A real tree and a true forest wagtail “discovered” – surprising new findings about two insular species

Alström, P., Jønsson, K., Fjeldså, J., Ödeen, A., Ericson, P.G.P. & Irestedt, M. 2015. Dramatic niche shifts and morphological change in two insular bird species. Royal Society Open Science. http://dx.doi.org/10.1098/rsos.140364

We present two previously unrecognised cases of dramatic change in appearance, habitat and feeding behaviour in connection with colonization of tropical forest- covered islands. The little-known bird Madanga ruficollis occurs exclusively on the small island Buru in Indonesia. The similarly poorly known São Tomé Shorttail Amaurocichla bocagii is only found on São Tomé in the Gulf of Guinea. The former has been considered to be an aberrant-looking white-eye (family Zosteropidae), whereas the affinities of the latter have been considered more uncertain. We have analysed DNA from two each of the few existing specimens of these , which were collected in the 1920s. To our great surprise, our results show that both belong in the and wagtails family (), Madanga among the pipits (Anthus) and the Shorttail among the wagtails (Motacilla). The strikingly different appearances of these birds compared to their closest relatives have totally obscured their true relationships. Madanga’s plumage does not resemble that of any of the world’s more than 40 species of pipits, although a close examination of its bill, toes and claws reveal typical pipit characteristics. The São Tomé Shorttail is very different-looking from all wagtails, in both plumage and structure. Also in habitat and feeding style, both Madanga and São Tomé Shorttail differ radically from pipits and wagtails. Both inhabit primary forest, where the former feeds like a nuthatch on epiphyte-covered branches and tree-trunks, while the latter feeds both on the ground and on tree trunks and branches. In contrast, nearly all pipits and all wagtails occur in open habitats, and all forage exclusively on the ground. We suggest that the extremely odd appearances of the Madanga and São Tomé Shorttail were triggered by the fundamental shifts in habitat and feeding behaviour following colonizations of forest-covered tropical islands. This was estimated to have happened some 4 and 3.3 million years ago, respectively. Interestingly, although not the focus of this study, the brightly coloured Yellow- throated Longclaw Macronyx croceus and Golden Pipit Tmetothylacus tenellus were found right among the dull-looking pipits.

Right: Relationships of the pipit and wagtail family (Motacillidae), including Madanga and São Tomé Shorttail. Illustrations Per Alström (from Alström P, Mild K. 2003. Pipits and wagtails of Europe, Asia and North America: identification and systematics. London: Helm/A&C Black; Princeton: Princeton University Press), Ren Hathway (from del Hoyo et al. Handbook of the birds of the world, vol. 9. Barcelona: Lynx Edicions) and Jon Fjeldså. The plumage variation among the more than 40 species of pipits in the world is minimal compared to most other similar-sized groups of birds, whereas the plumage of Madanga from the island of Buru in Indonesia is strikingly different. Moreover, Madanga’s arboreal habits are strongly divergent from the pipits’ terrestrial life style.

Nilgiri Pipit Anthus nilghiriensis Kerala, India, photo: Arka Sarkar

Tree Pipit Anthus trivialis Israel, photo: Göran Ekström Madanga Madanga ruficollis Buru, Indonesia, photo: Rob Hutchinson/Birdtour Asia