132 BULLETIN 208, UNITED STATES NATIONAL MUSEUM 



Another observation to the effect that the tail feathers are involved 

 in the production of the rustling sound is the following account, con- 

 tributed by Miss Clare Robinson of Cape Town in a letter to Dr. 

 Broekhuysen, who sent it to me, "On more than one occasion a 

 honey-guide has been known to fly low over our heads . . . rapidly 

 opening its tail like a fan and closing it again and repeating this sev- 

 eral times, thus making a 'wurring' noise. The bird would fly over- 

 head and then come back over us two or three times." 



Lack (1941, pp. 437-438) has brought together some data on the 

 postcopulatory display of a number of unrelated birds {Erithacus, 

 Muscicapa, Columba, and several species of Anatidae) and concludes 

 that such display presumably has little or no survival value but is to 

 be looked upon merely as an indication of the heightened internal 

 condition of the birds, causing them to go through some more or less 

 random bodily movements. Although he refers to these displays as 

 consisting of random movements, he states that the movements given 

 by one or both members of the pair immediately after coition are 

 "characteristic" for the species. Have we here in the "tooting" or 

 "rustling" diving flight of the male greater honey-guide something of 

 this sort, comparable perhaps to the strutting and crowing of a barn- 

 yard rooster after treading a hen? Unfortunately there are no data 

 for analysis, but there is one suggestive circumstance. As we have 

 seen, the honey-guide usually shows little or no precopulatory display 

 or other outward sign of internal excitement, and if we may assume 

 that coition is ordinarily and regularly accompanied by some such 

 heightened tension, may it not find expression afterwards? It is not 

 possible at present to do more than raise the question; a definite 

 opinion would be quite premature. 



It seems, from the data presented in detaU above, that we may 

 include the greater honey-guide (and, apparently also the lesser and 

 the scaly-throated species, although here the evidence is much less 

 ample) among those birds that show no true pair-formation, the sexes 

 meeting merely for copulation and then parting. Lack (1940b, pp. 

 269-270) has divided these birds into four types: those in which the 

 sexes meet at communal display grounds or "leks" (examples of which 

 are known chiefly among the gallinaceous birds, some limicoline 

 species, a few hummingbirds, and a few passerine species of unrelated 

 families); those in which the male is isolated and displays conspicu- 

 ously and the female comes to him (as in some gallinaceous birds, 

 birds-of-paradise and bower-birds) ; those in which the individual hens 

 visit the flocks of males but the individual males have no established 

 stations (as in the boat-tailed grackle); and parasitic birds (like the 

 cowbird and the European cuckoo) in which at times, but not regu- 

 larly, there may be formed a more lasting bond between the sexes. 



