The European robin
Songbirds mainly sing before dawn. There are several hypotheses as to why songbirds prefer the morning. One is that the combination of low light intensity with low temperatures would hamper invertebrate activity, reducing foraging success at dawn. The birds can then make better use of this time for other activities, such as singing.
Males start singing at dawn when increasing light intensity has reached a certain threshold. This threshold value varies from species to species and therefore also causes each species to start singing at a different time. When there is a lot of light pollution, this threshold is reached faster. As a result, birds in places with a lot of street lights start their dawn singing faster. This effect is greatest for species that in natural conditions start singing early, such as the European robin.
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