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Breeding Season Update Story dated: 10/13/2011 Now that the breeding season is almost over for barn owls we can reflect on how the year has treated them and in particular how they have been influenced by the availability of food and climate. Breeding began especially early for most barn owls in 2011 with eggs being laid in the first and second weeks of April, about three weeks earlier than usual. This suggested that field voles, their favourite prey, had survived the winter well, protected and insulated under a blanket of snow, the sudden change to mild conditions in February and March, allowing them to breed early too. Although the voles themselves survived the winter well under the snow, they were inaccessible to barn owls and many barn owls perished from starvation, particularly those in areas where even daytime temperatures were below -15oC. As a consequence in early spring, many of our ‘old faithfuls’ were missing from their regular nesting sites. Owls in northerly latitudes of Britain and those occupying high ground were especially affected. The frost-encrusted snow prevented access to their food for over two months. Consequently the occupancy of traditionally-used nest sites in these regions was particularly low. In some areas of northern England, Wales and Scotland the numbers of breeding pairs were down by 90% and back to the low levels last seen in the 1980s, following four decades of quite harsh winters. The lowered survival rate during the 2010/2011 winter was reinforced when I received details of a barn owl which had been found freshly dead in February. I had first ringed this bird as a chick in 1996 and because of this it could be aged accurately at 15 years 8 months, believed to be a longevity record for a British barn owl. This was a female owl and had probably bred successfully in most years, possibly producing about 40 young during its lifetime. Even in the lower ground regions of Britain some of our ‘old faithfuls’ were missing when we came to check their nestboxes in March and April. However, at a good proportion of sites young owls which had hatched in the summer of 2010 had successfully replaced the old birds. These young owls had, for the first time successfully tenanted newly installed or previously unused nestboxes. This clearly showed that they had survived the winter better than many of their adult counterparts, something we would not have predicted. Why did this happen? Adult birds remain faithful to their breeding area and do not move far away whatever the winter’s onslaught. Young owls on the other hand would have been dispersing out of their natal areas when the weather was at its worst in November and December. Because young owls are particularly mobile at this time they would have had the ability to permanently settle into areas where the conditions were least difficult for them. For the young owls, therefore, things were good in 2011. They paired up successfully and produced good numbers of young. This was particularly true in many eastern and midland counties of England and some areas of the south and west. Successful breeding was especially noticeable in areas where concerted conservation efforts had been directed during the last 25 years, as part of the national species recovery strategy. This strategy specifically recommended the targeting of conservation work into the river valleys of Britain and other areas of low ground where winter climate is generally less harsh and most suited to barn owls. We must always remember that the barn owl is at the northern limit of its world range here in the UK, being a species which is poorly adapted to survive during harsh winters. For some barn owls, perhaps as many as 30% of those which nested early, second clutches of eggs were laid in late July and early August. As is often the case these second clutches were larger than firsts with between seven and nine eggs being laid at some sites and between 10 and 14 at a few others. Although these pairs had produced up to seven large young by mid October not all survived well, with some clutches or broods of small young, abandoned. I am of the opinion that this is most likely the result of adult males having insufficient energy or inclination to hunt and to deliver food to their brooding partners after such a long season, which for these birds, began six months earlier in early March. The relatively high failure rate for second broods, although unfortunate, is not unusual here in Britain, whereas in warmer climes where occasionally three broods are produced in a single year, success rates are often much higher. The high abundance of voles in 2011 and the attempt of barn owls to double brood is likely to mean that it will be a less successful breeding year for this species in 2012 and 2013 when vole numbers which peak every three to four years, will be at the low phase of their cyclical abundance. Colin Shawyer BOCN Co-ordinator UK and Ireland Email: bocnenquiries@aol.com The Barn Owl is specially protected under Schedule 1 of the Wildlife and Countryside Act, making it unlawful to intentionally or recklessly disturb it whilst it is preparing to nest or is at the nest with eggs or young, or to disturb its dependent young. Inspection of nest sites can only be undertaken by experienced fieldworkers holding a licence issued by the appropriate countryside agency: Countryside Council for Wales, Natural England, Northern Ireland Environment Agency, Scottish Natural Heritage |
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Update on season Story dated: 5/30/2011 Earlier in the year I suggested that provided we did not get a further prolonged fall of heavy snow in March, Barn Owls should be able to achieve breeding condition for egg-laying at the normal time in April/May and go on to produce young in greater numbers than during the last three years. Nest visits during April indicated that vole numbers were especially high with many Barn Owls laying their first egg between 6th and 11th April, three weeks earlier than usual. Little Owls and Kestrels were not far behind. By mid-May chicks of all three species were hatching. (See Bob Sheppard's update on Little Owls on the BOCN Forum). Although at some traditionally-used Barn Owl sites we were missing the old time favourites, many had been successfully replaced by young first-year owls with the result that occupancy of nestboxes by breeding pairs remains high this year. I therefore, expect that most of the traditional Barn Owl territories, at least in low-lying regions of England and the river valleys in Wales and Scotland (below about 150m), will be occupied and that overall the breeding population of this species in Britain as a whole will have seen little change. Normally we can predict that when Barn Owls lay their first egg before mid-April, a proportion which choose not to moult will go on to double-brood in July. This April was the warmest in central England since records began more than 350 years ago and was the fourth sunniest in the UK in the past 100 years and the sixth driest. The only concern, which we believe caused problems last year, is the effect this spring drought might have on the growth of grass. Lush young stems provide field voles with a critical source of food and as we know, young barn owls rely on the abundance of this small mammal during the summer months for food. We, like the farmers, will be grateful for some rainfall. Colin Shawyer BOCN Co-ordinator UK and Ireland Email: bocnenquiries@aol.com The Barn Owl is specially protected under Schedule 1 of the Wildlife and Countryside Act, making it unlawful to intentionally or recklessly disturb it whilst it is preparing to nest or is at the nest with eggs or young, or to disturb its dependent young. Inspection of nest sites can only be undertaken by experienced fieldworkers holding a licence issued by the appropriate countryside agency: Countryside Council for Wales, Natural England, Northern Ireland Environment Agency, Scottish Natural Heritage |
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Newsflash Story dated: 5/4/2011 The Barn Owl breeding season has begun at an owl loft site in Cornwall. Camera footage has revealed that the Barn Owl laid her first egg on Saturday 2nd April, two days earlier than last year. The pair has been resident here for the last three years and have been on site throughout the winter. This is one of the very earliest breeding sites in the UK, both for last year and this year. The Barn Owl is specially protected under Schedule 1 of the Wildlife and Countryside Act, making it unlawful to intentionally or recklessly disturb it whilst it is preparing to nest or is at the nest with eggs or young, or to disturb its dependent young. Inspection of nest sites can only be undertaken by experienced fieldworkers holding a licence issued by the appropriate countryside agency: Countryside Council for Wales, Natural England, Northern Ireland Environment Agency, Scottish Natural Heritage |
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