Green-breasted Bush-shrike, Malaconotus gladiator, is an elusive, canopy-dwelling species which occurs at very low density in montane forest in western Cameroon and eastern Nigeria. It is currently considered 'Vulnerable' by Birdlife International (3) and consequently figures high on the menu of the increasing number of birders now visiting western Cameroon in search of the region's many endemics. Monteiro's Bush-Shrike, M. monteiri, is an even more elusive species, with only a handful of records from montane forest in Angola and western Cameroon, and is currently classed as 'Endangered' (3). Although considered by some authorities to be a race of Grey-headed Bush-shrike, M. blanchoti (6), the rationale for this treatment appears tenuous. The latter is primarily a lowland bush and woodland inhabitant with no zones of intergradation with monteiri. There are, however, similarities in the plumage and vocalisations of the two taxa.
Both Green-breasted and Monteiro's Bush-shrikes are best located by call. That of the former is described as a series of three mournful whistles each with an upward-terminating inflection1. While this appears to be the most frequent call, it has also been described as making a series of up to six mournful whistles, some lacking the upward-terminating inflection (5).
The call of Monteiro's Bush-shrike is described as similar to, but distinct from, that of Green-breasted, namely a series of five whistles, each shorter than those of the latter species, and lacking the upward-terminating inflection (1). The calls are described as being identical to those of Grey-headed Bush-shrike (5). However, recent observations I have made of Green-breasted Bush-shrike in south-west Cameroon suggest that its repertoire is more varied and may be confusable with the calls of Monteiro's.
On 20 June 1997 at Lake Edib, in the Bakossi mountains, I heard a calling Malaconotus sp. at 1,250 m in montane forest. The bird was using a long series of whistles each without any upward-terminating inflection. I whistled back, causing it to draw nearer where it remained in the canopy above me, calling persistently. When it eventually came into view, it proved not to be the expected Monteiro's but a Green-breasted Bush-shrike. The calls consisted of a series of 5-10 whistles, each slightly shorter than the bird's 'usual' calls and without any upward inflection at their end. I made tape-recordings of this bird and was able to clearly observe it calling, eliminating the possibility of there being two birds present. The calls sounded similar to some sequences given by Grey-headed Bush-Shrike and tape comparisons bear this out.
The following day I encountered what may have been the same calling bird in the same area, which I again 'whistled in'. The calls were identical to those of the previous day with the exception of two series of four whistles in which the two end notes in each series undulated up-and-down.
In addition, F Dowsett-Lemaire (FDL) reports (pers. comm. to G Kirwan 1998) that, of six different M. gladiator heard in the Kodmin area and several around Edib (both localities in the Bakossi mountains) in April 1998 none exhibited any upward-terminating inflection in their whistles. Two of these birds were observed. The same also holds true for two M. gladiator watched singing on Mt. Kupe, Cameroon in 1997 by the same observer. FDL has noticed two other call types in the repertoire of M. gladiator (which are shared by Grey-headed Bush-shrike), both of which she has heard frequently. 'Tearing' calls are given in series' of up to five; 'broken whistles' exhibit a distinct break in the middle of the 'song' with the second part being higher-pitched, and are interspersed with monotonous whistles. This call-type may correspond to those I heard on 21 June 1997, in which the song appeared to undulate. One bird observed by FDL at 1,200 m near Lake Edib in April 1998 gave all three call types.