DOMINATING CUCKOOS 189 
a rule “ conceive 33 an egg on any but her natural 
fosterers, and where these are in convenient 
numbers upon a desirable territory, there will she 
probably find a dominant Cuckoo in occupation. 
Without a territory of her own, or without the 
power to hold one for her exclusive use, a Cuckoo 
can have but few opportunities to perpetuate her- 
self. It is thus highly improbable that B laid many 
eggs in her second season ; it is even possible that 
she laid no more than the two discovered on the 
ground she occupied in her first year. 
We have Cuckoo A adhering solidly to her 
territory, successfully keeping out all opposition. 
Cuckoo E laid one egg only on the common in 
each of the years 1919 and 1921, but in each in- 
stance it was at the end of A’s season. Cuckoo F 
only did so once, in 1920, when, as has been 
already pointed out, there was a break in the 
regularity of A’s laying. 
The obvious conclusion is that Cuckoos E and 
F were wanderers in the vicinity, submissive to 
dominant Cuckoos, and anxious to trespass on A’s 
territory, but only able to lay a casual egg therein 
when her vigilance was relaxed. 
Of the territorial system in vogue amongst 
female Cuckoos there is superabundant evidence, 
