The Tropical Boubou is perhaps one of the most well known birds in Kenya and its rich bell-like duets are a feature of many gardens and woodlands throughout the country.
Altogether four subspecies occur in Kenya differing only in the amount or absence of any white in the wing. Nominate L.a.aethiopicus just reaches our area at Moyale; L.a.major is largely western from Elgon and Trans-Nzoia east to the central Rift Valley and south to the Lake Victoria basin, Trans-Mara, Loita and Nguruman hills and the Mara GR. L.a.ambiguus occupies the central highlands east of the Rift Valley from Mts Kulal and Marsabit south to Nairobi and the Chyulu Hills. The coastal lowlands are occupied by L.a.sublacteus north to Lamu and possibly the Boni Forest, and inland to Mt Kasigau, the Sagalla and Taita hills and along the Lower Tana to Garissa.
Beyond our borders along the Jubba and Shaabelle river valleys in southern Somalia we find the race L.a.somaliensis, and quite recently these Somali birds together with our own coastal ones have come under considerable scrutiny. In addition the occurrence of what has always been considered a rare all-black morph occurring in both our coastal areas and in southern Somalia has been investigated. The results have been quite remarkable, to such an extent that our understanding of coastal boubou shrikes in an area from Kilifi north to southern Somalia has changed considerably.
Firstly let us consider the rare and litle known all-black birds. In July 1878 Gustav Fischer collected an all-black boubou shrike from Kipini at the mouth of the Tana River. As a result the following year Reichenow named this single specimen Dryoscopus nigerrimus, and it was this bird that led to everyone believing that sublacteus was a polymorphic form with a rare and little known black morph. Meanwhile in southern Somalia, Baron von Erlanger had also collected several boubou shrikes including an all black bird from the Jubba Valley, and in 1905 Reichenow named the all-black one erlangeri, and the black and white ones somaliensis. Why Reichenow did not consider the all-black bird from Somalia the same as nigerrimus will never be known. Later Van Someren and his collectors obtained a fine series of both all-black birds as well as the more normal black and white ones from both southern Somalia and from Manda Island in Lamu District.
Recently Nguembock et al (2008) published a phylogeny of the Laniarius bush shrikes, and included in their sampled specimens was an all-black bird from southern Somalia. Their finding were that this all black bird was not a Laniarius aethiopicus and so recommended that the name Laniarius erlangeri be reinstated. Unfortunately Nguembock and his colleagues did not sample any of the black and white birds occurring in southern Somalia, but it is clear that they consider erlangeri to be a polymorphic species with both all-black and black and white individuals occurring. In addition, they also recommended that birds previously known as L.a. major and L.a.sublacteus also be treated as separate species from what we know as the Tropical Boubou Laniarius aethiopicus.
During April 2010 Nigel Hunter and Brian Finch visited Manda Island and obtained a remarkable series of sound recordings of both the all-black boubous as well as the normal black and white birds. It became abundantly clear that the all-black boubous were a completely different species to the black and white ones, and contrary to earlier beliefs that the all-black form was merely a dark morph (Turner et al 2011). Attention was then immediately drawn to the other all-black boubou shrikes. Specimens of Fischer's 1878 bird from Kipini and Van Someren's black birds from Somalia and Manda Island were scrutinized in the Berlin Zoological Museum and the National Museum in Nairobi. It soon became clear that all are exactly the same, and that Reichenow's name nigerrimus (1879) would take priority over erlangeri (1905), assuming that erlangeri is indeed the same as nigerrimus.
Concerning the black and white birds occurring in the East African coastal lowlands north to southern Somalia: the type of sublacteus is somewhat of a mystery. It formed part of the much larger Rivoli Collection amassed by Prince Massena pre-1840, and which was purchased for the Philadelphia Academy of Sciences in 1841. The collection was curated by James Cassin and in 1851 he named sublacteus with the type locality simply designated as East Africa. He differentiated this form from aethiopicus and major on account of it lacking any white in the wing.. The type locality was later restricted to Mombasa by Sclater 1930, but in 1947 Grant and Mackworth-Praed deemed that the type locality should be Lamu, but gave no reasons why.
Just where the type of sublacteus was obtained from will never be known. Meanwhile the very similar somaliensis (Reichenow 1905) needs to be looked at more closely. Vocalisations of birds from Kilifi and the Arabuko-Sokoke Forest near Malindi match those of the Manda Island birds, but there is currently some doubt that they match bird occurring in the Mombasa area, and sadly there are no recording of any Somali birds.
There is clearly a need for further DNA sequencing of these coastal boubous, and specimens are readily available. At present we do not know whether any erlangeri or somaliensis reach Kenya, but we suspect that the all black erlangeri is the same as the Kipini and Manda Island birds and therefore synonymous with nigerrimus (Reichenow 1879).
Alongside this mix we also have the Slate-coloured Boubou Laniarius funebris. It is truly remarkable that so many boubou shrikes can exist alongside each other in similar habitat. The Slate-coloured Boubou does not occur on Manda, but it does at Kipini and along the Jubba and Shaabelle in southern Somalia. Certainly we now know that the bird that we all knew as the Tropical Boubou is a far more complex species that was earlier known. Birds that were simply considered dark morphs are clearly a totally different species, but with affinities to what? Nguembock et al 2008 also suggest that there may be multiple black and white species occurring in East Africa, and so our understanding of what we knew of the Tropical Boubou is clearly changing.
Given the complexities of the issue, and realising that more work is required before we have a well defined picture, the question remains as to what protocol we should follow in the meantime when reporting on sightings, etc. We would like to suggest that for Kenya and Tanzania, the coastal black and white boubou is referred to as Tropical Boubou (sublacteus). However there is work needed to find out if birds from Mombasa south, also inland to the Taitas have the same vocalisations as the Kilifi to Manda birds. For the all black boubous, we would like to suggest that any sightings are referred to as the 'Black Boubou'. This would help in ascertaining if this species occurs beyond the shores of Manda Island and would avoid any challenge to an English name, prior to the further DNA determination that we hope will be undertaken sooner rather than later.
Don Turner, Brian Finch & Nigel Hunter