A tremendous effort is being made at the moment to monitor and visit as many Barn Owls nests as possible this summer. This is tied in with a large project with BirdWatch Ireland and Transport Infrastructure Ireland (T.I.I) to examine Barn Owl mortality on the M8 Motorway in Tipperary and the Tralee Bypass in Kerry, more of which anon.
Barn Owl chick, Tipperary, July 2016 (Photo: M.O'Clery, under licence from NPWS).
Results from the nest visits so far have been generally good, with 43 broods ringed so far, and several more to go so, in terms of numbers of broods ringed, it should be a record year. Brood sizes have been mixed, with nests in the Greater White-toothed Shrew range generally faring very well, with typically four chicks in most nests visited so far. Outside the shrew's range in, e.g., Kerry, brood sizes are well down on last year, with generally ones and twos at most nest sites, and only three nests with three chicks recorded so far.
Barn Owl, March 2016, at a roost site in a castle near Thurles, Co. Tipperary (Photo: M.O'Clery, under licence from NPWS).
Timing of egg-laying this summer is also notably different within and without the shrew's range, with Barn Owls nesting one to two weeks earlier than the average egg-laying date of 7th May wherever they are preying on the White-toothed Shrew, and one to three weeks later in the areas outside the shrew range. Sites in Kerry have been notably late this season with several still on eggs in late June.
Though the White-toothed Shrew seems to be having a positive effect on Barn Owl breeding numbers and brood sizes, there is still an issue with some nests within the shrew range where the chicks fall ill and die. The pattern is generally that the chicks start to lose weight around 25 to 30 days old, and die - seemingly of starvation - at around 30 to 40 days. Several such nests in Tipperary last week presented a particularly gruesome sight with, in one case, one weak and emaciated Barn Owl chick sharing a confined nest in a chimney with its three dead siblings. These fatalities occur in roughly 10 to 15 percent of nests within the shrew range, and is unknown outside of that, but the cause is as yet unknown. A parasite? Perhaps a virus, or bacteria unique to the shrew which is proving fatal to the chicks. It also seems to be an 'all or nothing' disease, whereby all the chicks in a brood succumb, or all are healthy and well.
Barn Owl nest site (circled) high on the inside gable-end wall of a castle in Tipperary. A site abandoned by the owls in recent years, but re-occupied again this summer. There were three chicks in the nest, all healthy and well fed. July 2016 (Photo: M.O'Clery, under licence from NPWS).
Site occupancy throughout Ireland seems particularly high this summer, with several cases of sites abandoned by Barn Owls in recent years being re-occupied this summer, particularly in counties Tipperary and Limerick. In Co. Kerry, despite the low brood sizes, the number of active sites is at least as high as the record year of 2015.
Barn Owl nest site in a castle, July 2016 (Photo: M.O'Clery, under licence from NPWS).
Barn Owl nest site in a castle, July 2016 (Photo: M.O'Clery, under licence from NPWS).
Thanks to this years extensive survey work, as well as an increase in the number of nest boxes, an increasing level of contact with interested farmers and landowners, and a huge input from volunteers it looks likely that, by the end of this breeding season in September, we might well have a record number of known Barn Owl sites.
More info on the Co. Kerry sites on the Kerry Birding Blog HERE
More info on the Co. Kerry sites on the Kerry Birding Blog HERE
