@misc{Tilgar_Vallo_(1973–_)_Breeding_1999,
 author={Tilgar, Vallo (1973– ) and Mänd, Raivo (1954– ) and Leivits, Agu},
 editor={Polska Akademia Nauk. Muzeum i Instytut Zoologii},
 editor={Meeting of the European Ornithologists' Union (2 ; 1999 ; Gdańsk)},
 copyright={Rights Reserved - Restricted Access},
 address={Warszawa},
 howpublished={online},
 year={1999},
 language={eng},
 language={pol},
 abstract={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 hypoleuca 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.},
 type={Text},
 title={Breeding in calcium-poor habitats: are there any extra costs?},
 volume={34},
 number={2},
 journal={Acta Ornithologica},
 publisher={Muzeum i Instytut Zoologii PAN},
 keywords={Great Tit, Pied Flycatcher, eggs, Estonia, congresses, calcium, calcium-poor habitat, Old World flycatcher, birds, Ficedula hypoleuca, Muscicapidae, Parus major, Paridae, Aves},
}