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The Barn Owl has not
only declined dramatically in Britain but also throughout
Europe. In 1932 George Blaker estimated that the British
population of Barn Owls was about 12,000 and even this estimate
revealed a substantial drop in numbers from what was once
Britain's commonest owl.
A
further survey of Britain and Ireland that was undertaken
between 1982-1985 concluded that there were approximately 4500
pairs breeding in Britain. Thus a further decline of more than
two thirds of the population had occurred between 1932 and 1985.
This has prompted it to be amber rated in the list of Birds of
Conservation Concern having had a moderate (25-49%) decline in
the UK breeding population or range over the previous 25 years.
In addition it is afforded Schedule 1 status and this special
protection applies to species, which are scarce or are rarely
breeding in the UK. Under the Wildlife and Countryside Act 1981
as amended by the Environmental Protection Act 1990, it is an
offence, liable to special penalty, to intentionally disturb any
wild bird included in the Schedule while it is building a nest
or is in, on, or near a nest containing eggs or young or to
disturb dependent young of such a bird. |
| Photo Richard Brooks |
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Barn Owls nest in hollow trees and also in buildings, some reasons
for this decline have included the loss of nest sites. Many trees
were lost during the Dutch Elm disease outbreak in the sixties and
also in the gales of 1987 and 1990, additionally many mature old
trees in some cases many hundreds of years old simply died of old
age. Traditional sites in old farm buildings have also been lost
as barns have been converted to other use including residential
occupation or have simply been allowed to deteriorate until they
collapsed or were demolished. Tea chests with a front and entrance
hole make ideal nest boxes, although sometimes Barn Owls opt to
nest in some other places such as disused water tanks or even
hoppers!
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Photos
John Middleton
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Most of the barn Owls that we monitor are
in nest boxes such as these although some are nesting in natural tree
cavities.
It is important to monitor this
species in order that the current population levels can be assessed to
determine whether any further declines have occurred. North West Norfolk
Ringing Group participate in a national project that was started in the
year 2000 and co-ordinated by the British Trust for Ornithology to
provide ongoing assessments of the UK Barn Owl population. Monitoring
consists of a visit to the nest site by specially trained and licensed
bird ringers in the breeding season. Details of occupancy rates, breeding performance and
survival are recorded and any
young are ringed with uniquely numbered leg rings provided by the
British Trust for Ornithology.
Currently we are monitoring over 400 potential nest sites. You can view
the nest sites that the Group monitor by clicking
distribution
map
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Naked and helpless
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Female and chicks
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These owlets begin to show the facial disc.
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Inquisitive youngsters,
the bird second from the left is almost certainly a female.
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Photos Richard Brooks
These young owlets have
probably already made some exploratory excursions outside the nest
box and are almost ready to fledge. The BTO leg rings enable us to
keep track of their movements. |
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If the young are too small or the female is
still incubating eggs a repeat visit is made after sufficient time has
elapsed for the eggs to hatch or the young to grow sufficiently large to
be ringed. |
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This is a recently
fledged youngster.
From the spotting on the breast and the pink/buff band we can
see this is a young female
Photo Richard Brooks |
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Juvenile Barn Owls remain in
the nest for approximately ten weeks but may venture outside the
nest box prior to fledging completely, and even when flying
strongly they may return to the nest site to roost during the day.
However after this time the young owls begin to move away from
their natal site to begin the process of finding a territory and a
mate of their own. Many young owls die during this time, becoming
road traffic casualties or starving and at this time they are very
vulnerable and juvenile mortality can be as much as 75%. If they
can survive until the following spring by then they have usually
ceased to wander, having found a territory and then the mortality
rate falls although adults still become victims to road traffic.
Most Barn Owls reported dead to the North West Norfolk RG move
between 5 and 25 kilometres from where they hatched although some
have moved as far as 100 kilometres.
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The
preferred prey item of Barn Owls is the field vole Microtus
agrestiss although they will take a variety of other small
mammals including Bank Vole Clethrionomys glareolus, Wood
and Yellow-necked Mice Apodemus sylvaticussandand A.
flavicollis, Common Shrew Sorex araneus, Pygmy Shrew Sorex
minutus, Water Shrew Neomys fodiens, Water Vole Arvicola
terrestris, Harvest Mouse Micromys minutus, House Mouse Mus domesticuss and Brown Rat Rattus
norvegicus.This list is not exhaustive and from
analysis of Barn Owl pellets other prey items including
Mole Talpa europaeaa and some bat species have been
recorded. The field vole population is cyclic, tending to
reach a peak and then falling off and then rising again
during the following years. |
Good berry crops and mild winters play their part in this
fluctuation of the small mammal population. Barn Owl breeding
success (or failure) fluctuates but depends largely on the
availability of small mammal prey. |
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