Q: When listening to birds in the early morning it always strikes me that they seem to sing loudest between the first glimpse of dawn and the actual sunrise. Is this true? If so, what is the reason?
A: There are several factors at work here. The first is that during the night, the air near the ground is cooler than the air above, so that sound is refracted downwards. As soon as the sun rises, the air near the ground heats up, becomes less dense and rises, so that sound is then refracted upwards.
The second is the simple case that before dawn, the background noise caused by human activity tends to be much less. As a commuter who has to catch a 6.30 am train, I notice that there is a considerable difference in traffic before and after dawn.
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Finally, and possibly most significantly, songbirds are more territorial in the mornings. Refreshed by a night鈥檚 sleep, they are ready to take on the world but, as the day proceeds, and the requirements of feeding a growing family take their toll, the area claimed by a songbird shrinks as the evening approaches.
Since neighbours have similar ambitions, this means establishing the ownership of a larger patch first thing in the morning is of great importance. As a result, the majority of territorial disputes also take place in the morning.