The Raven’s
loud, far carrying “cronk” call, often accompanied by a tumbling display
flight, is the most evocative sound of the uplands in late winter and early
Spring. The pair wheel and soar together, their flight so synchronised that the
wings appear to be joined at the tips. Ravens breed very early, and most eggs
are laid before the end of February.
Pairs are very
territorial, and nests are widely spaced, so the population is still small,
although it is increasing rapidly. The County population grew from around 50 to
around 175 breeding pairs during the 1990s. It has continued to increase since,
to around 250 pairs by 2003.
Mortality is high
– most Ravens die before they are two years old – so many young birds are
needed to ensure that enough reach breeding age. Therefore there are always more
immature birds, three years old or less, than there are adult breeding birds.
Flocks of up to 80 are now being seen. Large flocks (over 10) should be
reported to the
Ravens are
omnivorous, and mainly eat carrion. The population growth is attributed mainly
to a better food supply from the increase in carrion left lying round the
uplands – sheep carcasses used to be removed and taken to the knackers yard,
but the financial incentive for this disappeared when the Government changed the
regulations governing the use of materials reclaimed from carcasses, to combat
the spread of BSE, in the early 1990s. Increased carrion from lambing out on the
hillsides (dead lambs, and after-birth) has helped increase the number of young
birds fledging, and milder winters and reduction in illegal poisoning have also
reduced mortality.
The Shropshire
Raven Study Group has been following the fortunes of Ravens in the County since
1994. Little is known about how long
they live in the wild, how old they are before they start breeding, and how far
they move from their natal area to their adult breeding site. To answer these
questions, part of the Group’s work included putting a coloured ring on one
leg of each chick while it was still in the nest. Colour-rings were put on 781
nestlings from 223 nests in
Group members are
now visiting all known Raven nest sites, and trying to find new ones, to find
out where the colour-ringed birds are turning up in the breeding population. If
either of the nesting birds has a colour-ring, observing the colour, and reading
the letters, tells us how old the bird is, and where it came from.
In 2004, 45 adult breeding Ravens were found
with colour rings, with an average age of 7 years old. We managed to read 40 of
them. Both birds had rings at 7 sites. In 2005, 45 were found again (38 were
read), but 15 were different birds. The average age was almost 8 years old.
Since the Project started, we have read the rings on 167 occasions on 70
different individuals.
A female Raven
which fledged from a site close to the Welsh border in 1994 has been nesting
within a couple of miles of Church Stretton for the last few years.
In 2004, she became the first wild
We are thus
building up a picture of how old young birds are when they first breed, their
life span, and how far they move. Most birds are at least three years old before
they nest, usually older, and it appears that females move further from their
natal site than males – presumably a natural selection defence against
inbreeding. This is a nationally-important Study, as evidenced by grants from
the British Trust for Ornithology, and sponsorship from Swarovski Optik (provision of a telescope to read the rings).
With your help we can learn much more.
We need more help
to check known nest sites and find new ones, please. The Raven population is
increasing, and their range is expanding, so there must be many nest sites with
colour-ringed birds that we do not know about.
Raven nests might be found anywhere in the County now, where there are
suitable large trees for nests.
Even if you cannot
help with the fieldwork, you could still provide important information. We
particularly want breeding season records between February and May.
Please let us know immediately if you find:-
·
Evidence of a nest – the most commonly
observed evidence of an active nest is seeing Ravens drive off other predatory
birds (particularly Buzzards), but pairs displaying in February, repeated
territorial calling, being aggressive to humans, or carrying nest material or
food, are equally good evidence.
·
Ravens in places where they have not been
seen or heard previously.
·
Ravens with colour rings on (it is
possible to see whether or not a bird has a colour ring in good light, through
binoculars, if it is perched, or feeding on the ground, or flying low directly
overhead. A telescope is necessary only to read the letters on the ring, and we
can do that for you.
We
will come and check the nesting pair for colour-rings, and, if either bird has
one, we will be able to tell you its life history
If you know of a Ravens’ nest, or suspect
one, please don’t assume we know about it already, even if it has been there
for several years! Offers of help, and reports of Ravens, as soon as
possible, please,
to