Endogenous control of fuelling in a migratory songbird

Abstract

The Northern wheatear (Oenanthe oenanthe) isa small long-distance migratory songbird that breeds throughout the Northern hemisphere and winters in sub-Saharan Africa. The main components of its migratory behaviour, i.e. seasonal migratory restlessness and body mass changes, have been shown to be under endogenous control. However, it is still unknown whether the disposition to accumulate fuel re-serves is an inherited trait. We cross-bred Northern wheatears from two populations known to accumulate different amounts of fuel in a common-garden setup, and measured their maximum fuelling as the difference between the lightest and heavi-est body mass recorded over each year for 4 years or longer. We used the largest value as a measure of maximum voluntary fuelling potential. F1-generation "hybrids" showed intermediate values to those of the parent populations. It was previously shown that in the wheatear the amount of fuel accumu-lated is closely linked to the presence of large ecological bar-riers to cross. This study shows that this adaptation has been fixed at the genetic level, and that intermediate traits are trans-ferred to the next generation, with possible implications on the viability of such individuals in nature.