E.V. Ivankina

Large–scale geographical variation confirms that climate change causes birds to lay earlier

Advances in the phenology of organisms are often attributed to climate change, but alternatively, may reflect a publication bias towards advances and may be caused by environmental factors unrelated to climate change. Both factors are investigated using the breeding dates of 25 long–term studied populations of Ficedula flycatchers across Europe. Trends in spring temperature varied markedly between study sites, and across populations the advancement of laying date was stronger in areas where the spring temperatures increased more, giving support to the theory that climate change causally affects breeding date advancement.

Immune challenge affects basal metabolic activity in wintering great tits.

The costs of exploiting an organisms immune function are expected to form the basis of many life–history trade–offs. However, there has been debate about whether such costs can be paid in energetic and nutritional terms. We addressed this question in a study of wintering, free–living, male great tits by injecting them with a novel, non–pathogenic antigen (sheep red blood cells) and measuring the changes in their basal metabolic rates and various condition indices subsequent to immune challenge. The experiment showed that activation of the immune system altered the metabolic activity and profile of immune cells in birds during the week subsequent to antigen injection: individuals mounting an immune response had nearly 9% higher basal metabolic rates, 8% lower plasma albumin levels and 37% higher heterophile–to–lymphocyte ratios (leucocytic stress indices) than sham–injected control birds. They also lost nearly 3% (0.5 g) of their body mass subsequent to the immune challenge. Individuals that mounted stronger antibody responses lost more mass during the immune challenge. These results suggest that energetic expenditures to immune response may have a non–trivial impact upon an individuals condition.

Seasonal Variation of Singing Activity and Relative Effect of the Advertising Behaviour of Males With Different Plumage Colour in the Pied Flycatcher Ficedula hypoleuca

Abstract. From late April to the second 10-day period of June 1994–1999, in 76 unmated males the time-budget was measured during 304 hours in a 6.6 km2 area of mature mixed and coniferous forests near Moscow. In 1999, territorial males were counted at least once per pentade throughout the breeding season in a 35 ha plot with 180 nest-boxes. Dark (grades 2–3 on Drosts scale) and pale (grades 5–7) males had similar levels of singing activity, but in cold weather the former had higher song rates than the latter. The singing activity of all the males was relatively low at the beginning of the season (by the mid-May). Dark males sang mainly from open perches (67.6% of songs, compared with 23.2% for pale males). In dark males visual stimulation compensated for the relatively low acoustic activity in early spring when trees were still lacking leaves. The immediate vicinities of nest-boxes occupied by dark males were visited by females significantly more frequently than those of pale ones.

Estimation of heritability and repeatability of resting metabolic rate in birds by the example of free-living pied flycatchers Ficedula hypoleuca (Aves: Passeriformes)

Repeatability of a trait estimated over long time intervals and its heritability make it possible to assess whether it can serve as an individual characteristic and be subject to selection. Heritability and repeatability of energetic traits are still poorly studied in birds. The most important physiological characteristic of the homoiotherms is the minimal level of energy expenditure, referred to as the resting metabolic rate (RMR), which, in the absence of the expenditure for biomass growth, does not exceed the basal metabolic rate (BMR). We have estimated the BMR repeatability in adult free-living pied flycatchers in Moscow-region (55°44′ N, 36°51′ E; 1992–2008) and Tomsk (56°20′ N, 84°56′ E; 2008–2009) populations over intervals of 40 days to 3 years. In the Moscow-region pied flycatcher population, the BMR repeatability recorded during the same period of the reproductive season was τ = 0.34 ± 0.10 for a 1-year interval (n = 80), τ = 0.60 ± 0.15 for a 2-year interval (n = 19), and τ = 0.85 ± 0.13 for a 3-year interval (n = 6). In the Tomsk population, the BMR repeatability for the 1-year interval was τ = 0.49 ± 0.11 (n = 50). The repeatability of a trait is a measure of its constancy in time and specifies the upper limit of its heritability. RMR heritability was assessed in cross-fostering experiments in the Moscow-region free-living pied flycatcher population in 2003–2005. The RMRs of chicks and BMRs of their biological fathers displayed a positive correlation, whereas no correlation was found between the RMRs of chicks and their foster fathers. The RMR heritability value was h2 = 0.43 ± 0.17 (n = 210). The obtained estimates for repeatability and heritability of fundamental energetic traits in pied fly-catcher are rather high for a physiological trait and suggest the existence of evolutionary stable diversity of the avian population in the BMR.

Sympatric divergence and clinal variation in multiple coloration traits of Ficedula flycatchers

Geographic variation in phenotypes plays a key role in fundamental evolutionary processes such as local adaptation, population differentiation and speciation, but the selective forces behind it are rarely known. We found support for the hypothesis that geographic variation in plumage traits of the pied flycatcher Ficedula hypoleuca is explained by character displacement with the collared flycatcher Ficedula albicollis in the contact zone. The plumage traits of the pied flycatcher differed strongly from the more conspicuous collared flycatcher in a sympatric area but increased in conspicuousness with increasing distance to there. Phenotypic differentiation (PST) was higher than that in neutral genetic markers (FST), and the effect of geographic distance remained when statistically controlling for neutral genetic differentiation. This suggests that a cline created by character displacement and gene flow explains phenotypic variation across the distribution of this species. The different plumage traits of the pied flycatcher are strongly to moderately correlated, indicating that they evolve non‐independently from each other. The flycatchers provide an example of plumage patterns diverging in two species that differ in several aspects of appearance. The divergence in sympatry and convergence in allopatry in these birds provide a possibility to study the evolutionary mechanisms behind the highly divergent avian plumage patterns.

Specific immunity and polymorphism of breeding plumage in pied flycatcher (Ficedula hypoleuca) males (Aves: Passeriformes)

The relationship between the type of melanin-based plumage colouration and the strength of experimentally induced immune response was studied using as an example a pied flycatcher population from the Moscow region. The breeding plumage of pied flycatcher males exhibits the full spectrum of transitions from contrasting black-and-white to cryptic brownish, the latter being very similar to the colouration of females. In spite of numerous studies, the nature of this polymorphism still remains vague. Unlike many other avian species with monocyclic breeding, a considerable fraction of pied flycatchers overlaps two energy-consuming productive processes, breeding and moult, over the whole species range. During the main experimental treatment we activated the humoral immunity of free-living males in chick-rearing period by injection of nonpathogenic multifactorial antigen (sheep red blood cells, SRBC) and estimated the strength of the immune responses after repeated captures in 6–8 days. In addition, after each capture we evaluated the numbers of leucocytes (WBC), heterophil to lymphocyte ratios (H/L) and measured night time basal metabolic rates (BMR). Non-moulting males of different colour types showed the same immune responses. Among moulting birds, the strength of the immune response was significantly higher in pale males (morphs 4–7 by Drost’s scale) than in bright males with rich melanin-based colouration (morphs 2–3). This difference resulted from two opposite processes. During moulting, pale males heightened the antibody titer after immunization, while bright males tended to reduce the strength of immune response. Possibly such an asymmetry in immunocompetence at the first stage of moult reflects the different life strategies of pied flycatcher males—conspicuous birds less commonly overlap breeding with moult than cryptic ones.

Male Colour Type and Lifetime Breeding Success in the Pied Flycatcher Ficedula hypoleuca

Abstract. The lifetime breeding success of male Pied Flycatchers was evaluated over a period of nine years (1991–99). The breeding success of males recorded in at least two breeding seasons, and nesting at least once in the study area, was analysed. The lifespan number of offspring was positively and significantly correlated with longevity. The reproductive investment in the first year of life did not correspond with longevity, and hence nonbreeding males in the first year did not compensate for the losses in fecundity. There were no differences in longevity between dark, intermediate and female-like coloured males. Darker males were less successful in their breeding attempts in the first year than paler birds. Breeding in the first year of life positively influenced the future number of fledglings, and the greater investment in reproduction in this year positively affected future brood size in dark males. Among males successfully breeding in the study area from their first season, dark males reared significantly more offspring during their lifetime, and in the first year of life, than paler ones. Nevertheless, in the total sample, lifetime brood size did not vary between differently coloured males, perhaps because dark males are more vulnerable to predators. The general difference between differently coloured males lay in how breeding efforts were distributed during life. Dark males can maximise reproductive investment from the first breeding year, while paler males increased average brood size in the following years of life only.

The role of a social factor in exploration of a novel environment in great tits (Parus major) under conditions of limited space

Sequential tests in an open field (OF) and in an aviary were performed to study the exploration behavior of great tits, Parus major Each aviary of 2×2×2 m included a standard set of objects: trees, feeder, and shelters. Twenty-four aviaries included a single individual, and 49 aviaries included two heterosexual individuals. During the 15-min observation, a number of explored objects, the latent exploration period of each object (the time period from the start of observation to the first visit of each object), and the time period to the onset of feeding were recorded. The exploration rate of each individual was characterized by the sum of all latent periods (CLP). No association between the cumulative locomotor activities in OF and in an aviary was found. Probably, in the complex environment of an aviary, the frequency of directed actions increases, competing with the movement activity. Faster individuals in OF showed a shorter CLP; i.e., they were fast explorers. The exploration rate of a novel environment in the presence of socid partner was unrelated to exploration scores in OF. Interrelations of birds combined in an aviary were dependent on combinations of personality characteristics identified in OF.

Melanin-based coloration and immunity in polymorphic population of pied flycatcher, Ficedula hypoleuca

A specific interest in the persistence of color polymorphism in some populations of birds and other vertebrates is often linked to ideas about the signaling honesty of bright coloration. The evolution of conspicuous ornamentation could be associated with physiological costs including limitations of the immune system. The study of this process is crucial for an understanding of the maintenance of polymorphic coloration. Here we summarized the results of a study of a pied flycatcher population from the Moscow region (Russia) in 2010–2013. We experimentally induced antibody production by injecting sheep red blood cells (SRBC) and inflammatory swelling by injecting phytohaemagglutinin (PHA) after which we estimated the immune response in breeding males. We used leucocytes-to-erythrocytes and heterophils-to-lymphocytes (H/L) ratios as indicators of infectious, inflammatory processes and stress. The results showed that the feeding rates of males treated with SRBC decreased and negatively related to the intensity of their immune responses. Non-molting males of different color types did not significantly differ in antibody production. Among molting breeders, the immune response to SRBC was significantly higher in pale males than in bright ones with rich melanin-based coloration. In contrast to non-molting males, molting pale males had an increased antibody titer after immunization. The lower humoral immune response was associated with the higher H/L stress index before immunization. The change in H/L after immunization positively correlated with the intensity of the humoral immune response. As opposed to humoral immunity, we did not find any significant predictors, including coloration, molt, or their two-way interaction, to explain the variation in cutaneous inflammatory response to PHA. The results suggest that the apparent advantage of a cryptic male phenotype over a conspicuous phenotype occurring in one of two types of immune response has an impact on the maintenance of color polymorphism in the pied flycatcher.