Effects of anthropogenic noise on song sparrow song ( Melospiza melodia) across an urban gradient

    Animals use acoustic signals for alarm calls, territorial defense and mate attraction.  Song sparrows sing to attract mates and songs typically range in frequency from 1000 to 8000 Hz. Anthropogenic noise in urban areas are composed primarily of  low frequency sounds from 150 to 2,000 Hz that may overlap with song sparrow song. Anthropogenic noise is louder than bird song and may mask information from songs. Birds respond to anthropogenic noise in multiple ways to reduce masking, including singing during times when there is less noise, singing more frequently, and raising low frequency portions of songs to reduce overlap. Understanding how birds respond to excess noise may play an important role in conservation efforts. I hypothesize song sparrows in noisy urban sites will have songs with higher minimum frequencies and narrower bandwidths compared to song sparrows in quieter sites. Male song sparrow repertoires were recorded during the spring of 2010 and 2011 at three different sites varying in the level of background noise from low to high. Ambient noise levels at each location were measured with a sound pressure level meter. Individual male repertoires of over a 100 songs were then categorized in to song types and the following song characteristics were measured: minimum frequency, maximum frequency, and bandwidth. Sites varied with levels of anthropogenic noise: high 65.22 dBa (±SD 4.59), medium noise 54.57 dBa (±SD 2.59), and low noise 44.97dBa (±SD 5.01) Preliminary analysis reveals that many low frequency notes in the nosier habitat overlap with the anthropogenic noise.