64 Controversy is the surf that marks— 
Tiercel; if that is wrong, then all my observations of the inverted 
vole of the sexes in their care of the young goes by the board. 
Owing to constant association I soon found myself able to tell 
which bird was present, though, as in the shepherd’s ability to 
distinguish different members of his flock, it would not be easy to 
at once reduce the process to writing. The Tiercel of this pair had 
a much larger cere than the Falcon, 7.e., the yellow bare skin round 
the eye showing, as I have learned since, that he was the older of 
the pair. The cere, owing to foreshortening, disappears when the 
bird is seen full-face, and in the same way the pose and condition 
of the plumage, as well as changing expression, help to make identi- 
fication difficult, but there is also a massiveness about the Falcon 
which helps to distinguish her from the Tiercel. 
As regards the prey, there seemed no selection as to kind; 
it looked as if with the Falcon the only rule were first come, first 
served. In the same way I failed to trace any design in the condi- 
tion of the quarry as delivered. As far as I could make out, if she 
kept the Tiercel waiting, and presumably turned up with a freshly 
killed bird, it was intact, whereas the longer she had it in her keep- 
ing, the more thoroughly was it plucked and skinned; but this 
is purely surmise, as from my circumscribed outlook I got no 
proof of the Falcon waiting to be called. The natural way of 
feeding the young is for the adult to divide the prey among the 
young. If it were usual for the prey to be simply dropped into the 
eyrie, as happened when on occasions the Falcon brought a bird 
during the Tiercel’s absence, I think the young males would have 
stood a very poor chance beside their voracious sisters—that is, 
presuming I am right in concluding that the larger young are 
females. My friend, the late Colonel Moore, when I pointed out 
the difference in size among the 1910 brood, said that in the Raptores 
generally incubation starts with the first egg laid, and that the young 
vary in size accordingly. From what I had seen of two young 
ravens in the previous year, I dissented. I do not know what the 
books say about it, but I have since satisfied myself that as regards 
Peregrines this is a sexual difference, although I have not gone 
to the length of dissecting them. As I said at the beginning of 
the book, from the early appearance of this difference in size I 
