Are ecological compensation areas attractive hunting sites for common kestrels (Falco tinnunculus) and long-eared owls (Asio otus)?

Common kestrels (Falco tinnunculus) and long-eared owls (Asio otus) in intensively farmed areas in Switzerland decreased markedly as a result of declining vole (Microtus spp.) populations. In order to counteract the loss of biodiversity in intensively farmed areas, the Swiss agri-environment scheme stipulates several types of ecological compensation areas, which together should take up 7% of the farmland. Among them are wild flower and herbaceous strips, which are not mown every year and which in summer support up to 8 times more small mammals than ordinary fields and grassland. This study investigates whether kestrels and long-eared owls preferentially hunt on ecological compensation areas and whether preferred hunting areas are related to the density of small mammals or to the density and height of the vegetation. Both kestrels and long-eared owls mainly hunted on freshly mown low-intensity meadows and artificial grassland, despite low densities of small mammals. Therefore, vegetation structure was more important for the selection of hunting sites than prey abundance. However, both predators preferred to hunt on freshly mown grassland and meadows bordering a wild flower or herbaceous strip. Voles from these strips probably invaded the adjacent freshly mown grassland and became an easy prey for kestrels and owls. In intensively farmed regions, ecological compensation areas, particularly those not mown each year, are an important refuge for small mammals, although in summer the small mammals are not directly accessible to hunting birds. Hence, a mosaic of different habitat types with grassland mown at different times of the year together with undisturbed strips is best suited to provide a year-round supply of accessible food for vole hunters.     

Resource partitioning among forest owls in the River of No Return Wilderness,Idaho

Summary We studied resource partitioning among the forest owls in the River of No Return Wilderness, Idaho, during the winter and spring of 1980 and 1981. The owl assemblage consisted of five abundant species: pygmy (Glaucidium gnoma), saw-whet (Aegolius acadicus), boreal (A. funereus), western screech (Otus kennicottii), and great-horned (Bubo virginianus). Long-eared (Asio otus) and flammulated (O. flammeolus) owls were rarely observed. Information from the literature supplemented our data to describe the pattern of resource partitioning. Stepwise discriminant function analysis and multivariate analysis of variance revealed differences in macrohabitat and microhabitat. The saw-whet, boreal, western screech, and great-horned owls all preferred mammalian prey but exhibited habitat differences. They also differed in activity periods and food habits. The pygmy owl, a food and habitat generalist, foraged diurnally more than the other species and took a higher proportion of brids. The flammulated owl used areas within the territories of other owl species but specialized on forest insects. The observed pattern of resource use was interpreted to result from environmental factors, morphological limitations and interspecific competition. Differences in food and activity time, we suggest, result from environmental factors and differences in owl morphology, while present-day interspecific competition may be important in shaping habitat use. Experiments will be necessary to determine the causal factors responsible for segregation among the forest owls.     

Accumulation of lead and organochlorine residues in captive American kestrels fed pine voles from apple orchards

Pine voles (Microtus pinetorum) were collected from pesticide-treated orchards in New York (USA) and fed to three captive American kestrels (Falco sparverius) for 60 days to evaluate potential hazards from soil-borne persistent insecticides. Three control kestrels were fed uncontaminated laboratory mice (Mus musculus). The pine voles contained an average of 38 ppm lead, 48 ppm DDE and 1.2 ppm dieldrin (wet weight). The kestrels accumulated sublethal amounts of lead (1 ppm lead wet weight) in their livers. In contrast, DDE and dieldrin accumulated in the tissues and brains of kestrels to toxicologically significant concentrations. Control kestrels remained healthy and accumulated insignificant concentrations of the contaminants. The results indicated raptors may not be significantly at risk from lead residues in soil and biota following field applications of lead arsenate. However, sublethal effects may be expected from the level of contamination by organochlorine pesticides.     

Live blind snakes (Leptotyphlops dulcis) in eastern screech owl (Otus asio) nests: a novel commensalism

Summary Eastern screech owls bring live blind snakes to their nestlings, whereas all other prey are delivered dead. Some of the snakes are eaten but most live in nest debris, where they eat soft-bodied insect larvae from the decomposer community in fecal matter, pellets, and uneaten prey. Consumption of larvae may reduce larval parasitism on owl nestlings or larval competition with nestlings for food stored in the nest, because nestlings with live-in blind snakes grow faster and experience lower mortality than same-season broods lacking snakes. We propose a commensalistic association in which the screech owl benefits reproductively and the live-in blind snake is not affected.     

Owl melanin‐based plumage redness is more frequent near than away from the equator: implications on the effect of climate change on biodiversity

Climate change acts as a major new selective agent on many organisms, particularly at high latitudes where climate change is more pronounced than at lower latitudes. Studies are required to predict which species are at a high risk of extinction and whether certain phenotypes may be more affected by climate change than others. The identification of susceptible phenotypes is important for evaluating the potential negative effect of climate change on biodiversity at the inter‐ and intraspecific levels. Melanin‐based coloration is an interesting and easily accessible candidate trait because, within certain species, reddish pheomelanin‐based coloration is associated with adaptations to warm climates. However, it is unclear whether the same holds among species. We tested one prediction of this hypothesis in four owl genera (wood, scops, screech, and pygmy owls), namely that darker reddish species are more prevalent near the equator than polewards. Our comparative analysis is consistent with this prediction for the northern hemisphere, suggesting that pale reddish species may be adapted to cold climates and dark reddish species to warmer climates. Thus, climate change may have a larger negative impact on pale pheomelanic owls and favour dark pheomelanic species. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 573–582.     

Melanin‐Based Coloration in Juvenile Kestrels ( Falco tinnunculus) Covaries with Anti‐Predatory Personality Traits

Recent studies have shown that melanin‐based coloration is associated with the ability to cope with stressful environments, potentially explaining why coloration covaries with anti‐predator behaviours, boldness and docility. To investigate whether these relationships are consistent across species, we performed a study in the European kestrel ( Falco tinnunculus). Similar to our results found previously in the barn owl ( Tyto alba), nestling kestrels displaying a larger sub‐terminal black tail band stayed on their back longer (tonic immobility test) and breathed at a lower rate than individuals with a smaller black band when handled. However, in contrast to barn owls, nestling kestrels with a larger black tail band were more aggressive and more agitated. Our results strengthen the hypothesis that melanin coloration is related to stress response and in turn to the reaction to predators, a very important personality trait (i.e. boldness).     

Allometry of paracellular absorption in birds

Water-soluble nutrients can be absorbed across the intestinal epithelium by transcellular and paracellular processes. Recent studies suggest that small birds (<180 g) have more extensive paracellular absorption of glucose than nonflying mammals. This may be a feature that compensates for a reduced small intestine size because small birds have smaller mass-corrected intestinal length than do nonflying mammals, but the difference diminishes in larger birds. We hypothesized that if this explanation were correct, there would be a negative correlation between paracellular absorption and body mass in birds and that larger birds would have paracellular absorption comparable to that of nonflying mammals. We tested this hypothesis, using consistent methodology, by measuring the extent of absorption of a series of inert carbohydrate probes in heavier bird species (>300 g) selected from diverse taxa: American coots, mallards, pheasants, and pigeons. Absorption of carbohydrate probes was inversely related to body mass in birds, and absorption of these probes in large birds (>500 g) was comparable to absorption measurements in nonflying mammals. Higher paracellular uptake in the smaller avian species may offer a physiologically inexpensive means of nutrient absorption to compensate for a reduced small intestine size but may make those species more vulnerable to toxicant absorption.     

Mercury in waterfowl from a contaminated river in Virginia

Many bodies of water around the world are contaminated with mercury from historic industrial and mining activities or ongoing atmospheric deposition, resulting in numerous fish consumption advisories. However, concerns about mercury have only rarely led to consumption advisories on waterfowl. In contrast with fish, waterfowl frequently disperse long distances to new watersheds, so hunters and wildlife managers do not know whether waterfowl at a pristine site have spent time at a contaminated site elsewhere. We sampled tissue mercury concentrations of mallards (Anas platyrhynchos), wood ducks (Aix sponsa), and Canada geese (Branta canadensis) at a site contaminated with mercury, during the breeding and hunting seasons. We found that many mallards had bioaccumulated mercury to levels that had the potential to produce reproductive effects and exceeded consumption advisories set for fish by regulatory agencies, whereas this was true for only a few wood ducks and Canada geese. We also documented that mercury-exposed waterfowl from this contaminated site were harvested by hunters as far as 1,054 km away. Our results suggest the need for more proactive sampling of waterfowl for mercury, and likely other bioaccumulating contaminants, in order to allow hunters to make more informed choices about consumption of their harvest. © 2012 The Wildlife Society.     

Brain cholinesterase activity of nestling great egrets, snowy egrets and black-crowned night-herons

inhibition of brain cholinesterase (ChE) activity in birds is often used to diagnose exposure or death from organophosphorus or carbamate pesticides. Brain ChE activity in the young of altricial species increases with age; however, this relationship has only been demonstrated in the European starling (Sturnus vulgaris). Brain ChE activity of nestling great egrets (Casmerodius albus) collected from a colony in Texas (USA) increased significantly with age and did not differ among individuals from different nests. Brain ChE activity of nestling snowy egrets (Egretta thula) and black-crowned night-herons (Nycticorax nycticorax) collected in one colony each from Rhode Island, Texas and California (USA) also increased significantly with age and did not differ among individuals from different nests or colonies. This study further demonstrates that age must be considered when evaluating exposure of nestling altricial birds to ChE inhibitors.     

Removal of persistent organic pollutants from micro-polluted drinking water by triolein embedded absorbent

A new biomimetic absorbent, cellulose acetate (CA) embedded with triolein (CA-triolein), was prepared and applied for the removal of persistent organic pollutants (POPs) from micro-polluted aqueous solution. The comparison of CA-triolein, CA and granular activated carbon (GAC) for dieldrin removal was investigated. Results showed that CA-triolein absorbent gave a lowest residual concentration after 24 h although GAC had high removal rate in the first 4 h adsorption. Then the removal efficiency of mixed POPs (e.g. aldrin, dieldrin, endrin and heptachlor epoxide), absorption isotherm, absorbent regeneration and initial column experiments of CA-triolein were studied in detail. The linear absorption isotherm and the independent absorption in binary isotherm indicated that the selected POPs are mainly absorbed onto CA-triolein absorbent by a partition mechanism. The absorption constant, K, was closely related to the hydrophobic property of the compound. Thermodynamic calculations showed that the absorption was spontaneous, with a high affinity and the absorption was an endothermic reaction. Rinsing with hexane the CA-triolein absorbent can be regenerated after absorption of POPs. No significant decrease in the dieldrin removal efficiency was observed even when the absorption–regeneration process was repeated for five times. The results of initial column experiments showed that the CA-triolein absorbent did not reach the breakthrough point at a breakthrough empty-bed volume (BV) of 3200 when the influent concentration was 1–1.5 μg/L and the empty-bed contact time (EBCT) was 20 min.     

Pathogenicity of Eimeria lettyae Ruff, 1985 in the northern bobwhite (Colinus virginianus L.)

Sporulated oocysts of Eimeria lettyae were administered orally to 5-day-old or 18-day-old northern bobwhites (Colinus virginianus, L.). Five-day-old bobwhites were more susceptible based on higher mortality and reduced weight gain. A dose of 5 X 10(5) oocysts produced 25-43% mortality in 5-day-old bobwhites, but none in 18-day-old bobwhites. A dose of 1 X 10(6) oocysts/bobwhite produced 83-100% mortality in 5-day-old bobwhites, and 17-83% mortality in 18-day-old bobwhites. Body weight gain was reduced significantly with a dose of 1 X 10(5) oocysts or greater in 5-day-old bobwhites and with a dose of 5 X 10(5) oocysts or greater in 18-day-old bobwhites. Infection in all age groups reduced concentrations of plasma pigment and plasma protein, but did not affect packed cell volumes. No grossly visible lesions were present in the intestine although there was a shortening of the villi in the duodenum. In mature bobwhites, infection with E. lettyae did not cause mortality, but did reduce egg production and fertility.     

Fitness Evaluation of <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis> Exposed to Ni

The study aimed at determining the degree of mercury contamination of mallards, game waterbirds migrating from the regions of the unknown degree of contamination and establishing whether the consumption of their meat comprises a hazard to human health in view of the binding norms concerning the mercury content in food products. The investigations were carried out on 30 mallards shot during the duck shooting season in which mercury concentrations in the muscles, liver, and kidneys were determined using the cold vapor atomic absorption spectrometry (CV-AAS) method. The mean Hg concentration in the investigated tissues in all birds studied amounted to 0.110, 0.154, and 0.122 mg kg^?1 for the muscles, kidneys, and liver, respectively. The study indicated statistically significant (p ≤ 0.01) positive correlation between all of the organs examined. Animals were divided into two groups differing in both absolute values of Hg concentrations and those measured in individual tissues. In particular organs of birds representing the first group, the presence of highly significant correlation (p ≤ 0.01) was observed in all organs examined. In the second group, highly significant positive correlation between Hg concentrations in the liver and kidneys and highly significant negative dependence between the liver and muscles was noted. The examinations revealed that some birds must have come from regions of a high degree of mercury contamination.     

Roadway mortality of barn owls in Idaho,USA

We examined the temporal, spatial, and demographic factors that influenced roadway mortality of barn owls (Tyto alba) along a 248-km stretch of Interstate 84 in southern Idaho using systematic road surveys. Counts of dead animals from surveys can be underestimated because of sampling biases; therefore, we also conducted experiments to assess the effects of search and removal bias on the estimates of roadway mortality of owls. We conducted surveys every 2 weeks over a 2-year period and detected 812 dead barn owls (unadjusted mortality rate of 1.64 owls/km/yr). After adjusting this estimate for search and removal bias, we documented mortality rates of up to 5.99 owls/km/year. Owl mortality was not random in relation to sex, age class, or location along the highway. Females and juveniles, which represent individuals more likely to disperse long distances, were killed more frequently than males and adults. During the nonbreeding season, owls were killed more often near agricultural lands than in shrub-steppe, but this pattern was not apparent during the breeding season. Owls were also killed more often on portions of the roadway closer to the Snake River canyon, perhaps because of the availability of nest and roost sites. Mortality rates differed markedly between the 2 years of study, which could have been related to variability in weather and its subsequent effect on owl productivity. Our data suggest that barn owls in this region may not persist under this level of mortality without significant immigration or management. Thus, roadway management to reduce or prevent owl use of roadways, reduce rodent populations near major roads, alert motorists to the presence of owls, or otherwise reduce the chances that vehicles and owls collide would improve barn owl survival and population persistence. © 2012 The Wildlife Society.     

Patterns of space and habitat use by northern bobwhites in South Florida,USA

The manner by which animals use space and select resources can have important management consequences. We studied patterns of habitat selection by northern bobwhites (Colinus virginianus) on Babcock-Webb Wildlife Management Area, Charlotte County, Florida and evaluated factors influencing the sizes of their home ranges. A total of 1,245 radio-tagged bobwhites were monitored for 19,467 radio days during 2002–2007. The mean ( ± 1 SE) annual home range size, estimated using the Kernel density method, was 88.43 ( ± 6.16) ha and did not differ between genders. Winter home ranges of bobwhites (69.27 ± 4.92 ha) were generally larger than summer home ranges (53.90 ± 4.93 ha). Annual and winter home ranges were smaller for bobwhites whose ranges contained food plots compared to those that did not; however, the presence of food plots did not influence summer home ranges. We used distance-based methods to investigate habitat selection by bobwhites at two scales: selection of home ranges within the study site (second-order selection) and selection of habitats within home ranges (third-order selection). Across both scales, bobwhites generally preferred food plots and dry prairie habitat and avoided wet prairies and roads. This pattern was generally consistent between genders and across years. Our data indicate that management practices aimed at increasing and maintaining a matrix of food plots and dry prairie habitat would provide the most favorable environment for bobwhites.     

Plasma B-esterase activities in European raptors

B-esterases are serine hydrolases composed of cholinesterases, including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), and carboxylesterase (CbE). These esterases, found in blood plasma, are inhibited by organophosphorus (OP) and carbamate (CB) insecticides and can be used as nondestructive biomarkers of exposure to anticholinesterase insecticides. Furthermore, B-esterases are involved in detoxification of these insecticides. In order to establish the level of these enzymes and to have reference values for their normal activities, total plasma cholinesterase (ChE), AChE and BChE activities, and plasma CbE activity were determined in 729 European raptors representing 20 species, four families, and two orders. The diurnal families of the Falconiforme order were represented by Accipitridae and Falconidae and the nocturnal families of the Strigiforme order by Tytonidae and Strigidae. Intraspecies differences in cholinesterase activities according to sex and/or age were investigated in buzzards (Buteo buteo), sparrowhawks (Accipiter nisus), kestrels (Falco tinnunculus), barn owls (Tyto alba), and tawny owls (Strix aluco). Sex-related differences affecting ChE and AChE activities were observed in young kestrels (2-3-mo-old) and age-related differences in kestrels (ChE and AChE), sparrowhawks (AChE), and tawny owls (ChE, AChE, and BChE). The interspecies analysis yielded a negative correlation between ChE activity and body mass taking into account the relative contribution of AChE and BChE to ChE activity, with the exception of the honey buzzard (Pernis apivorus). The lowest ChE activities were found in the two largest species, Bonelli's eagle (Hieraaetus fasciatus) and Egyptian vulture (Neophron percnopterus) belonging to the Accipitridae family. The highest ChE activities were found in the relatively small species belonging to the Tytonidae and Strigidae families and in honey buzzard of the Accipitridae family. Species of the Accipitridae, Tytonidae, and Strigidae families were characterized by a BChE contribution that dominated the total ChE activity, while in the species of the Falconidae family, AChE activity dominated. With the exception of the barn owl, CbE activity (eserine-insensitive alpha-naphthyl acetate esterase [alpha-NAE] activity) in all species was almost absent or very low. The values obtained in this study for ChE, AChE, and BChE activities and the AChE:BChE ratios for buzzard, kestrel, barn owl, and tawny owl provide a good estimate of the normal values in free-living individuals of these European species. They can be used as a baseline to evaluate the effect of anticholinesterase insecticides in the field.     

Barred Owl Space Use and Habitat Selection in the Eastern Cascades,Washington

ABSTRACT Competition with barred owls (Strix varia varia) is an important factor contributing to the continued decline of threatened northern spotted owl (Strix occidentalis caurina) populations in the Pacific Northwest, USA, but basic information on habitat selection and space use patterns of barred owls is lacking for much of the region. We investigated space use and habitat selection by tracking radiotagged barred owls in the Eastern Cascade Range of Washington, USA, from 2004 to 2006. We surveyed for barred owls across the 309-km² study area and confirmed presence of barred owl pairs at 21 sites. We collected movement data on 14 barred owls from 12 sites. Mean annual 95% fixed-kernel home-range size was 194 ha for females (n = 4, SD = 70) and 288 ha for males (n = 5, SD = 114). Home ranges were located more frequently than expected in areas with low topographic position, gentle slopes, large overstory tree-crown diameter, high normalized difference vegetation index (NDVI), overstory tree canopy closure >72%, and a moderate amount of solar insolation. Within home ranges, areas that had large tree-crown diameters, low topographic positions, and gentle slopes were used more frequently than expected. The resource selection function we developed for barred owls in our study area indicated that barred owls used areas with the combination of low values for topographic position and slope and higher values for NDVI, solar insolation, and an interaction term for canopy closure and tree-crown diameter. In comparison to published information on northern spotted owls, barred owls used areas with similar canopy closure and tree size classes, but barred owl home ranges were much smaller and more concentrated on gentler slopes in valley bottoms. This information may contribute to the development of management practices that maintain forest characteristics appropriate for spotted owl habitat and prey in areas where spotted owls are least likely to be excluded by territorial barred owls in the Eastern Cascades of Washington.     

Comparison of warfarin sensitivity between rat and bird species

Scattering coumarin derivative rodenticides in broad areas have caused primary- and secondary-poisoning incidents in non-target wild birds. In this study, we compared factors determining warfarin sensitivity between bird species and rats based on vitamin K 2,3-epoxide reductase (VKOR) kinetics, VKOR inhibition by warfarin and warfarin metabolism assays. In VKOR characterization, chickens and ostriches showed significantly lower enzymatic efficiencies than rats (one-sixth and one-third, respectively), suggesting bird species depend more on a non-VKOR vitamin K source. On the other hand, the inhibition constants (K_i) of VKOR for warfarin were significantly different between chickens and ostriches (11.3 ± 2.5 μM and 0.64 ± 0.39 μM, respectively). Interestingly, the ostrich K_i was similar to the values for rats (0.28 ± 0.09 μM). The K_i results reveal a surprising possibility that VKOR in some bird species are easily inhibited by warfarin. Warfarin metabolism assays also showed a large inter-species difference in bird species. Chickens and ostriches showed higher metabolic activity than that of rats, while mallards and owls showed only a slight ability to metabolize warfarin. In this study, we clarified the wide inter-species difference that exists among birds in xenobiotic metabolism and sensitivity to a rodenticide.     

The ecology of small mammals in arable fields drilled with winter wheat and the increase in their dieldrin and mercury residues

A study was made of the dieldrin and mercury residues in small mammals inhabiting arable fields before and after they were drilled with dressed wheat. Results showed that Apodemus , which inhabited both field edge and open surface, fed on the dressed grain immediately. Mean whole body loads increased 68 times from 2.46 to 166.8 μg dieldrin (0.17 to 10.18 w/w p.p.m.) and 11 times from 0.62 to 6.57 μg mercury (0.04 to 0.39 w/w p.p.m.). Maximum body load recorded was 298 μg dieldrin and 13.8 μg mercury. Concentrations increased during the two weeks after drilling and in some specimens reached a level to cause mortality. A marked decrease in stored lipid with onset of cold weather may exacerbate the effect of dieldrin residues. Clethrionomys inhabits only the field edges and did not show these large increases except for occasional individuals. The uneven distribution of Apodemus over the field surface suggested the possibility that two populations existed, one foraging onto the field from the edge and one inhabiting the field surface continuously. There was an increase in body weight and in the ratio of males to females with increasing distance from the hedge into the field. The results indicate that even though there is a ban on the use of dieldrin in spring its continued use as a dressing for winter wheat would appear to present a similar danger for mammal-feeding predators such as the barn-owl and kestrel.     

栖木在越冬红隼（Falco tinnunculus）的觅食地与捕食方式选择中的作用

栖木是重要的生境因子,对于鸟类生境选择和利用具有重要意义。2003年9月-2004年3月,采用固定样地对照观测的方法,分析研究栖木在越冬红隼（Falco tinnunculus）的栖息地选择与捕食方式选择中的作用。研究结果表明,增加了栖木的试验区（下称试验区）,红隼的出现频率远大于未增加栖木的对照区（下称对照区）;试验区红隼个体平均停留时间显著长于对照区;在试验区红隼栖停捕食占捕食次数的77.24%,而在对照区红隼只进行飞行捕食,红隼捕食方式和样地中是否增加栖木具有极显著相关性;试验区,红隼栖停行为时间占51.8%,大于对照区（30.1%）,对照区中,红隼在空中的行为如飞行、翱翔、悬停等行为时间所占比例为34.8%,远高于试验区（12.1%）。这些结果表明,栖木在越冬红隼的栖息地选择和捕食方式选择中具有重要的作用,栖木的存在是栖停捕食的先决条件,冬季红隼偏好于具有较好栖木条件的栖息地,并且偏向于采取低消耗低收益的栖停捕食。     

Food consumption,energy, nutrient and mineral balances in a eurasian kestrel and a screech owl

• 1.1. The food consumption, energy, nitrogen, fat, ash, calcium, phosphate and magnesium balances of the Eurasian kestrel (Falco tinnunculus), and screech owl (Otus kennicotti) are compared.
• 2.2. Eurasian kestrel sample values were significantly greater than screech owl sample values in the energy, nitrogen, calcium, phosphate and magnesium content in pellets, and calcium content in excrement. Phosphate content in excrement was significantly greater in screech owl samples than in Eurasian kestrel samples.
• 3.3. The Eurasian kestrel ingested significantly greater amounts of calcium and phosphate, egested via excrement significantly greater amounts of ash, excreted or egested significantly greater amounts of energy, nitrogen, calcium and phosphate via excrement and pellets, and excreted significantly greater amounts of magnesium via excrement than did the screech owl. The screech owl assimilated significantly greater amounts of ash than did the Eurasian kestrel.
• 4.4. The metabolizability coefficient averaged 48.32% for the Eurasian kestrel, and 49.62% for the screech owl.