Noise pollution changes vocalization and response to conspecific intruders in two species of high-desert songbirds from the family Emberizidae

Background/Question/Methods

Anthropogenic noise is inescapable in our world. From airplanes and cars to gas wells and wind turbines the acoustic byproducts of industrialized society are here to stay. Although humans tend to drown out or even ignore industrial background noise, the effects on other species are intriguing. The culmination of these behavioral shifts on the community level is just starting to be explored. Birds are a common focus in the field of acoustic ecology, because of the importance of vocalization in their communication.  In the summers of 2009-2010 recordings of songs were made and playbacks of conspecific male songs were presented to territory holding male members of the family Emberizidae, chipping sparrows (Spizella passerina) and spotted towhees (Pipilo maculatus), at our study site in the oil fields of NW New Mexico. We predict that males holding territory within the loudest areas of RCHMA will exhibit a shift in territorial physical and vocal displays due to an interference with normal communication. Five-minute playbacks were made to approximately 20 individuals from each species within a gradient of noise levels to elicit territorial display and approximately 60 recordings were made of both P.maculatus and S. passerina to analyze vocalization parameters influenced by background noise.

Results/Conclusions

As predicted both species exhibited vocal and behavioral shifts in response to an increase in intensity of background noise levels. In response to increased background noise levels, S. passerina shifted both the duration of song and total note count per song as well as shifting perching location when confronted with a song from conspecific intruder. P. maculatus shifted the frequency of its vocalizations up “above” the background noise levels when sampled in loud habitat and altered several territorial response variables in response to noise, including signal jamming and latency to respond vocally to the intruder song. These results may indicate that these species modify vocal behavior within noisy habitats in an attempt to cope with noise; however, also exhibit what may be perceived as a difficulty to quickly and accurately perceive and engage threats from intruding conspecifics. Further research is needed to address the cumulative effects of these behavioral alterations on success of individual nesting attempts and populations across the study system.