Experimentally impaired female condition does not affect biliverdin-based egg colour

It has been proposed that blue-green egg coloration is a condition-dependent female sexual trait that may modify paternal care in a post-mating sexual selection scenario. This pattern may arise because the pigment responsible for eggshell colouration (biliverdin) may be a costly and limited resource, whose availability is linked to female health state. Thus, it can be predicted that females whose condition is compromised should be constrained in their capacity to deposit biliverdin in the eggshell, thus producing paler clutches. To test this hypothesis, we performed a handicapping experiment by clipping some feathers of female spotless starlings before egg laying and measuring the colour of their clutches. We expected the handicapping treatment to increase flying costs, impairing female overall condition and resulting in paler clutches. Our experiment was successful in lowering the weight gain of handicapped with respect to control females. However, in contrast to our expectations, we f...