Birds and Light ' I wonder' if you could explain
the behaviour of a blackbird which has nested near my house ?' writes a Coventry reader. Recently a continual tapping on the window attracted my attention. It was the male bird tapping with his beak on the glass. He did this for hours on end and I was much puzzled. A pot of forget-me-nots stood on the window sill and it occurred to me that perhaps the bird wanted to reach the flowers so I removed the pot and the bird went away. Can you explain this ? Have blackbirds a particular liking for forget-me-nots ?' I think it unlikely that the bird was attracted by the flowers at all but, because they were there as a background, the image of the blackbird was reflected and the bird attacked, thinking it was confronted by an enemy. Blackbird cocks are notoriously aggressive. Sparrows and other small birds frequently tap on windows and on occasions one hears of them doing so in the early hours when, with a subdued light or a low angle of sun- light, a mirror effect is produced on windows. Another extraordinary thing is that some birds fail to see glass and collide with it and this is often due to there being a.' daylight' back- ground from some other source such as french windows at the other side of a room which make the bird think it can dart through as it might pass through a hole in bushes or along a glade in a wood.
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