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We studied the fluctuation in 1975-1997 numbers of two species: the Pied Flycatcher Ficedula hypoleuca and the Collared Flycatcher F. albicollis breeding in natural cavities in the primeval deciduous stands of the Białowieża National Park (NE Poland). Both studied birds are commonly regarded as competitors if sympatric. Densities of two flycatchers are positively correlated within 7 plots (pooled data) investigated by a territory mapping method over 22 years (r = 0.71, p < 0.05) and 36 ha plot studied very intensively through 9 years (r = 0.35, p < 0.05). We found no evidence that the Pied Flycatcher density is negatively affected by the dominant Collared Flycatcher when that stronger species has a higher density. Clearly, both species fluctuated in a parallel way which contradicts an earlier generalization. The Pied Flycatcher breeds in Białowieża deciduous stands in much lower densities than the Collared Flycatcher does.
Wild birds breeding in acidified areas may have difficulties obtaining sufficient calcium for their eggshells, and shortage of land snails is shown to be the cause. The study found experimental evidence that Ca deficiency may affect reproductive traits also in birds breeding in non-acidified but naturally base-poor habitats. Positive effects of calcium supplementation on the egg volume, shell thickness, start of laying and fledglings' parameters of Great Tits Parus major and Pied Flycatchers Ficedula hy- poleuca breeding in base-poor pine forests in Estonia were revealed. The adverse effects of calcium shortage seem to be more pronounced in the years with the most unfavourable breeding conditions. Authors suggest that in such years birds may respond to calcium shortage by postponing egg-laying. The cost of egg formation in base-poor areas might be much higher than has been estimated on the basis of the energy and protein content of eggs. This fact should be considered more seriously in life history models of wild birds.
We investigated whether high−intensity road traffic affects the nestbox occupancy pattern of secondary hole−nesting birds. Field studies were carried out in two forests in south−eastern Poland (Lasy Janowskie forest and Polichna forest). Both complexes were included in NATURA 2000 network. In our knowledge it was first field experiment on road−traffic noise influence on forest birds, conducted in the Polish environmental conditions. The results of this experiment can be used in work on the impact of road projects on forest birds. Nestboxes were hung at twelve linear transects located perpendicularly to the busy road and they were regularly inspected in 2011−2012. Road noise was measured by use of a digital measurer of sound level at each nestbox. Monitoring the activity of predators on the study area was done with the help of digital trail cameras and experiment with use of artificial nest with eggs. Noise level decreased with distance from the road. In the first year of experiment we observed that the birds settled preferentially habitats in the vicinity of road. However in next season the number of occupied nestboxes was independent from the distance from road. We found that the pressure caused by predators on the study area was very low, creating safer nesting places for birds. Our results provide evidence that these birds are well adapted to cope with anthropogenic noise. Some species of birds preferred nesting in neighbourhood of road.
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