Egg-size variation in algerian populations of the Blue Tit (Parus caeruleus ultramarinus) : effects of altitude and habitat

Egg-size, as a component of life history, is expected to be traded-off with other components and, consequently, to display a pattern of variation between different habitats and altitudes. Relevant data being very scarcely available for just a few bird species caused us to study interhabitat and interaltitude variation in egg dimensions and mass in the Blue Tit Parus caeruleus ultramarinus, taking the advantage of the occurrence of this species in a variety of habitats and at different altitudes in North Africa (north-eastern Algeria). In 1991-1993 we selected 6 study sites representing two types of habitat (rich deciduous forests dominated by A lnus glutinosa and Quercus faginea vs poor evergreen forests of Quercus suber) at three elevations (30m asl, 500m als and 900-1000m asl). We analysed both multiple response variables characterizing egg dimensions and individual egg traits. Eggs tumed out to differ between altitudes (the lowest elevation against the two higher ones) but did not differ between habitats. They also display relatively high within-clutch repeatabilities, 0.6 on average for ali traits. Egg traits were not significantly correlated with clutch-size within study stations, but the analysis of a bivariate response variable composed of egg volume and clutch-size suggested that these components of life history were negatively linked. Moreover, this bivariate response variable differed both between habitats and altitudesLa taille de l'oeuf est un caractère que l'on s'attend à être lié à d'autres traits d'histoire de la vie de sorte qu'il devrait montrer des variations en fonction de l'habitat et de l'altitude. Fort peu de données probantes étant disponibles et pour un nombre limité d'espèces, nous avons conduit en 1991-93 une étude de la variation interhabitat et altitudinale des dimensions et du poids des œufs de la Mésange bleue Parus caeruleus ultramarinus, profitant de ce que cette espèce se montre dans toute une gamme d'habitats et d'altitudes en Afrique du Nord, notamment dans le nord-est de l'Algérie. Six stations d'étude ont été sélectionnées, représentant deux types d'habitat (les riches forêts caducifoliées dominées par Alnus glutinosa et Quercus faginea opposées aux forêts sempervirentes pauvres de Quercus suber) et trois altitudes (30 m, 500 m et 900-1 000 m). Nous avons analysé à la fois les variables à réponse multiple qui caractérisent les dimensions des œufs et les traits individuels de ces oeufs. Les œufs sont apparus différer selon l'altitude (opposition entre le plus bas niveau et les suivants) mais pas selon l'habitat, Ils montrent aussi un relativement fort degré de répétabilité intraponte, de 0,6 en moyenne pour tous les caractères. Ceux-ci n'étaient pas significativement liés à la taille de la ponte dans un même site mais l'analyse d'une variable bivariée intégrant le volume de l'oeuf et la taille de la ponte a suggéré que ces deux traits seraient négativement corrélés. De plus, cette variable bivariée différait à la fois d'un habitat et d'une altitude à l'autre

Interaction of climate change with effects of conspecific and heterospecific density on reproduction

We studied the relationship between temperature and the coexistence of great titParus majorand blue titCyanistes caeruleus, breeding in 75 study plots across Europe and North Africa. We expected an advance in laying date and a reduction in clutch size during warmer springs as a general response to climate warming and a delay in laying date and a reduction in clutch size during warmer winters due to density-dependent effects. As expected, as spring temperature increases laying date advances and as winter temperature increases clutch size is reduced in both species. Density of great tit affected the relationship between winter temperature and laying date in great and blue tit. Specifically, as density of great tit increased and temperature in winter increased both species started to reproduce later. Density of blue tit affected the relationship between spring temperature and blue and great tit laying date. Thus, both species start to reproduce earlier with increasing spring temperature as density of blue tit increases, which was not an expected outcome, since we expected that increasing spring temperature should advance laying date, while increasing density should delay it cancelling each other out. Climate warming and its interaction with density affects clutch size of great tits but not of blue tits. As predicted, great tit clutch size is reduced more with density of blue tits as temperature in winter increases. The relationship between spring temperature and density on clutch size of great tits depends on whether the increase is in density of great tit or blue tit. Therefore, an increase in temperature negatively affected the coexistence of blue and great tits differently in both species. Thus, blue tit clutch size was unaffected by the interaction effect of density with temperature, while great tit clutch size was affected in multiple ways by these interactions terms.Peer reviewe

Variation in clutch size in relation to nest size in birds

Peer reviewe

Variation in egg-size traits of the European Roller (Coracias garrulus) in eastern Poland

Life-history theory predicts that allocation of resources into offspring size and number should be traded-off. The trade-off may be masked in good environmental conditions and be expressed only in some reproductive attempts, when conditions are poor. In this paper we analyse variation in size-related traits of eggs in relation to clutch size in a marginal population of the European Roller (Coracias garrulus) in eastern Poland, declining as a result of agriculture intensification and habitat loss. Because large-bodied insects that constitute the main kind of food of Rollers are greatly affected by the weather in spring, we assumed that their abundance may differ from year to year in association with differences in weather conditions. We predicted that egg size-clutch size relationship and egg traits should differ between years in correspondence with environmental conditions prior to the time of egg laying. We also predicted that variation in egg size and shape should have some fitness-related consequences. We found that year and clutch size interacted in their influence on egg size: in one year egg size was positively and in another year negatively related to clutch size. We also found that egg shape (sphericity) was positively associated with clutch size and negatively related with the date of laying. Both egg size and spheric-ity in shape positively affected hatching success, thus confirming the existence of fitness-consequences of variation in the traits of Roller eggs. Our results are in general consistent with theoretical expectations, but we failed to find any specific links between egg size variation and the decline of the study population

Inter-annual and inter-habitat variation in breeding performance of Blue Tits (Cyanistes caeruleus) in central Poland

Studies at various locations in Europe show that nest-box populations of tits in urban areas lay earlier and produce fewer eggs than do birds in rural areas. Long-term data on laying date and clutch size were studied for Blue Tit (Cyanistes caeruleus) populations in two, structurally and floristically contrasting sites (an urban parkland and a rich decidu-ous forest, located only 10 km apart) in central Poland. The peak abundance of caterpillars, the optimal food of breeding tits, was also studied at both breeding areas. We focused on four environmental factors; year, site, insect availability and ambient temperature. Birds initiated breeding earlier in the urban area compared to the forest area and the laying date was highly correlated with air temperature during the period between 15 March and 15 April. At both study areas there was a similar negative temporal trend – birds started breeding earlier with later years. The number of eggs laid per breeding pair tended to be lower in the parkland than in the forest and it is likely that this is due to the habitat-specific pattern of food abundance and patchy environment in the parkland. This study provides new data on the reproductive biology of a model species and also fills up some knowledge gaps concerning inter-habitat and macro-geographic patterns

Spatial and temporal variation in heterophil-to-lymphocyte ratios of nestling passerine birds: comparison of blue tits and great tits.

Environmental factors affecting trophic conditions act as stressors on nestling altricial birds. Access of parental birds to a sufficient supply of food in a limited period of the nestling stage differ in time and space, depending on nesting habitat, prey density and weather conditions. Heterophil-to-lymphocyte ratio (H/L) is considered as a reliable indicator of prolonged stress reaction in birds. In this study we examine if variation in H/L shows consistent spatio-temporal patterns in nestlings of two parids, blue tit Cyanistes caeruleus and great tit Parus major. We found that blue tit nestlings had on average higher H/L than great tit nestlings, which corresponds with the ecological sensitivity of these species. In both species H/L was higher in a poor parkland habitat than in a high quality forest habitat. In nestling blue tits, higher H/L values occurred in years characterized by more extreme weather conditions and worse caterpillar availability. Such consistent patterns of variation in the H/L ratio of nestling blue tits and great tits suggest that, when age-dependent effects are controlled, the ratio can be used as an indicator of physiological stress that is generated by food-related stressors differing in space and time. In particular, elevated H/L ratios are indicative of human-induced changes in the structure of breeding habitats

Comparison of blue tit and great tit nestlings in relation to inter-site variation in mean H/L ratios.

<p>Sample sizes are shown as the number of nestlings and, in parentheses, as the number of broods.</p

Results of a mixed model ANCOVA for the H/L ratio of nestling blue tits, with wing length as covariate and year and site as factors.

<p>Results of a mixed model ANCOVA for the H/L ratio of nestling blue tits, with wing length as covariate and year and site as factors.</p

Descriptive characteristics of May weather in Łódź in the study years.

<p>Descriptive characteristics of May weather in Łódź in the study years.</p

Comparison of the forest site and the parkland site with respect to inter-annual variation in the peak abundance of tree-canopy caterpillars, as measured by the peak amount of caterpillar frassfall.

<p>Comparison of the forest site and the parkland site with respect to inter-annual variation in the peak abundance of tree-canopy caterpillars, as measured by the peak amount of caterpillar frassfall.</p