Grey Wagtail (Motacilla cinerea) Science Article 1
Negative effects of current reproductive effort on components of future reproduction, called the cost of reproduction’, have been shown experimentally in a wide range of avian species . A possible mechanism for the mediation of these costs between successive breeding se as ons may be the impairment of the postnuptial moult . Here I report the results of an experiment designed to test the hypotheses that a high reproductive effo rt leads to (1) a delayed onset and (2) an accelerated speed of moult . In the Grey Wagtail Motailla cinerea I experimentally altered the size of 44 first broods by adding or removing two nestli ngs . Parental effort of both males an d females, as measured by feeding rates and nestling time, differed between the two treatments . Frequency, timing, size, and success of second broods were not affected by the experiment neither in females nor in males. During moult, 18 experimental males, but none of the females could be re-captured. Males that raised reduced broods had significantly higher primary moult scores as compared to males with enlarged broods if re-capture date is controlled for (= Residual Moult Score) . Residual Raggedness Value, a good estimator of moult duration, was not affected by the manipulation. ql Return rates of males in the year after manipulation were not significantly different between the treatments, while none of the females returned and none of the experimental offspring were recruited into the study population . In contrast to a number of earlier studies, these results are in agreement with the hypotheses that there is a trade-off between the investment in ., r reproduction an d the timing of postnuptial moult.
Klemp S. 2000, Ardea 88(1) : 91-98