Page:The Zoologist, 4th series, vol 4 (1900).djvu/280

252 Not only does this index afford a means for a comparison of the specimens, but it should have the advantage also of giving a more accurate estimate of the real flight-feather area.

Table I. has been compiled from the indices thus obtained by placing them side by side, according to the respective sex and approximate age of the specimens, and in serial order of diminishing figures of these indices.

On the whole, the result of this investigation for eliciting additional evidence in proof of the establishment of a clearly defined line between males and females from the point of difference in the length of the flight-feathers cannot be said to have been a very satisfactory one—at any rate, not for this particular species. The same may very reasonably be inferred from the genus as a whole, to which this species belongs.

On the other hand, and which Table I. shows also, it has been productive of supplying an approximate estimation of the rates of percentages at which the two sexes participate in the maxima and the minima of excess or reduction respectively. Thus 18·5 per cent., or five males only, absolutely exceed in greatest length of flight-feathers; the 59·3 per cent.=nineteen individuals, indiscriminately represent males and females, as well as every range of length; these are Nos. 6 to 21 of Table I., or considerably over the half of this large series of birds. Of females, six only are absolutely inferior in length, forming 22·2 per cent, of the whole. By dealing, however, separately with the sexes, the five males just referred to, out of a total of sixteen, with absolutely higher indices, form 31·2 per cent. Similarly, of the eleven individuals constituting the female portion, six of them show indices absolutely inferior to the remaining seven, or 54·5 per cent., a little over the half for females.

The measurements obtained for the seventh or longest primary, when compared with the indices derived from the aggregates of all the flight-feathers in the wing, do not coincide always