Experimental manipulation of dietary lead levels in great tit nestlings: limited effects on growth, physiology and survival.
We manipulated dietary lead (Pb) levels of nestlings in wild populations of the great tit (Parus major L) to find out if environmentally relevant Pb levels would affect some physiological biomarkers (haematocrit [HT], fecal corticosterone metabolites [CORT], heat shock proteins [HSPs], erythrocyte delta-aminolevulinic acid dehydratase activity [ALAd]), growth (body mass, wing length), phenotype (plumage coloration) or survival of nestlings. The responses to three experimental manipulation (control, low and high: 0, 1 and 4 μg/g body mass/day) are compared with those in a P. major population breeding in the vicinity of a heavy metal source, a copper smelter. Our Pb supplementation was successful in raising the fecal concentrations to the levels found in polluted environments (high: 8.0 μg/g d.w.). Despite relatively high range of exposure levels we found only few effects on growth rates or physiology. The lack of blood ALAd inhibition suggests that the circulating Pb levels were generally below the toxic level despite that marked accumulation of Pb in femur (high: 27.8 μg/g d.w.) was observed. Instead, birds in the metal polluted environment around the smelter showed decreased growth rates, lower HT, higher CORT, less colorful plumage and lower survival probabilities than any of the Pb treated groups. These effects are likely related to decreased food quality/quantity for these insectivorous birds at the smelter site. In general, the responses of nestlings to metal exposure and/or associated resource limitation were not gender specific. One of the stress proteins (HSP60), however, was more strongly induced in Pb exposed males and further studies are needed to explore if this was due to higher accumulation of Pb or higher sensitivity of males. In all, our results emphasize the importance of secondary pollution effects (e.g. via food chain disruption) on reproductive output of birds.
Department of Biology, University of Turku, Turku, Finland, teeva@utu.fi.
Tapio
T
Eeva
Miia
M
Rainio
Åsa
Å
Berglund
Mirella
M
Kanerva
Janina
J
Stauffer
Mareike
M
Stöwe
Suvi
S
Ruuskanen
D000818:Animals; D001842:Bone and Bones / Q000737:chemistry; D002338:Carotenoids / Q000378:metabolism; D003345:Corticosterone / Q000378:metabolism; D004032:Diet; D005243:Feces / Q000737:chemistry; D005260:Female; D006360:Heat-Shock Proteins / Q000378:metabolism; D006400:Hematocrit; D007854:Lead / Q000008:administration & dosage / Q000032:analysis / Q000633:toxicity*; D008297:Male; D046109:Passeriformes / Q000254:growth & development* / Q000378:metabolism; D000623:Porphobilinogen Synthase / Q000378:metabolism; D012737:Sex Factors
D006360:Heat-Shock Proteins; D007854:Lead; D002338:Carotenoids; D000623:Porphobilinogen Synthase; D003345:Corticosterone