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Text Version Last Updated: January 2, 2014 19:30

Sunday 21st December, 2014

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Juvenile Little Owl Dispersal and Survival

Emily Joachim’s Trust-backed PhD study into the decline of the Little Owl in Britain Athene noctua vidallii is now underway. The Little Owl has suffered a dramatic decline across much of Europe since the 1950’s and has been classified as a Species of European Conservation Concern. An ideal Little Owl habitat provides prey availability, prey accessibility, roosting sites, nesting sites with limited predation pressure. Little Owls are able to cope with environmental change reasonably well, so their recent decline across much of Europe suggests that their tolerable limits are being exceeded.
The decline in the British population of Little Owls could be linked with a reduction in the number of juveniles that survive the post fledging period. As with most owl species, the owlet branches for a period before fledging, residing close to their natal site in their parent’s territory. Although the owlets are mobile at this stage, they remain dependant on their parents for at least another month, developing their life skills with the assistance of their parents. Dispersal occurs when a juvenile Little Owl leaves its natal territory to mature and find its own territory. A high mortality rate is associated with this stage as it is the first time that they are 100 % reliant on themselves to survive. If a juvenile Little Owl manages to gain enough experience, survives the post fledging period and secures a territory by October, they are much more likely to survive the winter and breed in the spring.

Tagged Little Owlet
Tagged Owlet

Radio-tracking is being used to look at juvenile survival rates, time of fledging, post-fledging dispersal patterns and the causes of mortality in Little Owls. Seventeen juvenile Little Owls from seven broods have been fitted with leg mount radio tags at around 3 to 4 weeks old. The radio tags release radio signals that can be picked up using a receiver, enabling Emily to follow and locate the tagged owlets. The Little Owls used in this study are part of the Imber Conservation Group Raptor and Owl Nestbox project that was initiated by Major Nigel Lewis MBE and their natal sites are all either on or in the vicinity of Salisbury Plain. Nigel has been supervising Emily’s field work.

The tagged juveniles are being monitored once in a 24 hour period during daylight hours and the distance between fixings, distance from natal site and dispersal patterns are being recorded on a daily basis. At the end of the study, the owlets will be recorded as either being lost, having died or dispersed. Little Owl survival and dispersal patters will be correlated with land use and weather.

Emily at work
Emily at work
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