Research and development
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County Barn Owl surveys
The most intensively surveyed areas in the whole of the UK are Devon (where the Barn Owl Trust is based) and Cornwall (a neighbouring county). Each county has now been surveyed twice: Devon in 1993 & 2003, and Cornwall in 1994 & 2004. The aim of each survey was to establish the number and distribution of known sites where Barn Owls were breeding or roosting and consisted of rechecking all the sites where Barn Owls had been recorded during the previous ten years.
After the second Devon survey, we were able to quantify changes in the number of known roost and nest sites in each local authority district as an aid to assessing the usefulness of the district Barn Owl Schemes we had carried out between 1997 and 2002. Fortunately the results showed that the county population estimate had gone up by 37% and that most of the increase was in the areas where we'd done most of our conservation work!
Just to give you some idea of the scale of these surveys, in one calendar year in Devon we checked 1,176 sites!
Population monitoring and BTO ringing
The Barn Owl Trust carries out detailed monitoring of the wild population within its main geographical area of Devon (the second largest county in England) and southeast Cornwall. Dotted across this vast area we have 72 Annual Monitoring Sites. These are sites where Barn Owls are likely to breed having nested there in previous years. By visiting the same sites each year we are able to quantify annual trends in site occupation and through licensed nest inspections we are able to quantify nesting success. At many of these sites we have also erected nestboxes and advised landowners on the species habitat requirements.
When we encounter broods of young Barn Owls we usually fit each one with a metal ring on one ankle. Each ring is uniquely numbered and provides a reliable and harmless method of identifying birds as individuals. This is part of the national ringing scheme organised by the British Trust for Ornithology (see Links). Ringing and the subsequent recovery of ringed birds provides a wealth of information on survival as well as mortality and is perhaps the most valuable tool available to ornithology. The information collected through ringing is vitally important for population monitoring, research, and most importantly, conservation.
Identifying priority areas for Barn Owl conservation in Britain
In 2005 Nick Askew, a student at the University of York, approached the Barn Owl Trust requesting support for a special research project he wanted to carry out during the final year of his PhD. The main project aim was to quantify the amount of good habitat needed by Barn Owls in various types of landscape and then combine this data with information on the habitats currently available across England, Scotland, and Wales. In so doing, Nick hoped to produce new maps showing the suitability (for Barn Owls) of every 1km square across all three countries - thus identifying priority areas for conservation work.
"How much habitat does a pair of Barn Owls need?" was by far the biggest and most important unanswered question in Barn Owl conservation so we were very pleased to support Nick's project. Indeed, we considered this research to be so important that it has it's own webpage. See link >
Fallen owlet investigation and the development of safer Barn Owl nestbox designs
Each year the Barn Owl Trust gets numerous Live Bird Emergency Calls concerning young Barn Owls falling from nests and unfortunately, in many cases, they don't survive. This can happen because they don't get enough food from their parents and/or because the nest place is not safe enough. Unfortunately, the adults often ignore nestlings that have fallen to the ground whilst other young remain in the nest. In an effort to combat this problem we radically changed the design of our nestboxes for use in buildings. Up to that time nestboxes usually had the access hole and exercise tray on the same level as the nest itself. From 1997 we started to erect hundreds of 'deep' nestboxes. These have a drop of 46 cm (18") from the bottom of the access hole to the nest. In the years that followed, we continued to get reports of owlets falling from ledges and old-style boxes but none from sites where Barn Owls were nesting in the new deep boxes.
In Spring 2006, thanks to the arrival of research volunteer Chiara Bettega, we at last had the time to search our own records and investigate recorded cases of fallen owlets. We uncovered 238 incidents! 75% of these were from old-style flat boxes and open fronted tea chests. Only 4% were recorded at 'deep nestbox' sites and in virtually every case this was because the effective depth had been reduced by the presence of Jackdaw nest material. When time allows we hope to produce a report on this subject.
Radio tracking Barn Owls
Radio tracking Barn Owls involves the use of a tiny transmitter that is attached to the owl in such a way that it has no effect on behaviour. The owls' movements are then followed using hand-held receivers and the position of the owl is determined by triangulation. Radio tracking helps answer questions such as: how do Barn Owls use the typical farmed landscapes and do they hunt mostly along hedges? Do they only hunt over grassland? To what extent do they use arable land? In 1998 and 1999 we carried out our first radio tracking study in collaboration with Spanish University students. Unfortunately we encountered major practical problems caused by equipment limitations and the effect of extremely hilly terrain and wet weather. However, we learned a huge amount about the practical problems of radio tracking.
In 2008 we radio tagged nine nestling Barn Owls in order to study their dispersal behaviour. Almost a year later we were still tracking one of them. In 2009 we tagged and tracked a further three nestlings and successfully followed their dispersal. In 2009 & 2010 we carried out a joint project with the Barn Owl Foundation (Hungary) and radio tagged breeding pairs in SW Hungary in SW England to determine home range sizes and compare temporal activity patterns in relation to weather. Our 2008 & 2009/10 projects were in collaboration with Ambios, a not-for-profit organisation that secures funding for voluntary trainee placements and the transference of skills across Europe. We are very grateful to Brian Cresswell at Biotrack for all his assistance. Results from our radio tracking studies were featured in the Barn Owl Conservation Handbook, published in July 2012
Survival and site fidelity of released captive-bred Barn Owls
Barn Owl reintroduction involves the deliberate release of captive-bred birds into an area from which the wild population has been lost with the long-term aim of establishing self-sustaining wild birds.
By the time the Trust started in 1988, its co-founders had already been running a breed-and-release scheme for three years. This was one of the few schemes that included extensive survey and monitoring work at every release site (both before and after), detailed record keeping, and the BTO-ringing of all birds prior to release. In 1989 we produced the first-ever report on the reintroduction of captive-bred Barn Owls in Britain comparing their survival with that of wild birds in the same region during the same years. This work resulted in the Trust being invited to join the Nature Conservancy Council Barn Owl Liaison Group, and later the Department of Environment (DoE) Barn Owl Working Group. At the request of the DoE (UK government), we produced the first ‘Code of Practice for the release of captive-bred Barn Owls'. In 2001 a second Barn Owl Trust Reintroduction Report was published detailing the release of 223 birds from 41 sites over a 6 year period.
Barn conversions and the effects of site loss on resident birds
The conversion of old barns to dwellings was commonplace in the 1980's (and still is in some areas) but its effect on resident Barn Owls was unknown. In April 1990 we designed a scientific research project to investigate the effect of site loss on the local Barn Owl distribution and status, the usefulness of incorporating provision for Barn Owls into conversions, overall site availability and the rate of site loss due to conversions, decay and demolition.
One of the important findings of the study was that the resident owls abandoned several sites when one occupied site was lost. However, where provision for Barn Owls was incorporated into conversions, the birds generally stayed. Following the publication of the full ‘Barn Conversion Research Project Report' we produced the first edition of ‘Barn Owls on Site, a guide for developers and planners' which now in its second edition and published by English Nature (now Natural England). Many local authorities have adopted some or all of the Trust's recommendations and often the possible future presence of Barn Owls is considered, and provision for the birds within conversions and other developments is required as part of the planning consent. Part of the original research project formed the basis for the Trust's first paper to appear in a scientific journal: Ramsden, D. J. (1998) Effect of barn conversions on local populations of Barn Owl Tyto alba. Bird Study 45, 68-76, BTO, Thetford.
The most thorough and up-to-date guidance on Barn Owls and rural developments was published in the Spring of 2009 by BOT, with funding and support by Natural England. "Barn Owls and Rural Planning Applications - a Guide" is aimed at applicants, ecologists and planners, indeed anyone involved with rural developments where Barn Owls are or might be an issue and includes detailed information on where, when, how and why provision for Barn Owls should be made during rural developments.
Major road mortality and its effect on Barn Owl populations
It is well known that Barn Owls are frequently found dead on roads - especially major roads such as motorways and dual carriageways. However until 2003 there was a severe shortage of published information on the reasons behind road mortality and its importance as a possible cause of population decline. After collecting all available research papers, in 1996 the Trust began producing a literature review, and preliminary analysis of our own extensive datasets. After several false starts (due to pressure of other work) we finally began to analyse data collected over a fifteen year period, and in 2003 the Barn Owl Trust produced the first published research highlighting the effects that major roads have on Britain's Barn Owl population.
Major roads cause the complete absence of breeding Barn Owls within 0.5 km either side of the road, severe depletion of their population within 0.5-2.5 km of the road and some depletion within 2.5-8 km of the road. Almost the entire British Barn Owl population is to some extent suppressed by the presence of major roads. The presence of major roads in rural England has removed Barn Owls from an area of between 8,100 and 16,200 sq km and depleted the population over an area of roughly 48,600 sq km - 40% of the total area of rural England. Our report ‘Barn Owls and Major Roads' recommended changes in the design and management of major road verges and the Trust is now consulted by the Highways Agency in connection with their Design Manual for Roads and Bridges.
There is more information on all of the above topics in the Barn Owl Conservation Handbook