Nest sites of nine common hole-nesting bird species were studied in the West Khentey Mountains, NE Mongolia. Among three excavators, the Great Spotted Woodpecker used more aspens, larger trees, and more living or intact dead trees than the Lesser Spotted Woodpecker or the Willow Tit. Among non-excavators, the Nuthatch used mainly old holes of the Great Spotted Woodpecker, and the Red-throated Flycatcher frequently used those of the Willow Tit. Thus, the nest site characters of these two species resembled those of the original excavators, and their nests were placed higher than those of other non-excavators. The Coal Tit and the Great Tit used mostly branch holes in living trees. With respect to nest site use, the Daurian Redstart behaved as a generalist while the Common Treecreeper specialized in long slits. The nest site selection of excavators might be governed by body size, territory size and their different abilities of excavation. The non-excavators were best differentiated by their preferred hole type, and their tree use and nest site characters were mainly a consequence of the location of such holes. Interspecific competition did not appear to be important in the nest site use of hole-nesting birds in the study area.

Radiographic examination of 35 birds (17 species) killed on roads revealed bone injuries in 17 (47%) cases. There were 30 different kinds of injuries to the skeletal system. In 29 cases these fractures concerned the long bones of the wings (n = 15) and the lower extremities (n = 14). One bird had a dislocated spinal column. Wing fractures affected the humerus (n = 6), radius (n = 6) and ulna (n = 3), while leg fractures affected the femur (n = 5), tibiotarsus (n = 8) and tarsometatarsus (n = 1). No relationship was found between the body weight and the location and number of bone injuries. In our opinion, the nature and type of skeletal injuries suggest that they were not the direct cause of death.

In the Water Rail the patterns of the two main types of vocalization were quite different: the announcement call was uttered throughout the breeding season with two peaks, one in April and the other in early June, but the courtship call occurred only in the pre-laying period. The vocalization period of the Little Crake is short but intensive, peaking before the start of incubation. In general, Water Rails produced more vocalizations in the evening than in the morning. The vocal activity of the Little Crake peaked at dawn. In both species a peak in vocal output occurred shortly before sunrise and before sunset.

The Capercaillie is one of the most seriously endangered bird species in Poland. It currently numbers around 650 individuals that live in four isolated populations (Lower Silesian Forest, Janów Lubelski Forest, Carpathians, Augustów Forest). This study investigated genetic variability based on the polymorphism of six microsatellite loci in the surviving Polish populations of the Capercaillie and compares the results with the analogous variability in two large, contiguous populations in Russia. The following parameters were estimated: mean number of alleles per locus, allelic richness, mean effective number of alleles per locus, heterozygosity in each of the populations investigated. Differentiation between pairs of populations was assessed using F_ST. The results show that despite some inevitable reduction in genetic variability, most of the Polish populations retained a substantial level of microsatellite polymorphism. Only in the population from Janów Lubelski Forest was there a significant reduction in variability, probably due to long isolation and the recent decline. That this population has long been isolated was also confirmed by the pronounced genetic differentiation from the other Polish populations. The Carpathian population of the Capercaillie was found to be genetically structured, and in the Lower Silesian Forest population heterozygosity was low, possibly as a result of the lek mating system and also the dramatic reduction in numbers.

The density and behavior of the Mistle Thrush in Niepołomice Forest (southern Poland) and adjacent open areas were studied during winter (December—February) in 1996/97, 1998/99 and 2000/01. Mistle Thrush densities differed significantly from winter to winter, and the abundance of thrushes decreased as the season progressed. Bird density and mistletoe clump density were correlated positively. Birds held territories or congregated in flocks. The latter were sighted in the forest only during winter 1996/97, when the largest density of birds was noted. Flock size decreased progressively during that winter, but at the same time, the number of territorial birds remained stable. This suggests that by the end of the winter 1996/97 some birds from the flocks had begun to hold territories. Flocks were also seen in open areas, and displayed a preference for foraging on pastureland. Each individual territory in the forest consisted of several clumps of mistletoe on a few adjacent trees, which were defended against both conspecifics and other species such as Pyrrhula pyrrhula, Turdus merula and Dendrocopos major. The aggressive encounter rate was correlated positively with bird density but negatively with the progress of winter (the latter was correlated negatively with the berry supply). Surprisingly, it was not correlated with mistletoe clump density or temperature. During abundant berry years, the density of birds may have been so large that defending the fruit against numerous neighbors would have been energetically less profitable than communal foraging.

The White-faced Whistling Duck is a waterfowl species lacking any differences in ornamentation, coloration, size or behavior between the sexes. For distant communication, this species uses loud whistles. We analyzed 12 spectral parameters of 344 whistles from 23 captive adult ducks (14 males and 9 females). Discriminant analysis showed 94% correct assignment to an individual (N = 279 calls from 14 birds; 15–22 calls per bird). Separately for 8 males (162 calls) and for 6 females (117 calls), discriminant analysis showed 99% and 93% correct assignment to individuals respectively. Discriminant analysis for sex (N = 86; 3 calls from each of 14 males and 5 calls from each of 9 females) showed 100% correct assignment. Intersexual differences were governed by frequency parameters, the values of which were significantly higher in females than in males. Cluster analysis showed that differences between sexes were expressed significantly more strongly than the individual differences. The fact that the “acoustical keys” differed as regards the identification of individual birds or their sex may significantly enhance the reliability of acoustical recognition systems in the White-faced Whistling Duck. The data are discussed in the context of the biology of the White-faced Whistling Duck and significant intersexual differences in syringial and tracheal anatomy, which may be responsible for the sharp distinctions between the sexes in the calls of this species.

Distribution of Three-toed Woodpeckers and that of dead wood were mapped in two fragments of the Białowieża National Park (BNP) differing in their management history — primeval (old-growth stands of natural origin, no human intervention) and logged (as the former but subject to 80 years of commercial forestry). Data were collected during the breeding seasons 1999–2001. In the end of April 2000, the whole BNP was systematically searched; playbacks of drumming were used to enhance detection of birds. Presence/absence of Three-toed Woodpeckers and of dead wood (standing and downed Norway spruces and snags of other trees) were recorded within each forest sub-compartments (ca. 28 ha). Data from censuses done in smaller plots in 1975–1999 showed that in the primeval forest the woodpeckers bred twice more frequently in swampy and coniferous forests than in the oak-hornbeam habitat. These preferred habitat types covered larger areas in the logged fragment than in the primeval part (66% vs. 41%). Yet despite this, Three-toed Woodpeckers were recorded there over twice less frequently (14% of 176 sub-compartments) than in the primeval (36% of 164 sub-compartments) part. These differences followed sharp contrasts in the dead wood availability; all but one sub-compartments in the primeval fragment contained some form of dead wood, whereas dead spruces were missing in almost 30% of sub-compartments in the logged part. This was the effect of continuous “sanitary” logging, purposeful removal of dying and dead spruces from the Forest. To restore Three-toed Woodpecker habitats it is necessary to ban removal of dead spruces in the managed part of BNP. However, the BNP area is too small, to assure the long-term survival of the Białowieża Forest population. To achieve this, it is necessary to resign from removal of dying and dead spruces in the whole Polish part of the Białowieża Forest (600 km²). This would create breeding habitat for a maximum 260–320 pairs.

Nest site selection in the Blackbird was investigated in two urban parks in Szczecin from 1997 to 2003. The age structure of the tree stands, the area of shrub coverage and the number of predators (apart from squirrels) were similar in both parks. 95% of the nests discovered at the beginning of the breeding season were found again in June and July. Any increase in the heights of the nest sites in successive periods of the breeding season and any changes in the type of vegetation selected for nest construction were recorded. In April, Blackbirds most often used coniferous trees. At the start of the season, when deciduous plants began sprouting leaves, Blackbirds preferred those whose leaves appeared earlier. But later in the season, no difference was found between the numbers of nests in trees developing their crowns earlier or later. The shorter period of nest use in conifers is probably due to their selective penetration by corvids. The selective penetration of such trees by predators probably reduces the frequency of nest building in them between the first (pentads 1–3) and second (pentads 4–6) period of the breeding season, despite the fact that they provide better concealment for nests. The selection of nest sites by the Blackbirds in this study confirms both the predator-pressure and the nest-concealment hypotheses.

During autumn migration across the Central Mediterranean, adult Honey Buzzards cross the sea at its narrowest point, between western Sicily (southern Italy) and the Cap Bon Peninsula (Tunisia). This study investigated the influence of prevailing winds and geography on the orientation behaviour of migrants during this sea crossing by observations over two islands, one on the northern side, the other on the southern side of the Channel of Sicily. The flock was taken as the sampling unit. Honey Buzzards reached the island of Marettimo, approx. 30 km off western Sicily and 130 km NE of the Cap Bon Peninsula, regardless of the direction of the prevailing winds (NW and S). By contrast, Honey Buzzards passed via Pantelleria, about 110 km SW of western Sicily and 70 km ESE of the Cap Bon peninsula, mostly during NW winds. Birds reached Pantelleria from the NE and left the island flying WNW They applied true navigational abilities in choosing the shorter crossing between Pantelleria and Tunisia and showing a curvilinear migration. Our results agree in part with the “optimal use of wind” hypothesis. In particular, wind, geography and navigational abilities seem to interact to shape the orientation behaviour of migrating Honey Buzzards, perhaps to minimize the risks of non-stop powered flight over the water.

Studies carried out in the vicinity of Rogów in central Poland showed a 47% rise in the population density of the Common Buzzard, inasmuch as the average number of breeding pairs in the study area of 105 km² increased from 18.2 in the years 1982–1991 to 26.7 in the years 2001–2003. Furthermore, an upward trend was observed for each separately investigated forest complex. Possible mechanisms underpinning this increase in density are discussed.

The diet of the Great Pampa-finch includes seeds rather than insects. Our objective was to study its diet during the winter season and, whenever possible, to record differences between the sexes in diet patterns. This species was studied at Guamini Lagoon, Buenos Aires Province, Argentina. The stomach content of 38 adult birds was investigated. The analysis shows that the food eaten by E. platensis consisted of seeds (60%) (Chenopodiaceae, Asteraceae, Ciperaceae and Poaceae) and insects (39%) (Bellostomatidae, Dytiscidae, Curculionidae, Coccinelidae, Formicidae and Apidae). Males ate more insects and, overall, more items than females. These, in turn, consumed a greater amount of plants. Niche breadth values were 2.9 for males and 3.1 for females. The seeds encountered were those of plant species typically associated with the pampas.

It is widely accepted that the first White Storks to arrive at a nest remain there to breed. In contrast to this belief, the paper describes the replacement of at least three males and at least one female at one nest in SW Poland during the spring of 1994. The first pair occupied the nest for 5–8 days, the second pair for one day, and probably only the third pair remained at the nest to actually breed. Additional data on arrival patterns show that such replacements of non-breeding storks may occur much more frequently than was previously thought, especially in areas of intense migration. Consequently, the most common phenological observations (e.g. the arrival dates of the first and second White Storks) are not really useful for defining the timing of breeding. It is suggested that the beginning of nest occupancy should be defined by the beginning of the permanent stay of the second partner, and not just by the date of the birds' first appearance.