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Population Ecology of Raptors

01 Jan 1979-
TL;DR: The relationship between the sexes dispersion breeding density winter density problems concerning nest-sites breeding strategies breeding rates behaviour in the breeding season fidelity to breeding areas movements mortality human persecution DDT and other organo-chlorines other pollutants and pesticides conservation management breeding from captive birds scientific names of raptors.
Abstract: Relationship between the sexes dispersion breeding density winter density problems concerning nest-sites breeding strategies breeding rates behaviour in the breeding season fidelity to breeding areas movements mortality human persecution DDT and other organo-chlorines other pollutants and pesticides conservation management breeding from captive birds scientific names of raptors.
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Journal ArticleDOI
TL;DR: Thirteen recommendations are made to enable the objective selection of an error assessment technique for ecological presence/absence models and a new approach to estimating prediction error, which is based on the spatial characteristics of the errors, is proposed.
Abstract: Predicting the distribution of endangered species from habitat data is frequently perceived to be a useful technique. Models that predict the presence or absence of a species are normally judged by the number of prediction errors. These may be of two types: false positives and false negatives. Many of the prediction errors can be traced to ecological processes such as unsaturated habitat and species interactions. Consequently, if prediction errors are not placed in an ecological context the results of the model may be misleading. The simplest, and most widely used, measure of prediction accuracy is the number of correctly classified cases. There are other measures of prediction success that may be more appropriate. Strategies for assessing the causes and costs of these errors are discussed. A range of techniques for measuring error in presence/absence models, including some that are seldom used by ecologists (e.g. ROC plots and cost matrices), are described. A new approach to estimating prediction error, which is based on the spatial characteristics of the errors, is proposed. Thirteen recommendations are made to enable the objective selection of an error assessment technique for ecological presence/absence models.

6,044 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compile the most recent information on urban impacts on avian populations and communities and identify the processes that underlie the patterns of population and community level responses, but several areas of have been identified as being important.

1,397 citations

Journal ArticleDOI
TL;DR: Experiments on nest site provision provide examples of different factors acting successively to limit breeding density at different levels, because shortage of nest sites must also limit the total numbers of breeders and non-breeders.

786 citations

Journal ArticleDOI
K. I. Jönsson1
01 Feb 1997-Oikos
TL;DR: In this paper, two general tactics of resource use that also include foraging decisions are discussed under the concepts of capital and income breeding, defined mainly from the temporal distribution of resource acquisition relative to resource use.
Abstract: In order to compensate for the resource demands of reproduction, organisms usually increase the amount of total food resources available. This may be achieved by different tactics of resource use that also include foraging decisions. Two such general tactics are discussed in this paper under the concepts of capital and income breeding. These are defined mainly from the temporal distribution of resource acquisition relative to resource use. A capital breeder acquires its resources in advance and store them endogenously or exogenously until they are needed to supply aspects of offspring production. An income breeder, on the other hand, adjusts its food intake concurrently with breeding, without reliance on stores. In a perfectly predictable environment without limited resources, income breeding is the best option since capital breeders may have to pay a number of energetic and demographic costs for their stored resources. However, under unpredictable food conditions, food/time limitations, and risky foraging conditions, capital breeding offers many benefits. The costing systems (pre- or postbreeding costs) induced by capital and income breeding will largely influence the opportunity for these energetic tactics to evolve. While capital and income breeders may potentially experience both pre- and postbreeding costs, capital breeders may be more exposed to prebreeding costs due to predation in connection with acquisition and carriage of stores.

747 citations

Journal ArticleDOI
01 Oct 2004-Ibis
TL;DR: The main aspects of agricultural intensification that have led to population declines in farmland birds over the past 50 years are reviewed, together with the current state of knowledge, and the effects of recent conservation actions.
Abstract: In this paper, the main aspects of agricultural intensification that have led to population declines in farmland birds over the past 50 years are reviewed, together with the current state of knowledge, and the effects of recent conservation actions. For each of 30 declining species, attention is focused on: (1) the external causes of population declines, (2) the demographic mechanisms and (3) experimental tests of proposed external causal factors, together with the outcome of (4) specific conservation measures and (5) agri-environment schemes. Although each species has responded individually to particular aspects of agricultural change, certain groups of species share common causal factors. For example, declines in the population levels of seed-eating birds have been driven primarily by herbicide use and the switch from spring-sown to autumn-sown cereals, both of which have massively reduced the food supplies of these birds. Their population declines have been associated with reduced survival rates and, in some species, also with reduced reproductive rates. In waders of damp grassland, population declines have been driven mainly by land drainage and the associated intensification of grassland management. This has led to reduced reproductive success, as a result of lowered food availability, together with increased disturbance and trampling by farm stock, and in some localities increased nest predation. The external causal factors of population decline are known (with varying degrees of certainty) for all 30 species considered, and the demographic causal factors are known (again with varying degrees of certainty) for 24 such species. In at least 19 species, proposed causal factors have been tested and confirmed by experiment or by local conservation action, and 12 species have been shown to benefit (in terms of locally increased breeding density) from options available in one or more agri-environment schemes. Four aspects of agricultural change have been the main drivers of bird population declines, each affecting a wide range of species, namely: (1) weed-control, mainly through herbicide use; (2) the change from spring-sown to autumn-sown cereal varieties, and the associated earlier ploughing of stubbles and earlier crop growth; (3) land drainage and associated intensification of grassland management; and (4) increased stocking densities, mainly of cattle in the lowlands and sheep in the uplands. These changes have reduced the amounts of habitat and/or food available to many species. Other changes, such as the removal of hedgerows and ‘rough patches’, have affected smaller numbers of species, as have changes in the timings of cultivations and harvests. Although at least eight species have shown recent increases in their national population levels, many others seem set to continue declining, or to remain at a much reduced level, unless some relevant aspect of agricultural practice is changed.

618 citations