The pied flycatchers take readily to nest boxes.
Dianne Oxberry visits a bluebell wood in the Lune Valley to visit a rare bird, the pied flycatcher.
In the upland oak woods, natural holes are scarce, so the birds take advantage of man-made bird boxes.
The North Lancs Ringing Group have been ringing the birds since 1967 to study population changes and migration and have ringed just over 6000 birds.
They've also seen the population increase from one or two pairs, to over 60.
Dianne Oxberry visited the wood to help ring the tiny baby birds with John Wilson, a retired warden from Leighton Moss nature reserve, and Ian Hartley from Lancaster University's biology department.
Careful hands are needed to add the rings, which will stay for life, to the tiny birds.
Mum also gets weighed - she only weighs 13.3g about the same as three 20p coins.
Birds that have been ringed in Lancashire have been found as far away as France, the Netherlands, Belgium, Spain, Portugal, Morocco and Italy.
Most of the birds return to the Lune valley woods but one adventurous bird was caught nesting in Denmark.