126 THE BIRDS OF BRITISH GUIANA. 
the Bill-birds, the Cotingas, the Firebirds, the Jacamars and 
such-like species give utterance to notes by no means sweet 
—in fact it might be said that the notes of the most striking 
of our voice-birds are quaint, discordant and harsh, or 
mysterious and ghostly, as will be recognized by any one 
who ever hears the cry of the Hannaqua or What-o’clock 
(Ortalis motmo?), the Bultata (Jbycter americana), the Calf- 
bird (Gymnocephalus calvus), the Giant Night-Jar (Vyctibius 
grandis), or the Who-are-you (Vyctidromus albicollis), It must 
not be imagined, however, that none of the tropical birds are 
sweet singers, for the notes of the native Thrushes, the 
Wrens, and many of the Tanagers and Hang-nests are ex- 
tremely sweet—the members of the two latter groups combin- 
ing both beauty andsong. The notes of the tropical Wrens, in 
fact, are far and away beyond those of their temperate 
brothers; and the cheeriness and sweetness of their notes, 
resounding through the gardens and houses, where they will 
perch and carol quite close to man, have earned them the 
common name also of “God-bird.” The commonest cry 
heard in Guiana, at any rate in the open lands and cleared 
parts of the coast, is the harsh challenge of the common 
Tyrant-shrike (Pitangus sulphuratus), whose “ Qu’est-ce 
qu’il dit” is to be recognized at all parts of the day. 
Most curious of all our birds, however, in structure, 
habits, affinities and food relations, it must be borne in 
mind, is the Hoatzin (Opésthocomus cristatus) already re- 
ferred to; and whose reptilian affinities have earned for it 
the distinctive title of the “ Reptilian Bird.” Quite recently 
the full relations of this bird have been made out, and papers 
on these points will be found in recent numbers of the 
Transactions and Proceedings of the Zoological Society of 
London, The “Ibis,” and “Timehri’” (Guiana). The 
presence (1) of well developed ungues on the wings, which 
are, on this account, grasping organs or legs, and are func- 
tional until the growth of the feathers when they disappear 
by disuse, (2) of a posterior carina sterni adapted for the 
