The decision of when to breed is crucial to the reproductive success and fitness of
seasonally breeding birds. The availability of food for adults prior to breeding has long been …

I quantitatively test the hypothesis that four taxa or" types"(species or subspecies) of Red
Crossbills (Loxia curvirostra) in the Pacific Northwest have diversified morphologically in bill …

The phenomenon of bird migration has fascinated people from time immemorial. The
arrivals and departures of different species marked the seasons, heralding spring and …

Abstract Knowledge of how phenotype influences fitness is necessary if we are to
understand the basis of natural selection and how natural selection contributes to adaptive …

Asymmetrical competition determines which of two seed predators drives the evolution of
lodgepole pine (Pinus contorta ssp. latifolia) cones. Red squirrels (Tamiasciurus …

Few studies have shown both reciprocal selection and reciprocal adaptations for a
coevolving system in the wild. The goal of our study was to determine whether the patterns …

OPTIMAL foraging theory is based on the assumption that natural selection favours animals
that forage most efficiently1–3. But such selection does not act directly on foraging efficiency …

LEKS, where males congregate to display and females attend only to mate, present one of
the most remarkable outcomes of sexual selection1. It is a common but untested belief that …

How birds use environmental cues to time breeding, migration and molt has been the
subject of intensive study for nearly 90years. Most work has focused on seasonal breeders; …

A major assumption of our work was that validation research will be conducted by agency
scientists and other researchers to corroborate our findings. As a preliminary step in the …