BTOCJ Garden Bird Watch - Blue Tit

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BTOCJ Garden Bird Watch - Blue Tit Powered By Docstoc
					Focus on the Carrion Crow
This is the only species of bird that takes two very different forms in different parts of
the British Isles. In the North-west of Scotland and in Ireland, the crows are Hooded
Crows with light grey bodies. The rest of us normally only see the completely black
Carrion Crows.
T     here have been many debates about the separateness – or
     otherwise – of the Carrion and Hooded Crows. The
concept of what makes a race of bird into a species is in flux at
                                                                       most of their nest predation when they have young themselves,
                                                                       and they only produce one brood a year. Most of their main
                                                                       prey species have several broods, including some before and
the moment. It is quite possible that there will be a change in        some after the most dangerous period. Chris Mead
the near future and the two forms of crow will be treated as
different species. This does seem very reasonable as these races
are very stable. Although there are thousands and thousands of
                                                                                      Carrion Crow
hybrid birds there are also vast areas of Europe where the forms
are totally pure. Hooded and Carrion Crows became separated
                                                                                     Fascinating Facts
during the last glaciation. It is believed that the genes for black
plumage became dominant in Iberia while ‘hoodie’ genes                 A smashing time
became the norm among an isolated population in the Balkans.           There are many reports of crows hammering away at
The races only came back together about 10,000 years ago as            windows and other reflective surfaces. This behaviour
the ice retreated. In Britain the area of overlap is basically along   can be very destructive with woodwork and putty
                                                                       destroyed. It is usually done by a territorial bird attacking
the Great Glen. This has changed considerably within recorded
                                                                       its own image, probably an inexperienced individual
history, indeed it has moved northwest by 30 km in the 20              newly ‘promoted’ from the non-breeding flock and just
years between the national volunteer surveys for our two Atlases       starting its territorial life. In one instance more than
of Breeding Birds (roughly 1970 to 1990). In Garden BirdWatch          £100,000 worth of damage was done to brand new
we treat them as one species. If you see a Hooded Crow in your         imported cars parked near a port. Windscreen seals
garden, please record ‘Carrion Crow’.                                  were pulled out, wipers torn off and wing mirrors trashed
       These crows are very different from the gregarious Rooks        – as well as scratches and dents caused to the paintwork.
with very well defended territories occupied by the breeding           Like Magpies, crows are on a small list of birds that can
pair throughout the year. These will normally be defended              be ‘controlled’. It is not correct to claim, as some
against intruders but if food resources in a territory become          opponents of bird protection have done in the press, that
very abundant, either temporarily (such as a dead sheep) or for        these birds are fully protected. However those who kill
                                                                       them have to be able to demonstrate that certain types of
an extended period (such as a rubbish tip), crows will share
                                                                       damage are being caused by the birds, as justification
them without too much squabbling. Sometimes as many as half            for their control. Vandalism to cars and windows is not
the crows in an area are non-breeding birds. These are not so          on the list!
territorial and may be seen in small flocks at almost any time of
year. They (and the territorial birds) sometimes form very big
                                                                       The gamekeepers armoury
communal roosts in the autumn and winter numbering
hundreds, or even thousands, of birds often with other species         One justification for control that is on the list is game
of crows. These attract birds from a very wide area and are            protection. Gamekeepers will not tolerate crows. It is easy
                                                                       to see what the killing range of a shotgun is in keepered
generally in woods – very noisy they are too!
                                                                       areas; rather less than the height that the wary and wily
       These are quite common birds in gardens with anything           crows are flying over you. There will always be a few of
up to a third of Garden BirdWatch forms reporting them each            these adaptable birds left alive! Using poison is definitely
year (compared with about 15% for Rook). Late spring and               not legal.This can indiscriminately destroy many other
early summer, when the birds are breeding, is the peak period          kinds of wildlife including rare and specially protected
for them to be seen. This is a peak period of conflict with garden     species. All incidents of wildlife poisoning (other than
owners, and pressure on the smaller birds in their gardens. The        ‘vermin’ such as rats or grey squirrels) should be reported
problem is that crows are expert nest finders and predate many         to the police or RSPB. However, trapping crows in cage
nests, especially in gardens where there are few places for            traps with a live bird as ‘bait’ is a common method of
thrushes and finches to conceal their open nests. In spring, crows     control that is perfectly legal as long as guidelines are
conduct their raids early, often just after dawn. The more             followed, so crow traps in the countryside should not be
                                                                       interfered with. Protected birds can be released unharmed
conspicuous Magpies that are obviously around the garden
                                                                       by the keeper if caught unintentionally.
during the day tend to get the blame. Like Magpies, crows do

                                                                       Crowing success
                                                                       There are probably as many as one and a quarter million
                                                                       breeding pairs of crows in Britain and Ireland. A third of
                                                                       a million are hoodies, ten or twenty thousand are hybrids.
                                                                       Many crows are unable to obtain breeding territory for
                                                                       several years, so there may easily be as many non-
                                              Carrion Crow             breeding birds in the population as well. This means
                                              photograph by            about five million adult birds in all, which would be about
                                              Mike Weston ©
                                              BTO                      2,500 tonnes of crow!

Reproduced from Bird Table                                                                                      No 24 - Winter 2000

				
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