COURTSHIP OF THE GREAT CRESTED GREBE. 521 
are connected by separate and perhaps roundabout mental paths 
with nest-building, courtship, and pairing; and that what we 
know is only an outline of the birds’ behaviour. 
(iv.) Relations of different pairs to each other. 
(Fuller details are given in Part J5)) 
The Great Crested Grebe, as we have already seen, pairs up very 
early in the season. What is the relation of the pairs of birds 
to one another ¢ 
Asa general rule, the two birds of a pair seem to take very 
little notice of the rest of their species. Oceasionally, however, 
there is some contact. There may be jealousy on the part of one 
bird, and this jealousy may, in any particular case, be merely 
precautionary, or actually justified by flirtatious behaviour on the 
part. of the other bird of the pair; or there may be hostility 
between members of one pair and members of another. 
Simple hostility is the rarer of the two: the only reason I can 
discover for it is the trespassing of one or both birds of a strange 
pair upon the * territory ” of another (p. 558). In its symptoms 
there is nothing very remarkable: the birds go into the threaten- 
ing Dundreary-attitude, often “barking” angrily at each other ; 
finally, one may fly or dive at the other and drive it away, but 
often the very mild form of hostility involved in staying quite 
still, assuming the threatening attitude, and barking at the 
enemy (who is also doing the same) is all that happens. 
Tt is much more interesting, however, to find in these birds 
what we had best call flirtation, aS an accompaniment to their 
monogamy. The whole thing is very human : when one member 
of the pair is rather excited and the other is either lethargic or 
far away, there 1s no channel for the relief of its excitement. If 
a bird of opposite sex is in the neighbourhood, however, this 
would provide the desired relief, and the result is that the 
“temptation ” is often too strong, and a bout of shaking ensues 
between two birds who are not mated. J have never actually 
seen such flirtations go beyond a bout of shaking; there is no 
yeagon that they should not, except that, as far as I could see, 
the birds did not seem to be used to each other, so to speak, 
Zand so their excitement often cooled down very quickiy. 
Tf the rightful mate sees what is going on, it is always 
roused to action, however lethargic it may have been before. 
Tt drives the odd bird away (often by a subaqueous attack with 
the beak) and then almost always has a strong pout of shaking 
with its mate. Thus all the anger of jealousy 1s directed against 
the usurper, not against the mate—which again 1s distinctly 
human! ‘The “erring spouse "is always equally ready to shake 
with his mate as with the tertium quid—and often more so. 
Here, again, the sexes are qualitatively alike—either will take 
