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3oRm Aspects oJT the 
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■1LS. 
1 • General. 
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During 1953 and 1954 I watched the behaviour of 
shags during the months of Itarch and April. l£ost of the 
observations were toad# at the nesting cliffs but the joint of 
observation in 1^53 was in full view of roc v » at the foot of 
the cliffs where the birds used to collect to reen and 
sleep when the rocks were uncovered by the tide. I found that 
all the courtshio behaviour might take place on the iretnlng rooks 
though leas co nonly than on the nests. In 1953 roost of the 
observations were made at the nesting cliffs near the Stack, 
especially on one cliff where three >alr» finally reared young, 
but in 1954 thie cliff was less interesting and I watched instead 
at a plae* on the porth-west of the island where two pairs 
reared young. In addition to the >aira which nested success- 
fully there were always several other airs which went through 
the courtship phase and even attempted to build u nest. There 
w#r« also unmated birds who regularly tried to occupy ledges or 
find mates. 
t 
It was soon very clear how important it would be 
if the individuals could be recognised and I found that the 
pattern of dark and light flecks on the yellow and black area 
at the base of the mouth could often be used. There were 
other small characters of the plumage which were also sometimes 
useful and in this way the identity of certain individuals 
could be established. Gome individuals were already ringed 
and In 1953 two raffles were colour ringed with chicken ring®. rj ne 
of the colour ringed birds had a rather strikin' and unusual 
yellow patch and the ringing confirmed that he retained this 
feature in the following year. It should be mentioned that 
as the » ason advance* the oiitllnea of the yellow patch of the 
adults becomes dulled and the yellow colour begins to Bores* 
along the lower mandible until th" winter condition is reached. 
Then in the winter or early spring the yellow recedes till it 
occupies, viewed from th© outside, only the are& around the 
base of the mouth. The new wire fori) in the surly oart of 
the soring when th© yellow natch la most striking and the crest 
is best develooed. I<lven before incubation begins both have 
become les-' lttpresslve. In Just the same way tie white rianr 
patches of the Cormorant, which seem to be used in pair formation, 
often disappear by the tiro© the eggs are 1 Id, 
I collected notes on the relation between the plumage 
of birds and the interest they took in reproductive afairs. ney 
showed that the earliest birds to come into breeding condition 
were those showing most completely the adult characters. A 
little later one saw other birds beginning who still retails, 
a trace of brownish on the chin or yellowing of the lower mandible 
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