An Improved Mechanical Owl for Efficient Capture of Nesting Raptors

Jensen, Meghan K.; Hamburg, Shanti; Rota, Christopher T.; Brinker, D.J.; Coles, Dustin L.; Manske, Mark A.; Slabe, Vincent A.; Stuber, Matthew J.; Welsh, Amy B.; Katzner, Todd E.

doi:10.3356/jrr-18-30

Cited by 5 publications

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References 13 publications

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“…To capture free‐flying Ferruginous Hawks, we used mist‐nets and a robotic Great Horned Owl Bubo virginianus lure placed near the nest (Jensen et al . 2019). We captured nestlings by hand in the nest or on the ground immediately after fledging.…”

Section: Methodsmentioning

confidence: 99%

Ferruginous Hawk movements respond predictably to intra‐annual variation but unexpectedly to anthropogenic habitats

Isted

Thomas

Warner

et al. 2023

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Birds exhibit flexible movement responses to environmental variation across the annual cycle, and those responses can provide insight into potential impacts that environmental changes may have on these species. To understand year‐round variation in space use by Ferruginous Hawks Buteo regalis, we tracked 12 birds breeding in southwestern Idaho, USA, using GPS telemetry collected over 207 bird‐months. Home‐range sizes of territorial adult hawks showed strong intra‐annual variation, being smallest from April to June and largest from July to October. In contrast, juvenile birds (< 2 years old) did not appear to hold territories and showed no detectable intra‐annual variation in ranging behaviour. Association with land‐cover types by territorial birds varied between breeding and non‐breeding months and was linked to home‐range size. Home‐range sizes of non‐territorial birds were larger than those of territorial birds, and that size did not vary across the year. Association with anthropogenic habitats (irrigated cropland habitats that can provide high rodent densities and increased foraging opportunities) was negatively associated with home‐range size in months of the non‐breeding season. Unexpectedly, the opposite was true in the months of the breeding season, such that use of croplands resulted in larger home‐ranges. Patterns in home‐range size were probably linked to intrinsic factors such as the timing of breeding and migratory behaviour, and to extrinsic factors such as prey availability associated with specific land‐cover types. These results have implications for our understanding of the response of Ferruginous Hawks and other similar species to predicted changes in land cover, and they suggest unexpected relationships between human activity and wildlife behaviour. Furthermore, because the birds we tracked used a large portion of western North America, they are probably relevant far beyond the small area where these individuals were trapped.

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Section: Methodsmentioning

confidence: 99%

Ferruginous Hawk movements respond predictably to intra‐annual variation but unexpectedly to anthropogenic habitats

Isted

Thomas

Warner

et al. 2023

Ibis

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“…The nestlings that contributed to these pooled samples were later resampled in the same year when they were older and larger, and 2 ml of blood was collected at this time. I also opportunistically collected whole blood from adult ferruginous hawks that other researchers in my study areas captured using a modified dho ghaza with a mechanical owl lure Jensen et al, 2019).…”

Section: Methodsmentioning

confidence: 99%

Prevalence of Anticoagulant Rodenticides in Ferruginous Hawk Nestlings and Evaluation of a Novel Method to Rapidly Assess Exposure

Dickson¹

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Anticoagulant rodenticides (ARs) are compounds commonly used to control rodent pests by inhibiting an enzyme critical for synthesis of clotting factors in their blood. Secondary and tertiary poisoning of non-target species frequently occur, especially of predators that consume rodents, including many species of raptors. Although raptor exposure to ARs has been documented on at least three continents, patterns, pathways and the sub-lethal effects of exposure are not well studied. This has created a substantial need to monitor the effects of ARs in free-living populations. I evaluated the prevalence of secondary, non-target exposure to anticoagulant rodenticides experienced by a predatory raptor, and I tested the performance and suitability of technology originally developed for human patients taking oral anticoagulant drugs as a novel way to rapidly assay for AR exposure in free-living raptors. To assess the risk of ARs to birds of prey in the western United States, I surveyed ferruginous hawk nestlings (Buteo regalis) in Idaho, Wyoming and Colorado. These hawks inhabit shrub steppes, grasslands, and deserts, many of which are modified by agriculture, wind power, and oil and gas development. Rodenticides are often deployed in or near developed areas to reduce numbers of burrowing mammals. Targeted species include ground squirrels (Urocitellus spp.) and prairie dogs (Cynomys spp.), which often compose a large proportion of ferruginous hawk diet. I evaluated the prevalence and concentrations of eight different ARs from 173 blood samples from ferruginous hawk nestlings at 60 nest sites in 2018 and 2019. I also collected 117 citrated plasma samples and analyzed them for biomarkers of AR exposure and indicators of sample quality: prothrombin time (PT), thrombin time (TCT), and fibrinogen concentration. To elucidate possible exposure pathways, I collected and analyzed 54 liver samples from hawk prey and four livers from opportunistically collected dead hawks. There were no ARs detected in any hawk blood or livers, but brodifacoum was present in one rodent liver at a minute concentration (0.003 ppm). Prothrombin time (PT) of 117 hawk nestlings averaged 29.8 ± 4.8 (SD) seconds (range: 21.3 – 41.2 sec). Sex was a strong predictor of PT, with female nestlings exhibiting longer PT. These findings aid in understanding the risk of AR exposure of ferruginous hawk nestlings in Idaho, Wyoming and Colorado and contribute important baseline information on PT of wild birds. I also evaluated the potential of a point-of-care device, the Coag-Sense® PT/INR Monitoring System manufactured by CoaguSense Inc. (Fremont, California), to rapidly detect AR exposure in living birds of prey. The Coag-Sense® device delivered repeatable (i.e., precise) PT measurements on avian blood samples collected from four species of migrating raptors (Intraclass Correlation Coefficient > 0.9). However, PT measurements reported by the Coag-Sense system from 81 ferruginous hawk (Buteo regalis) nestlings were not correlated (r = -0.017) to those measured by standardized laboratory techniques (i.e., the accuracy of the Coag-Sense® was low). The Coag-Sense® device therefore did not accurately measure PT in this species of bird and is unlikely to do so in other birds of prey, perhaps because it uses mammalian rather than avian thromboplastin as an activator of clotting. However, this device has potential use on non-human mammals.

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“…We sampled adult hawks either after capture at breeding territories or after they were admitted to rehabilitation facilities. We captured free flying birds using a mechanical owl and mistnets (Jensen et al 2019). Finally, a climber captured nestling hawks 4-7 weeks in age by hand and lowered them to the ground.…”

Section: Field Data Collectionmentioning

confidence: 99%

Lead exposure of North American raptors

Slabe¹

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Lead is an anthropogenic threat to terrestrial wildlife, has no physiological benefits, and is considered a neurotoxin. Legislation adopted in many developed countries restricts the uses of lead in consumer and industrial products such as pipe fittings, petrol, paint, and shot for use in waterfowl hunting. However, lead is currently categorized by the United States (US) government as a critical metal and common uses of lead still persist in North America. These include the use of rifle ammunition, shot in upland gamebird hunting, and fishing sinkers. Lead is also a byproduct of multiple industrial operations including smelters, coal power plants, oil refineries, and battery production facilities. As a consequence, there is regular deposition of potentially toxic amounts of lead in the environment. Anthropogenic lead influences the ecology and demography of multiple wildlife taxa, including a large number of avian species. Elevated lead concentrations are documented in avian scavengers as a result of ingesting lead fragments from hunter harvested animal carcasses. However, multiple forms of lead deposition exist in eastern North America, making the region ideal to study the pathways of lead exposure in wildlife. I documented the sources and pathways of lead exposure of raptors by studying novel species, seasons, regions and spatial scales. During the breeding season in the Chesapeake region of Maryland and Virginia, I found differences in blood lead concentrations among age groups of bald eagles but no difference between age groups of osprey. In the central Appalachians, I found that territorial red-shouldered hawks had higher blood lead concentrations in urban settings when compared to non-urban settings during the breeding season. I found that a community of facultative avian scavengers in eastern North America exhibited higher blood and liver lead concentrations during the fall and winter months compared to the spring and summer months when they scavenge to a lesser degree. On a nationwide scale, I found that 47% of bald eagles and 46% of golden eagles had femur lead concentrations above the threshold commonly accepted to indicate clinical lead poisoning. This work will provide information useful to the management of lead-influenced wildlife and identify potential opportunities for mitigation of environmental lead exposure and, using wildlife as sentinel species, help to understand potential human health hazards of lead exposure. v TABLE OF CONTENTS

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An Improved Mechanical Owl for Efficient Capture of Nesting Raptors

Abstract: BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Cited by 5 publications

References 13 publications

Ferruginous Hawk movements respond predictably to intra‐annual variation but unexpectedly to anthropogenic habitats

Ferruginous Hawk movements respond predictably to intra‐annual variation but unexpectedly to anthropogenic habitats

Prevalence of Anticoagulant Rodenticides in Ferruginous Hawk Nestlings and Evaluation of a Novel Method to Rapidly Assess Exposure

Lead exposure of North American raptors

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