White-crowned sparrows are very striking birds. The adult birds have contrasting white and black stripes on the crowns of their heads
and immatures have more muted gray and rusty-brown stripes on their heads.
The crowns of males are more vivid that those of females and the vividness of crowns varies among individuals within a sex/age group.
As part of their winter flocks, birds battle for access to food (especially at feeders). Adults dominate immatures (first-year birds) in these conflicts. Adult males are dominant to adult females and immature males dominate immature females (see
here and
here). Within a group, birds with more striking patterns typically dominate individuals that are more muted (and these social signals are associated with features linked to evolutionary superiority - see
here). But if
you paint the crown of a less-dominant bird to imitate a more dominant stage, the formerly subdominant bird wins these scraps more often. Of course, an “upgraded” bird cannot see the top of its own head, so this altered outcome must be due to the perception of the other bird that its “upgraded” antagonist must be a more dominant bird. [The scientist who conducted this research was a fellow gradual student at U.C.S.B.]. Similar patterns are found in a related species, golden-crowned sparrows, but there is also
evidence that birds learn to recognize the members of their flock and manipulating the crown coloration is not effective with birds that have prior experience with each other (but it does still work with inexperienced birds).
Steve
