A Great Grey Shrike population was studied in two large plots (220 km² and 176 km²) in western Poland in 1999–2003. During the study period densities varied from 11.4 to 14.1 breeding pairs/100 km² but numbers were stable. In all, 180 Great Grey Shrike nests were found — 114 (63.3%) in conifers, 66 (36.7%) in deciduous trees. This population's reproductive parameters were relatively high in comparison to those of other European populations: mean clutch size — 6.6, hatching success — 92.5%, mean brood size — 5.72, mean number of fledglings per pair — 4.1, mean number of fledged young per successful pair — 5.25. Eggs (mean 27.1 × 19.9 mm) were found to be larger than reported in the literature. Nesting success was similar in both study plots, but there was slight seasonal variability: 41.0%–52.6% from 99 nesting attempts in the first plot, 42.1%–43.7% from 37 nests in the second. Predation was the main cause of nest losses. Plastic string used as nesting material appeared to be the most important cause of partial failures: 13 (8.2%) of a total of 147 nestlings surviving to fledging perished as a result of becoming tangled up in it. Nestlings rarely starved. Nests in linear habitats suffered significantly higher breeding losses (78.6%) than those in non-linear habitats (50%). The high fitness values obtained from this population were probably due to traditional farming practices, the sparing use of pesticides and the good potential food source.

Broods of Pied Flycatcher nesting in natural tree holes and nest-boxes in Białowieża Forest (E Poland) were compared. Natural holes in primeval stands of the Białowieża National Park were located by following singing males, then monitored several times during the season. Nest-boxes situated in the managed part of the forest were inspected weekly. Flycatchers breeding in natural holes started laying eggs on average two days later (15 May) and laid smaller clutches (6.4 eggs) than birds breeding in nest-boxes (13 May and 6.7 eggs). The prédation rate was significantly lower in natural holes (av. 47%) than in nest-boxes (av. 65%). This result indicates that generalisations regarding the evolution of adaptations to predation by nest-box populations should be treated with caution.

The study was carried out in two sites — fluvial mires (FM) in Netherlands, and at salt marshes (SM) and at the borders of lagoons (BL) in Spain. All 58 nests were found in unmown and ungrazed vegetation. Carex species were dominant at the nesting sites FM, but not Phragmites australis. Juncus maritimus was dominant in the SM and at the BL. The plant communities at and around the nest sites of FM differed from those of SM BL. At nest height from the side the nest was mostly only poorly visible. Nests at nest height and eggs at observer eye level were invisible among dense clusters of Juncus maritimus tussocks. Visibility of eggs in reed stands mixed with Carex species and in Sparganium erectum stands was mostly poor and moderate respectively. This was in contrast to nests situated among Juncus maritimus stems. For the most part, an incubating Water Rail on the nest at eye-level was hardly visible in any of the various stands. The vegetation height of nest sites in SM and BL was considerably less than in FM owed to the absence of Phragmites australis. The nest height in tussocks of Juncus maritimus was greater. The other nests characteristics (diameter, depth and weight) were not significantly different in FM and SM BL. The nest material corresponded to the plant species in the immediate vicinity of the nest.

The aim of the study was to test whether the methods using the playback technique produce accurate data of population size when compared to the standard mapping and nest-searching methods. The three-visit method with audio-stimulation was found to produce data of the same accuracy (100%, n = 11 territories) as the standard mapping method, but the nest-searching method and single-visit with audio-stimulation yielded slightly lower estimates, 91% and 82% respectively, in comparison to the previously mentioned methods. However, the three-visit method with audio-stimulation was 2.2 times less time consuming than the five visits which used the standard mapping method (9h vs 20h). The three-visit method with audio stimulation could be appropriate for assessing distribution and abundance, and also for monitoring purposes.

Data on the density of Aquatic Warbler and plant associations in the marshes of the Sporovskiy reserve (Byelarus') were collected between 1996 and 2003. The species density changed between years from 135 to even 0 males per km². The density and numbers of these birds are governed mainly by changes in the groundwater table caused by floods, droughts or fires. Aquatic Warblers breed successfully when the groundwater table coincides with the topsoil level; the optimal water table lies in the range from 12 cm above the soil to 5 cm below it. Between 1981 and 2002 successful first-clutch breeding occurred 11 times (47.8%); in only 4 years was second-clutch breeding successful (17.3%). First and second clutches both failed in 9 years (39%). The pattern of changes in the population size and data on the recovery of the population size following such unfavourable years indicates that the key factors governing the overall population size are not migration or wintering conditions, but rather the state of the breeding biotopes. Active management of fenland still in its natural state is therefore of paramount importance.

The study was conducted in the Lake Karaś reserve (N Poland), where the density of Willow Warblers in osier and birch thickets reached 28.7–33.3 p/10 ha. Collar rings were used to collect the food brought to the nestlings. 487 food samples were collected from 26 nests, comprising 2573 food items. 167 of the samples were from females (652 individual food items), 95 from males (616 food items). The nestlings were fed mainly on Arthropoda (94.6%) and Mollusca (5.4%). The dominant food items were Diptera (29.8%), Homoptera (28.7%), Ephemeroptera (10.5%), Araneida (7.6%) and Trichoptera (6.5%). The composition of the dominant food items and the average mass of food deliveries changed markedly with nestling growth. The types of food brought by each sex also varied significantly. Males brought heavier portions of food consisting of larger numbers of lighter prey. However, the composition of these portions was not as diverse as those brought by females. This may be related to differences between males and females in their respective territories and foraging techniques.

117 nests of Red-breasted Flycatchers in Białowieża primeval forest (NE Poland) were characterised. Most nests (79%) were built in Hornbeam Carpinus betulus and lime Tilia cordata. Three types of nest sites were distinguished: chimney shaped (26.4%), half cavities (46.4%) or shelves — the nest was wedged under a piece of bark against the main trunk (27.3%). Most cavity entrances were exposed to the south. Compared to other species of secondary cavity nesters in Białowieża National Park, Red-breasted Flycatchers used cavities of a different shape, with a smaller bottom area and at a relatively low height above the ground ( = 4.9 ± 3.13 m). Nesting trees had a smaller diameter ( = 31.2 ± 21.4 cm) and were more often dead (29.8%) than trees used by the other secondary cavity nesters. Only four nest sites were used in consecutive seasons.

The study was carried out on 94 abandoned arable fields (0.1–83.5 ha) comprising a total area of 400 ha in the intensively farmed region of the Wrocław plain (54.8 km², SW Poland). A total of 101 Whinchat territories were found in the study area, all of them in abandoned crop fields with a well-developed layer of dried perennials from the previous year (Tanacetum vulgare, Artemisia vulgaris, Solidago sp.). Whinchats occupied 56 (60%) of the 94 fields surveyed. The probability of a Whinchat occupying a particular field was closely related to its size: the probability of occupation was 50% in fields of about 1.8 ha, and rose to 100% in fields larger than 13 ha. Single males occupied thirty-eight territories (37.6%). The number of Whinchat territories per occupied abandoned field lay between 1 and 14. Thirty-three fields held only a single Whinchat territory. The density of Whinchat territories was negatively correlated with the size of an abandoned field. Single males inhabited the smallest fields.

The accuracy of the territory-mapping technique for estimating the abundance of densely breeding Hawfinches was tested in an old and unfragmented lime-oak-hornbeam forest in the Białowieża National Park, E Poland. Hawfinch numbers estimated from counts of the whole bird community carried out with the application of the standards of the improved mapping technique were compared with seven-year data on the bird's true numbers, which are known from parallel intensive nest searches and persistent tracking of the movements of pairs. In a forest with a dense population of Hawfinches the mapping technique underestimated their numbers by 20% in years of moderate density and by 35% during high-density years. Even though the underestimation was negatively correlated with the true density of Hawfinches, the figures obtained by both methods reflected year-to-year changes in a similar way. An improvement in mapping data is achievable either by closer attention being paid to the species during standard visits (the best ones for surveying it), or post factum by the introduction of a correction factor into the mapping-technique figures.

The study was carried out in 3 plots in the province of Punjab (Pakistan) in November 2001. The total population of the Houbara Bustard was estimated at about 4 746 birds with an overall density of 0.147 ± 0.006/ km². The number of birds in Rajanpur/Rojhan was estimated at 685, in Thal at 672 and in Cholistan at 3 389.

Two cases of nest sharing by two Blackbird pairs each were recorded during a long-term urban study. In the first case, two females simultaneously incubated eggs in the same nest. The nestlings were later seen to be fed by the two pairs of adult birds. In the second case, a nest containing 4 eggs laid by one female wastaken over by another which, having chased the nest owner away, laid 5 eggs of her own. The likely cause of nest sharing in the first case was the loss of eggs at an early stage of laying by the second female. In the second case, nest sharing seems to have been caused by nest competition. The details of the parents and siblings of the females involved in the first case permits the conclusion that the absence of competition between the females (and even their co-operation in feeding the young) was not caused by their genetic affinity.

In 1996–2002, 227 breeding attempts were studied in a colour-ringed Sedge Warbler population. Although 11% of males in this population resumed singing in order to mate with another female after their first females had laid eggs, only two polygynous males (i.e. 0.6%) were recorded. This is a very low value in comparison to other studies (ca. 7% on average). The low level of polygyny is attributable to the low food abundance in a natural floodplain, as the nestlings in this population were fed on predominantly small food items. Both polygynous males were recorded in 2002; this year was unusual, because flooding in early June (around the hatching date) destroyed most of the broods. This could have led to an influx of new females into the study area, a change in the operational sex ratio, and new mating opportunities for males.