The study was carried out between 1996 and 1998 on a plot covered by mixed woodland near the southern boundary of the city of Warsaw. A total of 39 nests were investigated. The woodpeckers laid their eggs during the last ten days of April and at the beginning of May. The mean clutch size was 5.6 (n = 18). The number of young reared differed from season to season and was associated with the fledging date. More fledglings left nests with earlier broods. 81% of broods were successful, i.e. at least one young was reared. The duration of the breeding season — from the laying of the first egg to the fledging of the last chick — was 40–42 days.

The analysis covered 1332 Tree Sparrow eggs, 1053 of them hatched, in 257 clutches of which 114 were fully successful, 119 partially so, and 24 were deserted. The mean egg mass in deserted clutches was lower than in clutches where hatching success was total or partial but not significantly so. The mean hatching success per clutch increased with the mean egg mass. The individual eggs in fully hatched clutches weighed significantly more (2.21 g) than those in partially hatched clutches (2.17 g), and were also heavier than “infertile” eggs (2.14 g). During nest inspections to ascertain the egg laying sequence, the egg mass in 5-egg clutches with full and partial hatching success was found to be higher than in deserted clutches. The eggs in fully hatched clutches were broader than “infertile” eggs.

The nest sites and habitat features of the area around nests in a population of Jackdaws breeding in the centre of Rome, Italy, were studied. Occupied nests (n = 41) had a predominantly south-easterly exposure and were located on average 20 ± 8 m above the ground. The availability of suitable nest holes positively influenced the size of breeding colonies. The preference for SE-facing holes could be affected by winter winds, which blow from the NW. To describe the habitat conditions in 20 Jackdaw nesting areas in Rome, in comparison with 14 randomly selected sites from the same area, 25 variables in plots within a 28.8 ha area were measured. Built-up districts covered on average 77% and 78% of the total area of occupied plots and random plots, respectively. Ruderal areas covered 5% of the total area in occupied plots and 0.4% in random ones, wooded areas correspondingly 20% and 12%. Stepwise discriminant function analysis carried out on habitat variables in nesting areas and random plots provided a model based on the proportion of ruderal areas and gardens that correctly classified 90% of cases. Jackdaws are associated with habitats characterised by the interspersion of ruderal areas, gardens, and built-up districts that provide suitable nest sites. Effective protection measures in urban areas should concentrate on the conservation both of suitable cavities in old buildings and of relict patches of ruderal and open habitats bordering city centres.

The proportion of different nest predators robbing nests of the Collared Flycatcher Ficedula albicollis population breeding in natural cavities in the Białowieża National Park was studied during 1988–1998. Robbed nests were examined for signs betraying the predator. Mustelids, (mostly Martes martes) destroyed no more than 25% of the Collared Flycatcher nests, while rodents (mostly Apodemus flavicollis), and woodpeckers (Picoides major) were together responsible for the destruction of c. 75% of all the Collared Flycatchers broods. Rodents destroyed significantly more nests with eggs, whereas woodpeckers and Martes martes destroyed mostly broods with nestlings.

The 1995–1999 results of the mapping technique censuses carried out in permanent plots situated in three types of old-growth primeval BNP stands (ash-alder riverine, oak-hornbeam, mixed coniferous) are presented and contrasted with the data gathered in the same plots in the late 1970s. Most community parameters, such as composition of breeding avifauna, species richness, make-up and cumulative proportion of dominants, remained basically unchanged. Only the overall bird density has increased considerably, by 13–38% in different plots. This has been due to parallel increases in numbers of several species, widely differing in their nesting sites, food requirements and migratory habits. As numbers increased simultaneously in all the plots, the density differences across habitats remained the same, from highest densities in riverine stands at the forest edge (up to 124 p/10 ha), through oak-hornbeam stands, to lowest in the coniferous stands (48–50 p/10 ha). Despite this differentiation the breeding avifauna in individual plots was quite similar (density similarity index exceeding 50% ), indicating that their breeding assemblages constituted samples from a single bird community. In most cases the numerical increases could not be attributed to changes in local environmental factors, such as food resources, weather conditions or changes in habitat structure. Only in the coniferous stands, could habitat changes leading to diversification of their structure (gap formation, increasing number of deciduous trees) have been responsible for increasing species richness and abundance there. The apparent lack of a relationship between changes in bird numbers and the local situation suggests that the factors acting on a larger scale (outside the study area) could have been involved. Despite the directional changes in bird abundance observed in the Białowieża Forest, its breeding bird assemblage, when compared with amplitude of changes recorded over the same period in other areas and habitats, stands out as an example of remarkable stability.

In 1773 Caetano Monti's paper “Sur l'oiseau qui porte à Bologne le nom de Pendulino, et en Pologne celui de remiz” was reprinted in Paris. It played a decisive role in the scientific description of Penduline Tit and it's nest, and provided the first significant information relativing to the biology of this species. Monti was also the first to correct number of inaccuracies in earlier zoological treatises considered as “classics”. His own work was recognized throughout Europe, and quoted by German and French naturalists as Buffon. Linnaeus referred to it in his own description. Monti's analysis also enables us to gain precious information concerning the way in which ornithologists worked at the time, and the methods they used: analysing classical writings, “interviewing” bird catchers and peasants, information from missionaries, field work, analysis of specimens from zoological collections, and preparing descriptions and iconographies.