Heliangelus regalis

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Freile, J. F.; Piedrahita, P.; Buitron-Jurado, G.; Rodriguez, C. A.; Jadan, O.; Bonaccorso, E. 2011. Observations on the natural history of the Royal Sunangel (Heliangelus regalis) in the Nangaritza Valley, Ecuador . Wilson Journal of Ornithology 123: 85–92.

Graves, G. R., Lane, D. F., O’Neill, J. P., Valqui, T. 2011. A distinctive new subspecies of the Royal Sunangel (Aves: Trochiliformes; Heliangelus regalis) from the Cordillera Azul, northern Peru. Zootaxa 3002: 52–58.

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Merkord, C. L.; Mark, T.; Susanibar, D.; Johnson, A.; Witt, C. C. 2009. Avifaunal survey of the Río Chipaota Valley in the Cordillera Azul Region, San Martín, Peru. Ornitologia Neotropical 20: 535-552.

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Schulenberg, T.S., O'Neill, J.P., Lane, D.F., Valqui, T., Albújar, C. 2001. Birds. In: Alverson, W. S.; Rodríguez, L. O.; Moskovits, D. K. (ed.), Perú: Biabo Cordillera Azul. Rapid Biological Inventories Report No. 2, pp. 146–155. Fied Museum, Chicago.

Seddon, N.; Barnes, R.; Butchart, S. H. M.; Davies, C. W. N.; Fernandez, M. 1996. Recent observations and notes on the ecology of the Royal Sunangel Heliangelus regalis. Bulletin of the British Ornithologists' Club 116: 46-49.