シロビタイアマツバメ Cypseloides storeri

Poorly known and rarely seen medium-sized swift. Very local in west Mexico and very rarely identified in the field. Like many swifts, nests behind waterfalls. Rather stocky and large-headed, with a squared tail tip. About the same size as much commoner Chestnut-collared Swift, with which White-fronted can associate. Plumage looks wholly black unless seen close in good light, when white forehead can show up. Beware, slightly larger Black Swift has similar white forehead.