Egg cooling associated with nest size in a passerine bird.

Breeders evolved adaptive responses to rapid changes in ambient temperature. In birds, nests are expected to reduce egg cooling when the incubator is temporarily off the eggs. Here we present the results of two complementary laboratory experiments aiming at testing the association between egg cooling and the thickness of the nest under and surrounding the eggs in a non-domesticated avian model species (great tit, Parus major).

Surface temperatures of non-incubated eggs in great tits (Parus major) are strongly associated with ambient temperature.

Temperature is one of the best investigated environmental factors in ecological life-history studies and is increasingly considered in the contexts of climate change and urbanization. In avian ecology, few studies have examined the associations between thermal dynamics in the nest environment and its neighbouring air. Here, we placed avian nests and non-incubated eggs inside nest boxes at various air temperatures that ranged from 0.

Effects of interspecific coexistence on laying date and clutch size in two closely related species of hole-nesting birds.

Coexistence between great tits Parus major and blue tits Cyanistes caeruleus, but also other hole-nesting taxa, constitutes a classic example of species co-occurrence resulting in potential interference and exploitation competition for food and for breeding and roosting sites. However, the spatial and temporal variations in coexistence and its consequences for competition remain poorly understood. We used an extensive database on reproduction in nest boxes by great and blue tits based on 87 study plots across Europe and Northern Africa during 1957-2012 for a total of 19,075 great tit and 16,729 blue tit clutches to assess correlative evidence for a relationship between laying date and clutch size, respectively, and density consistent with effects of intraspecific and interspecific competition.

Nest design in a changing world: great tit nests from a Mediterranean city environment as a case study.

Investigations of urbanization effects on birds have focused mainly on breeding traits expressed after the nest-building stage (e.g. first-egg date, clutch size, breeding success, and offspring characteristics).

Disentangling drivers of reproductive performance in urban great tits: a food supplementation experiment.

Worldwide urban expansion induces degradation of the natural environment, resulting in new constraints in terms of breeding sites, anthropogenic disturbances as well as food resources. The alteration of resource abundance and type may induce non-adaptive investments in reproduction from urban dwellers. Food availability and quality have been identified as potential drivers of the decline in passerine body mass and fledging success in urbanized landscapes, particularly if birds misinterpret cues of food abundance used to adjust their reproductive investment.

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

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.

The design and function of birds' nests.

All birds construct nests in which to lay eggs and/or raise offspring. Traditionally, it was thought that natural selection and the requirement to minimize the risk of predation determined the design of completed nests. However, it is becoming increasingly apparent that sexual selection also influences nest design.

Female blue tits with brighter yellow chests transfer more carotenoids to their eggs after an immune challenge.

Female ornaments are present in many species, and it is more and more accepted that sexual or social selection may lead to their evolution. By contrast, the information conveyed by female ornaments is less well understood. Here, we investigated the links between female ornaments and maternal effects.

Aromatic plants in nests of the blue tit Cyanistes caeruleus protect chicks from bacteria.

Several bird species add fresh fragments of plants which are rich in volatile secondary compounds to their nests. It has been suggested, although never tested, that birds use fresh plants to limit the growth of nest microorganisms. On Corsica, blue tits (Cyanistes caeruleus) incorporate fresh fragments of aromatic plants into their nests.

Local individual preferences for nest materials in a passerine bird.

Background: Variation in the behavioural repertoire of animals is acquired by learning in a range of animal species. In nest-building birds, the assemblage of nest materials in an appropriate structure is often typical of a bird genus or species. Yet plasticity in the selection of nest materials may be beneficial because the nature and abundance of nest materials vary across habitats.

Circulating corticosterone levels in breeding blue tits Parus caeruleus differ between island and mainland populations and between habitats.

Little is known about whether adaptations to an insular life also involve adaptations in basal corticosterone levels or in the adrenocortical stress response, thus being part of a genetically based island syndrome. However, differences in corticosterone between island and mainland may also be a direct phenotypic response to differences in environmental conditions or may depend on individual characteristics of the animal such as body condition or parental investment. In this paper, we investigated whether insular (Island of Corsica) and mainland (nearby Southern France) blue tits Parus caeruleus populations differed in baseline and handling-stress induced corticosterone levels during the breeding season as a response to biological changes of insular biota.

Early seasonal development of brain song control nuclei in male blue tits.

In songbirds, the seasonal growth of the song system is generally thought to be controlled by the spring increase in plasma levels of testosterone and/or related changes in singing activity. Here we report an extremely early seasonal growth (before February) of the song control nuclei HVC and RA in Corsican blue tits (Parus caeruleus) indicating that the vernal development of these nuclei occurs well before the vernal increase in plasma testosterone, testes size and song activity. The development of HVC and RA occurred simultaneously in two populations that are known to breed consistently 1 month apart as an adaptation to heterogeneous landscapes (predominance of broad-leaved deciduous versus evergreen oak trees).

Endocrine correlates of the breeding asynchrony between two Corsican populations of blue tits (Parus caeruleus).

Analyses of the development of the reproductive system in seasonally breeding birds in the framework of long-term ecological studies are rare. Here, we present the first results of such a study in two Corsican populations of a European passerine bird, the blue tit (Parus caeruleus). The two study populations occupy different oak habitats and are separated by only 25 km.

Habitat quality as a predictor of spatial variation in blue tit reproductive performance: a multi-plot analysis in a heterogeneous landscape.

Vertebrate studies have rarely investigated the influence of spatial variation in habitat richness on both short-term (breeding) and long-term (offspring recruitment) reproductive performance using simultaneously multi-patch, multi-habitat type and multi-year approaches at landscape level. Here we present results of such an approach using the influence of two oak tree (Quercus ilex, Q. humilis) species on reproductive performance in Corsican blue tits (Parus caeruleus ogliastrae) as a model system.

Physiological ecology of Mediterranean blue tits (Parus caeruleus L.): effects of ectoparasites (Protocalliphora spp.) and food abundance on metabolic capacity of nestlings.

The consequences of nest ectoparasites, such as Protocalliphora larvae, on nestling birds have been the subject of numerous studies. Despite observed reductions in mass and hematocrit of chicks from parasitized nests, no studies have found any effect of Protocalliphora on nestling survival, suggesting that fitness consequences of Protocalliphora are either weak or occur after fledging. From experiments on the metabolic performance of chicks, we found that parasitized chicks suffer from reduced thermogenic and metabolic capacities as a result of decreased mass and hematocrit.

Parasitism reduces the potential for evolution in a wild bird population.

We tested the effect of detrimental environmental conditions during growth on the heritability of chick body size in a wild population of blue tits (Parus caeruleus) highly parasitized by blowfly larvae. During nine years, we experimentally induced deparasitized broods, whereas unmanipulated control broods remained heavily infested by two species of Protocalliphora ectoparasites. The heritability of tarsus length was significantly higher in deparasitized broods than control broods, due in part to a very low common brood environment effect in deparasitized broods.

Climate variation and regional gradients in population dynamics of two hole-nesting passerines.

Latitudinal gradients in population dynamics can arise through regional variation in the deterministic components of the population dynamics and the stochastic factors. Here, we demonstrate an increase with latitude in the contribution of a large-scale climate pattern, the North Atlantic Oscillation (NAO), to the fluctuations in size of populations of two European hole-nesting passerine species. However, this influence of climate induced different latitudinal gradients in the population dynamics of the two species.

Aromatic plants in bird nests as a protection against blood-sucking flying insects?

The nest protection hypothesis suggests that some of the fresh plant material, brought by some bird species to their nests, contain secondary compounds that repel parasites or mask the chemical cues that parasites use to find the host. Corsican blue tits (Parus caeruleus) bring pieces of several species of aromatic plants to the nest at dusk, suggesting a protection against nocturnal agents such as blood-sucking flying insects. The potential repellent or masking effect of these aromatic plant species, alone or in mixture, was experimentally investigated in the mosquito Culex pipiens, using domestic chicks as bird hosts.

Is the small clutch size of a Corsican blue tit population optimal?

In an attempt to test predictions of the optimisation hypothesis of life history traits in birds, we estimated fitness consequences of brood size manipulations. Experiments were carried out over a period of 4 years in a Mediterranean population of blue tits Parus caeruleus which is confronted with a particular set of environmental constraints. Effects of brood size manipulation were investigated in relation to year-to-year variation in environmental conditions, especially caterpillar abundance.