Vertebrates Removed by Mechanical Weed Harvesting in Lake Keesus, Wisconsin

Mechanical weed harvesting has been used to control nuisance vegetation in Lake Keesus since 1979. Fish, turtles, and amphibians often become entangled in the vegetation and are incidentally removed from the lake while harvesting weeds. Mechanical harvesting removed 2 to 8% of the standing crop of juvenile fish in harvested areas in Saratoga Lake, New York (Mikol 1985) and 32% of the fish population in harvested areas in Orange Lake, Florida, representing an estimated replacement value of $6000 per ha (Haller et al. 19890). Engle (1990) found mechanical harvesting removed 21,000 to 31,000 fish per year from Lake Halverson, Wisconsin, representing 25% of the fry in the lake. Little other current information has been published concerning aquatic vertebrate removal by mechanical weed harvesting in Wisconsin, though it is a commonly used management tool. Additionally, only Engle (1990) reported information on the removal of turtles relative to weed harvesting, but none on amphibians. The objective of this study was to document the number, species, and size of vertebrates removed by mechanically harvesting weeds in Lake Keesus

Gyrfalcon Breeding Biology In Alaska

Thesis (Ph.D.) University of Alaska Fairbanks, 2010This dissertation addresses specific research needs identified by a panel of experts on Gyrfalcon biology and conservation convened on 3 September, 2003 at the Raptor Research Foundation Scientific Conference in Anchorage, Alaska. The first chapter is a significant update and revision of the 1994 Gyrfalcon Birds of North America (BNA) species account, using all published papers and available grey literature from 1994--2007 and personal expertise from over 3,000 hours of coordinated observations. The second chapter reports results from a spatially explicit model, based on the best available compiled data from Alaska, that predicted Gyrfalcon breeding distribution and population size across Alaska. The model predicted that 75% and 7% of the state had a relative index of nest occurrence of 60%, respectively. Areas of high predicted occurrence primarily occurred in northern and western Alaska. Using environmental variables, the model estimated the size of the breeding Gyrfalcon population in Alaska is 546 +/- 180 pairs. In Chapter 3, I used repeated aerial surveys to estimate detection probabilities of cliff-nesting raptors from fixed-wing aircrafts and helicopters. Detection probabilities ranged from 0.79--0.10 and varied by species, observer experience, and study area/aircraft type. Generally, Gyrfalcons had the highest detection probability, followed by Golden Eagles, Common Ravens, and Rough-legged Hawks, though the exact pattern varied by study area and survey platform. In the final chapter, I described for the first time in North America Gyrfalcon nest site fidelity, breeding dispersal, and natal dispersal using molted feathers as non-invasive genetic tags. Gyrfalcons were highly faithful to study areas (100% fidelity) and breeding territories (98% fidelity), but not to specific nest sites (22% fidelity). Breeding dispersal distance averaged 750 +/- 870 m, and was similar between sexes. Natal dispersal of three nestlings representing 2.5% recruitment varied from 0--254 km. Mean territory tenure was 2.8 +/- 1.4 yrs and displayed a bimodal distribution with peaks at 1 and 4 years. Mean annual turnover at one study site was 20%. Gyrfalcons in one study area exhibited low, but significant population differentiation from the other two study areas

Gyrfalcon Feeding Behaviour during the Nestling Period in Central West Greenland

We studied gyrfalcon (Falco rusticolus) food delivery and feeding behavior during the nestling period in central West Greenland during the 2000 and 2001 field seasons. We used time-lapse video cameras installed at three nests to record 2677.25 hours of nestling video. Ptarmigan delivered to nests were usually plucked prior to delivery and included the breast and superior thoracic vertebrae. Arctic hare leverets were rarely plucked and often delivered in parts. The most commonly delivered leveret part was the hind legs attached to the lower back. Passerines were rarely plucked and usually delivered whole. After feeding the young, adults removed 20.9% of prey items from the nest, which included items both with and without obvious muscle still attached. Prey delivery rates were similar among nests and increased as nestlings aged. Prey delivery frequency peaked in the morning and evening, with a distinct lull in the late evening and early morning hours. Male and female adults delivered a similar number of prey, though males typically delivered smaller prey than females. Gyrfalcons cached and re-delivered at least 9.1% of all items delivered, and one item was cached and retrieved three times.Durant les campagnes sur le terrain de 2000 et 2001 dans le centre du Groenland occidental, on a étudié chez le faucon gerfaut (Falco rusticolus) l'apport en nourriture et le comportement alimentaire pendant le séjour au nid. À l'aide de caméras vidéo filmant à intervalles, installées à trois nids, on a enregistré 2677,25 heures de vidéo au nid. Les lagopèdes apportés au nid étaient en général plumés avant d'y être déposés et comprenaient la poitrine et les vertèbres supérieures du thorax. Les jeunes lièvres arctiques étaient rarement pelés et étaient souvent apportés en morceaux. La partie du levraut la plus communément apportée était les pattes arrière rattachées au bas du dos. Les passereaux étaient rarement plumés et étaient en général livrés entiers. Après avoir nourri leurs petits, les adultes enlevaient du nid environ 20,9 % des parties des proies, comprenant des morceaux qui pouvaient comporter ou non du tissu musculaire évident. Le rythme de l'apport des proies était semblable parmi les divers nids et augmentait avec l'âge des oisillons. La fréquence de l'apport des proies passait par un maximum le matin et le soir, avec une accalmie très nette tard dans la soirée et au petit matin. Les mâles et les femelles adultes apportaient le même nombre de proies, mais les mâles livraient en général de plus petites proies que les femelles. Les faucons gerfauts dissimulaient dans une cache puis ressortaient par la suite au moins 9,1 % de tous les morceaux apportés, et un morceau a été dissimulé et ressorti trois fois

Nonrandom Territory Occupancy by Nesting Gyrfalcons (\u3ci\u3eFalco rusticolus\u3c/i\u3e)

We know little regarding how specific aspects of habitat influence spatial variation in site occupancy by Arctic wildlife, yet this information is fundamental to effective conservation. To address this information gap, we assessed occupancy of 84 Gyrfalcon (Falco rusticolus Linnaeus, 1758) breeding territories observed annually between 2004 and 2013 in western Alaska. In line with the theory of population regulation by site dependence, we asked whether Gyrfalcons exhibited a nonrandom pattern of site selection and if heterogeneous landscape attributes correlated with observed occupancy patterns. We characterized high- and low-occupancy breeding territories as those occupied more or less often than expected by chance, and we evaluated land cover at 1 and 15 km circles centered around nesting territories to identify habitat variables associated with observed occupancy patterns. We tested 15 competing models to rank hypotheses reflecting prey and habitat variables important to nesting Gyrfalcons. We confirmed a nonrandom pattern of site selection but found only weak evidence that the distribution of prey habitat was responsible for this pattern. We reason that preferential habitat use by nesting Gyrfalcons may be determined by spatial scales other than those we measured or may be driven by landscape-level attributes at time periods other than during the brood rearing period

Short-Eared Owl Land-Use Associations During the Breeding Season in the Western United States

The Short-eared Owl (Asio flammeus) is a species of conservation concern in the western USA, with evidence for declining population sizes. Monitoring of Short-eared Owls is complicated because of their low site fidelity and nomadic movements. We recruited community-science participants to implement a multi-year survey of Short-eared Owls across eight states in the western USA, resulting in a program of sufficient temporal and spatial dimensions to overcome many of the challenges in monitoring this species. We implemented both multi-scale occupancy and colonization/extinction modeling to provide insights into land-cover use, and to identify which cover types supported higher occurrence. Short-eared Owls were associated with native and anthropogenic land-cover types, but site occupancy varied among these categories and at different scales. Native grasslands, marsh/riparian, hay/fallow agriculture, and cultivated croplands were occupied most consistently across years. Occupancy rates differed at different scales (e.g., marsh/ riparian was the only land-cover type positively associated with occupancy at both transect and point scales). Contrary to expectations, native shrubland was negatively associated with occupancy at the point scale, and exhibited low colonization and high extinction rates. Our results suggest that conserving native landscapes in general, and grasslands, marsh, and riparian areas specifically, would benefit Short-eared Owls. Furthermore, Short-eared Owl occupancy was positively associated with hay/fallow land-cover types, suggesting that some nonnative land-cover types can function as Short-eared Owl habitat. Lastly, our results highlight how developing a broad-scale community science survey can inform conservation for a species not well monitored by existing survey programs

Gyrfalcon Food Habits in Central West Greenland During the Nestling Period

I used time-lapse video, pellet, and prey remains analysis to study the food habits and feeding behavior of nesting gyrfalcons (Falco rusticolus) in central West Greenland during the 2000 and 2001 field seasons. I collected 2,677.25 hours of videotape from three nests, representing 93.7, 87.3, and 49.3% of the nestling period at each nest. The video recorded 921 deliveries of 832 prey items. I placed 95.3% of the items into prey categories. The image quality was very good, but did not reveal enough detail to identify most passerines to species. I found no evidence that gyrfalcons were negatively affected by the video system after the initial camera set-up. The video system experienced some mechanical problems, but was a reliable technique to document nesting gyrfalcon food habits in West Greenland. Most gyrfalcons exhibited similar feeding behavior during the nestling period. Ptarmigan delivered to nests were usually plucked prior to delivery and included the breast and superior thoracic vertebrae. Arctic hare leverets were rarely plucked and often delivered in parts. The most common leveret part delivered was the hind legs attached to the lower back. Passerines were rarely plucked and usually delivered whole. After feeding, adults removed almost 20% of prey items including those with and without obvious meat still attached. Prey delivery rates were similar among nests and increased as nestlings aged. Prey delivery frequency peaked in the morning and evening, with a distinct lull in the late evening and early morning hours. Male and female adults delivered a similar number of prey, though males typically delivered smaller prey than females. Gyrfalcons cached and re-delivered at least 9.1% of all items delivered and cached some items multiple times. Gyrfalcons relied heavily on rock ptarmigan (Lagopus mutus) and arctic hare (Lepus arcticus). Combined, these species contributed 79.2 - 90.6% of the total diet, depending on the method used. Passerines contributed the third most percent biomass and percent pellet composition. All three methods documented at least one seasonal shift in diet composition and the video revealed two shifts. The first was a shift from ptarmigan to hare in mid-June. The second change in diet composition was an influx of passerine fledglings in late June. Assuming video results best approximated the actual diet, prey remains and pellets overestimated ptarmigan and underestimated arctic hare in the diet. Prey remains underestimated the proportion of passerines in the diet, while pellets overestimated passerines with the same severity. The video-monitored gyrfalcons consumed 94.0 - 110.1 kg of food per nest during the nestling period, higher than previously estimated. Video and prey remains data gave 1.47 and 1.28 Shannon Wiener H-values, similar to the mean of other gyrfalcon diet studies. Using a combination of the three methods was important to accurately document gyrfalcon diet

Dietary Plasticity in a Specialist Predator, the Gyrfalcon (\u3ci\u3eFalco rusticolus\u3c/i\u3e): New Insights into Diet During Brood Rearing

Climate and landscape change are expected to affect species’ distributions and interactions, with potentially harmful consequences for specialist predators. Availability of optimal prey can affect reproductive success in raptors, especially in the Arctic, where dramatic differences in prey availability occur both within and between years. However, behavioral responses of dietary specialist, resident predators such as Gyrfalcons (Falco rusticolus) to changes in prey availability remain poorly understood. To improve understanding of how climate-driven changes in prey availability may affect diet of avian predators in the Arctic, we characterized Gyrfalcon diet on the Seward Peninsula, Alaska, in 2014 and 2015 from images representing 2008 prey items obtained by motion-activated cameras at 20 nests.We documented two important dietary shifts: the proportion of ptarmigan (Willow Ptarmigan [Lagopus lagopus] and Rock Ptarmigan [L. muta]) in the diet declined throughout the brood-rearing period in both years, and also differed between years. In both cases, ptarmigan were replaced by Arctic ground squirrels (Urocitellus parryii) in the diet. Despite shifts in prey composition, dietary breadth did not change, which revealed a facultative shift in prey use in which Gyrfalcons relied on prey of large size rather than prey of a particular taxon. We describe previously undocumented prey-use patterns during Gyrfalcon breeding, specifically an interchange between two prey species that are keystones in tundra ecology. These results are important for informing predictive models of climate change and adaptive species management plans. Further study of the interchange between prey types described in this study can strengthen insight into key ecosystem processes, and the cause and effect of potential decoupling of predator-prey interactions

Preening Behavior of Adult Gyrfalcons Tagged with Backpack Transmitters

Radio transmitters provide data that enhance understanding of raptor biology (Walls and Kenward 2007) and are now used to answer a multitude of research questions (Meyburg and Fuller 2007). However, transmitters affect the birds that carry them (Barron et al. 2010), and it is important to document and evaluate such effects (Casper 2009). For example, decreased survival has been documented in Prairie Falcons (Falco mexicanus; Steenhof et al. 2006), Northern Goshawks (Accipiter gentilis; Reynolds et al. 2004), and Spotted Owls (Strix occidentalis; Paton et al. 1991) tagged with radio transmitters. However, no such effects were reported for Peregrine Falcons (Falco peregrinus; Fuller et al. 1998, McGrady et al. 2002) and a number of other species (Kenward 2001). White and Garrott (1990) noted that in general, animals tagged with radio transmitters often altered their behaviors for 1–14 d after release during an adjustment period that included increased preening and grooming frequencies. Although more than 90 Gyrfalcons (Falco rusticolus) have been tagged with radio transmitters (e.g., Burnham 2007, McIntyre et al. 2009, T. Booms unpubl. data), the effects of transmitters on this species are not well documented. Anecdotal information suggests some Gyrfalcons might be negatively affected by radio-tagging (Booms et al. 2008). As part of a study investigating Gyrfalcon breeding biology, we conducted opportunistic, focused observations on two radio-tagged adult female Gyrfalcons and their unmarked mates. We here describe and quantify preening behavior of Gyrfalcons shortly after radio-tagging

Comparing Apples to Oranges: What is the Relative Nutritive Value of Avian and Rodent Prey to an Apex Arctic Predator?

Effective conservation and management of raptors necessitates an understanding of their diet and feeding habits, especially in environments highly susceptible to anthropogenic change. The Gyrfalcon (Falco rusticolus) is an apex avian predator of the Arctic tundra ecosystem that specializes on Willow Ptarmigan (Lagopus lagopus), Rock Ptarmigan (L. muta), and Arctic ground squirrels (Urocitellus parryii). Despite being approximately equal in overall biomass, the relative nutritive value of ptarmigan and squirrels to breeding Gyrfalcons is unknown. Because Gyrfalcon habitat and dietary specialization make them particularly susceptible to changing prey distributions and abundances resulting from climate-induced landscape changes, we compared the nutritive value of ptarmigan and ground squirrels collected from the Seward Peninsula, Alaska. We isolated the edible biomass of twenty ptarmigan and ten ground squirrels through lab dissections, and prepared tissue samples for protein, fat, and energy assays. We found that ptarmigan contain significantly more edible biomass than squirrels (243.2 g and 114.9 g for ptarmigan and squirrels, respectively). Further, 45% of a ptarmigan’s total body mass is edible compared to only 25% for a squirrel, suggesting that ptarmigan yield more nutritive benefit than squirrels per prey delivery. Results from tissue assays were not available at the time of this presentation. Our preliminary results suggest that Gyrfalcon populations may be disproportionately affected by changes in ptarmigan abundances or distributions than those of ground squirrels