Abstract. Analysis of habitat use based on radio-tagged animals presents difficulties inadequately addressed by current methods. Areas of concern are sampling level, data pooling across individuals, non-independence of habitat proportions, differential habitat use by groups of animals, and arbitrary definition of habitat availability. We advocate proportional habitat use by individual animals as a basis for analysis. Hypothesis testing of such nonstandard multivariate data is done by compositional analysis, which encompasses all MANOV A/MAN COY A-type linear models. The applications to habitat use range from testing for age class effects or seasonal differences, to examining relationships with food abundance or home range size. We take as an example the comparison of habitat use and availability. The concepts are explained and demonstrated on two data sets, illustrating different methods of treating missing values. We compare utilized with available habitats in two stages, examining home range selection within the overall study area first, then habitat use within the home range. At each stage, assuming that use differs from random, habitats can be ranked according to relative use, and significant between-rank differences located. Compositional analysis is also suited to the analysis of time budgets or diets.
Failure to address many of the difficulties inherent in the analysis of carnivore faeces has hitherto limited the value of this technique in comparing carnivore diets or quantifying carnivore food consumption. In this review, major problems are discussed, and improved procedures designed to overcome them are recommended. The principal improvements recommended for laboratory procedures address the microscopic fraction of faeces, which cannot be analysed visually. This fraction may be derived from a variety of sources, leading to bias in previous techniques, particularly with regard to the importance of earthworms and birds. Attention to the microscopic fraction is necessary for correct comparison or quantitative determination of diet. Particular attention is given to statistical procedures which quantify the errors that arise in collection of samples, or during analysis. Clear statement of such errors will lead to greater comparability between studies. The procedures recommended here define the limits to accuracy in relation to sample size, total faecal production, and laboratory methods. In conjunction with adequate pilot studies, these techniques will allow more effective design of ecological studies relating to carnivore diet and food consumption.
Summary1. An 8-year-field experiment on moorland in northern England manipulated the abundance of legally controllable predators whilst maintaining consistent habitat conditions. Subsequent changes in both the breeding success and abundance of five ground-nesting bird species were monitored: lapwing Vanellus vanellus, golden plover Pluvialis apricaria, curlew Numenius arquata, red grouse Lagopus lagopus scoticus and meadow pipit Anthus pratensis and the abundance only of snipe Gallinago gallinago and skylark Alauda arvensis. 2. Control of fox Vulpes vulpes, carrion crow Corvus corone, stoat Mustela ermina and weasel Mustela nivalis reduced the abundance of fox ()43%) and crow ()78%); no changes were detected in already low stoat or weasel abundances. 3. Reductions in foxes and crows led to an average threefold increase in breeding success of lapwing, golden plover, curlew, red grouse and meadow pipit. 4. Predator control led to subsequent increases in breeding numbers ( ‡14% per annum) of lapwing, curlew, golden plover and red grouse, all of which declined in the absence of predator control ( ‡17% per annum). 5. Synthesis and applications. Controlling predators is a potentially important management tool for conserving a range of threatened species. Considerable sums of public monies are currently spent on habitat improvement for conservation and some of these public funds should be used to underpin habitat works with predator removal.
and {The Game Conservancy Trust, Fordingbridge, Hampshire SP6 1EF, UK Summary 1. Corn buntings Miliaria calandra have declined steeply in Britain and north-western Europe since the mid-1970s; changes in farming practice are believed to have been partly responsible. 2. We studied nesting corn buntings on the South Downs in west Sussex between 1995 and 1997 to examine the possible eects of agricultural intensi®cation on breeding success. The abundance of invertebrates around individual nests was sampled by sweep-netting in July. 3. Corn buntings provisioning nestlings foraged in grassy margins more than any other habitat relative to their availability within the maximum foraging range. The other habitats used more than expected were spring-sown barley, unintensi®ed grass and set-aside. Those used less than expected included winter-sown wheat and intensively managed grassland. The invertebrates most commonly fed to chicks were more abundant in foraging areas than elsewhere. Their density was negatively correlated with the number of insecticide applications both when cereal ®elds only were considered and when all foraging habitats were included. 4. The lower the abundance of chick-food invertebrates close to nests, the greater the distance from the nest at which parents foraged, and the longer such trips were in duration. The weights of nestlings, corrected for age using tarsus length, were positively correlated with the abundance of chick-food invertebrates. 5. The probability of nest survival was negatively correlated with the abundance of chick-food invertebrates close to the nest, apparently as a result of an increased risk of predation. 6. Agricultural intensi®cation in Britain, including the increased use of pesticides, has led to a widespread decrease in the availability of chick-food invertebrates on lowland farmland. If our results are typical of corn buntings in an arable environment, this decrease correlates with reduced breeding success. Depending on the mortality rates for¯edged chicks and older birds, this reduction may have contributed to the corn buntings' decline and may hamper recovery. 7. Farming practices that increase invertebrate availability ought to bene®t breeding corn buntings. Large-scale measures such as set-aside and the spring-sowing of cereals (especially if undersown with grass) depend heavily on overall agricultural policy. Small-scale initiatives might therefore be more feasible; these include the provision of grassy margins or beetle banks and selective spraying of headlands.
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