Introduction; Variation. 
65 
The psychological differences of the sexes. - The rule found among mammals 
— that the male is more active and wars and works for the sake of the female, 
while the female is more passive and gentle and devotes herself more to the care 
of the young — holds good also for large numbers of birds, but in many others 
the sexes seem to be much alike in temperament and to share duties, while in 
some species the rule is more or less completely subverted, the male iinderta ing 
the “female duties”, and the female assuming the usual role of the male, i e 
fact is important, as it shows that there are no mental peculiarities origin- 
ally bound up with the primary fact of sex. It appears, moreover, that 
these psychological conditions often (but not always) accompany the t lee 
ditions of develoimient of plumage and structure mentioned above, ^ nam y, 
when the male is more highly developed than the female, he is noisy, com- 
bative and extravagant of display in his courtship, while the female builds 
the nest or most of it, incubates the eggs, and takes the chief or sole caie o 
the voung; when the sexes are alike, the males are less quarrelsome in t 
breeding season, less demonstrative in their courtship and share the woi 
incubating the eggs and rearing the young; when the female is the moie hig y 
developed, she is noisy, pugnacious with other females and ma 
leaving him to do most or all of the work of hatching the eggs and caring for the 
young Thus the highly coloured males of the Trochdrdae.m^ny AnaUdae an 
GalUnae seem not to concern themselves for the brood to whic le pain o 
ing female devotes herself most faithfully, whereas the large anc an some 
Turnix roams about and calls and fights other females, leaving t e sma ® 
plainer male to attend chiefly to the incubation of the eggs and the we ° 
chicks, though indeed she does most of the nest-building and assists a i e in 
hatching the eggs (Krohn, Gefied. Welt, 1894, 190). The fema e o one 
the Emus which is larger than the male and wears a slight top- not as een 
observed in captivity not only to leave the entire work of incubation to the male 
but apparently to use her utmost endeavours to destroy her young w en 
(Darwin, Descent of Man 1871, II, p- 205). „,niVh 
Among species the sexes of which ai-e much alike m 
share the duties of incubation may be mentioned the 
Warblers, SyirWos; some Larks, Alaudidae-. some 
Knches, FringitHdae-. Woodpeckers, Picidae, and others; while in ^ 
male feeds the brooding female and sometimes relieves ei in © 
male leeus rue uiuuuiug a. , , , i qo /1 tV <1*1 and in many other 
time fcf e <y Naumann’s Vogel Deutschlands, 1824, i , • i • i 
time (^ci. e. g. rsaumanu » » 
I'll a res' Pint it is bv no means always the case the , , i -n k a 
places;. Put It IS by n ^o ^uch the more he (or she) will abandon 
IS in comparison with the othe^, 
the nest, eggs an vouig instances 
they are in appearance, m Ostrich, which, though the finer 
to the contrary may e menio Birds-of-prey, 
ththtetuW^^^ to the males in point of si.e (though not in coloration), 
Meyer & Wigleeworth. Birds of Celebes (May 5tb, ISOS). 
