Red-wing blackbird reproductive behaviour and the palatability, flight performance, and morphology of temperate pierid butterflies (Colias, Pieris, and Pontia)

In presentation experiments to red-wing blackbirds in eastern Washington, palatability of pierid butterflies varied over the birds' breeding season. The cloudless sulphur Colias eurytheme/philodice was always more palatable than the cabbage white Pieris rapae and the western white Pontia occidentalis. Pontia and Pieris had similar payabilities when demand for resources by the nesdings was relatively low. When demand for resources increased at the height of the birds' breeding season, the payabilities of all three species increased. Moreover, Pontia was eaten more frequently than Pieris, although the difference was not significant. Differences in palatability among species were associated with differences in capturability in artificial predation experiments. Colias flew for greater durations and distances than the other species prior to capture. The three species did not differ in flight speed. However, Colias was missed more often, suggesting that the species differed in manoeuverability. Two indicators of flight performance in tropical butterflies, flight muscle ratio (thoracic mass/body mass) and the position of centre of body mass, ordered with capturability of these temperate species as predicted.