20 BULLETIN 2 08, UNITED STATES NATIONAL MUSEUM 



{indicator, minor, variegatus, and exilis), but there is some doubt as 

 to the identification of some of the parasites involved. Barbets and 

 woodpeckers offer the greatest number of multiple parasite host 

 species, two species of each (Lybius torguatus, Trachyphonus vaillantii, 

 Campethera nubica, and Campethera abingoni) being recorded as 

 victims of each of three species of honey-guides, while three other 

 barbets (Stadolaema anchietae, Pogoniulus pusillus, and Tricholaema 

 leucomelan) and one other woodpecker (Dendropicos fuscescens) are 

 known to be parasitized by two species of honey-guides. 



Aside from the genus Prodotiscus, as yet known to parasitize only 

 small passerine birds, it seems that the "typical" honey-guides (genus 

 Indicator, and probably Melichneutes) victimize picarian and coracii- 

 form birds primarily, and only such passerine forms as utilize old 

 nesting sites of these birds or other tunnels fairly similar to theirs. It 

 may be pointed out that the other parasitic birds of Africa (cuckoos 

 and weavers), with the exception of the great spotted cuckoo, Clamator 

 glandarius, rarely affect hole-nesting species; consequently, there is 

 little if any conflict or competition for brood hosts between them and 

 the typical honey-guides. Two species of starlings (Spreo bicolor and 

 Lamprocolius nitens) are the only hosts known to be parasitized fre- 

 quently by both a cuckoo {Clamator glandarius) and a honey-guide 

 {Indicator indicator). In no one nest have eggs of both of these para- 

 sites been found together. 



Mandibular books of nestlings 



The presence of needle-sharp, semitransparent hooks on the tips 

 of the maxilla and mandible of nestling Indicator indicator and Indi- 

 cator minor, and probably of other species of the genus, seems to be 

 a remarkable specialization that is of adaptive significance to the 

 nest life of a parasitic bird. These structures are definitely known 

 only from two species, I. indicator and J. minor, and from an un- 

 feathered chick attributed to I. variegatus on inconclusive evidence. 

 Haagner and Ivy (1907a, p. 4) write that while the "hooks appar- 

 ently fall off when the bird is fully adult . . . there are traces of 

 their existence in the slightly flattened end of the premaxilla, and 

 the membranous scaly appearance of the terminal portion of the 

 mandible of several adult specimens of Indicator sparrmani [=1. 

 indicator] and I. minor examined by us. The beaks of the adult 

 specimens of Indicator have the culmen and genys much more curved 

 than that of the young bird under discussion, and it is therefore easy 

 to see where the hooks part from the beak, and by the distinctly 

 welded appearance of the whole structure they are very obviously 

 only superficially comiected." 



