Chimneys make up about a third of all Barn Owl nests and, though they can be in the smallest of cottages or the largest of derelict castles, they are usually only made suitable for the owls by the nest-building activities of Jackdaws.
Jackdaw (M.O'Clery)
From early spring to early summer these industrious crows set about building their stick nests, and when they find what might be a suitable nesting cavity, their instinct is to keep adding sticks until it is full enough to make a suitable shallow nesting platform. In a relatively short time they can fill a large Barn Owl nest box almost to the top with a mix of sticks, lambs wool and various bits of rubbish, tinfoil, twine and whatever else might have caught their eye. In one notable instance, an almost full pack of cigarettes was included in the structure. No doubt some farmer nearby was wondering where on earth his 20 Silk Cut Blue went.
Huge pile of sticks created by Jackdaws, Co. Tipperary, May 2016 (M.O'Clery).
Many a householder who has had to clear the debris of a Jackdaw nest from a blocked chimney can appreciate just how much material can be added and in larger cavities in buildings, such as chimneys and attic spaces, sticks can be added in an almost constant stream, creating some enormous piles. In the example above, the sticks reached a height of eight feet, nearly three metres, inside a derelict house in Co. Tipperary. How many hours of stick-collecting might this represent?
In another example below, Jackdaw sticks dropped down the high, open top of a chimney of a ruined house in Co. Kerry accumulated under the open base, rising to over head height, on top of which was a perfect secluded platform on which Barn Owls nested this summer.
Inspecting a Barn Owl nest on top of Jackdaw sticks, Co. Kerry, July 2016 (M.O'Clery, under licence from NPWS).
So although Jackdaws and Barn Owls are often competing for the same nest sites, Barn Owls are usually reliant on Jackdaws making the chimney suitable in the first place.
Below, some examples of Barn Owl nests in chimneys from this summer, all of which would not be suitable for the owls were it not for the hard work of the Jackdaws.
Three chicks in the blocked chimney of a derelict mansion, Co. Kerry (M.O'Clery, under licence from NPWS).
This small cottage in Co. Kerry has its chimney blocked by a Jackdaws nest (M.O'Clery).
The same cottage chimney with a female Barn Owl and two chicks on their nest on top of the chimney blockage (M.O'Clery, under licence from NPWS).
Barn Owl chick in its nest site in a castle in Co. Tipperary, an old Jackdaw nest in a chimney shaft (M.O'Clery, under licence from NPWS).
Four Barn Owl chicks deep in the blocked chimney of a derelict house in Co. Tipperary. A perfectly dry and safe nest site (M.O'Clery, under licence from NPWS).
Two Barn Owl chicks in a relatively shallow blocked chimney in Co. Kerry. Such nests can be vulnerable to heavy rainfall, as they offer little shelter from directly above (M.O'Clery, under licence from NPWS).
