The Megaceryle kingfishers were formerly placed in Ceryle with the Pied Kingfisher, but the latter is genetically closer to the American green kingfishers.
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The underparts may be white or rufous, and all forms have a contrasting breast band except male Ringed Kingfisher.
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They have dark grey or bluish-grey upperparts, largely unmarked in the two American species, but heavily spotted with white in the Asian Crested Kingfisher and the African Giant Kingfisher.
The Belted Kingfisher's Latin species name (Megaceryle alcyon) also references her name.
The Ringed Kingfisher, Megaceryle torquata, a more distant relative, also occurs on the same rivers, but is twice as heavy as the Amazon Kingfisher.
The Megaceryle large green kingfishers were formerly placed in Ceryle with the Pied Kingfisher, but the latter is closer to the Chloroceryle American green kingfishers.
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The Belted Kingfisher's closest living relative is the Ringed Kingfisher (M. torquata), and these two in all probability originated from an African Megaceryle which colonized the Americas.
Syndactyly, as it occurs in birds, is like anisodactyly, except that the third and fourth toes (the outer and middle forward-pointing toes), or three toes, are fused together, as in the Belted Kingfisher Megaceryle alcyon.
The Megaceryle kingfishers were formerly placed in the genus Ceryle with the Pied Kingfisher, but the latter is genetically closer to the American green kingfishers.