Pollution-related changes in diets of two insectivorous passerines

Abstract

Insectivorous birds living in polluted areas are not only exposed to pollutants but they may also be affected by changes in their invertebrate food. The populations of many invertebrate species are affected by environmental pollution and such changes may lead to differences in the diet of insectivorous birds. We examined nestling food quality (invertebrate composition and heavy metal levels) and breeding performance of two cavity-nesting passerines, the Great tit, Parus major, and the pied flycatcher, Ficedula hypoleuca, in an area with long-term heavy metal pollution by a copper smelter. There were no differences in feeding frequencies or the amount of food that parents provided to their nestlings between polluted and unpolluted sites, but food quality in a polluted area differed from that of the control area in both bird species. P. major took more beetles and variable "flying insects" and less caterpillars (of smaller size) and moths in the polluted area as compared to the unpolluted one. F. hypoleuca ate more beetles and larvae and less moths and spiders in the polluted area. Breeding success of P. major was better when the nestling diet contained a large proportion of caterpillars and the relationship was especially strong in the polluted area. On the contrary, F. hypoleuca broods succeeded equally well with variable diets. Our data suggest that a more opportunistic forager, F. hypoleuca, is less vulnerable to a changing invertebrate composition caused by human environmental impacts than a caterpillar specialist, P. major. In a heavy metal polluted area, F. hypoleuca seems to be more sensitive to a decreased amount of Ca rich food items (e.g. snails) while P. major suffers especially from the lack of carotenoid rich caterpillars. Our results emphasize the importance of secondary environmental changes, like food quality, in addition to direct impacts of pollutants.

Selection on laying date is connected to breeding density in the pied flycatcher

“…The reason for this may be the less strict food availability peak in Finland. The period when moth caterpillars are available is relatively long (Eeva et al 1997), and alternative food items such as saw-fly caterpillars occur during a period that overlaps with and extends after that (Eeva et al 2005). Thus, we suppose that the critical factor in our study population is the food availability in space (territory quality) instead of food availability in time (food peak).…”

Environmental Pollution Affects the Plumage Color of Great Tit Nestlings through Carotenoid Availability

“…Animals are not able to synthesize carotenoids de novo, so they need to acquire them from their diet (Brush, 1978). Therefore, a possible reason for the observed human-related change in plumage color could be dietary changes in polluted and urban areas (Eeva et al, 2005). For example, environmental pollution may affect birds' diet if the availability of carotenoid-rich food, like caterpillars, is reduced.…”

Polluted environment and cold weather induce laying gaps in great tit and pied flycatcher

“…Elevated heavy metal concentrations occur in the soil and biota of the polluted area due to current and historical deposition, and metal contents decrease exponentially with increasing distance from the smelter, approaching background levels at sites further than 5 km from it (Eeva and Lehikoinen 1996;Derome and Nieminen 1998). For example, heavy metal levels in diet and tissues of F. hypoleuca and P. major nestlings are increased in the polluted area (Eeva and Lehikoinen 2000;Eeva et al 2005). The forests in the area are dominated by Scots pine (Pinus sylvestris), which forms mixed stands with spruce (Picea abies) and birch (Betula spp.).…”