Permanent changes in the surrounding environment cause long-term stress in birds, which, when lasting days or weeks, affects the activity of the immune system and increases susceptibility to diseases, leading to changes in the levels of haematological parameters. The heterophil-to-lymphocyte ratio (H:L-ratio) is generally considered an independent and robust indicator of stress level in birds. This parameter allows in a simple way to evaluate activity of the immune system and individual health state of adult and nestling birds. It also enables assessing a body response to short- and long-term stress induced by, among others, the surrounding environment, social stress, blood parasites or a greater energy expenditure of females during breeding. Under conditions of field work the determination of the H:L-ratio is not difficult because what is only needed to conduct a blood smear test is a drop of blood that can be easily obtained even from birds of a small body mass. Moreover, an increase in the H:L-ratio is observed after about an hour from the moment of catching a bird contrary to other measurements like the determination of a baseline level of corticosterone.

In this article available literature that discusses the impact of various factors on the H:L-ratio in the Great Tit as a species of ‘fast-paced’ life is reviewed. In adult and nestling birds the H:L-ratio is influenced by various factors — ecological and ecophysiological ones. In some cases the same factor, e.g. brood size manipulation or a type of habitat, can significantly influence the level of the discussed stress indicator as well as it may not show any impact at all. While interpreting the H:L-ratio one must take into account an impact of various ecological and ecophysiological factors on health state, such as habitat, phase of the annual cycle, differences between brood attempts, sex, age as well as on relations with other indicators of condition e.g. body mass or total blood haemoglobin concentration.

This study explored meadow passerine capacity to select habitat conditions likely to preserve their breeding success. We observed the variation in bird abundance, assessed with the point count method, over a 25-year period (1993–2017) within two phytosociological facies of the hay-meadows in the lower Saône Valley (3.000 ha), eastern France: a meso-hygrophilic facies characterized by increasingly early mowing, and a hygrophilic facies mown later, with thereby a lower risk of nesting failure. At the beginning of the monitoring (1993–2001), birds were evenly distributed within the two facies. Later on, as more than 90% of meso-hygrophilic meadows were already mown by July 1, birds became more abundant in the hygrophilic facies. This trend was observed in each of the two most abundant species, the Whinchat Saxicola rubetra and the Corn Bunting Emberiza calandra. In two hygrophilic areas (55 and 76 ha) and two meso-hygrophilic areas (49 and 116 ha), passerine territories were mapped in 2011 with the territory mapping method and invertebrates were captured weekly on transects with colour plates and Barber traps. In spite of substantially higher invertebrate abundance, passerine territory density was lower in meso-hygrophilic study sites (6.4 territories/ 10 ha vs. 10.6). Within each study site however, captured invertebrates were more abundant in the areas selected by territorial birds. In fact, bird abundance estimated from point counts in 2011 varied negatively with the percentage mown by July 1 within a 200m-radius in 2010. This apparently adaptive behaviour leading to a selection of later mown fields seemed to be successful since bird abundance increased until 2010. However, after a succession of extreme climatic events (droughts, late floods), passerine abundance declined thereafter in both facies.

Sexual selection is generally thought to be weak in cooperative breeding species, largely because polygamous mating patterns that drive sexual selection can erode the kin-selected benefits of cooperation. Social selection, on the other hand, is expected to be strong among cooperative species especially because of the intense competition over status and resource access. In support of this view, several studies have shown monogamous mating and little sex difference in cooperative species. However, most previous studies have focused on species with relatively simple social systems and few studies have examined how mating patterns, social organization and ecological attributes have influenced the evolution of ornamentation in cooperative species. Here I used secondary data to examine several hypotheses and shed some light on how social and sexual selection influenced the evolution of phenotypic sex traits in cooperatively breeding birds. Despite the broad assumption that cooperative breeding species are monomorphic, results demonstrate that sex differences and the presence of ornamentation are widely spread in the group. Stable environments with higher precipitation are associated to the strongest differences between sexes. Results indicate that although extrapair matings and environment attributes are determinant to the evolution of sex differences, males and females of cooperative species seem to be more alike than their non-cooperative counterparts. The extent of mutual ornamentation found in cooperative species indicates that the combination of both sexual and social selection are imperative to determine how evolution has shaped phenotypic attributes in cooperative species.

Land use changes occurring in Europe in recent decades are generating important changes in the forest landscape characteristics and are having important effects on avian species richness and abundance. This is particularly important for some bird species of particular conservation concern that require heterogenous landscapes where breeding habitats are proximal to foraging habitats. Among these birds, the European Turtle Dove Streptopelia turtur is particularly important because of its marked population decline. In southern Europe, forest landscapes have been considered important breeding areas for Turtle Doves. We assessed the influence of the foraging area characteristics — distance to cereal crops and wild seed species abundance — and water availability on Turtle Dove breeding habitat suitability in a Mediterranean forest landscape in southern Spain. Forty-six point locations were surveyed during the spring of 2014 and 2015 on two nearby farms of a forest protected area. The average local abundance of Turtle Doves found at each point location was 1.25 ± 1.31 males, and it was significantly higher at the point locations closest to cereal crops, as well as at nesting sites where the wild seed species included in its local diet were abundant, especially Echium plantagineum. Distance to water in the studied range (average distance 475 m) did not show a significant effect on Turtle Dove local abundance, although the high availability of water in the study area could have a positive influence on the overall Turtle Dove breeding habitat suitability. To benefit Turtle Dove breeding habitat suitability, cultivated areas with cereals/legumes near those forest areas where Turtle Doves reproduce should be promoted. Likewise, the promotion of those herbaceous species that are locally important in the Turtle Dove diet, available, for example, through specific grazing management, should be taken into account when nesting habitat restoration is designed in forest areas, regardless of whether the distances to food resources are long.

Dispersal distance and burial mode of acorns are two of the most important characteristics in renewal processes of oaks that result from the food hoarding ecology of the Eurasian Jay Garrulus glandarius. To obtain the dispersal distance and to locate precisely the caches with scattered acorns we used radio-tracked transmitters with flexible 13 cm long sticking out antennae injected into drilled acorns. From mid-September to mid-October acorns of Pedunculate Oak Quercus robur with transmitters were mixed with untagged acorns and exhibited on five feeders distributed from each other at a distance of at least 1.3 km (max. 3.8). We obtained information on 121 tagged acorns scattered by Jays in two consecutive years (2014 — 42 records, 2015 — 79 records). For both seasons, mean dispersal distance was 115.7 metres (SE = 9.2). The maximum detected distance was 456 m, the minimum was 3 m. Most of the acorns (52.6%) were deposited by Jays up to 100 m from the source. Dispersal distance differed significantly between the two years of research and between feeders. Mean dispersal distance was much higher in 2014 (166 m, N = 42) than in 2015 (86 m, N = 72) and differed between seasons while the seed crop was similar and low. Only four acorns (3.5%) were found on the litter with no signs of hiding, which suggests accidental loss during transport (dyszoochory). Most of the cached acorns (44.6%) were deposited in the Scots Pine Pinus silvestris litter or moss cushions no deeper than 0.5 cm. The additional covering of caches with pieces of bark or leaves were noted accidentally in nine cases (9.8%).

Facultative scavengers often forage on organic wastes from urban dumps. Despite being a major scavenging raptor in many urban areas, studies on Indian subspecies of Black Kites Milvus migrans govinda are very few. We studied the pattern of offal preference by Black Kites foraging in the dumping sites adjoining two major markets of Kolkata, India through cafeteria experiments, where successful foraging events and abundance of foraging Black Kites were recorded. We also carried out questionnaire surveys among 156 meat and fish sellers of 32 markets of this area to assess their offal disposal practice and understand their attitude towards Black Kites. During questionnaire surveys majority of the respondents (77.92%), indicated that Black Kites consume various kinds of offal, particularly chicken offal from garbage dumps of Kolkata. 51.92% respondents opined that Black Kite population has declined in Kolkata, and 41.03% of them believe such decline is due to food scarcity. Still many respondents (64.74%) sell their offal, which reflect their indifferent attitude towards this scavenging raptor. During ‘cafeteria experiments, we noticed that foraging kites pick up small pieces of offal from the garbage dumps, particularly chicken, mutton and fish offal (in 15.45 ± 7.749, 9.7 ± 4.542 and 9.95 ± 4.951 successful foraging events/h respectively). Energy content (cal/g) of sun-dried samples of each type of offal substances revealed that the energy (calorie) of swine offal was highest followed by beef offal, mutton offal, chicken offal and fish offal. In spite of being energetically rich, beef and swine offal were less selected by Black Kites possibly because they are visibly larger than other offal, thus requires greater handling time and invites higher risk of kleptoparasitism. Successful foraging events were significantly influenced by offal type, but not by months, study sites or by the relative abundance of foraging Black Kites.

Many traits influence birdsong diversity. Patterns observed in the acoustic parameters can be a result of morphological constraint and can also be explained by phylogenetic relationships. Understanding morphologic mechanisms that can act on song structure might account how they can catalyze speciation and how they evolve in lineages sort. We analyzed the evolution of beak volume and song constraints in “finch-like” species of Neotropical seedeaters. We tested if beak volume limits the song structure of territorial songs, based on differences in the beaks of 19 species from the genus Sporophila (Thraupidae, tanagers). We also tested (1) if body size constrained song structure, and (2) if beak volume and body size were related to each other. The relationship of song parameters (e.g. maximum and minimum frequencies, frequency bandwidth and note rate) to these two morphological variables was evaluated through an analysis which phylogenetic relations were controlled (PGLS), testing a null and Brownian model. To perform a faithful analysis between morphologic and acoustic parameters, our data was based on measurements of the beak and territorial song for each individual that we analyzed. None of the analyzed parameters was related to beak volume or body mass, and beak volume was not associated with body mass. Beak volume, note rate, and minimum frequency showed a phylogenetic signal. These results do not support the theoretically motivated prediction that beak size acts as a limit on song structure in oscine birds. The shape and variations of song in Sporophila tanagers (Seedeaters) may be a consequence of the species’ phylogenetic history, since the seedeaters showed wide plasticity in many acoustic parameters, unrelated to their beak volume and body mass. Song structure was better explained by the evolutionary relationships among the species than by morphological constraints.

The Black Grouse Tetrao tetrix populations in Europe have become fragmented and reduced in numbers. These processes affected genetic diversity of the species, altering patterns of gene flow and genetic structure. In Poland, the Black Grouse is one of the most endangered bird species, however very little is known about diversity of this native population, bordering on to the area of Europe in which the species maintains a continuous range. To complete the knowledge of genetic structure of European populations, we analysed microsatellite polymorphism in 97 native Polish birds, along with 39 introduced individuals, originating in Belarus and at a breeding centre in Poland, regarded as representing the gene pool from the north-eastern part of the country. The results confirmed that isolation of populations and recent decreases in their sizes have reduced genetic diversity in Poland's populations of the Black Grouse. The results also indicated the presence of two genetic groups in Poland, involving birds of the north-eastern part of the country and the Carpathians Foothills in a first group, and the population from the Sudetes (Izerskie and Karkonosze Mountains) in a second. We suggest that the conservation effort should treat these two groups as independent units. We also analysed a fragment of the mitochondrial Control Region (CRmtDNA). The comparisons of sequences obtained with data from other Eurasian populations indicate that populations of the Black Grouse in Poland should be included within a large Conservation Unit — the northern tetrix — which comprises birds from Eastern and Northern Europe.