Allotments 4 All

I had a blackbird successfully raise 3 chics from a nest in my back garden.
( a Sparrowhawk got one yesterday though)
The chicks left the nest about 10 days ago.
The hen Blackie was hanging about a lot so I had a look inside the old nest and she's laid another cluch of eggs... in the same nest.Is this unusual ?
I'm assuming it is the same pair.

It's not unusual especially if they have their first clutch very early. Our's is sitting again after the magpies took her first lot. :(

we've got two babes hopping around the garden, hope the second ones make it, moudie  ;D

Checked yesterday - nest empty  :'( Magpies probably >:(

This Blackie just wont give up - I seen the bird near the old nest today so I checked  and she's sitting on 5 eggs. :-\