Birds of Celebes; Pittidae. 
339 
ORDER PASSERES. 
To this order belong pre-eminently the Song-birds, the males of the majo- 
rity of which have the habit in the breeding season ■ — in many cases at other 
times of the year also — of uttering a sequence of notes almost always pleas- 
ing to the human ear (and doubtless still more so to the singer and his part- 
ner), though a few, such as the Crows, have no song properly so called, while 
some birds belonging to other orders, such as, for instance, the common Fowl 
and the Redshank, have a very appreciable form of song. The Passeres number 
some 6000 species, ranging in size from the most minute to the Raven and 
Lyre-bird. The great majority of them feed upon insects and other inverte- 
brate organisms, seeds and fruits, some few occasionally on carrion, and occa- 
sionally (Laniidae, Corvidae) on small birds and other small vertebrates. As 
architects they are the most skilful nest-builders in the bird-world, and those 
which breed in holes as a rule (if not always) form a comfortable lining thereto, 
wherein they differ from certain “Picariae”, such as Merops, which do not line 
their nesting-holes. The young are hatched blind and naked. 
There is no difficulty in distinguishing the Passeres from other groups of 
birds, except from certain Picarian forms, such as the Swifts, which, approach 
the Swallows in external appearance and habits, and the Rollers, which are of 
a corvine appearance, or the Broad-hilled Rollers, which resemble the Eury- 
laemidae. For the distinction of the Passeres, avian anatomists attach most 
importance to the toes and their flexor tendons, to the palatal bones, and to 
the syrinx. 
The toes are normal, that is, there are three in front and the hallux behind, 
and the hallux is served by a free flexor tendon, not united to the flexor tendon 
of the three anterior toes, excej>t in the Eurylaemidae, which are now commonly 
allowed to rank as a distinct suborder, or order. 
The palate is aegithognathous (as it is indeed also in certain Picarian 
forms). “In the true aegithognathous structure the vomer is broad, abruptly 
truncated in front and deeply cleft behind, so as to embrace the rostrum of the 
sphenoid; the palatals have produced postero- external angles, the maxillo-palatals 
are slender at their origin, and extend obliquely inwards and backwards over 
the palatals, ending beneath the vomer in expanded extremities, not united 
either with one another or with the vomer” (Newton, D. B. p. 2). 
The syrinx has received great attention esj)ecially from Garrod and Gadow. 
The former used it as the diagnostic for forming two main groups of the 
Passeres, viz. 
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