The risk to passerine birds of predation by the Sparrowhawk (Accipiter nisus) was analyzed with respect to differences in plumage brightness, body mass, and density of prey species, while taking into account phylogenetic relatedness of species. Data were collected from published sources in five separate areas along a south–north geographical gradient in Finland and consisted of 2214 prey remains collected from Sparrowhawk nests. Prey plumage brightness was the most important factor determining vulnerability to predation. In adults, male brightness was more important than female brightness in explaining prey vulnerability. Prey abundance did not affect the relationship between predation vulnerability and plumage brightness, because both rare and common species with bright plumage suffered higher predation. Prey species with large body mass were more vulnerable to predation in northern Finland, suggesting that in northern harsh conditions, Sparrowhawks may prefer large prey in order to fulfill their daily energy requirements. Our analyses provide evidence that predation may impose viability costs on sexually selected traits such as plumage brightness and body size.

Nests are structures built to support and protect eggs and/or offspring from predators, parasites, and adverse weather conditions. Nests are mainly constructed prior to egg laying, meaning that parent birds must make decisions about nest site choice and nest building behavior before the start of egg-laying. Parent birds should be selected to choose nest sites and to build optimally sized nests, yet our current understanding of clutch size-nest size relationships is limited to small-scale studies performed over short time periods. Here, we quantified the relationship between clutch size and nest size, using an exhaustive database of 116 slope estimates based on 17,472 nests of 21 species of hole and non-hole-nesting birds. There was a significant, positive relationship between clutch size and the base area of the nest box or the nest, and this relationship did not differ significantly between open nesting and hole-nesting species. The slope of the relationship showed significant intraspecific and interspecific heterogeneity among four species of secondary hole-nesting species, but also among all 116 slope estimates. The estimated relationship between clutch size and nest box base area in study sites with more than a single size of nest box was not significantly different from the relationship using studies with only a single size of nest box. The slope of the relationship between clutch size and nest base area in different species of birds was significantly negatively related to minimum base area, and less so to maximum base area in a given study. These findings are consistent with the hypothesis that bird species have a general reaction norm reflecting the relationship between nest size and clutch size. Further, they suggest that scientists may influence the clutch size decisions of hole-nesting birds through the provisioning of nest boxes of varying sizes.

Published results concerning metal levels in feathers of birds of prey were listed and evaluated. Mercury concentrations have been studied most and the background values normally vary between 0.1 and 5 mg/kg dry weight the highest concentrations being in birds from aquatic food chains. Pollution causes elevated levels of mercury in feathers. The concentrations of cadmium, copper, lead and zinc show reasonable variation between species, areas and time periods. Feathers of birds of prey have proved to be good indicators of the status of environmental heavy metal pollution. Special attention should be paid to clean sampling and preparation of samples. Interpretation of the results requires knowledge on food habit, molting and migration patterns of the species. Several species representing different food chains should be included in comprehensive monitoring surveys. Chick feathers reflect most reliably local conditions.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Wiley and Nordic Society Oikos are collaborating with JSTOR to digitize, preserve and extend access to Ornis Scandinavica. Stability of a bird community in southern FinlandTapio Solonen Solonen, T. 1986. Stability of a bird community in southern Finland. -Ornis Scand. 17: 106-116.Stability patterns of a South Finnish bird community breeding in an area of 30 ha were studied on the basis of mapping censuses made in 1971-80. Fluctuations were characterized by the variation in the number of species (CV = 3.6), density of pairs (9.3), diversity (4.9), and evenness (4.6). The average annual species turnover was 9.0 and the average individual turnover 3.0%. These values are more typical of bird communities in Central than in Northern Europe. Long-term changes explained, on an average, 25?25 (SD) % of the annual population fluctuations. The number of pairs decreased significantly but their biomass, energy consumption, and production remained rather stable during the study. Diversity and evenness increased significantly. Twenty-eight species showed no trend and 19 of them remained fairly stable but there were 15 species showing more or less increasing trends and 6 species (including most dominants of the community) showing declining trends. The passerines, especially the dense nest-box population of Pied Flycatchers Ficedula hypoleuca, dominated fluctuations of the community. While fluctuations of the non-passerines were somewhat compensatory, fluctuations of the passerines, as well as those of the entire community, were largely parallel. However, there were also compensating fluctuations that tended to balance parallel ones, resulting in relative stability. Compensatory fluctuations and density levels without trends suggest that numbers of birds were regulated by density-dependent factors, but parallel fluctuations and the occurrence of striking trends suggest that fluctuations were largely determined by densityindependent factors.

The increase in size of human populations in urban and agricultural areas has resulted in considerable habitat conversion globally. Such anthropogenic areas have specific environmental characteristics, which influence the physiology, life history, and population dynamics of plants and animals. For example, the date of bud burst is advanced in urban compared to nearby natural areas. In some birds, breeding success is determined by synchrony between timing of breeding and peak food abundance. Pertinently, caterpillars are an important food source for the nestlings of many bird species, and their abundance is influenced by environmental factors such as temperature and date of bud burst. Higher temperatures and advanced date of bud burst in urban areas could advance peak caterpillar abundance and thus affect breeding phenology of birds. In order to test whether laying date advance and clutch sizes decrease with the intensity of urbanization, we analyzed the timing of breeding and clutch size in relation to intensity of urbanization as a measure of human impact in 199 nest box plots across Europe, North Africa, and the Middle East (i.e., the Western Palearctic) for four species of hole‐nesters: blue tits (Cyanistes caeruleus), great tits (Parus major), collared flycatchers (Ficedula albicollis), and pied flycatchers (Ficedula hypoleuca). Meanwhile, we estimated the intensity of urbanization as the density of buildings surrounding study plots measured on orthophotographs. For the four study species, the intensity of urbanization was not correlated with laying date. Clutch size in blue and great tits does not seem affected by the intensity of urbanization, while in collared and pied flycatchers it decreased with increasing intensity of urbanization. This is the first large‐scale study showing a species‐specific major correlation between intensity of urbanization and the ecology of breeding. The underlying mechanisms for the relationships between life history and urbanization remain to be determined. We propose that effects of food abundance or quality, temperature, noise, pollution, or disturbance by humans may on their own or in combination affect laying date and/or clutch size.

The use of artificial nest boxes has led to significant progress in bird conservation and in our understanding of the functional and evolutionary ecology of free-ranging birds that exploit cavities for roosting and reproduction. Nest boxes and their improved accessibility have made it easier to perform comparative and as the extent to which publications on these birds describe the characteristics of exploited artificial nest boxes in their ''Methods'' sections. More than 60% of recent publications did not provide any details on nest box design (e.g. size, shape, material), despite several calls [15 years ago to increase the reporting of such information. We exemplify and discuss how variation in nest box characteristics can affect or confound conclusions from nest box studies and conclude that it is of overall importance to present details of nest box characteristics in scientific publications.

Summary Secondary hole‐nesting birds that do not construct nest holes themselves and hence regularly breed in nest boxes constitute important model systems for field studies in many biological disciplines with hundreds of scientists and amateurs involved. Those research groups are spread over wide geographic areas that experience considerable variation in environmental conditions, and researchers provide nest boxes of varying designs that may inadvertently introduce spatial and temporal variation in reproductive parameters. We quantified the relationship between mean clutch size and nest box size and material after controlling for a range of environmental variables in four of the most widely used model species in the Western Palaearctic: great tit Parus major, blue tit Cyanistes caeruleus, pied flycatcher Ficedula hypoleuca and collared flycatcher F. albicollis from 365 populations and 79 610 clutches. Nest floor area and nest box material varied non‐randomly across latitudes and longitudes, showing that scientists did not adopt a random box design. Clutch size increased with nest floor area in great tits, but not in blue tits and flycatchers. Clutch size of blue tits was larger in wooden than in concrete nest boxes. These findings demonstrate that the size of nest boxes and material used to construct nest boxes can differentially affect clutch size in different species. The findings also suggest that the nest box design may affect not only focal species, but also indirectly other species through the effects of nest box design on productivity and therefore potentially population density and hence interspecific competition.

The brood size in the Finnish Northern Goshawks seems to be associated with the breeding habitat and the availability of suitable prey. In this study, we examined these relationships in three study areas of different landscape structure in southern Finland, including a recently colonized urban area. The most abundant prey categories found in the food remains of the goshawk included corvids, turdids, columbids, gallinaceous birds, and squirrels. Corvids dominated in the diet samples of all the study areas. The number of turdids and columbids in the samples was significantly higher in both the rural and the urban habitats than in the wilderness area. The number of gallinaceous birds was significantly higher in the wilderness area than in other habitats. Gallinaceous birds, particularly tetraonids, the traditional staple food of the Northern Goshawk in Finland, seemed to be largely compensated by corvids in the wilderness area and by corvids and columbids in the rural and urban areas. The amount of corvids in prey showed a positive relationship with brood size, suggesting some particular importance of this prey in the goshawk diet. In all, diet seemed to explain partly betweenlandscape variations in the brood size of the goshawk. The brood size was significantly higher in the urban landscape than elsewhere.