The White-tailed Swallow Hirundo megaensis is a threatened and poorly known bird endemic to southern Ethiopia, where it is restricted to a small area of Acacia savanna. Despite the paucity of previous nest records, we found 67 nests in the years 2010–14, commonly in village huts lived in by people, and report the first confirmation of nesting (two certain records) in termite mounds. Its nests are small mud cups lined with grass and animal hair, fixed to roof joists and similar to those of its sister species, the Pearl-breasted Swallow H. dimidiata of southern Africa, although it appears to lay larger clutches (3–4 pure white eggs) and breed less frequently, producing one brood in each of its two rain-driven breeding seasons (April–June and October–November). The same nests are reportedly used in these two seasons, presumably by the same pairs. Incubation lasts 16–17 days, with some broods showing clearly smaller chicks and hence presumably asynchronous hatching. Study of nestlings in the hand and museum skins confirmed that juveniles can be determined by their shorter tails, browner heads and frequently also wings, and reduced white in the tail. Although birds are typically seen singly or in pairs, flocks of up to 50, sometimes mixed with other hirundines, can occur. The breeding range appears to be almost identical to that of the Ethiopian Bush-crow Zavattariornis stresemanni but regular sightings of White-tailed Swallows since 2005 at the Liben Plain, 120 km to the east of the core area, suggest that the birds are frequent visitors there.