218 THE ZOOLOGIST. 
feeding, the warming of the young bird was again repeated. 
After a good quarter of an hour in my hiding-place I left the 
spot without disturbing the old bird. 
All through my period of observation in this part of the 
forest I had noticed the unusual frequency of the calls of the 
male Cuckoo. I counted at least six individuals challenging 
one another with their songs. In the higher wood close by I 
had listened at short intervals to the furious blows of the wing 
exchanged in combat by the males and to the call-notes of 
both sexes. I had an entertaining view of the proceedings of 
the amorous birds, as I passed on my way shortly afterwards. 
On the tops of the oaks and pines sat the excited males, with 
their tails carried high and their wings drooping down, 
repeating their usual call-notes, among which the ordinary 
“ cuckoo” was often prolonged into “ cuc-cue-koo,” and in other 
cases was shortly and abruptly broken off in the middle. 
Every now and then they dived into the branches in pursuit of 
the hens, which were recognizable by their paler and browner 
coloration. In short, this particular spot in the forest was 
evidently a special rendezvous of Cuckoos. In spite of the 
unseasonable weather this day (overcast sky and frosty wind), 
there was a singing and fighting going on which could hardly 
have been exceeded in the warmest day of May or June. 
Anxious to ascertain the reason of such a concourse of 
Cuckoos at this spot, I dived into the surrounding wood, 
which was that from which I had seen the mother Cuckoo 
bring food for her young one. I discovered here, on a group 
of oaks, a large colony of caterpillars of T'ortria viridana, 
which were easily seen from a distance hanging by their silky 
webs, and found also many of them on the leaves. No doubt 
this colony was the attraction that caused the concourse of 
Cuckoos. 
What I have stated renders it quite clear:—(1) That the 
Cuckoo, in exceptional circumstances, incubates and hatches one 
or more of its own eggs, which, in these cases, it apparently lays 
together in a safe place on the ground without preparing any 
nest. (2) That the eggs of the same Cuckoo may be very 
different in colour and markings. If this be so, the purely 
theoretical idea held in certain quarters that each hen Cuckoo 
lays eggs of the same colour and markings or of “one peculiar 
