Blackbirds many nests


i have a blackbird who is building nests (yes plural!) in my veranda- there are rafters jutting out from wall creating an overhang and she has built 5 nests so far along this section. She did exactly the same last year so there are now 10 blackbird nests in a row outside my back door! The veranda was only built last year so this has not happened before 

last year she didn’t appear to hatch a brood as one of the nests was attacked and on the floor.

this year now she is back to her frantic nest building exploits!

I’ve never encountered this before so would love to know if anyone can shed some light on it

many thanks Lisa