THE BIRDS OF NORTHERN THAILAND 217 



The pied hornbill is rather common throughout the North, occur- 

 ring in tall lowland evergreen and sometimes in quite open forest or 

 even in extensive bamboo brakes. It is a bird of low elevations, seldom 

 ascending the hills as high as 2,200 feet. In the dry jungle on the 

 lower slopes of Doi Suthep I found it uncommon and present only 

 from November to February, but it could usually be observed in the 

 evergreen forest near Ban Pong, at the southern base of the moun- 

 tain. In addition to the localities listed above, it is known from Huai 

 Pu, where Eisenhofer took a male, May 22, 1912 (Hannover) , and from 

 Doi Ang Ka, where I found it from the vicinity of Ban Mae Klang up 

 to 2,000 feet. 



This small species is usually seen in flocks that travel rapidly from 

 tree to tree, crossing open spaces one or two birds at a time. It flies, 

 like the larger hornbills, with alternate flapping and sailing but, 

 unlike them, with silent wings ; on the other hand, it is a highly vocal 

 bird, constantly uttering shrill cries, cack-cack-cack-cack, from which 

 the vernacular name is derived. 



The breeding season in our provinces is not certainly known, but I 

 took a very young example, still in postnatal molt, at Ban Hai Huai 

 Som, June 17. A female collected at Muang Fang, July 22, is in molt. 



De Schauensee records that a female had the irides light brown; 

 the orbital skin and the naked area at the base of the mandible bluish 

 white; the bill ivory and black; the feet, toes, and claws black. 

 Gyldenstolpe states that an adult had the feet and toes greenish 

 yellow. In dried skins I find that the adult male has the entire bill 

 ivory except for a broad, black transverse bar across the apical half 

 of the casque ; the adult female has the entire apical half of the casque 

 and the apical half of the culmen black and the extreme base of the 

 mandible black, preceded by a patch of dark red. 



This genus has the casque long and high, sharp-edged and project- 

 ing in front. The adult of the present species has the chin, throat, 

 neck, upper breast, and entire upperparts black, more or less highly 

 glossed with green; the primaries (except the two outermost pairs) 

 and the outer secondaries broadly tipped with white, so that the out- 

 spread wing is conspicuously margined behind with a white band ; the 

 rectrices (except the central pair) with the apical third white. 



Judged from material I have seen, birds from more northern and 

 eastern Indo-Chinese localities and also from Arakan have the inner- 

 most secondaries so long as wholly to conceal the longest primaries 

 in the folded wing, while more southern examples have them much 

 shorter than the longest primaries. I have not enough specimens to 

 decide whether this difference is to be explained by individual or by 

 geographical variation. 



