Proceedings of 
the United States 
National Museum 
SMITHSONIAN INSTITUTION - WASHINGTON, D.C. 
Volume 125 1968 Number 3655 
Parallel Evolution in 
the Small Species of Indicator 
(Aves) 
By Herbert Friedmann ' é 
Ornithologist Emeritus, Department of Vertebrate Zoology 
One of the aspects of avian taxonomy that inevitably has to wait on 
the gradual amassing of considerable material is the appreciation, and 
the consequent elucidation, of sympatric sibling species. Until suf- 
ficient numbers of specimens become available, the investigator can 
only treat the minor differences that he may notice as inconsistent, 
but apparently individual, variations in a not completely homogeneous 
taxon. 
The genus /ndicator presents an unusual array of sympatric, closely 
similar species distinguished primarily by size. In the Acacia grasslands 
of much of eastern Africa there are three similar species (in descending 
order of size): minor, meliphilus, and narokensis. In the forests of 
western and central Africa there are conirostris (a race of minor), 
exilis, willcocksi, and pumilio. Not only are the species of the two 
groups similar in appearance, but their habits vary but slightly. Chapin 
(1962) found pumilio and exilis (pachyrhynchus) together at Tshibati 
and saw no difference in their behavior. We can infer that minor and 
meliphilus also must be extremely similar in their actions and vocalisms, 
or variances would have been recorded by the numerous observers who 
1 Director, Los Angeles County Museum of Natural History, Los Angeles, 
California 90007. 
1 
