Air raid precaution .......

I was watching this Great Tit when it suddenly looked up and froze, sure enough the silhouette of a Sparrow Hawk passed over, not in hunting mode but a potential threat.

Its amazing how these little birds remain alert whilst going about their daily business both individually and as mixed flocks in a given area. Blackbirds in particular seem to be very alert to potential dangers.

I suppose the question is, was it alerted by nearby birds or did it sense the presence of the raptor itself ?.