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Submitted by kruzzoli on Fri, 12/14/2018 - 13:07

Males sing with different trill rates during the morning and during the day. When unpaired during the afternoon, they sing at a much higher rate than in the early mornings when they are paired and calling out to other males. This study was interested in the effects of noise and structure on the male song used to broadcast signals to other females, so only recordings from the day were used and none from the early dawn when they are calling to other males. They took recordings between 7 am and noon in April and May of 2011 and 2012 from the same area in Michigan. Taking recordings from the same time of day and the same season ensures consistency in the behavior of bird calls because calls can change seasonally depending on breeding or taking care of young or finding new habitat. Using the same location also ensure population similarities and that the differences found are not based on different environments or population differences. The sites of recordings varied from large rural areas with little noise and only a few man made structures to to sites that were highly urbanized and contained a lot of noise and a high proportion of sound reflecting surfaces and structures. One to three males were recorded from each site and each site was separated by at least .5 m to ensure there was not overlap and there was a reduced chance that the same male was recorded more than once. During song analysis, the birds were assigned random numbers so that they were unaware of the location of the bird to avoid bias on analysis.