Rooks are today a familiar
sight and sound within the landscape of Mainland Orkney. It has not always been
so and it is likely that this species is a quite recent coloniser of our
islands due to its observed preference for tall trees in which to nest and its
close association with human agricultural activity (Balmer et al 2013). In Scotland, Scots Pine Pinus sylvestris, is the most frequently used tree for nesting (Forrester and Andrews 2007) but in
Orkney it is Sycamore Acer pseudoplatanus
that is favoured (pers obs), and all
the major rookeries in the county are established in trees of this species.
Rook
Corvids, similar to the crows
we are familiar with today, probably evolved about 17 million years ago. The
pre-historic record of Rook is confused as the species is difficult to separate
from Carrion Crow and other congeners unless the skull is available. Typically
information from the Pleistocene in the UK involves single bones found in caves
(Harrison 1987). In Orkney the early Holocene
was characterised by the retreat of the ice which most likely departed Orkney
16,000 years ago (www.landforms.eu). Once the ice had gone
the vegetation of the islands rapidly established itself and the transition
from grassland to woodland began to take place in the warming climate. Between
8 – 9,000 years ago woodland began to expand across the county and this
vegetation type remained dominant in the West Mainland until 5,600 years ago (Bunting www.landforms.eu). The
woodland community was mainly Hazel Corylus avellana, Birch Betula
and Willow Salix and possibly Alder Alnus glutinosa at wetland
edges, however evidence for the presence of Oak Quercus and Scots Pine Pinus
sylvestris are within the pollen record (Bunting www.landforms.eu). The decline of
woodland coincided with human agricultural activity and the cooling of the
climate, and in this period it is possible that Rook was present as the mix of
woodland and human agricultural activity would have created the preferred
conditions for the species where it is found in most abundance today. This is
pure conjecture, and there is currently no evidence that Rooks were present in
Orkney at this time. Within a relatively short time the “woodland period”
passed and with the trees eliminated the islands, devoid of suitable nest
sites, became an unsuitable habitat for Rook.
Rookery, Nisthouse, Harray
In Scotland, Rook was believed
to be historically common but it declined during the 18th century (Forrester and Andrews 2007). The Rev
George Low in his A Tour Through the Islands of Orkney and Shetland 1774 stated
that “Rook was of doubtful occurrence”. Rook was recorded as “Never seen on any
of the islands” by Salmon in 1831. The first evidence of Rook occurring in
Orkney is found in the Vertebrate Fauna of Orkney (Buckley
Thomas E, John Alexander, Douglas D, A, 1891). This publication records “a small flock near Papdale in 1846”. By 1878 the same reference records “about 30
nests near Muddiesdale.” These dates correspond closely to the timing of the
establishment of Sycamore Acer
pseudoplatanus in the county, a tree species that was perhaps only
successfully introduced into the UK in the 1760s. Indeed there was no Gaelic
name for Sycamore until 1772, suggesting it was not well known in Scotland
prior to that date and it is known that the tree was not extensively planted in
the country until the later part of the 19th century(M. Palmer www mikepalmer.co.uk). It would seem that,
increased agricultural activity by humans, and the availability of suitable
nesting sites in Sycamore, along with another warming of climate in the later
years of the 19th century, combined at this time to make Orkney suitable
for colonisation by Rook.
David Lack was
present in Orkney between March and August 1941 as part of his National Service
and during this time he visited as many of the islands as he could and recorded
the birds he found, his findings were published in Ibis in two parts, in
October 1942 and January 1943 (Lack D.
1942 and 1943). On Mainland Lack found Rook breeding at Berstane, St Ola, a
few nests in Kirkwall and a few other small colonies. On Hoy he found a colony
in Sycamore near Orgil but none at Melsetter where a colony had apparently
existed in the past. One pair was nesting at St Margaret’s Hope, South
Ronaldsay. Lack did visit Rousay but found no breeding Rooks there. Rooks were
seen on Shapinsay but there were no breeding pairs on that island. Unfortunately
Lack does not record the number of nests he found at any of the sites bar St
Margaret’s Hope.
In more recent times there
have been a number of surveys of the rookeries of Orkney. The last survey of
Orkney rookeries by E.R. Meek and R.J. Simpson took place in 2010. The
rookeries had previously been surveyed irregularly, see Table 1, and it seemed timely
to repeat the work. Field work was conducted during April and May, with the
majority of counts taking place in the last two weeks of April. The results are
shown in Table 1 below which includes the counts from the previous five
surveys.
Table 1. Results of rookery surveys, Orkney, 1975 –
2017.
Rookery
|
1975
|
1982
|
1987
|
1996
|
2010
|
2017
|
Rousay
|
||||||
Westness
|
52
|
1
|
18
|
0
|
0
|
0
|
Trumland
|
0
|
0
|
0
|
19
|
0
|
0
|
Evie
|
||||||
Woodwick
House
|
244
|
140
|
57
|
363
|
273
|
191
|
Harray
|
||||||
Nisthouse
|
0
|
50
|
88
|
0
|
71
|
56
|
The Manse
|
0
|
0
|
0
|
0
|
0
|
79
|
Hybreck
|
0
|
0
|
0
|
0
|
0
|
7
|
Firth
|
||||||
Binscarth
|
8
|
218
|
168
|
216
|
129
|
44
|
Heddle Rd
|
0
|
0
|
0
|
0
|
68
|
91
|
Kirkwall
|
||||||
Town
|
307
|
389
|
566
|
640
|
467
|
551
|
Berstane
|
225
|
337
|
224
|
338
|
288
|
182
|
Holm
|
||||||
Graemeshall
|
0
|
17
|
44
|
0
|
0
|
0
|
Tankerness
|
||||||
Whitecleat
|
0
|
0
|
0
|
10
|
28
|
0
|
The Mount
|
0
|
0
|
0
|
1
|
0
|
0
|
Orphir
|
||||||
Grindelay
|
29
|
80
|
89
|
144
|
121
|
137
|
Gyre
|
0
|
0
|
21
|
0
|
0
|
0
|
Stromness
|
||||||
Town
|
39
|
115
|
142
|
167
|
186
|
137
|
Hoy
|
||||||
Bu
|
43
|
0
|
0
|
0
|
0
|
0
|
Melsetter
|
10
|
0
|
2
|
0
|
0
|
0
|
Totals
|
957
|
1347
|
1419
|
1898
|
1631
|
1475
|
(Meek E.R. and Simpson R.J. 2010)
Additionally, the Orkney Bird
Report of 2002 reports that there were “almost 2,000 pairs” across the county (Williams J. 2003).
The total of 1,475 nests in
2017 is a decrease on the 2010 total by 9.6%. The decrease since the peak count
of 1,898 in 1996 is 22.3%. These decreases should be seen in the context of the
increase between 1975 and 2017 of 498 nests or 52.0%. Between 1975 and 1996
there was a national and UK increase in the number of Rooks of about 40% (Marchant and Gregory 1999), the increase
in Orkney within this period was 98%. There is evidence of a small decline
across the UK in the decade to 2011 (Balmer
et al 2013) so it is not unexpected to find that decline reflected in
Orkney. Elsewhere in Scotland changes in agricultural practice have resulted in
significant changes to the Rook population. There is little evidence of any
wide-scale persecution of Rook in Orkney which has demonstrably had an impact
on breeding numbers elsewhere (McGhee H.
2000). Continuing to survey rookeries throughout the county on an
occasional basis in order to monitor the number of breeding pairs would be a
worthwhile activity. Relating fluctuations in breeding Rook numbers to any
changes in agricultural practice could prove to be of particular interest.
References
Balmer Dawn et al; Bird Atlas
2007 – 11, 2013.
Buckley Thomas E, John Alexander, Douglas D, A Vertebrate Fauna of the Orkney Islands, 1891.
Bunting Jane
http://www.landforms.eu/orkney/holocene%20vegetation.htm
Forrester Ron and Andrews Ian
(eds); The Birds of Scotland, 2007.
Harrison. C.J.O. Proc. Univ. Bristol
Spelacol.Sac,198,18(I), 81-104 Pleistocene and prehistoric birds of south-west
Britain,1987.
Lack D. The
Breeding Birds of Orkney, Ibis Vols 84 and 85, 1942 and 1943.
Marchant J.H. & Gregory
R.D; Numbers of nesting Rooks Corvus
frugilegus in the United Kingdom in 1996, Bird Study, 46:3, 258-273, 1999.
McGhee H. Scottish Birds 21,
2000.
Meek E.R. and Simpson R.J; Orkney Bird Report 2010; 2011.
Palmer M. www mikepalmer.co.uk
Williams Jim (ed); Orkney Bird
Report 2002.
www.landforms.eu
Acknowledgements
My thanks to the various
landowners who permitted access for the survey counts to take place.
A number of observers
contributed to the survey counts and I am particularly grateful to Dawson
Shearer who counted in Kirkwall town. Malcolm Russell and Helen Crabtree also
contributed counts to this survey. Other advice and observations came from Alan
Leitch, Christine Hall, Brian Ribbands, Tim Dean and Ian Cunningham.
Alastair Forsyth
April 2018
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