The Barn Owl is by far the most commonly nest recorded owl species in the UK and Ireland (1,823 nest records in 2011, compared with 476 Tawny Owl and 143 Little Owl). The Barn Owl has benefited from all the hard work volunteers have put into increasing the number of possible nesting sites through Schedule 1 licenced nest box schemes all over the country. With the increase in nesting sites, Jackdaw, Stock Dove and Kestrel also nest in these boxes.
We have just heard from Adrian Blackburn concerning a Barn Owl box that has been used by Barn Owls for the last 3 years. When this box was checked on 05/06/2012 it had 5 white Barn Owl eggs and also 4 Kestrel eggs (below) that were being incubated by a female Barn Owl. This would normally mean that the owl had evicted the female Kestrel and laid her own. However when the next check was done, there were 5 tiny Barn Owl chicks and one tiny Kestrel chick, two warm Kestrel eggs and one addled Kestrel egg. The next box check had 3 Barn Owl chicks and the unhatched Kestrel egg.
As owls usually incubate from when the frst egg is laid, the owl chicks will hatch about a day apart, giving the earlier hatching chicks a better chance of survival during lean times. This is done by eating their siblings and in this case the smaller Kestrel chicks would probably be on the menu.
Adrian and his team have had dual occupation in their boxes before i.e. Barn Owl / Kestrel and Barn Owl / Stock Dove but never with a Barn Owl incubating the other species eggs and hatching them out!
Thanks to Jill Pakenham for the Barn Owl picture and Jim Lennon for the egg picture.