2 CHARACTEKS OF PASSERES 



ditious is rarely found outside the group Passeres ; and any 

 Hon-Passerine bird, the foot of which conforms with the fore- 

 going description, may be recognized by some collateral fea- 

 tures. The foot of a Hawk or Owl, for instance, is strictly 

 insessorial in character, and, in fact, possesses very great 

 grasping powers ; but the bill of these birds is furnished with 

 a soft cere, which no Passerine bird exhibits. In a Pigeon, 

 with decidedly insessorial feet, the covering of the feet, like 

 that of the bill in part, is soft and skinny, not perfectly horny. 

 A Hummingbird, the foot of which is perfectly insessorial, is 

 ascertained to be non-Passerine by the fact that it has but six 

 wingquills of the secondary series — all Passeres having more 

 than six. And, in general, closely as some of the Picarian 

 birds of this country may resemble the Passeres, some peculiar- 

 ity of the feet will snfiSce for their recognition. Thus, in the 

 Parrots, Cuckoos, and Woodpeckers, the toes are in pairs, two 

 before and two behind ; in the Kingfishers, the toes are exten- 

 sively soldered together, the covering of the tarsus is rather 

 soft, and, moreover, the tibia is naked below; in the Swifts and 

 Goatsuckers, either the hind toe is elevated above the plane of 

 the rest, or it is turned sideways, or there is a web at the bases 

 of the front toes, or these last have an unusual number of joints, 

 or several of these features occur in combination. Humming- 

 birds, the only remaining North American PicaricB, have, as 

 already said, a nearly Passerine foot ; but, in this case, the 

 above-mentioned feature of the secondaries is distinctive. 



There is also a peculiarity of the wing of Passeres that serves 

 to distinguish birds of this group from those of probably any 

 one of the others, excepting Picarice, and even from the ma- 

 jority of Picarice. In a Passerine bird, the row of " greater " 

 wing-coverts — those that overlie the secondary quills — are not 

 more than half as long as these quills; while in most non- 

 Passerine birds — perhaps in all birds below Picarice — the re- 

 verse is the case. 



The details of structure of the tarsal envelope of Passeres may 

 be noticed in passing. In the majority of the birds of this 

 group, the tarsus is covered on each side with a horny plate, 

 nearly or quite undivided, meeting its fellow in a sharp ridge 

 behind ; and, in some cases, this general fusion of the envelope 

 proceeds so far that the front of the tarsus likewise presents a 

 nearly or quite undivided surface, the whole tarsus being then 

 encased in a '.' boot," as it is called. The more complete con- 



