of general post lwttten th© ledges. On successive mornlngo 
ono could observe again and. again the sane na it© rn of changes 
which became cod 1 flat! as new birds appeared in the circle of * 
hrbl tuees or old ones disappeared. Often it was difficult to 
decile whether the interest of an intruder ms re&Uy in the 
ledge or in a mate, and Indeed both occurred,, “but after a time 
aorae critical situation often arose so that one could decide. 
Th# study of the relationships of the individual a also 
t m the means by which they recognised on# another, 
done times the birds made ulsta>e which showed that they did 
not^ use the sane characters to recognise their acquaintances as 
Ud. I saw this for e«sr le In the relation of Nestor and the 
" • #ir * during th© period of day when th® birds were usually at 
th# colony th® female spent moat of her time at the neat while 
th® -ale, Leander*, frequently set off on trios to collect 
heat rate rial. But if Nestor where in the colony at th® tine 
he would at one© Interfere and leave hie ledge to circle 
ana 'and by Lottie. Occasionally however It was Lottie who left 
th# ledge, to go and feed or bathe. As she flew out I could 
often recognise her clearly xk by the conspicuous aluminium 
ring on one leg which was -la inly visible in flight both to re 
and XXx He* tor. i’o other bird In the colony had such © ring. 
But Nestor mistook thr departing bird for the sale and at once 
set out to try and land on the ledge by the defenceless female, 
»• h» thought. Bo was made rudely aware of his error and had to 
change direction at the last moment to avoid being violently 
attacked by the enraged Leander. 
L® rch 
time 
Attempted copulations were first 
and from that date mountings became 
eggs were Id, la a 
seen in th© middle of 
commoner up to the 
the role of the sale 
bird in copulation is to mount the female bit in some, including 
the shag, reversed copulations occur in which the female mounts 
the rrale. Hot only th© act of mounting but the rellalnary 
behaviour as well la reversed and the female may even attempt 
eloaeel contact fro® above. It is difficult to be sure whether 
this is ever achieved. Certainly it is lees common than in 
mountings with the male on top. The reason that shags (and 
cormorants) should have reverse copulations is still mysterious 
but certain consistencies are beginning to appear which 
may ultimately suggest a solution. 
X tried to find out how th© occurrence of co ulatlons 
varied with time, of day. A watch of thro© 3-hour periods or 
longer mas I on o p 9 and 23 April 1954 from first light to 
9s.m. f < and from 4 , m, till darV. ?:.a codings and 
goings of the is ivlduals was noted and also ths occurrence of 
mountings. These data have not been fully worked out yet but 
certain features are already clear. The frequency of mountings 
should obviously be relate! to the length of time the pair ie 
together at th® nest rather then th© complete period th® colony 
wo e under observation. Calculated on this basis the following 
