Showing papers by "Ruedi G. Nager published in 2007"
TL;DR: It is demonstrated that parental age can influence offspring performance via variation in incubation environment, and that females are more susceptible than males to conditions experienced during embryonic development.
Abstract: The quality of conditions provided by avian parents will have consequences for both parental and offspring fitness. While many components of avian reproduction appear to vary with parental age, the effect of age on incubation has largely been ignored so far. In this study, we tested whether young herring gulls provide a different incubation environment from mature ones and whether this has consequences for offspring performance. Laying and rearing conditions were standardised using a cross-fostering protocol. Egg predation rates tended to be higher in the nests of young parents. However, nest site, nest construction and egg temperature during incubation did not vary with parental age. Overall, the duration of incubation was shorter in young compared to mature birds and this reflected the later laying date of the former, since incubation duration generally decreased across the season. However, male eggs incubated by young parents had longer incubation periods than predicted for their laying dates. In contrast, incubation length of female eggs incubated by young pairs, and of male and female eggs incubated by mature birds did not deviate from the expected for any given laying date. Offspring that had been incubated by young parents had considerably poorer survival than those incubated by mature pairs, despite being reared under standardized, favourable conditions (singly, by mature parents). This was due to increased mortality among female chicks that had been incubated by young parents. The chicks incubated as eggs by young and mature birds, which survived until fledging, did not differ in body mass and size growth, or body condition. The results of this study demonstrate that parental age can influence offspring performance via variation in incubation environment, and that females are more susceptible than males to conditions experienced during embryonic development.
29 citations
TL;DR: Results suggest that exposure to doramectin residues in dung on grazed pastures may have sublethal effects on the insects developing in that dung, but there was no evident avermectin effect on the abundance of adult S. stercoraria occurring in the pastures.
Abstract: The effects of avermectin exposure on natural populations of the yellow dung fly, Scathophaga stercoraria Linnaeus, were investigated at the field scale on farms in south-west Scotland. Pastures forming the focus of the study were grazed with either untreated cattle or cattle receiving standard, manufacturer-recommended treatment regimes of an avermectin product. Flies were sampled between April and July in 2002 and 2003 using dung-baited pitfall traps. Abundance and wing asymmetry in S. stercoraria populations were examined in relation to a range of environmental and management variables (including avermectin exposure, pasture management intensity, weather and season). Data used for abundance analyses were collected in fields where treated cattle had been dosed with either doramectin or ivermectin, while the data for the asymmetry analyses were from a subset of fields where treated cattle had been dosed with doramectin only. While abundance of S. stercoraria varied significantly between years and with season, there was no difference in their abundance between fields grazed by avermectin-treated or untreated cattle. Asymmetry was significantly higher in fly populations in fields grazed by doramectin-treated cattle, suggesting that exposure to doramectin during development could have imposed some degree of environmental stress. While these results suggest that exposure to doramectin residues in dung on grazed pastures may have sublethal effects on the insects developing in that dung, there was no evident avermectin effect on the abundance of adult S. stercoraria occurring in the pastures.
22 citations