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Abstract Urbanization is one of the most extreme forms of land transformation and results in changes to ecosystems and species compositions. As a result, there are strong directional selection pressures compared to nearby rural areas. Despite a surge in research on the different selection pressures on acoustic communication in urban and rural areas, there has been comparatively little investigation into traits involved with visual communication. We measured the plumage of museum specimens of white-crowned sparrows (Zonotrichia leucophrys) from urban and adjacent rural habitats in San Francisco, CA, to assess the effects of divergent habitats on plumage. We found significant differences in dorsal plumage, but not crown plumage, between urban and rural populations that have been diverging over the past 100 years. Urban birds have increasingly darker and duller dorsal plumage, whereas rural birds in adjacent areas have plumage with richer hues and more color complexity. Our findings suggest a newly observed adaptation to urban environments by native species and suggest that many traits, in addition to acoustic signals, may be changing in response to urban selection pressures. Additional collections in urban areas are needed to explore likely divergences in plumage coloration between urban and rural environments.
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Use of visual display in dark, cluttered environments
Abstract Animals living in dense vegetation are limited in their use of visual signals due to the transmission constraints in these dim, cluttered environments. Birds in such habitats are often drab in appearance and thought to rely predominately on acoustic signals for conspecific communication. Here, we investigate the presence and use of a concealed underwing patch in the family Cettiidae. We find that this distinct white patch is widely present in the genus Horornis, with limited evidence for its presence in other genera. In response to simulated territorial intrusions, 2 species, Horornis fortipes (Brownish-flanked Bush Warbler) and Cettia castaneocoronata (Chestnut-headed Tesia) perform wing-flicking displays that results in a flashing effect in H. fortipes. The presence of white underwings raises interesting possibilities about the role of hidden achromatic patches in facilitating visual communication in habitats traditionally thought to be unprofitable for this modality.
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- PAR ID:
- 10596684
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Ornithology
- Volume:
- 142
- Issue:
- 2
- ISSN:
- 0004-8038
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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