Saturday, 22 July 2017

Ashridge barn owl success

One of the new barn owl boxes at Ashridge were put to good use with fantastic results. The barn owl boxes made by National Trust volunteer, Phil Penn, were erected last summer around the Ashridge estate. The grasslands of the Ashridge Estate form the largest continuous area of chalk grassland in the Chilterns. With the variety in structure including mixed scrub, arable reversion grassland and short turf species-rich areas there is plenty of habitat for small mammals and owls as well as the more typical flora and insect fauna associated with this habitat.

One of the boxes built by Phil was chosen to house two rescued barn owls that had been cared for at Tiggywinkles Wildlife Hospital and were ready for release. The area had been carefully assessed to make sure that there was sufficient good hunting habitat around the box site and there were no other owls already using the area and then the pair of rescued owls were placed in the box with a few days food supply. After that was used up they would have to rely on their own hunting skills to find enough food.

When the box was checked in May it was empty but Emily, the National Trust ranger accompanied by Katy from Tiggywinkles were thrilled to find two barn owls fly out of a second box that was sited close by. Certain that these were the released owls the box was left undisturbed for another month. When I went with Emily to check in mid-June we were extremely pleased to find an adult female barn owl with two small chicks in the box.

The chicks were a bit too small to ring so we left them for another month with fingers crossed that the adults would continue to find enough food to keep both chicks alive. At the next visit on 13th July, we found two beautiful large chicks in the box and they were taken out to be ringed, measured and weighed.

The young barn owls are carefully taken out of the box.

Barn owl chick approximately 6 weeks old.
The chicks were approximately six weeks old and the adult feathers were half grown. One chick was more developed than the other which is normal as the chicks hatch asynchronously although they actually weighed almost exactly the same 335g - 340g. The older chick was possibly a female as there were already signs of black flecking on the adult feathers but the primaries and tail were quite pale.
Black flecking on the thigh
smallest chick

Adult feathers half grown through the down.

The chicks were returned to the box still calm and sleepy. Fantastic work by everyone involved.

(NB Emily is a licenced BTO ringer with Tring Ringing Group and has the appropriate schedule 1 licence to disturb a barn owl nest site for the purpose of ringing and nest recording.)

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