Variation in Surrogate Breeding Habitat Quality Between Continuously Grazed Rangelands and Late-Cut Hayfields for a Threatened Grassland Birds

Rangelands and hayfields provide a large portion of remaining surrogate habitat for many species of declining grassland birds in North America. We compared late-cut hayfields and continuously grazed pastures at low to moderate cattle densities for providing suitable breeding habitat in eastern Canada for the nationally threatened Bobolink (Dolichonyx oryzivorus). To examine the quality of both habitats, we conducted point counts and monitored 87 nests during the 2015 and 2016 breeding seasons. Bobolink abundance and daily survival rate (DSR) of nests were modeled sequentially by habitat and sex as a function of vegetation structure, prey availability, and agricultural management. Year and habitat were the strongest predictors of abundance. When analyzed separately for pastures and hayfields, vegetation height was most important for female abundance in pastures while pasture size was most important for males. Nests in hayfields had significantly higher daily survival (DSR = 0.98 ± 0.01) than nests in pastures (DSR = 0.94 ± 0.01). Nesting success was highest in hayfields with taller vegetation, while in pastures, no microhabitat variable showed a clear relationship with DSR. Within pastures, cattle stocking densities of ≤ 1 animal units (AU) · ha^? 1 were not related to DSR. This study provides evidence that late-cut hay is of highest quality, but that small-scale beef farms with low to moderate stocking densities are suitable targets for conservation efforts of Bobolinks in eastern North America.     

The impact of land use/land cover scale on modelling urban ecosystem services

Context

Urbanisation places increasing stress on ecosystem services; however existing methods and data for testing relationships between service delivery and urban landscapes remain imprecise and uncertain. Unknown impacts of scale are among several factors that complicate research. This study models ecosystem services in the urban area comprising the towns of Milton Keynes, Bedford and Luton which together represent a wide range of the urban forms present in the UK.

Objectives

The objectives of this study were to test (1) the sensitivity of ecosystem service model outputs to the spatial resolution of input data, and (2) whether any resultant scale dependency is constant across different ecosystem services and model approaches (e.g. stock- versus flow-based).

Methods

Carbon storage, sediment erosion, and pollination were modelled with the InVEST framework using input data representative of common coarse (25 m) and fine (5 m) spatial resolutions.

Results

Fine scale analysis generated higher estimates of total carbon storage (9.32 vs. 7.17 kg m^?2) and much lower potential sediment erosion estimates (6.4 vs. 18.1 Mg km^?2 year^?1) than analyses conducted at coarser resolutions; however coarse-scale analysis estimated more abundant pollination service provision.

Conclusions

Scale sensitivities depend on the type of service being modelled; stock estimates (e.g. carbon storage) are most sensitive to aggregation across scales, dynamic flow models (e.g. sediment erosion) are most sensitive to spatial resolution, and ecological process models involving both stocks and dynamics (e.g. pollination) are sensitive to both. Care must be taken to select model data appropriate to the scale of inquiry.

     

Habitat functional response mitigates reduced foraging opportunity: implications for animal fitness and space use

Context

Animals selectively use landscapes to meet their energetic needs, and trade-offs in habitat use may depend on availability and environmental conditions. For example, habitat selection at high temperatures may favor thermal cover at the cost of reduced foraging efficiency under consistently warm conditions.

Objective

Our objective was to examine habitat selection and space use in distinct populations of moose (Alces alces). Hypothesizing that endotherm fitness is constrained by heat dissipation efficiency, we predicted that southerly populations would exhibit greater selection for thermal cover and reduced selection for foraging habitat.

Methods

We estimated individual step selection functions with shrinkage for 134 adult female moose in Minnesota, USA, and 64 in Ontario, Canada, to assess habitat selection with variation in temperature, time of day, and habitat availability. We averaged model coefficients within each site to quantify selection strength for habitats differing in forage availability and thermal cover.

Results

Moose in Ontario favored deciduous and mixedwood forest, indicating selection for foraging habitat across both diel and temperature. Habitat selection patterns of moose in Minnesota were more dynamic and indicated time- and temperature-dependent trade-offs between use of foraging habitat and thermal cover.

Conclusions

We detected a scale-dependent functional response in habitat selection driven by the trade-off between selection for foraging habitat and thermal cover. Landscape composition and internal state interact to produce complex patterns of space use, and animals exposed to increasingly high temperatures may mitigate fitness losses from reduced foraging efficiency by increasing selection for foraging habitat in sub-prime foraging landscapes.

     

Book reviews

Food Quality Control, Foods of Animal Origin, by H. V. Hagstad and W. T. Hubbert, 1986. viii+148 pp. illustrated. Ames, The Iowa State University Press. £12.95. ISBN 0 8138 0702 6.

Animal Nutrition, by A. A. Bond, 1987. English edition. 540 pp, illustrated. Chichester, John Wiley & Sons. ISBN 0 471 90375 2.

Egg Quality—Current Problems and Recent Advances—Poultry Science Symposium 20, Edited by R. G. Wells and C. G. Belyavin, 1987. 302 pp. illustrated. London, Butterworths. £35.00. ISBN 0 470 00470 X.

The Microbiology of Poultry Meat Products, Edited by F. E. Cunningham and N. A. Cox, 1987. ix+359 pp. illustrated. Orlando, Florida, Academic Press. £54.00, $65.00. ISBN 0 12 199880 0.     

Heartworm in dogs in Canada in 1986

In late December 1986, 1224 institutional veterinarians and small and mixed animal clinics across Canada were sent a questionnaire in order to assess the status of Dirofilaria immitis in Canada in 1986; 46% of them responded. Veterinarians reported that 150,989 dogs were blood-tested for microfilariae and 869 dogs were found with heartworm. Another 65 dogs were amicrofilaremic but diagnosed with heartworm disease and one was found with heartworm at necropsy to give the total number diagnosed in 1986 as 935 (0.62%).

Heartworm was reported from Manitoba, New Brunswick, Ontario and Quebec, but most (810) of the cases were from Ontario. South-western Ontario continued to be the primary focus of the infection in Canada. There were 103 cases reported from Quebec, mostly from and around Montreal, and 21 cases from Manitoba, from Winnipeg and surrounding areas. Heartworm was found most frequently in companion dogs over three years of age maintained mainly outdoors in rural areas. About 33% of the cases were observed with clinical signs of heartworm disease and 81% had a history of not having left Canada.

     

Effectiveness of oxibendazole against benzimidazole-resistant strongyles in horses

Twenty-eight horses with a residual burden of strongyle eggs in the faces after treatment with mebendazole (MBZ) paste were treated with a suspension of either MBZ or oxibendazole (OBZ). Fecal samples were collected before and 14 days after these treatments. The number of strongyle eggs/g (epg) of feces for each horse was estimated using the Cornell-McMaster dilution and the Cornell-Wisconsin double centrifugation procedures. The epg for each horse was transformed using log (× + 1) and in an analysis of variance of the reduction in egg count for each horse on the logarithmic scale, there was a highly significant difference between the treatments. The mean epg was increased in the MBZ-treated horses and reduced in the OBZ-treated horses, but the reduction was only by 82% with an upper confidence limit of 89%. Subsequently, the horses were retreated with MBZ and OBZ suspensions without significant reduction in the mean epg for OBZ-treated horses.     

Effectiveness of ivermectin paste for removal of nematodes in the horse

Thirteen Standardbred horses, two to five years of age, were treated with ivermectin paste per os at 200 μg/kg of body weight and 13 were untreated. Two weeks after treatment, previously untreated horses were given the paste. Fecal samples were collected from all horses at the time of treatment and periodically thereafter up to 14 weeks and were examined for nematode eggs using the Cornell-McMaster dilution and the Cornell-Wisconsin double centrifugation procedures.

All horses consumed the paste readily and had no signs of toxicosis. Strongyle eggs were found in the feces of all horses before treatment but not at two to three weeks after treatment. At five to six weeks after treatment only two horses had eggs in the feces. At eight, ten, 12 and 14 weeks after treatment 27, 69, 88 and 100% of the horses examined, respectively, had a few strongyle eggs but these were no greater than 18% of that of the pretreatment samples. Ivermectin oral paste, therefore, appeared to be highly effective against both adult and immature strongyles.