Synergistic effect of light and noise pollution on dawn and dusk singing behavior of urban European blackbird: Changes during nesting season.

Artificial light at night (ALAN) and noise pollution in urban ecosystems change the behavior of birds in many ways, one of these being in their singing. These changes are crucial because singing is highly important in bird communication. As birds rely on the spread of acoustic information, they were found to modify their singing activity in urban areas under the influences of artificial light at night and noise. They can adjust their behavior to the rhythm of night and day (e.g., by timing their dawn song according to changing light intensities or shifting their singing to higher frequencies to prevent possible masking of the signal by noise). In this study, we assessed the effects of light pollution, noise, day in the year, and meteorological variables on the morning and evening timing and duration of singing in blackbirds. We found that light and noise pollution significantly affect the onset of blackbird dawn singing. Blackbirds started singing earlier in localities with ALAN and noise pollution. The effects of light and noise pollution on the morning song of the blackbird diminish through the breeding season after peaking at the beginning of the nesting season; and they are only minimal on the evening vocal activity of this species. With growing intensity of noise pollution, the influence of light pollution also increases. Light and noise pollution have greater influence on the morning vocal activity of blackbirds than do current weather conditions. • Light and noise pollution significantly affect blackbird singing activity. • Effect on blackbird's morning song diminishes through the breeding season. • Increasing noise pollution amplifies the influence of light pollution. • Light and noise pollution are more influential than are current weather conditions. • Impact on singing activity is strong in morning, minimal in evening. [ABSTRACT FROM AUTHOR]