LIFE AXD BEHAVIOR OF THE CUCKOO 
181 
correcth' identified as owners of the introduced egg, and if so 
whether such conduct might not be evidence of association or 
of a recrudescence of parental impulses, as well as of watchful 
care, directed in the manner implied. 
14. To Wetterberg is due the doubtful observation that the 
cuckoo turns the eggs of the nurse with her bill, as the opportunity 
offers, and pushes her own egg into the center of the nest. Such 
actions, if performed, would surely be useless, since birds turn and 
stir their own eggs with bill or feet, when entering the nest or when 
incubating. I have repeatedly seen the black-billed cuckoo grasp 
an egg with her foot when settling down, and draw it under her, 
and have photographed the great herring gull in the act of turning 
her eggs with the bill, and both that bird and the cuckoo in the 
act of moving an egg with the foot, and placing it under the bod^-. 
If the observation referred to above has any value, it shows the 
persistence of what is undoubtedly a very ancient and useful 
instinct. 
15. The cuckoo's 'eggs are laid according to some observers 
at intervals of two or three days, and of six or seven days, accord- 
ing to Baldamus, and to the number of five or six, and rarely seven 
in the season, the ovaries and oviducts closely resembling those 
in other birds. Eggs are found in middle Europe from the end of 
April to the beginning of July, but for the most part only 
during the second half of June, but rarely to the end of July. 
(Baldamus.) 
16. According to most observers the cuckoo's egg is thought 
to hatch about twenty-four hours earlier than those of most nurses. 
A similar precocity was attributed to the eggs of our cowbird by 
Alexander Wilson, who was the first to describe its pecuHar habits. 
No exact determinations, under proper control, have yet been 
made upon this interesting question. 
17. Fate of the eggs and young of the foster-parents. All authori- 
ties agree that as in the case of the nest-mates of the cowbird, 
the entire progeny of the cuckoo-nurse is destroyed, but there is 
a curious disagreement between observers in Great Britain and 
on the Continent as to how this is brought about. 
English naturalists, from the classical observations of Dr. 
