The effects of increased ambient urban noise levels on the vocalization pitch of European starling nestlings (Sturnus vulgaris)

Abstract

Anthropogenic noise has had documented detrimental effects on animal health and communication within urban areas. Decreased fitness along with impaired nestling-parent communication have been detected in a few urban avian species. The purpose of this study was to examine the effects of artificially increased ambient urban noise on nestling begging calls. It was hypothesized the nestlings will increase the sound frequencies of their calls to overcome the masking effects of higher noise levels. I predicted that the nestlings would shift the sound frequencies upwards and increase the call sound frequency ranges with noise playing. Vocalizations were recorded within 8 nests for each of two groups: a) the experimental group, subjected to artificially increased noise for 7 hours a day (3.5 continuous hours twice a day) from days 5 to 15 (day 0 is hatch day), and b) the control group. Recordings were made on day 14 in control (over one hour) and in experimental nests (an hour with extra noise being played, and an hour with no extra noise). Twenty minutes of continuous calls were selected for analysis for each group. Five values were obtained for each nest: the 5%, 25%, 50%, 75%, and 95% sound frequencies (kHz). From these, a calculated weighted mean was derived. Nestlings in the experimental nests called at significantly higher frequencies, with significantly larger call frequency ranges, when extra noise was played than in the control nests. However, there was no significant increase in call sound frequency and call frequency ranges when comparing the experimental group after the noise stopped and the experimental group with noise playing and the control group. These findings suggest that the nestlings significantly increase their call sound frequency in the immediate presence of higher noise levels to overcome the effects of masking.