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Scientific research
Barn Owl Dispersal Project
Introduction
The purpose of the Barn Owl Dispersal Project is to find out what happens to young barn owls in their first year of life. We want to know when, how far and to where they disperse, where they roost and what they eat. Sadly, many of the juvenile barn owls will not survive the winter, and we want to discover the main causes of mortality. This latter aspect of the study is very important. There is very little reliable information about causes of death in barn owls because the alternative method to collect these data (ringing) is biased towards particular circumstance, such as road accidents, where there is a much higher chance of a body being found.
Radio tags
The range of the tags varies with the location of the owl, and the local habitat and topography. The best range (e.g. > 10 km) will be achieved when tracking from a hill to an owl that is roosting in a tree. If the owl is dead in a ditch, the range could be only a few hundred metres. Whatever the location of the owl, tracking from high points will always improve the signal range and is the best way to search for birds when they go missing. Effects of tags on owls The tags and harnesses were tested on juvenile barn owls in a pilot study in East Sussex in 2003. We used remote infra-red video recordings of barn owl nestlings before and after tagging to look for possible adverse effects on their behaviour, and we recaptured tagged owls several months after they fledged to check that the harnesses were not damaging their skin or feathers. We found that the young owls habituated to the tags immediately and there was no damage from the harness on the owls after they became free-flying. The radio-tagging is done under a licence issued to Brian Cresswell by the British Trust for Ornithology (BTO). Dispersal behaviour The young owls should stay near the nest site for the first few weeks after fledging, they may then disperse several kms (the average ringing recovery distance is 3-4 km, most are < 10 km). Eventually, if they survive, they should settle in one location and spend the winter there. This should have happened by the end of October, but the behaviour of individual birds will vary.
Supporting Organisations The Barn Owl Dispersal Project has received support from Wetland Trust Ltd and Beale Park. Biotrack Ltd. For more information about the E. Sussex pilot study (funded by Wetland Trust and Biotrack Ltd) please contact Brian Cresswell |
One of the young female birds we tagged in 2004 had a family of her own in a box about 2km from where she was raised. We tagged two of her chicks and at the time this report was written (Februaury 2006) one of these birds seems to have settled at a site near Shilingstone. The other sadly died. The main cause of death for the tagged barn owls has, as far as we can tell, been starvation. The has olny been one road casualty.