una amenaza. Tomando como base los estudios de campo que evalúan las respuestas comportamentales y fisiológicas, por lo general se asume que las aves perciben un riesgo menor de parte de los drones que de los depredadores. Sin embargo, no se han realizado estudios que controlen los múltiples efectos contrapuestos. Nuestro objetivo fue establecer la variación en el grado de percepción de riesgo de las aves frente a drones comunes y a un modelo de depredador, considerando diferentes tipos de acercamiento de vuelo. Evaluamos las respuestas de comportamiento de individuos de Agelaius phoeniceus frente a tres tipos de drones: un modelo depredador, un modelo de ala rígida parecido a un avión y un modelo multi-rotor, todos acercándose ya sea de frente o por encima. Los individuos de A. phoeniceus se alertaron antes (por 13.7 s), realizaron llamados de alarma más frecuentemente (por un factor de 12), regresaron a forrajear más tarde (por un factor de 4.7) y aumentaron la vigilancia (por un factor de 1.3) en respuesta al modelo de depredador comparado con el multi-rotor. A. phoeniceus también percibió el modelo de ala fija como más riesgoso que el multi-rotor, pero menos riesgoso que el depredador. La mayoría de los acercamientos por encima, considerando todos los tipos de drones, no provocaron el vuelo de A. phoeniceus, y ningún individuo de A. phoeniceus voló en respuesta al multi-rotor, ya sea en los acercamientos de frente o por encima. Nuestros resultados demuestran que las aves perciben a los drones con características de depredador como más riesgosos que los modelos de drone comunes (i.e. de ala fija o multi-rotor). Recomendamos que los drones sean modificados con estímulos adicionales para aumentar el riesgo percibido cuando se los usa como dispositivos de intimidación, pero evitar modificarlos si se los usa para monitoreo de fauna silvestre

A Sonic Net reduces damage to sunflower by blackbirds (Icteridae): Implications for broad-scale agriculture and crop establishment

Blackbirds, such as red-winged blackbirds (Agelaius phoeniceus), are notorious agricultural pests and damage crops at multiple stages of growth. Our aim was to test a novel deterrent, the use of sound designed to mask communication among birds (termed a “Sonic Net”), to deter blackbirds (Icteridae) from target areas of maturing sunflower crops. The Sonic Net masks communication of a target species by delivering “pink noise” that overlaps with the frequencies that the species uses for acoustic communication. If birds cannot hear predators or conspecific warning calls their perceived predation risk increases, and they relocate to an area with lower predation risk. Working with local sunflower producers in North Dakota, USA we set up experimental sites in three sunflower fields that were actively used by mixed-species blackbird flocks. In each field, we established two 0.2 ha plots and measured the initial area of damage for 63 individually-marked sunflowers. We applied the Sonic Net treatment to one of the paired plots in each field. At the end of the 20-day treatment period, we measured the total area damaged on the individually-marked sunflowers from each plot to calculate the change in damage for each sunflower. In all three fields, Sonic Net treatments substantially reduced percent damage to sunflowers, by 28.6% (95% CI: 12.5–41.7%), 63.6% (57.2–69.0%) and 22.6% (16.6–28.1%) for fields in Burleigh, McIntosh, and Emmons, respectively. In addition, sunflowers with a higher initial area of available seed experienced higher damage. We predict that the effect of the Sonic Net treatment may be greater in other crop phases and types, such as in the establishment phase or ground cover crops. During crop establishment there is a relative lack of tall, three-dimensional vegetational structure, which would allow for more effective spread of the Sonic Net sound and offer fewer physical refugia for birds to lower their perceived predation risk. We suggest both larger scale agricultural tests of the Sonic Net and efficacy tests for protecting crops at early growth stages to further explore the usefulness of this technology for crop protection