Carriker : List of the Birds of Costa Rica. 329 



while standing perfectly still in the forest I have heard the rapid whirr 

 of wings, and, turning cautiously, have seen a humming-bird poised 

 within a yard or two of my head, now advancing, now retreating, 

 and all the while turning its tiny head from side to side in its efforts 

 to solve the identity of the curious creature which has invaded its 

 domain. At the slightest movement of head or arm it is gone like a 

 flash, and many have been the rare humming-birds which I have seen 

 thus, never to see again in the same locality. Phaethornis longirostris , 

 P. guy coruscus, P. ado/phi, Oreopyra cinereicauda, Threnetes ruckeri, 

 Chalybura melanorrhoa, Microchera parvirostris, and Thalurania co- 

 lombica are much addicted to this habit. 



All the terrestrial Formicariidce are very shy, and some would be 

 almost impossible to collect in any numbers were it not for the curious 

 habit they have of answering to their call when skillfully imitated by 

 the collector, who may call them to his very feet in this manner ; but, 

 like the humming-birds, at the first movement they disappear and can- 

 not be called back. 



The birds of the jungle have another curious habit, that of collecting 

 in little bands and moving here and there through the forest in search 

 of food. The collector may walk for an hour or more and scarcely see 

 a bird, when he will suddenly find himself in the midst of a crowd 

 of tanagers, warblers, vireos, and arboreal ant-thrushes, which are 

 flitting along, all in the same direction, now high up in the trees, now 

 low down, chirping and twittering as they search for food. After a 

 few quick shots all will have disappeared and again the forest is silent 

 and deserted. Ant-thrushes, some of the tree-creepers, and insect-eat- 

 ing tanagers are very fond of following in the wake of a swarm of 

 migrating ants, picking up the stragglers as they stream over the 

 ground and up the small trees and shrubs. At this time they are 

 quite silent, and, when disturbed, sneak off abruptly, only to return 

 shortly to the feast. If one can put up with the fierce bites of the 

 ants many rare things may be taken on such occasions. 



There is another state of affairs which always impresses the collector 

 and which cannot always be satisfactorily explained. This is the 

 apparent scarcity of certain species and abundance of others. Why 

 should ant-thrushes such as Formicarius nigricapillus, F. castaneiceps, 

 Pittasoma michleri zetedoni, Grallaria guatemalensis princeps, and 

 Hylopezus dives be so extremely hard to find, while Formicarius 

 umbrosus, F. moniliger Jwffmani, Hylopezus lizanoi, and H. intermedins 



