Search birdRS Box

Search birdRS blog posts

Browse the Blog Posts

Or scan through the blog archive below for items of interest as only the latest post is shown below, thanks.

Thursday, 27 November 2014

Song characteristics track bill morphology along a gradient of urbanization in house finches(Haemorhous mexicanus) Giraudeau et al. Frontiers in Zoology 2014, 11:83

Song characteristics track bill morphology along a gradient of urbanization in house finches(Haemorhous mexicanus)
Frontiers in Zoology 2014, 11:83

pdf: LINK
Web

Mathieu Giraudeau 1,2*, Paul M Nolan 3
Caitlin E Black 4, Stevan R Earl 5
Masaru Hasegawa 6, Kevin J McGraw 1

* Correspondence: giraudeau.mathieu@gmail.com 
1. School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
2. Present address: School of Biological Sciences A08, University of Sydney, Sydney, NSW 2006, Australia
3. Department of Biology, The Citadel, Charleston 29409, SC, USA
4. Department of Biology, The College of Charleston, Charleston 29424, SC, USA
5. Global Institute of Sustainability & School of Sustainability, Arizona State University, Tempe 85287-5402, AZ, USA

6. Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba-shi 305-8572, Ibaraki, Japan


Abstract
Introduction: Urbanization can considerably impact animal ecology, evolution, and behavior. Among the new conditions that animals experience in cities is anthropogenic noise, which can limit the sound space available for animals to communicate using acoustic signals. Some urban bird species increase their song frequencies so that they can be heard above low-frequency background city noise. However, the ability to make such song modifications may be constrained by several morphological factors, including bill gape, size, and shape, thereby limiting the degree to which certain species can vocally adapt to urban settings. We examined the relationship between song characteristics and bill morphology in a species (the house finch, Haemorhous mexicanus) where both vocal performance and bill size are known to differ between city and rural animals.

Results: We found that bills were longer and narrower in more disturbed, urban areas. We observed an increase in minimum song frequency of urban birds, and we also found that the upper frequency limit of songs decreased in direct relation to bill morphology.

Conclusions: These findings are consistent with the hypothesis that birds with longer beaks and therefore longer vocal tracts sing songs with lower maximum frequencies because longer tubes have lower-frequency resonances. Thus, for the first time, we reveal dual constraints (one biotic, one abiotic) on the song frequency range of urban animals. Urban foraging pressures may additionally interact with the acoustic environment to shape bill traits and vocal performance.

Keywords: Urban impacts, Bill shape, Singing behavior, Noise pollution, Vocal communication


Figure 1. 
Relationship between (A) the average bill width and length at each of our eight study sites for which we gathered data on bill traits (±SE) and (B) the average bill length and the urbanization PC1 scores at each of our eight study sites for which we gathered data on bill traits (±SE).


'Thus, bill length increased and bill width decreased at sites where less land was covered by native undisturbed habitat.'



No comments:

Post a Comment