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Mean all bird abundance (2004–2005) in WCSP, commercial sunflower and other nonsunflower row crops with associated standard errors.—Letters A, B and C represent a 5 0.05 differences (Tukey's post hoc pair-wise comparisons among habitat types)
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Agricultural fields are often overlooked as post-breeding and migratory bird habitat, even though many species use row-crop fields in the northern Great Plains. We monitored bird use, crop and non-crop vegetation characteristics and abundance, and land use around (≤2.4 km) 35 8-ha Wildlife Conservation Sunflower Plots (WCSP) and one commercial sunf...
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... in commercial non-sunflower row- crops (mean 5 0.8 species/ha; Table 1). Birds occurred at greater densities (P , 0.01) but similar diversities in WCSP (mean 5 24.4 birds/ha, SE 5 2.7; Div 5 0.88), followed by commercial sunflower (mean 5 12.7 birds/ha, SE 5 1.7; Div 5 0.88) and non-sunflower row- crops (mean 5 7.2 birds/ha, SE 5 1.1; Div 5 0.80; Fig. 1). We recorded sufficient detections of individuals (n $ 85) to generate species-specific detection probabilities and densities for four species in WCSP, five species in commercial sunflower and two species in other non- sunflower row-crops (Table ...
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Fall flocks of red-winged blackbirds (Agelaius phoeniceus) are well known for their ability to damage crops such as sunflower (Linz and Hanzel 1997). In response, wildlife managers have considered local population reduction as a strategy for reducing blackbird damage. Male red-winged blackbirds are logistically easier to remove than females because...
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... Future studies should consider landscape factors as explanatory variables, including the prevalence of alternative forage or refugia adjacent to the field (White 2021). Decoy crops might improve the efficacy of drones in protecting agriculture by providing forage and refugia where birds are not harassed (Hagy et al. 2008(Hagy et al. , 2010Kotten et al. 2022). ...
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.
... Third, it is possible that our experimental design used less energy than previous studies on the Sonic Net (Werrell et al. 2021, Woods et al. 2022, which could potentially cost crop producers less monetarily while still reducing target bird abundances with the Sonic Net. Last, if perceived predation risk from playbacks is truly high enough to reduce blackbird abundances during the non-breeding season, then non-target species of conservation concern utilizing agricultural habitat could also be affected, such as early-autumn neotropical migrants (Hagy et al. 2010). We do not think late-season playbacks would conflict with the reproduction of non-target species, as non-target species of conservation concern known to nest in habitat around agricultural fields in Illinois, such as the state-endangered Upland Sandpiper (Bartramia longicauda), are also mostly done breeding at this time (Walk et al. 2010, VanBeek et al. 2014. ...
Perceived predation and brood parasitism risks strongly influence nesting habitat selection in several bird species. Here, we report on a playback experiment evaluating whether perceived predation or brood parasitism risk can reduce Red-winged Blackbird (Agelaius phoeniceus) abundances in agricultural nesting habitat. We broadcast Cooper’s Hawk vocalizations (Accipiter cooperii, a predator of adult blackbirds and nests), Brown-headed Cowbird vocalizations (Molothrus ater, a brood parasite of many passerine species, including blackbirds), and the “Sonic Net” as treatments, the latter of which is broadcast of frequencies that overlap with blackbird vocalizations and prevent blackbirds from accessing intraspecific communication informing of predator and brood parasite risks. Neither the hawk, cowbird, nor Sonic Net treatments reduced blackbird abundances at sites early in the breeding season (April to May), when blackbirds were selecting nesting habitat. In contrast, late in the breeding season (July to August), hawk vocalizations and the Sonic Net reduced blackbird abundances at sites, but cowbird vocalizations did not. Our late-breeding season results suggest that blackbirds may flexibly change responses to perceived predation risk based on their stage of reproductive investment. Perceived predation risk could potentially be used to manage pest birds that nest in agricultural landscapes, at least for crops that are vulnerable to birds late in the breeding season.
... Although conversion to cropland results in habitat loss for some species, cropland also provides resources used by many wildlife species. Cropland provides habitat for migratory birds, for example, in the northern Great Plains of North America during and before migration (Hagy et al. 2010). Agricultural crops can provide a reliable and nutritious source of forage for wildlife including migrating waterfowl (Fox et al. 2017) and ungulates (Smith et al. 2007, Carrollo et al. 2017, Thinley et al. 2017, Barker et al. 2019). ...
Pronghorn (Antilocapra americana) are a grassland specialist that have experienced a >60% reduction in their historical range due to habitat fragmentation and encroachment of woody vegetation. Pronghorn populations are increasing in the Texas Panhandle despite conversion of grassland to cropland (27–43% of the regional landscape) and associated fragmentation. We hypothesized that pronghorn avoid cropland when selecting seasonal home ranges and avoid cropland within their home ranges. We captured 64 adult pronghorn of equal sex ratios in both the High Plains (n = 32) and Rolling Plains (n = 32) ecoregions of Texas, USA, during February 2017 and fitted them with iridium satellite global positioning system (GPS) collars. We collared 27 additional pronghorn in 2018 to account for mortalities and collar failures. We estimated resource selection functions for the High Plains and Rolling Plains populations using mixed‐effects logistic regression at the home range (second order) and within home range (third order) scales separately for each ecoregion and season (fawning, summer, rut, and winter). Our hypothesis that pronghorn avoid cropland was supported in the Rolling Plains ecoregion at the home range scale; otherwise, cropland was inconsistently and seasonally important in resource selection. Furthermore, pronghorn often avoided paved roads more strongly than cropland. At the home range scale during 2017–2019, female pronghorn in the High Plains selected cropland during rut and winter. Males exhibited weak selection for cropland during rut. Within home ranges in the High Plains, female pronghorn avoided cropland during fawning in 2017, during rut in 2017 and 2018, and during winter 2019 but selected areas closer to cropland in winter 2017 and fawning 2018. Males selected areas farther from cropland during all sampling dates in 2017 and winter 2019. Avoidance and selection of cropland within home ranges also varied among seasons and years in the Rolling Plains. Overall, pronghorn avoided cropland when selecting home ranges in the Rolling Plains and cropland was otherwise inconsistently and only seasonally important in resource selection at the home range and within home range scales. We speculate that loss of pronghorn habitat to cropland in the High Plains and Rolling Plains of Texas may outweigh temporary nutritional benefits from seasonal use of crops. Pronghorns avoided cropland in the Rolling Plains but not in the High Plains of Texas. Loss of habitat to cropland may outweigh temporary nutritional benefits of crops to pronghorn.
... Emphasis has also been placed on understanding the bird conservation values of marginal grasslands (i.e., small linear grassland habitat) compared to conservation reserves (Best et al. 1995, Klug et al. 2009, Cox et al. 2014, the influence of rangeland and hayfield management (Blackwell and Dolbeer 2001, Klug et al. 2010, Faria et al. 2016, and grassland plantings for biomass production (Conkling et al. 2018). Despite the prevalence of row-crops, limited research has evaluated direct use of monoculture cropland by birds (Best et al. 1990;Hagy et al. 2007Hagy et al. , 2010Iglay et al. 2017). ...
... Along with crop species, the diversity of crops across landscapes and the seasonal timing of crop maturation also impacts bird communities (Benton et al. 2003, Krapu et al. 2004. For example, sunflowers (Helianthus annuus L.) provide conservation value as evidenced by the diversity of birds using the crop and a later harvest that allows bird use during their molt and migration (Hagy et al. 2010), albeit at levels that create human-wildlfie conflicts. ...
... While we provide initial evidence as to avian species using hemp, or indirectly so, further research is needed to determine densities that may occur with broadscale adoption and large commercial fields (e.g., bird diversity in sunflower; Hagy et al. 2010). For example, we observed 116 mourning doves in a 0.01-ha plot, which would not likely translate to 5,800 birds ha -1 in larger fields (up to 230 ha). ...
Industrial hemp (Cannabis sativa L.) is an emerging crop in the United States with little known about bird use or the potential for birds to become an agricultural pest. We identified birds associated with hemp fields, using repeated visits to oilseed plots in North Dakota, USA (n = 6) and cannabinoid (CBD) plots in Florida, USA (n = 4) from August to November 2020. We did not control for plot area or density; our observations were descriptive only. We observed 10 species in hemp, 11 species flying over hemp, and 11 species both foraging in and flying over hemp fields in North Dakota. In Florida, we observed 4 species in hemp, 5 species flying over hemp, and 4 species exhibiting both behaviors. When we observed birds in hemp, we found them perched in the canopy or foraging on the ground. Counts were highest in oilseed and lowest in CBD varieties. The Florida sites were mainly CBD varieties, which explains lower species diversity and raw counts of birds given the lack of seeds produced. Maximum raw counts of the most common birds (mourning doves [Zenaida macroura] = 116, house finches [Haemorhous mexicanus] = 53, and American goldfinches (Spinus tristis] = 40) using very small fields (116-324 m2) in North Dakota suggest oilseed hemp could suffer yield losses, but potentially benefit farmland bird conservation and act as a decoy crop to protect other commodities (e.g., sunflower, Helianthus annuus L.).
... By enhancing the diversity and heterogeneity of agroecosystems, it is expected that measures implemented for hamsters will be suitable for other farmland species or will even provide extended services in such systems [9]. Sunflower has, for instance, many benefits for biodiversity and agriculture [68][69][70]. It attracts birds, some of which reduce pest populations [68,69]. ...
... Sunflower has, for instance, many benefits for biodiversity and agriculture [68][69][70]. It attracts birds, some of which reduce pest populations [68,69]. It also provides key benefits for pollinators, considering its major medicinal values for bees [70,71]. ...
Farmland species face many threats, including habitat loss and malnutrition during key periods of their life cycle. This is aggravated in conventionally managed monocultures, leading to nutrient deficiencies that impair the survival and reproduction of farmland wildlife. For instance, protein deficiencies in wheat or vitamin B3 deficiency in maize reduce by up to 87% the reproductive success of the critically endangered common hamster (Cricetus cricetus), a flagship species of European farmlands. It is urgent to identify and implement agricultural practices that can overcome these deficiencies and help restoring hamsters’ reproductive success. As part of a conservation program to diversify farming habitats in collaboration with farmers, we tested whether associations between wheat or maize and three supplemental crops (soybean, sunflower and fodder radish) supported hamsters’ performance during hibernation and reproduction. We observed that maize–sunflower, maize–radish and wheat–soybean associations minimized hamsters’ body mass loss during hibernation. The wheat–soybean association led to the highest reproductive success (N = 2 litters of 4.5 ± 0.7 pups with a 100% survival rate to weaning), followed by maize–sunflower and maize–radish. These crop associations offer promising opportunities to overcome nutritional deficiencies caused by cereal monocultures. Their agronomic potential should promote their implementation on a large scale and benefit farmland biodiversity beyond the common hamster.
... After rice, corn (maize) and sunflower are the temporary primary crop types most often identified as being preferred by migratory birds. These crops are actively selected over other crop types by numerous waterfowl, crane, raptor, and passerine species (Galle et al., 2009;Hagy et al., 2010;Pearse et al., 2011;Cai et al., 2014;Krapu et al., 2014). Corn in particular can constitute up to 90% of ingested material in cranes (Gruidae) and geese (Anatidae), while other crops generally make up less than 10% of ingested material (Krapu et al., 2014(Krapu et al., , 1995. ...
... While relatively few prior studies have compared farm types, it is possible to draw several general conclusions about the effects of different farming practices on migration stopover preferences. Rice, corn, and sunflower appear to be preferred over other crops by a diverse set of migrants (Hagy and Bleier, 2007;Hagy et al., 2010;Stafford et al., 2010;Pearse et al., 2011;Cai et al., 2014;Krapu et al., 2014), which may be due to the comparatively high levels of metabolizable energy in these crops (Joyner et al., 1987;Galle et al., 2009;Stafford et al., 2010). All three crops also retain a high degree of spatial complexity, resulting in higher potential for roosting and predator avoidance. ...
An estimated 17% of migratory bird species are threatened or near threatened with extinction. This represents an enormous potential loss of biodiversity and cost to human societies due to the economic benefits that birds provide through ecosystem services and ecotourism. Conservation of migratory bird species presents many unique challenges, as these birds rely on multiple geographically distinct habitats, including breeding grounds, non-breeding grounds, and stopover sites during migration. In particular, stopover habitats are seldom studied relative to breeding and non-breeding habitats, despite their importance as refueling stations for migratory birds. In this study, we summarize the current research on the use of temporary primary crops by birds during migration and we assess the species characteristics and agricultural practices most often associated with the use of cropland as stopover habitat. First, we conducted a systematic review of the literature to document the effects various farming practices and crop types have on the abundance and diversity of migratory birds using agricultural areas for stopovers. Second, we analyzed the ecological correlates of bird species in the Northern Hemisphere that predict which species may use these areas while migrating. We ran a GLMM to test whether primary diet, diet breadth, primary habitat, habitat breadth, or realm predicted stopover use of agricultural areas. Our review suggests that particular crop types (principally rice, corn, and sunflower), as well as farming practices that result in higher non-cultivated plant diversity, encourage the use of agricultural areas by migrating birds. We found that cropland is used as stopover habitat by bird species that can utilize a large breadth of habitats, as well as species with preferences for habitat similar in structure to agricultural areas.
... To further reduce the number of possible independent variables, we built individual models for each independent variable and compared AIC c scores between these models and the null model (intercept-only). We excluded those variables from further analyses which had a greater AIC c score than the null model due to lack of support resulting in different health parameters being included in each final model set for each dependent variable (Anderson 2010;Hagy et al. 2010). Within the final model set for each dependent variable, we ran all possible combinations of independent variables and second-order interactions that represented biologically plausible relationships (PROC GLMMIX in SAS v 9.4). ...
... For candidate models within each model set, we calculated model weight and considered models within four ΔAIC c of the top model to be competitive (Arnold 2010;Burnham et al. 2010;Chiavacci et al. 2015). We assessed relative variable importance within each response variable model set by summing the model weights (ωi AIC c ) of each independent variable across all candidate models (Burnham and Anderson 2002;Hagy et al. 2010). Sums of weights (∑ωi) were calculated and compared across all response variables for interpretation of variable importance. ...
Thousands of lesser scaup (Aythya affinis) die during spring and fall migrations through the upper Midwest, USA, from infections with Cyathocotyle bushiensis and Sphaeridiotrema spp. (Class: Trematoda) after ingesting infected intermediate hosts, such as non-native faucet snails (Bithynia tentaculata). The lesser scaup is a species of conservation concern and is highly susceptible to these infections. We collected female lesser scaup from spring migratory stopover locations throughout Illinois and Wisconsin and assessed biochemical and morphological indicators of health in relation to intestinal helminth loads. Helminth species diversity, total trematode abundance, and the infection intensities of the trematodes C. bushiensis and Sphaeridiotrema spp. were associated with percent body fat, blood metabolites, hematological measures, and an index of foraging habitat quality. Helminth diversity was negatively associated with percent body fat, albumin concentrations, and monocytes, whereas glucose concentrations displayed a slight, positive association. Total trematode abundance was negatively associated with blood concentrations of non-esterified fatty acids and albumin. Infections of C. bushiensis were positively related to basophil levels, whereas Sphaeridiotrema spp. infection intensity was negatively associated with packed cell volume and foraging habitat quality. Thus, commonly measured health metrics may indicate intestinal parasite infections and help waterfowl managers understand overall habitat quality. Intestinal parasitic loads offer another plausible mechanism underlying the spring condition hypothesis.
... term wildlife conservation sunflower plots to wildlife conservation/ood plots (WCFP) to include all food varieties provided to attract wildlife. WCFP (also known as lure, decoy, food, trap, supplemental feeding, and diversionary plots) typically are small acreages (0.8-1.6 hal strategically placed to provide food for wildlife (Cummings et at. 1987;Hagy et at. , 2010Tranel et at. 2008; U.S. Department of Agriculture 2013; Kubasiewicz et at. 2016). Entire fields are sometimes planted to a bird-susceptible crop (e.g . . , wheat, sunflower, corn, rice) or planted to attract wildlife that might otherwise forage in commercial crops (Gustad 1979;Cummings et at. 1987;Knittle and Porter 1988). Aside from re ...
... planted to attract wildlife that might otherwise forage in commercial crops (Gustad 1979;Cummings et at. 1987;Knittle and Porter 1988). Aside from reducing damage in a commercial field where damage >5% is economically important, food remaining in WCFP is available for both migrating birds and resident animals (Tranel et at. 2008;Galle et at. 2009;Hagy et at. 2010). Additionally, WCFP might be considered to support a population of an endangered species (Ewen et at. 2015). ...
... A.!though the results were promising, no government entities were willing to formally implement a WCFP program. Hagy et al. (2007Hagy et al. ( , 2008Hagy et al. ( , 2010 revisited the use ofWCFP as a bird management tool in 2004 and 2005. Scientists offered candidate sunflower producers US$375.00/ha to plant 35 8-ha WCFP near cattail-dominated wetlands with histories of elevated blackbird damage ( Figure 10.2). ...
... To further reduce the number of possible predictor variables, I built individual models for each predictor variable and compared AICc scores between these models and the null model (interceptonly). I excluded those predictors from further analyses which had a greater AICc score than the null model due to lack of support(Anderson 2010;Hagy et al. 2010). This method resulted in different health parameters being modeled for each model set.Within the reduced model set for each dependent variable, I ran all possible independent variable combinations and second order interactions if biologically plausible (PROC GLMMIX in SAS v9.4).Because I was mainly interested in the relative importance of relationships between the various helminth infection metrics and parameters of scaup health, I incorporated the variables year and region of collection as random effects within all candidate models. ...
... For candidate models within each model set, I calculated model weight and considered models within seven ∆AICc of the top model to be competitive(Arnold 2010;Burnham et al. 2010;Chiavacci et al. 2015). Then, I assessed relative variable importance within each response variable model set by summing the model weights (ωi AICc) of each predictor variable across candidate models(Burnham and Anderson 2002;Hagy et al. 2010). Sums of weights (∑ωi) were calculated and compared across all response variables for interpretation of predictor variable ...
The continental breeding population of Lesser Scaup (Aythya affinis) reached a record low of 3.2 million in 2006 and has since remained below the goal of 6.3 million set by the North American Waterfowl Management Plan. Although many factors have been identified as possible contributors to the decline, the Spring Condition Hypothesis proposes reduced recruitment resulting from females in reduced condition as the most influential cause. Since 2002, infections with non-native trematodes transmitted by the invasive Faucet Snail (Bithynia tentaculata) have resulted in the deaths of tens of thousands of Lesser Scaup in the upper Midwest, USA during migrations. To determine if parasitic intestinal helminths were associated with reduced body condition and health, I collected 130 apparently healthy female Lesser Scaup and identified and enumerated helminths within their intestinal tracts. I also measured a suite of health parameters to identify associations between intestinal helminth infections and their sub-lethal effects on Lesser Scaup. Forty helminth taxa (20 trematodes, 14 cestodes, 4 nematodes, and 2 acanthocephalans) were identified, including one digenean (Plenosoma minimum) for the first time in Lesser Scaup and in the Midwest. Helminth species diversity and mean total helminth abundance were greatest in northern portions of the study region along the Mississippi River, and mean total helminth abundance was less in 2015 than in 2014. Host age and body size were not associated as factors contributing to helminth assemblage, which may be due in part to physiological changes experienced during migration. The intestinal helminth infracommunities of Lesser Scaup were found to vary across the four regions and two years of the study. Variations in helminth infracommunity structure were likely due to geophysical variation within the study area, prey item (intermediate host) diversity, and weather pattern variations that occurred between years thus affecting migration chronologies and prey abundance. Varying associations were detected between 11 health parameters and seven response variables of differing helminth metrics. Most notably were the relationships observed between helminth species diversity and body fat, albumin, glucose, and percentage of white blood cells that were monocytes. Total trematode abundance was negatively related to the plasma metabolite concentrations of non-esterified fatty acids and albumin. Total nematode abundance showed a strong negative association with plasma bilirubin concentrations. The daily lipid dynamic index, a ratio of blood metabolites used as an index of foraging habitat quality, showed a negative association with total cestode abundance and Sphaeridiotrema spp. intensity. Cestode total abundance was also negatively associated with the heterophil:lymphocyte ratio, an indicator of long-term stress, but displayed a strong, positive relationship with plasma bilirubin concentrations. The introduced trematodes responsible for annual die-offs of Lesser Scaup in the upper Midwest displayed varying relationships with health parameters. While a positive relationship was detected between the introduced Cyathocotyle bushiensis and basophil white blood cells, negative associations were observed between Sphaeridiotrema spp. and bilirubin concentrations, packed cell volumes, and habitat quality variables. These biochemical and hematological measurements are important to physiological homeostasis and serve as indicators of condition at a critical period of the Lesser Scaup annual cycle. The associations between the health parameters, helminth metrics, and habitat quality measurements reported herein provide additional evidence for possible mechanisms underlying the Spring Condition Hypothesis in the upper Midwest, USA.
... An understanding of how environmental factors are associated with blackbird abundance beyond the local scale, or how such factors behave across scales, could aid in the management of these species. Minimizing crop damage caused by blackbirds also has additional benefits for wildlife management, because agricultural crops are widely used by other species of conservation interest such as migratory songbirds (e.g., Hagy et al. 2010). We evaluated the influence of landscape composition and configuration along with weather variables on red-winged blackbird (Agelaius phoeniceus), yellow-headed blackbird (Xanthocephalus xanthocephalus), and common grackle (Quiscalus quiscula) relative abundance in the Prairie Pothole Region of the United States, where these species are responsible for the majority of the sunflower crop damage (Peer et al. 2003). ...
Knowledge of factors influencing animal abundance is important to wildlife biologists developing management plans. This is especially true for economically important species such as blackbirds (Icteridae), which cause more than $100 million in crop damages annually in the United States. Using data from the North American Breeding Bird Survey, the National Land Cover Dataset, and the National Climatic Data Center, we modeled effects of regional environmental variables on relative abundance of 3 blackbird species (red-winged blackbird, Agelaius phoeniceus; yellow-headed blackbird, Xanthocephalus xanthocephalus; common grackle, Quiscalus quiscula) in the Prairie Pothole Region of the central United States. We evaluated landscape covariates at 3 logarithmically related spatial scales (1,000 ha, 10,000 ha, and 100,000 ha) and modeled weather variables at the 100,000-ha scale. We constructed models a priori using information from published habitat associations. We fit models with WinBUGS using Markov chain Monte Carlo techniques. Both landscape and weather variables contributed strongly to predicting blackbird relative abundance (95% credibility interval did not overlap 0). Variables with the strongest associations with blackbird relative abundance were the percentage of wetland area and precipitation amount from the year before bird surveys were conducted. The influence of spatial scale appeared small—models with the same variables expressed at different scales were often in the best model subset. This large-scale study elucidated regional effects of weather and landscape variables, suggesting that management strategies aimed at reducing damages caused by these species should consider the broader landscape, including weather effects, because such factors may outweigh the influence of localized conditions or site-specific management actions. The regional species distributional models we developed for blackbirds provide a tool for understanding these broader landscape effects and guiding wildlife management practices to areas that are optimally beneficial. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
