Pollution-Related Variation in food Supply and Breeding Success in Two Hole-Nesting Passerines

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 differentsized 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.

A review on exposure and effects of arsenic in passerine birds

“…a pollution-related reduction in food availability and changed food quality may be less critical for an opportunistic forager as the pied flycatcher than for great tit (Eeva et al, 1997(Eeva et al, , 2005b.…”

“…However, wild birds are often exposed to a mixture of heavy metals and other contaminants, making it difficult to demonstrate a causal link between environmental levels of specific metals and health impairments. In addition, long-term pollution may produce changes in plant and animal communities, which can cause changes in food quantity and quality and secondary effects on bird species (Eeva et al, 1997(Eeva et al, , 2005b. Therefore, experimental studies are also needed to explore the direct effects of As on birds.…”

Climate change, breeding date and nestling diet: how temperature differentially affects seasonal changes in pied flycatcher diet depending on habitat variation

“…Birds raising their young in coniferous ⁄ other habitats therefore seem less affected by spring temperatures, and hence, climate change may influence these trophic interactions to a lesser extent. Mixed habitats of birch and pine trees seem especially suitable: the early caterpillars on deciduous trees were replaced by species emerging on pine later in the season (Eeva, Lehikoinen & Pohjalainen 1997). Pine trees also show much lower yearly fluctuations in timing and abundance of Lepidoptera larvae (Veistola, Eeva & Lehikoinen 1995).…”

Different responses to cold weather in two pied flycatcher populations

“…Our southern study area was established in 1991 in Harjavalta, SW Finland (61°20%N, 22°10%E). Eleven study sites, with 30 -50 nest-boxes in each, were selected so that their habitat characteristics were as similar as possible (Eeva et al 1997). Four new sites were added in 1992 and 1994 and the number of nest-boxes varied from 540 to 845 according to year.…”

“…The forests in the area are dominated by Scots pine, which forms mixed stands with Norwegian spruce Picea abies and birch Betula spp. The nest-box sites were originally established to study the effects of aerial emissions from a copper smelter on birds (Eeva et al 1997). To ensure that pollution effect did not bias the geographic comparison, we omitted the sites closer than 3 km from the polluting factory complex, as we had not observed any detrimental effect beyond this distance (see Eeva and Lehikoinen 1996).…”