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Comprehending symbiont abundance among host species is a major ecological endeavour, and the metabolic theory of ecology has been proposed to understand what constraints symbiont populations. We parameterized metabolic theory equations to predict how bird species’ body size and the body size of their feather mites relate to mite abundance according to four potential energy (microbial abundance, uropygial gland size) and space constraints (wing area, number of feather barbs). Predictions were compared with the empirical scaling of feather mite abundance from 26,604 birds of 106 passerine species, using phylogenetic modelling and quantile regression. Feather mite populations were strongly constrained by host space (number of feather barbs) and not energy. Moreover, feather mite species’ body size was unrelated to their abundance or to the body size of their host species. We discuss the implications of our results for our understanding of the bird-feather mite system and for symbiont abundance in general.

[EN] Differential traits (e.g., feeding at different heights in trees) have evolved to allow the coexistence of putative competitors; such traits have been well studied in small passerines (e.g., Paridae), mainly during the winter. However, few studies have been carried out during the breeding season, when competition could be more intense. We applied here a multidimensional approach, examining ecological (prey type and size, and nesting habitat characteristics) and life history (timing of maximum nestling food demand) traits that might help to explain the coexistence of great (Parus major), crested (Lophophanes cristatus), and coal (Periparus ater) tits breeding in a Mediterranean pine forest. The diets of great and crested tit nestlings were equally diverse, and more diverse than that of coal tit nestlings. Prey size diversity was similar among species. Great and crested tits consumed longer caterpillars than coal tits. This last species preferred to build its nests in nest boxes surrounded by mature vegetation, while great tits preferred immature vegetation and crested tits preferred intermediate vegetation stages. Finally, the breeding cycles of both great and coal tits overlapped to a great extent, while crested tits bred earlier. In summary, each species has a unique combination of niche characteristics that might contribute to the coexistence of the 3 tit species., [FR] Différents traits bioécologiques (ex. une alimentation à différentes hauteurs dans les arbres) ont évolué pour permettre la coexistence des présumés compétiteurs. Ces traits ont été bien étudiés chez les petits passereaux (ex. chez les paridés) principalement en hiver. Cependant, peu d'études se sont attardées à la saison de reproduction, alors que la compétition est peut être plus intense. Nous avons utilisé une approche multidimensionnelle comprenant une étude de traits écologiques (type et taille des proies, caractéristiques de l'habitat de nidification) et de traits d'histoire de vie (période où la demande alimentaire des oisillons est maximale), des traits qui pourraient aider à expliquer la coexistence des mésanges charbonnière (Parus major), huppée (Lophophanes cristatus) et noire (Periparus ater) nichant dans une pinède méditerranéenne. Le régime alimentaire des mésanges noires était moins diversifié que celui des mésanges charbonnière et huppée dont la diversité était similaire. La diversité dans la taille des proies était semblable chez les 3 espèces. Les mésanges charbonnière et huppée consommaient des chenilles de plus grande taille que ne le faisait la mésange noire. Cette dernière préférait construire son nid dans des nichoirs situés dans une végétation mature, tandis que la mésange charbonnière préférait la végétation immature et la mésange huppée les stades intermédiaires de végétation. Finalement, les périodes de reproduction des mésanges charbonnière et noire se chevauchaient en bonne partie, tandis que la mésange huppée se reproduisait plus tôt. En résumé, chaque espèce de mésange présente une combinaison unique de caractéristiques de niche écologique pouvant contribuer à la coexistence des 3 espèces., We would like to thank J. L. Gre o, who helped in the field tasks. The study was financed by the Ministerio de Educacion y Ciencia (MEC, projects CGL2004-00787, CGL2007-61395, and CGL2010-21933-C02-02). F. Atienzar had an FPU grant from the Ministerio de Educacion y Ciencia (AP2004-0907). Vegetation data used in the present study were processed at the Netherlands Institute of Ecology (NIOO-KNAW) thanks to M. E. Visser and the late L. J. M. Holleman. We thank Sierra Mariola Natural Park and the land owners for their collaboration. Most of the analyses and writing for the present paper were done during a short stay at the NIOO thanks to a grant awarded to F. Atienzar by the Ministerio de Educacion y Ciencia (2008).

Forest type and habitat structure can have profound effects on different aspects of avian life histories. These effects may, however, strongly differ across and within forests that vary in vegetation composition and structure, especially when an ancient forest has been replaced by a new forest. To test for these differences in effect, we studied Great Tit Parus major life-history traits (280 first clutches) in two Mediterranean evergreen forests during 2005–07: an ancient Holm Oak Quercus ilex and a reforested pine forest. A comparison between forests revealed that females breeding in the Holm Oak forest started laying one week later, and produced larger clutches and broods both at hatching and at fledging. Chicks raised in the Holm Oak forest also fledged in better condition. Within forests, however, the reproductive success was not higher for pairs breeding in nestboxes surrounded by oaks within the pine forest, and also reproductive success was not lower in nestboxes surrounded by pines within oak forest. Instead, vegetation maturity around nestboxes, rather than tree species composition, affected hatching success. Surprisingly, hatching success was higher in nestboxes surrounded by immature vegetation. We suggest that this may be due to a lower nest predation rate in nestboxes surrounded by immature vegetation, compared to nestboxes surrounded by mature vegetation. We suggest that different factors appear to affect variation in breeding success in Mediterranean Great Tits comparing across forests (e.g. food availability) vs. within a forest (e.g. nest predation).

Most bird species show specific habitat requirements for breeding and feeding. We studied the pattern of habitat occupation, nestling diet and breeding performance of Crested Tits Lophophanes cristatus in a "typical" (conifer- ous) and an "atypical" (Holm Oak Quercus ilex) forest in eastern Spain during 2005-2007. We aimed to determine which microhabitat characteristics in the Holm Oak forest could account for the presence of Crested Tits, and checked whether the nestling diet in the Holm Oak forest resembled that obtained in the pine forest. Vegetation maps were produced using GIS from observations made in the field (tree species, tree and shrub cover). Nestling diet was recorded through video surveillance. Crested Tits bred in mature, low-density areas in the pine forest. Those breeding in the Holm Oak forest built their nests in areas including pine trees and avoided densely forested areas. Birds breeding in the pine for- est started laying by mid-April and the average clutch size was 5 eggs. In the Holm Oak forest, birds started laying by the end of April and average clutch size was also 5 eggs. Fledglings weighed around 12 g in both forests. Nestling diet, prey size and feeding frequency by the parents did not vary between the forests. The main prey types consumed were Lepidoptera larvae and Diptera.

Capsule Nestling provisioning rates depend on nestling age and number, and on time of season, but not on time of day. Aims To determine patterns of nestling provisioning, the effort made by the parents, and the factors which affect them. Methods Mechanical counters to determine food provisioning patterns in 229 Great Tit Parus major nests over 4 years. Results Feeding frequency per chick showed a linear increase with nestling age and total feeding frequency stabilized towards the end of the nestling period. The number of visits per nest increased linearly, while those per nestling decreased linearly with brood‐size. Feeding rates per nest declined throughout the breeding season parallel to the seasonal brood‐size decline; feeding frequencies per nestling did not vary seasonally. Adult effort was almost constant throughout the day, independently of variations in brood‐size, ambient temperature and date. Conclusion Previous studies of nestling provisioning patterns were either contradictory or poorly suppor...

Feather mites are arthropods that live on or in the feathers of birds, and are among the commonest avian ectosymbionts. However, the nature of the ecological interaction between feather mites and birds remains unclear, some studies reporting negative effects of feather mites on their hosts and others reporting positive or no effects. Here we use a large dataset com- prising 20 189 measurements taken from 83 species of birds collected during 22 yr in 151 localities from seven countries in Europe and North Africa to explore the correlation between feather mite abundance and body condition of their hosts. We predicted that, if wing-dwelling feather mites are parasites, a negative correlation with host body condition should be found, while a mutualistic interaction should yield positive correlation. Although negative relationships between feather mite abundance and host body condition were found in a few species of birds, the sign of the correlation was positive in most bird species (69%). The overall effect size was only slightly positive (r = 0.066). The effect of feather mite abundance explained < 10% of variance in body condition in most species (87%). Results suggest that feather mites are not parasites of birds, but rather that they hold a commensalistic relationship where feather mites may benefit from feeding on uropygial gland secretions of their hosts and birds do not seem to obtain a great benefit from the presence of feather mites.

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.