Tomasz D. Mazgajski

The design of artificial nestboxes for the study of secondary hole-nesting birds: a review of methodological inconsistencies and potential biases

Abstract. The widespread use of artificial nestboxes has led to significant advances in our knowledge of the ecology, behaviour and physiology of cavity nesting birds, especially small passerines. Nestboxes have made it easier to perform routine monitoring and experimental manipulation of eggs or nestlings, and also repeatedly to capture, identify and manipulate the parents. However, when comparing results across study sites the use of nestboxes may also introduce a potentially significant confounding variable in the form of differences in nestbox design amongst studies, such as their physical dimensions, placement height, and the way in which they are constructed and maintained. However, the use of nestboxes may also introduce an unconsidered and potentially significant confounding variable due to differences in nestbox design amongst studies, such as their physical dimensions, placement height, and the way in which they are constructed and maintained. Here we review to what extent the characteristics of artificial nestboxes (e.g. size, shape, construction material, colour) are documented in the ‘methods’ sections of publications involving hole-nesting passerine birds using natural or excavated cavities or artificial nestboxes for reproduction and roosting. Despite explicit previous recommendations that authors describe in detail the characteristics of the nestboxes used, we found that the description of nestbox characteristics in most recent publications remains poor and insufficient. We therefore list the types of descriptive data that should be included in the methods sections of relevant manuscripts and justify this by discussing how variation in nestbox characteristics can affect or confound conclusions from nestbox studies. We also propose several recommendations to improve the reliability and usefulness of research based on long-term studies of any secondary hole-nesting species using artificial nestboxes for breeding or roosting.

Bird casualties on European roads — a review

Abstract. Road traffic affects the natural environment in numerous ways. The most striking of these is the death of wild animals and birds as a result of collisions with moving vehicles. In this paper the available data on bird mortality on roads are reviewed. Estimates of annual mortality for some European countries (350 000 to 27 million birds), the monthly distribution of casualties, their distribution among sex and age classes, as well as the methods used in the study of this problem are presented. The species composition of birds killed in this way is compared for several countries. In western Europe sparrows and Blackbirds are the species that most frequently die on the roads, but in Central and Eastern Europe not only sparrows but also corvids and Barn Swallows make up a high proportion of the victims. Analysis of the monthly distribution of casualties in 10 species shows this to differ between countries, probably because of the geographic variation of certain aspects of their biology (migration, breeding etc.). Several factors affecting the frequency of casualties are discussed, and some suggestions for the prevention of bird casualties are also given.

Green plant material in avian nests

Some bird species place in their nests fresh green plant materials, e.g. leaves, sprigs or branches of herbs, shrubs and trees, which are not a part of the basic nest structure. These additional materials are often characterised by a high content of volatile secondary metabolites and constitute a non-random, small fraction of plants available in the habitat. Several non-mutually exclusive hypotheses have been proposed to explain the function of green material in avian nests with three of them attracting the most attention. The courtship hypothesis proposes that green material is used by males in order to attract females to nesting sites. The nest protection hypothesis posits that birds place in the nest green material rich in volatile compounds to reduce the abundance of parasites and pathogens which, in turn, should mitigate their negative impact on the host. According to the drug hypothesis green material directly positively affects the health and development of nestlings, e.g. through stimulation of some components of the nestlings’ immune system. Here, we present an overview of hypotheses explaining the phenomenon of green material in avian nests with a thorough description of three most frequently tested hypotheses and suggest the directions for future studies.

Variation in clutch size in relation to nest size in birds

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.

Nesting Phenology and Breeding Success in Great Spotted Woodpecker Picoides major Near Warsaw (Central Poland)

Abstract. The study was carried out between 1996 and 1998 on a plot covered by mixed woodland near the southern boundary of the city of Warsaw. A total of 39 nests were investigated. The woodpeckers laid their eggs during the last ten days of April and at the beginning of May. The mean clutch size was 5.6 (n = 18). The number of young reared differed from season to season and was associated with the fledging date. More fledglings left nests with earlier broods. 81% of broods were successful, i.e. at least one young was reared. The duration of the breeding season — from the laying of the first egg to the fledging of the last chick — was 40–42 days.

Dependence of Nest Mass on Nest Hole Depth in the Great Tit Parus major

Abstract. Predation is considered an important factor affecting the life histories and breeding strategies of hole nesting birds. Breeding losses in this group of birds are related to such nest site characteristics as entrance size, nest site depth and danger distance - the distance between the outer edge of the entrance to the centre of the nests bottom, which determines how far a predator unable to enter the hole would have to reach to obtain its contents. It is suggested that birds assess predation risk and adjust their breeding investments accordingly. We tested the hypothesis that in shallow nest sites, birds build smaller nests to maintain the largest danger distance possible. During the experiment, two types of nestboxes were available to birds: those typical for small passerines (with a depth of 21 cm), and shallower ones (with a 16 cm depth). Breeding parameters were obtained by controlling nestboxes, the distances between eggs and entrances were measured, and nests were weighed just after the young fledged. Breeding phenology and clutch size did not differ between the types of nestboxes. Nest site depth influenced nest mass, and according to our assumptions, nests were significantly lighter in shallow nestboxes. A clear, negative relationship was found between nest mass and the danger distance — eggs in larger (heavier) nests were closer to the entrance. Breeding success (number of fledglings per eggs laid) was lower for shallow nestboxes compared to normal ones, and nest mass negatively influenced the number of fledglings and breeding success. The results of this study suggest that Great Tits perceive nest site depth and adjust nest building according to predation risks. Nest size (mass) in shallow sites may be limited by the danger distance, but it is also possible that the number of trips with nest material, which could lead to the detection of the site, is also important. However, both explanations are not mutually exclusive, and both are related to avoiding predator pressure.

Clutch-size variation in Western Palaearctic secondary hole-nesting passerine birds in relation to nest box design

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 79610 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.

Interspecific variation in the relationship between clutch size, laying date and intensity of urbanization in four species of hole-nesting birds

Abstract 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.

Residues of chromium, nickel, cadmium and lead in Rook Corvus frugilegus eggshells from urban and rural areas of Poland.

We examined the concentrations of chromium (Cr), nickel (Ni), cadmium (Cd) and lead (Pb) in Rook Corvus frugilegus eggshells from 43 rookeries situated in rural and urban areas of western (=intensive agriculture) and eastern (=extensive agriculture) Poland. We found small ranges in the overall level of Cr (the difference between the extreme values was 1.8-fold; range of concentrations=5.21-9.40 Cr ppm), Ni (3.5-fold; 1.15-4.07 Ni ppm), and Cd (2.6-fold; 0.34-0.91 Cd ppm), whereas concentrations of Pb varied markedly, i.e. 6.7-fold between extreme values (1.71-11.53 Pb ppm). Eggshell levels of these four elements did not differ between rural rookeries from western and eastern Poland, but eggshells from rookeries in large/industrial cities had significantly higher concentrations of Cr, Ni and Pb than those from small towns and villages. Our study suggests that female Rooks exhibited an apparent variation in the intensity of trace metal bioaccumulation in their eggshells, that rapid site-dependent bioaccumulation of Cu, Cr, Ni and Pb occurs as a result of the pollution gradient (rural<urban), and that Cd levels are probably regulated physiologically, even though these were relatively high, which could be treated as an overall proxy of a heavy Cd load in the soil environment.

The origins of Great Spotted Woodpeckers Dendrocopos major colonizing Ireland revealed by mitochondrial DNA

Capsule Although necessarily based on a small number of samples, comparisons of molecular data from the newly established Great Spotted Woodpecker populations in Ireland with those in Britain and continental Europe revealed that Britain was the more likely source area of the Irish populations.