It occasionally happens that young blackbirds are frightened out of the nest by rats or some other animal a day or two before they would have voluntarily left it; they make a brave attempt to fly, but occasionally one will knock into something in the course of a short flight and fail to the ground. I have known a small dog, on seeing this happen in a garden, go over to smell the young bird, without any intention of harming it. The watchful parent birds dashed at the dog immediately, and, by pecking the animals head, or appearing to peck it, chased it away.
Anyone who spends much time in woods and country places is familiar with the warning notes of the blackbird in the hedge when it has detected the presence of some prowling enemy, such as a weasel or a stoat. On these occasions the warning is immediately heeded by all the birds within hearing.
While blackbirds are very devoted to their young when they are in a helpless condition, they do not spend much further time on them after the youngsters are able to look after themselves.
I have known a blackbird in my own garden to start laying another clutch of eggs exactly one week after the former brood had left the same nest.