The correlates of intraspecific variation in nest height and nest building duration in the Eurasian blue tit Cyanistes caeruleus

Birds build nests primarily as a receptacle to lay their eggs in, but they can also provide secondary benefits including structural support, camouflage and adjustment of the microclimate surrounding the eggs and offspring. The factors underlying intraspecific variation in nest characteristics are poorly understood. In this study, we aim to identify the environmental factors that predict nest height variation and the duration of nest building in blue tits Cyanistes caeruleus, evaluating latitude, elevation, temperature and the timing of egg-laying as predictors of nest height, while also taking into account female and male parental identity. Using 713 nest height observations collected over a period of five years along a 220 km transect in Scotland, we found that if the annual mean timing of egg-laying was earlier, nests were taller. However, there was no correlation between nest height and elevation, latitude, the minimum temperature in the 14 days pre-egg-laying or the phenology of birds within a year. Female parental identity accounted for a large amount of variation in nest height, suggesting that individual behaviour has an influence on nest structure. We also found that nest building duration was shorter when egg laying occurred earlier in the year, and that across all observations taller nests took longer to build. Overall, our results show that blue tits are able to alter their nest characteristics based on environmental gradients like latitude (in the case of building duration) and the annual mean phenological variation of egg laying, and that birds build relatively taller nests faster

The roles of temperature, nest predators and information parasites for geographical variation in egg covering behaviour of tits (Paridae)

This is the final version. Available from Wiley via the DOI in this record. Abstract Aim Nest building is widespread among animals. Nests may provide receptacles for eggs, developing offspring and the parents, and protect them from adverse environmental conditions. Nests may also indicate the quality of the territory and its owner and can be considered as an extended phenotype of its builder(s). Nests may, thus, function as a sexual and social signal. Here, we examined ecological and abiotic factors—temperature, nest predation and interspecific information utilization—shaping geographical variation in a specific nest structure—hair and feather cover of eggs—and its function as an extended phenotype before incubation in great (Parus major) and blue tits (Cyanistes caeruleus) across Europe. We also tested whether egg covering is associated with reproductive success of great tits. Location Fourteen different study sites and 28 populations across Europe. Taxon Parus major, Cyanistes caeruleus. Methods We recorded clutch coverage estimates and collected egg covering nest material from the tit nests. We also measured nest specific breeding parameters and phenotypic measurements on adults. We tested whether mean spring temperatures, nest predation rates and flycatcher (Ficedula spp) densities in the study areas explain the large‐scale geographical variation of clutch coverage and reproductive success of tits. Results The degree of egg coverage of great tits increased with lower mean spring temperature, higher nest predation rate and higher flycatcher density. We did not find egg covering of blue tits to be associated with any of the ecological or abiotic factors. Moreover, egg covering of great tits was not associated with reproductive success in our cross‐sectional data, yet a rigorous assessment of fitness effects would require long‐term data. Main conclusions Our findings suggest that, in great tits, egg covering may simultaneously provide thermal insulation against cold temperatures during egg‐laying in spring and also represent a counter‐adaptation to reduce information parasitism by flycatchers and nest predation. Hence, geographical variation in interspecific interactions, and consequently in co‐evolutionary processes, may affect the evolution of nest characteristics besides environmental conditions.Biotieteiden ja Ympäristön Tutkimuksen ToimikuntaAgencia Estatal de Investigación, Ministry of Economy, Industry and Competitiveness, Spanish Research Council

Strengthening the evidence base for temperature-mediated phenological asynchrony and its impacts

Climate warming has caused the seasonal timing of many components of ecological food chains to advance. In the context of trophic interactions, the match–mismatch hypothesis postulates that differential shifts can lead to phenological asynchrony with negative impacts for consumers. However, at present there has been no consistent analysis of the links between temperature change, phenological asynchrony and individual-to-population-level impacts across taxa, trophic levels and biomes at a global scale. Here, we propose five criteria that all need to be met to demonstrate that temperature-mediated trophic asynchrony poses a growing risk to consumers. We conduct a literature review of 109 papers studying 129 taxa, and find that all five criteria are assessed for only two taxa, with the majority of taxa only having one or two criteria assessed. Crucially, nearly every study was conducted in Europe or North America, and most studies were on terrestrial secondary consumers. We thus lack a robust evidence base from which to draw general conclusions about the risk that climate-mediated trophic asynchrony may pose to populations worldwide

Geometry in Islamic Art

Geometric patterns in two and three dimensions comprise one of the key characteristics of arts and architecture of the Islamic world in many cultural traditions from the central Islamic lands of the Middle East to Spain, India, Indonesia, and sub-Saharan Africa (Bloom & Blair, 2009; Broug, 2013; Ettinghausen, Grabar, & Jenkins-Madina, 2001; Gerdes, 1999; Hillenbrand, 1994, 2009). Although geometry is present, either by conscious human choice in design or as an inherent feature of architectural production in all cultures, it seems to have assumed a much higher significance in Islamic centers of civilization (Grabar, 1992). Often attributed to a proscription against figural images, this interpretation is not borne out historically with reference to palace wall painting, ceramics, ivory, woodwork, and book illustration rich with pictorial narrative

Facultative interspecific brood parasitism in tits: a last resort to coping with nest-hole shortage

We studied the occurrence of facultative interspecific brood parasitism (eggs from two species incubated by a single female) in two bird species, the blue (Cyanistes caeruleus) and the great tit (Parus major). These species are secondary cavity nesters. We monitored 38 forest plots of variable size over 3 years. We found a total of 39 mixed-species clutches in 1285 nests, representing a prevalence of 3.0 %, but it reached 7.2 % in small woodlands. Seventeen mixed-species clutches involved blue tit facultative interspecific brood parasitism, with the same number of great tits usurping and directly laying in blue tit clutches. The higher the nest-box occupation rate, the greater the prevalence of mixed-species clutches of any origin. However, the two tit species behaved differently when faced with nest-hole shortage, with blue tits dumping one or two eggs into clutches incubated by great tits and these taking over the entire blue tit clutch. Nest takeovers were more frequent at the end of the season. These differences in behaviour are likely mediated by differing dominance status, with great tits being larger. The difference in size could also explain why great tit chicks presented larger hatching and fledging rates than their blue tit broodmates. These rates were lower in blue tit chicks from mixed-species broods compared with pure ones, and no advantages were found in usurper great tit chicks compared to pure broods. Mixed-species clutches appear to be a response to nest-hole shortage, a concept that we have termed the ‘last resort hypothesis’.Peer reviewe