The Noisy Miner is a large, aggressive Australian honeyeater which has benefited from land clearing and is probably increasing in range and abundance. It is postulated that the Noisy Miner may contribute to rural tree decline (dieback) by excluding small insectivorous birds from eucalypt woodland remnants, thereby reducing the level of predation upon defoliating insects. Noisy Miner abundance was experimentally reduced at seven small woodland remnants and this resulted in increased populations of small insectivorous and nectarivorous birds at six remnants. Colonising populations of small birds have the potential to reduce insect infestations and may assist in the recovery of dieback-affected woodland remnants. To test this hypothesis, leaf damage caused by defoliating insects, general tree health and insect numbers have been monitored quarterly for 3½ years at seven treatment and eight control sites to ascertain whether increased numbers of small insectivorous birds result in improved health of small woodland remnants. 

Key words: Noisy Miner Manorina melanocephala, Eucalypt dieback, aggression, exclusion, defoliating insects

Tracking samples of biennial breeding Diomedea chionoptera from South Georgia, Diomedea antipodensis from Antipodes Island and Diomedea sanfordi from the Chatham Islands have been undertaken in the Southern Hemisphere using ARGOS satellites during the 1990s. Harnesses and programming of intermittent transmissions to extend battery life for long-term deployments have enabled sampling of breeding and non-breeding ranges. Different feeding ranges for breeding birds of each species have been recorded, with close patterns (<600 km) over continental shelf, commuting (>2000 km) to continental shelf edge, and wide ranging (>5000 km) over deep water being demonstrated. Mapping of concurrent tracks by D. antipodensis and D. sanfordi showed demarcation along the 2000 m undersea contour. Non-breeding D. sanfordi wintered along the Argentinean coast. There they were confined to locations at <1000 m undersea contour over the continental shelf. Breeding D. chionoptera from South Georgia feeding chicks fed on the continental slope nearby at depths >1000 m. Sample data confirm distinctive sub-hemispheric separations between feeding locations for breeding and wintering non-breeding adults of each species. 

Key words: Great albatrosses, ARGOS satellite, feeding niche, transmitter, non-breeding

Empirical knowledge on positive interspecific interactions in birds have accrued to the point where it merits more theoretical attention. When selecting a site for breeding, sampling for its relative quality with respect to predation risk, food and other resources may be expensive for migrant birds in terms of time and energy. In experimental studies we have shown that migrants use resident birds as a reliable and fast surrogate for direct sampling resulting in heterospecific attraction. Here we adopted a modelling approach to survey ecological conditions favouring the evolution of heterospecific attraction. A migrant assessing potential breeding sites was let to select between source and sink patches. A proportion of the source patches were occupied by residents. Migrants using residents as a cue gained benefit in terms of lowered costs when assessing occupied source patches; non-users score similar costs in assessing all habitat patch types. We varied the intensity of competition between residents and migrants and the proportion of sink, empty source and occupied source patches in the landscape, as well as the costs of assessing. The results indicate that migrants using residents as a cue have higher fitness in a wide array of ecological conditions. This promotes the evolution of heterospecific attraction particularly if competition is relatively weak. 

Key words: heterospecific attraction, community structure, interspecific interactions, migrant birds, resident birds

Key words: fragmented habitats, oak-dominated forests, Bryansk Polesia, reproduction.

We studied the possible effects of habitat structure on forest bird populations in forest fragments differing in size and isolation. We examined relationships between various vegetation parameters and the population sizes of a number of forest birds in nine plots scattered in a large contiguous forest block. Thereafter, we sampled the same vegetation parameters in five smaller forest patches. By comparing the different sets of vegetation parameters, we were able to predict population sizes in the fragments based on differences in vegetation structure. Variance in population sizes between the large forest block and the sets of fragments, that could not be explained by variation in vegetation structure alone, could then be examined by fragmentation parameters. We examined 15 understorey species. Two were negatively affected by fragmentation. Twenty-three mid-canopy and canopy species were examined. One was positively affected by fragmentation and three negatively affected. Understorey and arboreal, insectivore foliage gleaners were negatively affected by fragmentation and that of mid-canopy and canopy frugivores positively affected. Overall, the understorey forest generalists were positively affected by fragmentation and that of mid-canopy and canopy forest specialists negatively affected. 

Key words: tropical forest, vegetation structure, relative abundance, forest species, feeding guilds, forest dependancy

The effect of grass mowing and artificial impaling of prey items on space use and nestling growth rate of Red-backed Shrikes Lanius collurio was monitored during the breeding season. The movements of individuals were followed by radio tracking and applying a laser range finder in combination with a compass. In the experimental territories, grass was mowed and feeding site choice of shrikes was observed. To separate the effects of change of insect availability and loss of perch sites perch sites were offered in the mowed part of the territory. Growth rate of nestlings was also recorded daily. The insect availability and diversity was sampled weekly in mowed and non-mowed parts of the territory. Prey items available to parents were also manipulated by impaling grasshoppers and mice daily for the breeding pairs. Changes in territory use and growth rate of chicks were compared to control nests. Shrikes hunted mainly in the non-mowed parts of the territory, where both insect availability and diversity was higher than in the mowed parts. The presence of perch sites did not alter this pattern of space use. Parents provided with artificially impaled prey increased significantly number of nest visits per hour, but fewer hunting trips were performed, and smaller part of territory was used while impaled insects were available. Average growth-rate of experimental clutches was not different from control nests. 

Key words: space-use, impaling, nestling growth, radiotelemetry, Red-backed Shrike

The main factors influencing the life history and ecology of birds have, thus far, been considered to be food and predation. The objective of this study was to analyse whether the life history, ecology, and biogeographic distribution of birds can additionally be explained by their migratory behaviour. I collected life history (clutch size, broods per year, annual fecundity), ecological (habitat choice), and biogeographic data (distribution over main biogeographic provinces) of all North American and European land bird species. The results demonstrate that long-distance migrants have smaller clutches, fewer broods per year, and lower annual fecundity than short-distance migrants and residents. The biogeographic distributions of long-distance migrants are almost exclusively restricted to either the Old or the New World. In contrast, residents and short-distance migrants frequently have Holarctic distributions. This pattern supports the hypothesis that long-distance migrants are derived from tropical ancestors, expanded their breeding ranges to the North, and were then subject to constraints that prevented further range expansion between North America and Eurasia. Furthermore, North American long-distance migrants are preferentially found in forested, and European long-distance migrants in open habitat types. These differences might be a phylogenetic heritage from their Neotropical and Paleotropical ancestors, respectively. The analyses demonstrate that migratory behaviour has a profound influence on all aspects of the biology of birds and is essential for understanding the evolution of temperate bird communities. 

Key words: biodiversity, phylogeny, habitat choice, reproduction, evolution of bird communities

The Blackcap is an abundant western Palaearctic species. Populations migrate over distances between 0 and more than 5000 kilometres per season. Wing length, wing shape index, wing area, wing-tail ratio, outermost primary-wing ratio, alula-wing ratio and notch index of more than 800 Blackcaps of 19 populations and hybrids between migratory x non-migratory populations were analysed. I found no differences between the sexes but large differences between age groups in most variables. With increasing migration distance, variables indicating a more energy-efficient wing for steady flight increased and those for high manoeuvrability were reduced. Though body size also increases with migration distance, this pattern is not only an effect of allometry. The non-migratory populations of the western Atlantic islands show differences among the islands and in comparison to their non-migratory mainland conspecifics. Hybrids show intermediate patterns in length, shape and area of the wings but patterns close to the non-migratory parent population in other variables. Experimental results give evidence for a lower manoeuvrability in individuals of a long-distance migrating versus those of a non-migrating population. Body size, age, migratory distance, demands for manoeuvrability and genetic preconditions are the main factors forming the flight apparatus in Blackcaps. 

Key words: migration, wing, tail, alula, hybrids