Blackbirds nest building already

[grand cherokee]

this morning one of my Blackbirds is collecting straw/twigs etc and taking away presumably for nest building

I know they start early but never seen them this early especially in the frozen north

I have about fifteen in the garden and its all out war - constant fighting and not happy with fighting each other they also attack every other bird

even Roland my resident rat has come under attack - Roland has been with me for two years, never seen another rat?