Observations on nesting Beautiful Long-tailed Sunbirds Cinnyris pulchellus in The Gambia revealed that some females have dark or partially dark bibs, contrary to most accounts in the literature. Furthermore, all fledglings seen in The Gambia also had dark bibs and some males in eclipse plumage or lacking tail-streamers engaged in breeding activity. The conclusion that some adult female C. pulchellus have dark bibs and that some, probably all, juveniles have dark bibs was confirmed from museum specimens. It is further demonstrated, based on specimens, that some adult females and juveniles of Gorgeous Sunbird C. melanogastrus also have dark bibs.
Beautiful Long-tailed Sunbird Cinnyris pulchellus is a widespread species occurring in savanna and Sahelian habitats from Senegal in West Africa to Eritrea in the east, reaching south into parts of Kenya, Uganda and Democratic Republic of the Congo. A close relative, formerly considered a subspecies of C. pulchellus, is Gorgeous Sunbird C. melanogastrus found in west and central Kenya and parts of Tanzania. Most textbooks describe the black bib on the throats of Beautiful and Gorgeous Sunbirds as characteristic of juvenile and immature males (e.g. Bannerman 1948, the text but not the plates [Figs 10b and 10c of Pl. 42 are transposed] in Barlow et al. 1997, Cheke & Mann, 2001, 2008), with females lacking such markings being plain-throated, but sometimes having a yellow wash. An exception is Fry et al. (2000) who stated ‘juvenile like adult female but with chin and throat dusky grey’, but this account did not make it explicit that the remark applied to both sexes. It was therefore of interest that between 2010 and 2019 CRB observed that all fledglings from many successful nests of C. pulchellus in his garden and vicinity at Brusubi (13.3925°N, 16.7545°W), in the coastal Western Region of The Gambia, were dark-bibbed, this being the standard feature on pulli and fledglings, and apparently also the case at other sites in The Gambia.
In February 2014 CRB observed a dark-bibbed female, accompanied by a male lacking any tail-streamers but otherwise in full breeding plumage, feeding and attending a fledgling. Then on 15 March 2018 he observed and photographed a dark-bibbed female, albeit with a pale-centred throat, carrying nesting material. When this was reported to CFM & RAC they initially surmised that helpers of various ages were involved. CRB's rejection of this possibility prompted RAC & CFM to examine specimens of both C. pulchellus and C. melanogastrus at the Natural History Museum, Tring (NHMUK), to re-examine the occurrence of dark-bibbed plumages in these species. Here we describe some breeding observations and the results of our specimen examination, and conclude that (1) some or all of both sexes of fledglings / juveniles of C. pulchellus and C. melanogastrus have dark bibs; (2) some adult females of C. pulchellus retain the bib even when nestbuilding, incubating and feeding young, and (3) male C. pulchellus in breeding plumage without streamers or in eclipse plumage are sometimes involved in breeding activities.
Nesting by Cinnyris pulchellus at Brusubi
On 26 February 2014 CRB noted a very recently fledged C. pulchellus being fed by a pair of colour-ringed, apparently adult, birds in a Bougainvillea hedgerow bordering a road. The adult male (colour-ringed with a single yellow 7, when it had full-grown streamers, on 22 October 2013; Fig. 1.) was in full breeding plumage but lacked tail-streamers and the female had a dark bib, which it also had when initially trapped almost one year earlier (colour-ringed single green on 11 April 2013; Fig. 2). Observations were made for a week and, as both presumed adults were colour-ringed, it was possible to confirm that these were the only birds feeding the single fledgling, which also had a dark bib, thus the possibility of attendant helpers in juvenile plumage was eliminated. Fig. 3 illustrates the dark bib on another recently fledged juvenile but of unknown sex.
On 15 March 2018, during a nesting effort in the same garden an apparently adult female with a black bib, but with a pale-centred throat, was photographed collecting nesting material during multiple visits to leaf litter in a flower pot (Fig. 4). On 12 January 2019 CRB observed a female with a dark bib collecting and carrying away bark fibres from an Acacia sp. on a number of visits to the tree's bole at Bantakunku Beach (13.3405°N, 16.8123°W) coastal Gambia, but no nest was located.
Although the bird in Fig. 1 may have simply just lost its streamers, there is other circumstantial evidence that males that are not in full breeding plumage engage in breeding activity. For example, on 27 June 2019 CRB observed a male in almost full eclipse plumage without tail-streamers that was in full song, and he has also seen a male in three-quarters eclipse plumage visiting a nest and displaying to a female.
Adult female C. pulchellus and C. melanogastrus.—Fig. 5 shows specimens of adult female C. pulchellus from which it is clear that although some females have unmarked throats, the two in the centre of the image have narrow and broad expanses of black on their throats, respectively. All are labelled as females, with NHMUK 19184.108.40.206 reported as containing eggs and having a brood patch. Fig. 6 illustrates two additional black-throated females. There are similar specimens of female C. melanogastrus, including one collected by R. E. Moreau (Fig. 7). However, presumably in the belief that all birds with black throats must be males, someone has annotated the label of this bird ‘young male'. A similar annotation is present on the labels of black-throated birds claimed as being female by their collectors, including on that of NHMUK 19220.127.116.11 (collected by G. Blaine) and a ‘?’ has been inserted in blue ink ahead of the female symbol on NHMUK 1964.15.1 (collected by C. H. Fry, apparently the only author to suggest that both sexes could have dark throats). This raises the issue of whether some or all of the black-throated birds, claimed as being female by their collectors, were perhaps incorrectly sexed. However, NHMUK 1918.104.22.168 (Fig. 8), collected on 24 June 1939 south-west of Sokoto, Nigeria, which has some black on the throat, but not an extensive amount, was collected at its nest by W. Serle who reported that it had enlarged ovaries. A similar specimen (NHMUK 1922.214.171.1240) with a slightly darker throat was collected by G. L. Bates north of Rei Buba, Cameroon, at an altitude of c.400 m on 6 April 1925, and labelled as having small eggs (Fig. 8).
Juvenile C. pulchellus and C. melanogastrus.—Confirmation that some juvenile females of both species have black throats is provided by the specimens illustrated in Fig. 9. The label for NHMUK 19126.96.36.199, collected by G. L. Bates, includes the note ‘ovary small'. Many similar specimens labelled as juveniles or immatures of both sexes with extensive black throats are also present in the NHMUK collection.
As only female C. pulchellus are involved in nestbuilding, there is no doubt from the above observations made by CRB (see Figs. 2 and 4) that some females possess dark feathers on their throats. The bird in Fig. 2 was undoubtedly more than one year old, being probably at least 15 months old, and, given that it is unlikely that immatures would build nests, we consider that there is little doubt that some adult females have dark bibs or streaks on their throats. This conclusion is supported by museum specimens (Figs. 5, 6 and 8) and is also the case for C. melanogastrus (Fig. 7). However, some females do have completely pale throats, sometimes washed yellow. There is also evidence that males that are not in full breeding plumage may breed or perform activities associated with breeding such as singing, displaying or visiting nests. It is also clear that some juveniles of both sexes and both species may have dark throats but, as yet, we are unsure if this is always true.
Our findings contradict most accounts in the literature. Bannerman (1948) stated of C. pulchellus that the ‘adult female differs in every particular from the male and lacks any metallic colour, the whole plumage being dull' and continues subsequently ‘Chin and throat whitish, the rest of the undersurface washed more or less strongly with yellow'. He described immature males as resembling ‘the adult female in having upperparts brown but have the throat blackish…' and that immature females are distinguished from immature males ‘by not having any dusky black on the chin and throat which is white'. It is probable that these descriptions led to the widespread assumption that only males ever have dark throats. Indeed, it is possible that the female-labelled specimens at NHMUK that were ‘corrected’ to being assigned to the male sex were so re-labelled by Bannerman. Given this salutary lesson in the dangers of following the literature uncritically (although the account in Fry et al. 2000 is an exception, implicitly but not explicitly), we now wish to re-examine the situation in other sunbirds, such as other species of Cinnyris with dark throats and Chalcomitra spp. that are similarly endowed, and to follow-up whether all or only some juvenile C. pulchellus have dark throats, with The Gambia being an ideal location for further such field work.
We are grateful to Alex Bond and Mark Adams, at NHMUK, for permission to examine specimens and to the referees for their comments. The Dept. of Parks & Wildlife Management (DPWM) gave permission for colour ringing of the sunbirds and Dave Montreuil supplied Figs. 1–2.