The Chapin's free-tailed bat is listed as Data Deficient (DD), inadequate information to make a direct, or indirect, assessment of its risk of extinction, on the IUCN Red List of Threatened Species.
[...] This African Dweller sports a two-coloured crest on top of its head. Like male bats of many species, a male Chapin's bat has scent glands that are used to attract females. The crest helps spread the male's perfum.
~Information found on Wikipedia and in Celia Bland's Bats edition of Nature's Wild.
If it helps, I have some spare info on a similar species, Tadarida chapini. It's also called Chapin's Free-tail. I don't know if it's from my book being outdated and the name having changed since then, but it's something at least.
"Males have prominent internaural crests which are erectile, while these are poorly developed in females. In subadult males, the crest is also little developed. In adult males, the base of the crest is associated with a prominent land, a feature common to some other molossids which lack this degree of development of the crest. Tadarida chapini weigh about 10 grams and are widespread but uncommon in Africa." - Communication in the Chiroptera by Fenton
"Males have prominent internaural crests which are erectile, while these are poorly developed in females. In subadult males, the crest is also little developed. In adult males, the base of the crest is associated with a prominent land, a feature common to some other molossids which lack this degree of development of the crest. Tadarida chapini weigh about 10 grams and are widespread but uncommon in Africa."
- Communication in the Chiroptera by Fenton
I must qualify as impaired some mornings ...
Adore the 'hawk though. XP