Stabilizing selection on a plumage-based foraging adaptation: hooded warblers with average-sized white tail spots live longer

Avian flush-pursuit insectivores typically use contrasting white plumage
patches in their tails or wings to startle potential prey. Although
experimental evidence indicates that the extent of white has been
fine-tuned by natural selection to optimize foraging performance, the
hypothesis that within-population plumage variation directly influences
survival or lifetime reproduction and is subject to stabilizing selection
has not been tested. Here I provide such a test using data collected as
part of a 14-year study of a colour-ringed breeding population of the
hooded warbler (Setophaga citrina), a migratory flush-pursuit insectivore
that shows inter-individual variation in the extent of white in the tail
that is highly repeatable across molts and likely heritable. As expected
under stabilizing selection, warblers with average-sized white tail
patches achieved significantly higher long-term apparent survival than
individuals with either a lesser or greater extent of white in the tail.
Evidence of stabilizing selection was especially strong in males, an
observation that is likely related to pronounced sexual habitat
segregation on the wintering range. My results provide infrequently
observed evidence of stabilizing selection operating in a natural
population and also illustrate how stabilizing selection can act on avian
plumage traits outside the context of sexual and social signaling.