A1 Journal article – refereed
Pollution-related variation in food supply and breeding success in two hole-nesting passerines




List of Authors: Eeva T, Lehikoinen E, Pohjalainen T
Publisher: ECOLOGICAL SOC AMER
Publication year: 1997
Journal: Ecology
Journal name in source: ECOLOGY
Journal acronym: ECOLOGY
Volume number: 78
Issue number: 4
Number of pages: 12
ISSN: 0012-9658

Abstract
We studied to what extent changes in the breeding performance of two insectivorous passerines, the Pied Flycatcher (Ficedula hypoleuca) and the Great Tit (Parus major) were associated with pollution-induced variation in the biomass of invertebrate prey (spiders and insects on the ground, lepidoptera and sawfly larvae in tree canopies) in an air pollution (copper smelter) gradient. At the nestling time of both species, larvae were scarce in Scotch pine (the dominant tree species) close to the factory complex, peaked in the moderately polluted zone 2-4 km from the factory, and tended to decrease farther away. Both bird species preferred pine, particularly in the moderately polluted zone, where the proportion of larvae in the diet of P. major was high. Ground-living arthropods were scarce near the factory, but among-site variation was high even in the cleanest area. Breeding success of both bird species correlated positively with prey biomass, but only in P. major was food abundance correlated with nestling growth. Also, the productivity of different-sized clutches was affected in P. major, but not in F. hypoleuca. Large F. hypoleuca clutches produced more fledglings than did smaller clutches in all parts of the pollution gradient. For P. major this was true only in the moderately or slightly polluted parts of the gradient; in the most polluted areas, clutches of 6-11 eggs invariably produced 3-4 fledglings. The stronger impact of food on P. major than on F. hypoleuca probably resulted from a different diet. F. hypoleuca, which forages much from the ground layer, was susceptible to direct effects of pollutants at the egg stage, whereas P. major; a caterpillar specialist, suffered from the shortage of larvae in the late nestling period. Our results indicate that the reduced breeding performance of birds in the polluted area may be due to various reasons; one species may respond directly to toxicity, and the other species to reduced food supply.

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