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| Distribution map of the three Hirundo species |
There are two endemic bird species in southern Ethiopia which live in almost an identical range: Ethiopian Bush-crow and White-tailed Swallow. But apparently their respective ancestors come from very different parts of the world. The closet relatives of Zavattariornis - ground jays of the Genus Podoces - live in Central Asia, whereas the relatives of Hirundo megaensis are all from Africa. Dor et al (2010) describe the relationship of the swallows as follow:
"...the ‘Pearl-breasted Swallow’ clade, is comprised of the Pearl-breasted (Hirundo dimidiata), White-tailed (H. megaensis) and Pied-winged swallows (H. leucosoma). ... Phylogenetic relationships of the White-tailed Swallow, a species endemic to a small region in southern Ethiopia, have not been previously examined, but based on plumage traits it was expected to be close to the Pearl-breasted Swallow (Sibley and Monroe, 1990; Turner and Rose, 1989), and our analysis confirmed this affinity. Indeed, the genetic divergence between H. megaensis and H. dimidiata (0.7%) is by far the smallest existing among species in the genus (otherwise, range = 2.0–11.6%) and is equivalent to the divergence among populations of the polytypic H. rustica (range 0.25–1.6%). H. megaensis and H. dimidiata inhabit similar habitats, but are separated by a range disjunction of about 1,500 km..."
It remains one interesting question: Why share Zavattariornis stresemanni and Hirundo megaensis a nearly identical tiny range in spite of a very different history of colonization?
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| White-tailed Swallow (Hirundo megaensis) feeding. Nest inside a Borana hut. May, 2011. Dida Hara, near Yabello. |
