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Specimen collections are repositories and generators of ecological and evolutionary knowledge, and variation among individuals is one of the most important issues in biology. Indeed, there would be no evolution without variation among individuals, and the only way we can assess variation is by studying many individuals. |
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These specimens were due to the pioneering research of Professor DeWolfe, who sadly passed away shortly before this issue of the newsletter was finalized. |
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The adult is clearly a male based on the brightness of his central white crown strip. Note how
the immature has the same basic crown appearance as the adult
but the black and white
are replaced with dark and light brown stripes. Photos courtesy of Lynn Watson. |
The enigma arises because, unlike antlers, some of these signals, like bright colored plumage in birds, are cheap to produce, and if they are easy to produce one has to wonder why the subordinate individuals would develop signals that advertise their lowly status. But they do, so an evolutionary enigma arises because natural selection should favor subordinates that “cheat” on the signaling system and develop dishonestly bright signals. To determine whether adult sparrows two years old or older with black and white striped crowns dominate immatures with brown striped crowns because these older, brighter birds are more experienced or simply because the older birds have brighter colors, Professor Rothstein and his students altered immature sparrows so that their crowns matched the bright ones of adults. Invariably, these “experimentally created cheaters” dominated immatures whose crowns had the usual dull brown colors, and this was the first convincing experimental demonstration of status signaling in birds. They also found that males dominated females within each age class, but this didn’t look like status signaling because the White-crowned Sparrow was believed to lack sexually dimorphic plumage. But a careful analysis of hundreds of our museum specimens showed that this belief was wrong.
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| Variation in crown colors of White-crowned Sparrows. |
Within both age classes, males have greater contrast between their dark and light crown stripes than do females. The research team was able to make this discovery about a species thought to be one of the most well studied birds in the world only because there were many specimens in the vertebrate museum.
These specimens were due to the pioneering research of Professor DeWolfe, who sadly passed away shortly before this issue of the newsletter was finalized. Professor DeWolfe studied White-crowned Sparrow vocalizations, physiology and life history (and many other things as well) during her long and productive life. A future newsletter will provide an overview of her extraordinary accomplishments. But for now, it’s worth contemplating that science and conservation will continue to benefit from her efforts long into the future, not just because of her own research, but also because of the invaluable specimens of sparrows and other species she placed in the UCSB vertebrate museum and because of her dedication and enduring support for museums such as ours. |
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