Widely recognised for his work on the study and conservation of owls and raptors, professional ecologist Colin Shawyer has collaborated with the BTO on projects such as Project Barn Owl (1995-1997) and the Barn Owl Monitoring Programme (2000-2009). As founder and co-ordinator of the Barn Owl Conservation Network (BOCN), Colin is in regular contact with Barn Owl experts across the country and oversees the annual monitoring of over 3,000 Barn Owl nest sites.
Good vole numbers predicted for 2016
On 13 April, my colleagues and I visited a sample of fifteen Barn Owl nest sites in the east of England. Pairs were present at most of them, the females weighed were all close to 400g—well above the typical 365g threshold for breeding—and all but one bird was developing a brood patch, suggesting that egg-laying would start in the next 15-20 days. Elsewhere in England there had already been reports of eggs in the first week of April, and indeed one of the females we encountered had such a well-developed brood patch that it could have started any day. Males were in good health too, weighing on average 350g.
This sample from one of our regular study sites suggests that Field Vole abundance, having gone through an expected trough in July and August 2015, has since increased enough to allow a good proportion of Barn Owls to get into breeding condition this year. In keeping with regular cycles, it’s likely that, in much of the UK, vole numbers will continue to increase throughout this year, leading to a peak in 2017.
Timing of breeding
As most Barn Owl recorders will know, I have been undertaking these early-season sampling exercises annually since the 1990s in order to help others plan their visits to Barn Owl sites efficiently and avoid too many visits before egg-laying begins, which is when pairs are at their most sensitive to disturbance. This year, I expect most females will have begun to lay at the end of April and the beginning of May, meaning many will have had full clutches by the third week in May. The majority of our nest inspections in England to examine chicks will begin during the third or fourth week of June.
I hope that this information will be useful to my BOCN and BTO colleagues and I wish everyone well for what should be a reasonably good breeding season—certainly compared to last year.
Barn Owl Conservation Network Co-ordinator – UK and Ireland