Blackbirds nest

This is absolutely normal behaviour Kevin, Blackbirds are fantastic protective parents and will literally try and do anything to take the focus away from their nests and young! That includes ferocious dive bombing, if you were to go too close, they would squark really loudly & fly very, very close above your head. Normally, it is the male which shows the most aggressive behaviour.
Its a shame that not many Blackbird chicks make it to Adulthood, considering how hard they are protected.

Elle
xx