Museum & Institute of Zoology, Polish Academy of Sciences,Wilcza 64, 00-679 Warsaw, POLAND
Abstract. Both the Buzzard and the Goshawk nested mainly in pines. The mean clutch size in the former was 2.8, in the latter 3.6 eggs per breeding pair. There were statistically significant differences in clutch sizes in the Buzzard in particular breeding seasons. The mean number of hatchlings was 2.3 in the Buzzard and 2.6 in the Goshawk. Brood losses were similar in both raptors - 19% in the Goshawk and 24% in the Buzzard. The breeding success (the ratio of the number of fledglings to the clutch size) in the Buzzard was highest in clutches of 3 and 4 eggs, whereas in the Goshawk a similar level of success was achieved with smaller clutches (2 or 3 eggs). Only in the case of the Buzzard there were significant differences in clutch sizes and numbers of fledglings in the various years. In this species the mean number of fledglings was positively correlated with the rodent availability index in a given year. There was no such relationship between the abundance of prey items found in Goshawk nests and the number of fledglings. The correlation between the number of newly-fledged Buzzards and Goshawks in a given year could have been due to diet overlap between the two species.
Key words: clutch size, brood size, Common Buzzard Buteo buteo, Goshawk Accipiter gentilis, variability of breeding
Key words: clutch size, brood size, Common Buzzard Buteo buteo, Goshawk Accipiter gentilis, variability of breeding
Abstract. Data were collected in a medium-sized town. During five years 342 nests were found. The densities of breeding pairs varied over this period between 4.5 and 5.9 p/10 ha. The distribution of breeding pairs was uneven throughout the study area. The preferred nest sites were roadside trees, where 88.9% of the nests were built. The mean onset of egg-laying was 22 April (range 19-26 April). There was a tendency to start breeding earlier in warmer springs. The mean clutch size was 5.07 ą 0.74. There was a positive correlation between clutch size and the date of egg-laying. These data suggest that there was a compromise between the tendency towards earlier breeding and clutch size. In the study area the Greenfinch is a double-brooded species. Unlike other studies it was noted that the average clutch size increased in the second half of the breeding season. The maximum clutch size coincides with the second or replacement clutches. Hatching, fledging and breeding success were lowest when clutch sizes were largest. The nesting success estimated with the Mayfield and the "traditional" method was approximately similar (0.40 and 0.44 respectively). Cats and mustelids were probably the cause of most breeding failures. Corvids were not responsible for nesting failures.
Key words: Greenfinch, Carduelis chloris, breeding biology, nest-site, timing of breeding, clutch size, breeding success, nesting success
Kostelecka-Myrcha A., Chołostiakow-Gromek J. 2001. Body mass dependence of the haemoglobin content to surface area ratio of avian erythrocythes. Acta Ornithol. 36: 123-128.
Abstract. Data from 75 bird species weighing between 6 g and > 16 kg confirmed a supposition that the amount of haemoglobin per unit surface area of erythrocyte is not dependent on body mass. It showed a constancy across the range reflecting adjustment of the total surface area of erythrocytes in relation to blood haemoglobin concentration. This conclusion is based on an inverse correlation between the numbers and sizes of red blood cells.
Key words: birds, body mass, haemoglobin, erythrocytes
Kuźniak S., Bednorz J., Tryjanowski P. 2001. Spatial and temporal relations between the Barred Warbler Sylvia nisoria and the Red-backed Shrike Lanius collurio in the Wielkopolska region, W Poland. Acta Ornithol. 36: 129-133.
Department of Avian Biology & Ecology, Adam Mickiewicz University, Fredry 10, 61-701 Poznań, POLAND
Abstract. The Red-backed Shrike and the Barred Warbler are a pair of species engaged in breeding association. Whilst the arrival time of both species from their wintering grounds was not correlated, they differed in median arrival time by only one day. The majority of the Barred Warbler territories were located within those of the Red-backed Shrike, in both forest and farmland plots. The two species differed significantly in their selection of nest sites, at least in farmland. Unlike the Red-backed Shrike (n = 297), the Barred Warbler (n = 60) preferred blackberry bushes and small deciduous thornless shrubs, and avoided elder, conifers and hawthorn. The Barred Warbler nests were placed significantly lower than those of the Red-backed Shrike. The results show that no special ecological relationships exist as was suggested in earlier papers for other areas.
Key words: Barred Warbler, Sylvia nisoria, Red-backed Shrike, Lanius collurio, phenology, nest sites
Ptaszyk J. 2001. Nesting of the House Martin Delichon urbica in the city of Poznań (1976-1978 and 1982-1989). Acta Ornithol. 36: 135-142.
Abstract. Observations of nesting populations of the House Martin were carried out on three study plots in the city of Poznań: a city centre area (599.0 ha) and two housing estates (567.1 ha and 125.6 ha), a total area of 1291.7 ha. Throughout the 1980s House Martin numbers increased continuously over the whole area, the greatest population density being 4.6 occupied nests per 10 ha. The number of breeding pairs in the city centre was stable, and the density there varied from 2.1 to 3.0 occupied nests per 10 ha. The highest density of occurrence was recorded in the new housing estates, where increases in the House Martin population were recorded. These was related to the construction of new buildings, which provided fresh nesting sites. The nests were built at heights from the first to the fifteenth storey. Over 96% of the nests in the housing estates were built in the corners of the window openings. In the entire study area the preferred nesting sites were on the southern (35.2%), northern (26.1%) and eastern (13.3%) sides of buildings. In the city centre the greatest number of nests had south-facing entrances, while in one of the other study plots, the entrances to most nests faced north. No more than 7% of the total number of martins' nests available in a given year were occupied by Passer domesticus.
Key words: House Martin, Delichon urbica, nesting biology, urban habitats, population dynamics, nest-site
Siriwardena G. M., Freeman S. N., Crick H. Q. P. 2001. The decline of the Bullfinch Pyrrhula pyrrhula in Britain: is the mechanism known? Acta Ornithol. 36: 143-152.
British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK.
Abstract. The Bullfinch has declined in Britain and elsewhere in Europe, but definitive evidence about the cause and demographic mechanism has yet to be published. We review current knowledge, concentrating on analyses of demography, and present new integrated population modelling analyses designed to reveal the demographic changes most important in the decline. It is likely that changes in brood size and clutch size have not been important and our models suggest that the decline can be explained without invoking variation in numbers of breeding attempts or post-fledging survival rates. However, although changes in the egg period daily nest failure rate provide the best explanation for population change during the years of steepest decline, nestling period failures, adult survival and first-year survival could all have been equally important. Egg period nest failure rates have been higher in the preferred habitat, woodland, than in farmland and have fallen over time in farmland, where a larger decline has occurred (65% versus 28%), arguing against a causal link with abundance. Despite evidence for a negative effect of agricultural intensification on Bullfinch presence, little evidence exists clearly linking any demographic rate to environmental change, and agricultural land-use has had little effect on nest failure rates. Predation appears to have had no significant impact. Future work should focus on contemporary investigations of the importance of hedgerow structure and woodland understorey vegetation.
Key words: Bullfinch, Pyrrhula pyrrhula, demography, population models, bird conservation, granivorous birds
Varuzza P., Capizzi D., Santini L., Apollonio M. 2001. Barn Owl Tyto alba predation on small mammals in relation to the Mediterranean (Pisa Province, Italy) environment. Acta Ornithol. 36: 153-160.
1Department of Zoology and Biologic Antropology, University of Sassari, via Muroni 25 I-07100 Sassari, ITALY
Abstract. The diet of the Barn Owl was investigated in 13 localities in Pisa province, Central Italy. In each locality, the percentage of forest and cultivated land, and the linear development of roads and rivers were recorded. To estimate the prey availability, the small mammal communities in seven different localities within the same province were sampled during live trapping sessions. Barn Owls preyed mainly upon rodents (79.4%) and insectivores (18.8%), while birds were eaten only to a small degree (1.8%). The main prey taxon was Apodemus sp. (39.7%), followed by Microtus savii (26.1%). The relative frequencies of these two prey items were negatively correlated. Statistically significant differences were detected in the mean prey weight in the thirteen localities. This was positively associated with the area of woodland and negatively with the area of cultivated land. A positive relationship between prey diversity and cultivation was recorded. This indicates that Barn Owls which forage in cultivated habitats tend to prey on smaller species, mainly shrews and voles, and to have a more diversified prey spectrum. By contrast, owls foraging in wooded areas were more specialized and preyed on larger animals.
Key words: Barn Owl, Tyto alba, feeding ecology, owl pellets, small mammals
Montalti D., Kopij G. 2001. Bird community of inner La Plata city, Argentina. Acta Ornithol. 36: 161-164.
Abstract. During the years 1991-2000, 101 bird species were recorded in the city of La Plata, Argentina, 47 of which were breeding species. The most abundant species were Zenaida auriculata, Columba livia, Funarius rufus, Pitangus sulphuratus, Zonotrichia capensis and Passer domesticus. Columba maculosa, C. picazuro, Furnarius rufus, Turdus rufiventris and Molothrus bonariensis have increased in number, while Passer domesticus has decreased. Zonotrichia capensis may successfully compete for food with Passer domesticus. Sturnus vulgaris and Acridotheres cristatellus are new species in the breeding avifauna of La Plata city.
Key words: urban ornithology, Argentina, La Plata city, changes in avifauna
Rejt Ł. 2001. Feeding activity and seasonal changes in prey composition of urban Peregrine Falcons Falco peregrinus. Acta Ornithol. 36: 165-169.
Abstract. Despite the increasing populations of Peregrine Falcons in European cities, detailed quantitative studies of their diet composition and feeding activity in urban environments are rare. The results from observations in Warsaw have added to the knowledge of the feeding ecology of urban raptors. In 2000 and 2001 the same pair of Peregrines bred successfully in nest boxes situated on two different buildings in the city centre, rearing three and four chicks in the respective years. During the breeding seasons from hatching to fledging, the nests were monitored with a video camera. Only diurnal observations were used in the detailed analysis of feeding activity - 428 h in 2000 (33 days) and 384 h (24 days) in 2001. Two peaks of parental activity were noted: in the morning and in the afternoon. Additional data collected in 2000 showed that the falcons also fed their young at night. In 1998-2001 486 prey remains were collected on the buildings occupied by the Peregrines. In Warsaw these falcons preyed most often on Feral Pigeons (32%), and also on various thrush species (23.5%), Skylarks (8%) and Corncrakes (5.6%). Seasonal variations in prey composition were identified. During the spring and autumn migrations, the proportion of pigeons in the falcons' diet was 10-19%, while in summer and winter it was over 40%. The trend was reversed with regard to migrant species, which were prevalent in the diet in spring and autumn, but less numerous in summer and winter.
Key words: Peregrine Falcon, Falco peregrinus, urban area, diet, feeding activity