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Wildlife Sunflower Conservation Plot located near a blackbird roost in North Dakota. Photograph: Heath M. Hagy.
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Even though avian damage to sunflower (Helianthus annuus L.) is a worldwide economic issue, several of the current methods used to reduce sunflower damage were developed and tested in the Prairie Pothole Region of the United States. An intensive research program was conducted in that area because of the regionalized concentration of sunflower produ...
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... In the northern Great Plains, high acreage of sunflower (Helianthus annuus) and cattail (Typha spp.) creates a conflict scenario wherein blackbirds (Icteridae) transitioning to molt and migration aggregate in large, mixed-species flocks and use sunflower for their energetically expensive migration (Bansal et al. 2019). Tools to reduce crop damage include physical frightening devices, chemical repellents, exclusion devices, and lethal control (Linz et al. 2011;Linz, Avery, et al. 2017;Klug et al. 2023). Flock-size estimates serve as indicators of tool efficacy whether documenting a change in bird numbers after tool use or tool efficacy with respect to flocks of differing sizes. ...
In human-wildlife conflict, estimates are important for quantifying animal abundance and assessing tool efficacy to disperse wildlife and reduce damage. We used drones to capture images of mixed-species blackbird (Icteridae) flocks damaging sunflower (Helianthus annuus) in North Dakota (August to October). We evaluated the ability of 20 biologists to make estimates close to an automated count (i.e., ImageJ). While estimates were highly correlated (Spearman: R = 0.94, p <0.001), biologist estimates (range = 25–50,000 birds) were on average 16% lower and 69% different (absolute value of difference) than automated counts (range = 57–6,272 birds). Biologists were closer to automated counts when observing smaller flocks and images later in the photoset. We found no effect of self-reported experience. Although drone imagery provides a standardized method to count flocks at far distances, in-field estimates are needed given entire flocks are not easily captured in a single frame. Drone imagery can be used to train biologists and reduce estimation errors among and within observers when flock sizes vary and reach large aggregations. Additionally, autonomous drone systems could use real-time imagery during hazing to target nuisance species of certain flock sizes for efficient resolution of human-wildlife conflict.
... In response to these challenges, various bird damage control methods have been implemented to mitigate agricultural losses (Klug et al. 2023), usually divided into lethal and non-lethal strategies. The use of lethal methods involves strategies such as shooting, nest destruction, poisoning, and trapping (Betz Heinemann et al. 2020;Linz et al. 2011) to reduce bird numbers. These approaches are rarely monitored and display short-term effectiveness when applied to abundant populations with high fecundity and dispersion capacity (Betz Heinemann et al. 2020;. ...
... Ongoing research is exploring alternative, non-lethal strategies for bird management to balance crop protection and wildlife conservation (Day et al. 2012;Destrez et al. 2022). Traditional approaches, such as auditory deterrents (e.g., propane cannons and distress calls) and visual scare tactics (e.g., balloons and scarecrows) (Linz et al. 2011), are commonly employed but exhibit only short-term effectiveness due to rapid habituation by birds (Esther, Tilcher, and Jacob 2013;Klug et al. 2023). Non-lethal methods also include sowing practices' adjustments, such as deeper seed placement and increased spacing between seeds (Canavelli et al. 2014;Huang et al. 2023). ...
... However, these substances have mainly been tested on captive populations or wild corvids held in captivity (Hile et al. 2004;Avery et al. 2005;Linz et al. 2007;Day et al. 2012;Esther, Tilcher, and Jacob 2013;Destrez et al. 2022). These studies often overlook critical factors such as birds' ability to choose food under natural conditions and individual feeding preferences, both of which are likely essential for evaluating the effectiveness of damage prevention measures (Linz et al. 2011;Day et al. 2012). Furthermore, the responses of free-ranging populations can differ significantly from those of captive birds due to confounding factors absent in controlled environments (Day et al. 2012;Esther, Tilcher, and Jacob 2013;Sausse and Lévy 2021). ...
Birds can cause significant damage to agricultural fields, notably in Europe, where corvid species like carrion crows (Corvus corone) and rooks (Corvus frugilegus) target spring crops, posing challenges for conservation and wildlife management. Among targeted crops, sunflower and maize suffer the highest levels of damage from corvids' foraging. While both lethal and non‐lethal strategies are employed to mitigate bird damage, their effectiveness is limited and context‐dependent. Consequently, there is growing interest in identifying natural bird repellents. To improve our understanding of corvid food selection and explore potential non‐lethal management strategies, we conducted (1) cafeteria trials with five common seed types (maize, sunflower, soy, pea, and wheat) and (2) two‐choice color tests with maize seeds in four colors (blue, green, orange, and red) on an urban population of carrion crows accustomed to human presence. Results indicated a marked preference for sunflower and wheat, while soy and pea were largely avoided, and maize was moderately consumed. The crows also demonstrated a preference for green‐colored maize over blue, orange, red, and natural maize seeds. These findings suggest that strategic planting of preferred crops like wheat alongside sunflower or maize may help mitigate damage. Further, incorporating colors into repellent seed coatings could reinforce the aversive learning process in birds, although color may play a less significant role in food selection when seeds are sown.
... nets), and lethal control (e.g. shooting and toxicants; Linz et al. 2011, 2017. However, many of these tools have significant drawbacks including 1) immobility, 2) lack of negative stimulus, 3) habituation, and 4) cost or labor involved, resulting in perceived ineffectiveness by farmers (White 2021). ...
Multiple management strategies exist to combat bird damage to agriculture. We explored combining two tools, drones as frightening devices and an avian repellent, to assess effectiveness of an integrated method to deter large flocks on complex landscapes. We evaluated the ability of a spraying drone (DJI Agras MG‐1P) deploying Avian Control (i.e. active ingredient: methyl anthranilate; hereafter MA) or water to elicit abandonment, flock reductions, latency to return, and behavioral changes of blackbirds (Icteridae) foraging in sunflower Helianthus annuus. Following hazing and spraying (MA = 32; water = 32 trials), the percent of flocks abandoning, partially abandoning, or remaining was 56%, 31%, and 13% for MA and 50%, 25%, and 25% for water, respectively. Following full abandonment, 14% more flocks returned following MA (83%) than water (69%), averaging 3.96 min ± 3.51 (SD) to return (MA = 4.12 min ± 4.03; water = 3.73 min ± 2.68). When reduction occurred, average decline was 47% ± 35 (SD) with MA and 44% ± 39 (SD) with water. Site conditions impacted the ability to maneuver the drone and observe flock behaviors, potentially resulting in variables other than treatment explaining the probability of abandonment and flock reduction. When controlling for flock size, number of lift‐offs following water treatments (0.23 min⁻¹ ± 0.17 SD) was statistically less than the pre‐hazing period (0.43 min⁻¹ ± 0.28 SD), however no relationship existed for MA treatments (post: 0.29 min⁻¹ ± 0.32 SD; pre: 0.31 min⁻¹ ± 0.20 SD). This difference may be due to a longer latency to return, decreasing the post‐hazing time period, or flightier birds after MA exposure. We found eight mins of hazing, and a 9‐l tank of repellent, was insufficient to elicit differences between water and repellent applications. We suggest extended hazing or additional negative stimuli (e.g. multiple drones, increased repellent) to increase efficacy.
... A head with less inclination is also prone to predation by birds (Seiler, 1997). A variety of management strategies exist to limit damage to the crop, such as scare devices, repellents, and habitat management (Linz et al., 2011). However, these strategies are not always effective. ...
Sunflower (Helianthus annuus) is a widely cultivated crop that exhibits a trait known as capitulum (or head) inclination at maturity. This trait is influenced by various structural factors, including head weight, stem traits, and plant height. A sunflower head should be at an angle at which the head faces the ground to avoid damage from the sun and birds. While this desired inclination range is known, current methods, including visual estimation and a model of measuring inclined length of the stem, fail to provide precise measurements of angle. This study introduces novel approaches to mathematically measure the head inclination angle. The research, which was conducted over the 2022 and 2023 growing seasons, involved an aluminum rod equipped with a ruler and a digital protractor to measure various height and angle components. Using the data collected, three methods were applied for measuring inclination: a previously published model as a control, a trigonometry‐based approach using angle and height measurements, and other model‐based approaches. A linear model resulted in a formula to calculate the head angle of any plant based solely on two height measurements, the highest point of the plant at both bloom (R5) and maturity (R9). Calculations of heritability and correlation suggest this method has created a precise alternative to existing estimation methods. The resulting formula has the potential to be paired with measurements from high‐throughput phenotyping methods, such as those facilitated with drones and ground robots, to fully automate the process of collecting head inclination data.
... Shanahan et al. (2001) Birds can incur harm to the yields as well as loss to the agronomists in every phase of yields directly from planting until harvesting (Dhindsa et al., 1993;Dhindsa and Saini, 1994;Manakadan & Pittie, 2001;Malhi, 2008;Kale et al., 2014;Grimmett et al., 2014;Kler and Kumar, 2015a). Globally, avian pests cause severe damage to crops in many agricultural systems (Linz et al., 2011;2015). Australia, for example, loses a$290 million annually to crop damage by 60+ bird species (Tracey et al., 2007). ...
The present paper discusses the frugivorous bird and mammalian pest species on cultivated fig, Ficus carica L. in Punjab, India. This study was conducted for 10 years from 2014 to 2024. A total of 11 frugivorous pests including 9 bird species namely; Indian Grey Hornbill Ocyceros birostris (Scopoli), Asian Koel Eudynamys scolopacea (Linnaeus), House Crow Corvus splendens (Vieillot), Jungle Babbler Turdoides striata (Dumont), Red-vented Bulbul Pycnonotus cafer (Linnaeus), Common Myna Acridotheres tristis (Linnaeus), Brown-headed Barbet Megalaima zeylanica (Gmelin), Coppersmith Barbet Megalaima haemacephalus (Statius Muller), Rose-ringed Parakeet Psittacula krameri (Scopoli) falling under 5 orders and 8 families and two mammals (Indian flying fox, Pteropus giganteus (Brunnich) and Northern palm squirrel, Funambulus pennantii (Wroughton) were recorded to act as pests of fruits of F. carica at the three locations of the Punjab state, India. Passeriformes was found to be the dominating amongst all with birds of four families damaging the fruits. Amongst all, Rose-ringed parakeet and Northern palm squirrel were observed causing significant damage to the fruits throughout the fruiting season. Rose-ringed parakeet was observed causing damage at all the three locations surveyed. All the recorded species are of least concern status as per IUCN. These pests caused 18.3-29.4 per cent damage on fig fruits at different locations in Punjab.
... a population of about 75 million individuals occurs throughout the PPR, and their migration overlaps with the ripening of commercially grown sunflower (Helianthus annuus; Linz et al. 1983Linz et al. , 2011Twedt and Linz 2015;Klug et al. 2019). Sunflower seeds are an important food resource for many migrating birds, as the seeds contain fats and proteins necessary to fuel energetic demands posed by feather molt and long-distance flights (Besser 1978, Homan et al. 1994. ...
... Sunflower seeds are an important food resource for many migrating birds, as the seeds contain fats and proteins necessary to fuel energetic demands posed by feather molt and long-distance flights (Besser 1978, Homan et al. 1994. Consequently, the economic impact of blackbird damage to sunflowers in this region exceeds US $28 million annually (Linz et al. 2011, Ernst et al. 2019, and individual sunflower producers can experience field damage surpassing 20% crop loss (Klosterman et al. 2013). After reviewing the history of blackbird damage management strategies, Linz et al. (2017) identified the mobility of blackbird flocks as the greatest challenge and conceded that a cost-effective solution remains elusive. ...
... Longer drone flights are more effective (e.g., White 2021; 52% of the flocks abandoning after 10 minutes of hazing); however, contracting drone services or independently operating drones will likely cost producers money and time, warranting a cost-benefit analysis before regulations and technology allow for completely autonomous systems (Linz et al. 2011). Nevertheless, 80% of sunflower farmers responding to a survey about blackbird damage indicated they would allow blackbirds to be hazed by drones on their property and 7% of respondents have already added drones for such use to their agricultural practices (White 2021). ...
Crop depredation by blackbirds (Icteridae) results in substantial economic losses to the United States sunflower industry, and a solution to effectively reduce damage remains elusive. We evaluated the utility of uncrewed aircraft systems (UAS), or drones, as hazing tools to deter foraging blackbirds from commercial sunflower ( Helianthus annuus ) fields in North Dakota, USA, between September and October 2017. We compared the efficacy of 3 drones: a fixed‐wing predator model mimicking the form of an aerial raptor, a fixed‐wing airplane of similar size, and a multirotor drone. Multirotor drones are relatively easy to fly and are a multifunctional tool for agricultural use; however, they may not be an effective avian deterrent due to a lack of similarity in appearance with natural predators. Free‐ranging blackbird flocks ( n = 58) reacted to every drone approach by initiating flight and took flight 1.6 times sooner for the fixed‐wing predator model (flight initiation distance [FID] = 90 m) and 1.8 times sooner for the fixed‐wing airplane (FID = 98 m) compared to the multirotor drone (FID = 55 m). However, the probability of a blackbird flock ( n = 53) abandoning a field was greater with smaller field and flock sizes, rather than the specific drone deployed. In an applied setting, the performance of drones as avian hazing devices will likely depend on a combination of factors including platform selection, drone trajectory, duration of use, season, landscape context, and natural history of the pest species.
... This is even though we are in an era of literature explosion [66]. Furthermore, it is widely recognized that variations of effectiveness across sites and habituation are two major challenges for many kinds of technical mitigating measures for vertebrates [14,[67][68][69][70][71]. However, the research efforts on mitigations are particularly spatial biased with over 70% of the studies (n = 35 out of 48) being conducted in a single country (i.e., the United States of America) (Fig C in S1 Text), and these experiments were mainly conducted during one crop season. ...
Birds share lands with humans at a substantial scale and affect crops. Yet, at a global scale, systematic evaluations of human–bird coexistence in croplands are scarce. Here, we compiled and used meta-analysis approaches to synthesize multiple global datasets of ecological and social dimensions to understand this complex coexistence system. Our result shows that birds usually increase woody, but not herbaceous, crop production, implying that crop loss mitigation efforts are critical for a better coexistence. We reveal that many nonlethal technical measures are more effective in reducing crop loss, e.g., using scaring devices and changing sow practices, than other available methods. Besides, we find that stakeholders from low-income countries are more likely to perceive the crop losses caused by birds and are less positive toward birds than those from high-income ones. Based on our evidence, we identified potential regional clusters, particularly in tropical areas, for implementing win-win coexistence strategies. Overall, we provide an evidence-based knowledge flow and solutions for stakeholders to integrate the conservation and management of birds in croplands.
... The methods described above afford certain degree of protection against harmful birds. As such one method alone may not be giving complete protection to the crop, hence Integrated Post Management (IPM), a combination of two or three methods is well suited for effective bird pest management so that the food or fruit crops are protected in a better way (Linz et al., 2011). ...
Agriculture has long been troubled by the destructive actions of several non-insect pests, resulting in drastic output reductions. Pests are constantly being introduced to new areas, either intentionally or unintentionally, and some organisms that are intentionally introduced become pests. Increased numbers of invasive non-native pest species have been introduced to new locations as a result of global commerce. Other than insects, there are a group of animals known as non-insect pests viz., rodents, birds, mollusks, monkeys, mites, snails, slugs and wild animals are all included that cause significant output losses in agricultural crops. The most recent pest management issues are produced by non-insect pests, which cannot be controlled by planting a resistant type and necessitate the use of pesticides. Controlling these invasive species is a global task unlike any other.
... In Algeria, pest bird species include doves, the rose-ringed parakeet, house and hybrid sparrows, bulbuls, and the starling. In South Africa, van Niekerk (2009) reported that European turtle doves (Streptopelia turtur) damaged 12.7 % of the crop, while in 2007, birds caused the loss of 0.9 % of the sunflower crop in Argentina (Linz et al., 2011). In Egyptian wheat fields, the loss rates caused by sparrows can reach 50.01 % (Khidr and Yacoub, 2021). ...
Bird intake and damage to fruits of Phoenix dactylifera is a common problem in date palm cultivation regions. Though plant vegetative characteristics and fruit nutritional values influence frugivory behavior in passerines, there is little knowledge about these parameters for sparrows feeding on dates, as most previous studies have focused on the impact of farm organization and location on the feeding choice made by sparrows. This study aimed to examine the effects of date palm tree traits and its fruit morphology and biochemical traits on the level of damage caused by hybrid sparrows to date fruits of three different date palm cultivars. In a traditional date palm plantation, three date varieties (Degla-Beida, Deglet-Nour and Ghars) were analyzed. The estimates of date production loss were correlated to several tree morphometrics and fruit morphological and biochemical traits, including the number of bunches/tree, bunch height, number of pedicels/bunch, number of dates per strand, total production/tree, and date fruit traits (length, width, weight, volume, pulp weight, ratio pulp weight/date weight, sugar content, water content and pH). We demonstrated that sparrows were attracted to bunches with low height and high fruit density, but they showed no interest to number of bunches per tree, number of pedicels per bunch, total number of dates and production per tree. Regarding date morphology, large and heavy dates were more likely to be selected by sparrows, although an unclear relationship was found between production loss per tree and date length, width and volume. In terms of fruit biochemical traits, sparrows damage rates increased with the increase in fruit pH, moisture, and total and reducing sugars. The average rate of lost dates per tree was 9.2 ± 7.66%, 8.4 ± 5.16%, and 3.9 ± 1.71% for Ghars, Deglet-Nour, and Degla-Beida, respectively. Significant differences were observed between cultivars in the amounts of damaged dates still on bunches or fallen on the ground. The hierarchical choice of dates by sparrows was also confirmed. Our results showed that soft dates were more preferred by sparrows than semi-soft and dry ones. The findings of this study indicated that it is necessary to provide extensive protection for highly attacked cultivars in palm groves.
... However, socially acceptable alternatives are not currently in use or available for farmers. It is therefore important to consider other mitigation strategies for human-wildlife conflicts that might have fewer negative tradeoffs, such as promoting the use of parallel cords and offering incentives for aquaculture farmers, habitat modification (e.g., reduce potential breeding habitat for feral Rock Doves Columba livia) and crop intensification controls to manipulate behavior of conflictcausing species (Horgan & Kudavidanage, 2020), decoycrops and scare devices (Linz et al., 2011), and/or provide habitats for predator species which deter pest birds (Lindell, 2020), and study pest activity patterns to plan for the setting of proper deterrent devices at optimal times (Malmqvist et al., 2018). Further studies should investigate the efficacy of less deleterious, but low-cost alternatives that are practical for farmers. ...
Nets are used across a wide variety of food production landscapes to control avian pests typically resulting in deaths of entangled birds. However, the impact of nets on bird populations is a human-wildlife conflict that remains mostly unquantified. Here, we examined the scale of netting in the central plains of Thailand, a region dominated by ricefields, among which aquaculture ponds are increasingly interspersed. Nets/exclusion types, number of individual birds and species caught were recorded on 1312 road-survey transects (2-km length x 0.4-km width). We also interviewed 104 local farmers. The transect sampling took place in late-September 2020, and from December 2020 to April 2021. Each survey transect was visited only once. We found 1881 nets and barriers of parallel cords on 196 (15%) of the transects. Counts of nets and barriers were~13 times higher than expected in aquaculture ponds based on their areal proportion, and vertical nets were the most commonly observed type (n = 1299). We documented 735 individuals of at least 45 bird species caught in the nets and parallel cords, including many species not regarded as pests. Approximately 20% of individuals caught in ricefields and 95% at aquaculture ponds were non-target bycatch. Our interviews suggested that 55% of respondents thought nets were ineffective while only 6% thought they were effective. We suggest imposing a ban on netting, considering other mitigation strategies to reduce conflicts such as promoting the use of parallel cords, and prioritizing conservation actions with community participation. Further studies should investigate the efficacy of less deleterious deterrents.
