* 7 - 
for the pair would than have to conquer the a po t which Eight 
have been used for laying In the absence of the owner. 
Why should the terns need an advertising . display 
flight as well as a ground display to attract females ? Though 
they do nest (mnlnly) in the open the territories are relatively 
small so that the female, flying around, would si jul taneeusly 
he si thin sight *^nd sound of & number of stales *be ops ssekiog 
to attract her, Kales who develop® 1 an aerial display would 
not only be ©hie to press a their attentions more assiduously 
hut they would bo able to attract females fro® a ©u oh greater 
distance than if they could only a. t tract females by their 
postures and ©alls on the ground , One need not emphasise that 
a flying bird la more conspicuous than on® on the ground, If 
only by reason of the greater movement . Such advantages would 
accrue to no at 8 posies of birds and Indesd in n any different 
. groups a oowtshlp flight has been evolved to advertise the 
unrated a is, The gulls have an aerial threat display and 
this my have given rise to the aerial courtship of the terns. 
Th© la ok of aerial ©ouri in the gulls nay be 
due in part to their grantor relucts. nee to t» se 
flight than the smaller terns, . ■ . • - . • 
After the pair is firmly established the male bring® fish 
which are fed to the female. This is foreshadowed in the 
earlier retail e of the pair wh m m carries a fish, 
Unrated males who ere visited by s eve rift, female a may carry a fish 
©nd even in the serial display before the birds have visited 
a territory and, it Is report?*, on migration a fish may be held. 
One can aee that females arc attracted more readily to wales who 
carry fish than to sales ®h© don t. This might just be bee&ftse 
the f aval a is always hungry but sometimes it is more than that 
because after getting the fish ah® holds it without swallowing. 
The reaction of a female to a male with a fish la evidently 
not merely « result of her tinnier but of sow® thing conn® o tod 
with her getting a mate* 
A male my spend son® time on his territory reacting 
to flying birds and others and theft fly off and return with a 
fish. At ones a striding difference . coses 'over his behaviour 
which, a® s o on as the fish Is lest or swallowed* rtftrli to its 
earlier node. When he has s fish he spends far acre time in 
the aerial advertl clones t flight than in the ground advertisement* 
He also shows a greater inclination to visit birds who by their 
posture look like females. The actual Is plays them elves, 
as opposed to their frequency soft their effect on females, do 
not seem to change * He may succeed in leading a female to his 
territory but for the female the possession, though often not 
the swell owing, of the fish seems to be her ala, She trios to get 
the fish asms by fair means (a special begging beta vl our) or by 
foul (snatching it). Consequently a male who gets a fish may not 
keep it long but may lose it to one of the females who visit him. 
Or he may swallow it himself* la cither case at once he changes 
