Family Hummingbirds (Trochilidae)

Least Concern

Long-tailed Sylph (Aglaiocercus kingii)


French: Sylphe à queue d’azur German: Himmelssylphe Spanish: Silfo de King
Other common names: Green-tailed Sylph, Green-throated Sylph, Emma's Sylph (emmae), Blue-throated Sylph (kingii)

Trochilus kingii


, 1832,

Jamaica; error = Bogotá, Colombia


Closely related to A. coelestis and A. berlepschi, and all three sometimes lumped but differ in morphology and altitudinal range; hybridization seems very limited in areas of contact. Race emmae has been considered a separate species, usually incorporating caudatus or mocoa, or both, as races. Thorough review required: specimen material more variable than suggested from written diagnoses, and new arrangements of species and subspecies may emerge. Proposed forms Chalcostigma purpureicauda and Zodalia thaumasta, both known only from single specimens, are apparently hybrids of present species and Lesbia victoriae; Neolesbia nehrkorni, known only from two specimens, appears to be a hybrid of present species with Ramphomicron microrhynchum, or perhaps with Thalurania furcata or T. colombica. Six subspecies recognized.

Subspecies and Distribution
  • A. k. margarethae (Heine, 1863) – mountains of NC and coastal Venezuela (Falcón E to Miranda).
  • A. k. caudatus (Berlepsch, 1892) – Sierra de Perijá, and Andes of W Venezuela (Lara S to Táchira) and N Colombia (Norte de Santander).
  • A. k. emmae (Berlepsch, 1892) – C Andes of N Colombia to W Andes of S Colombia and NW Ecuador (S to Pichincha).
  • A. k. kingii (Lesson, 1832) – E Andes of Colombia (Santander S to Cundinamarca).
  • A. k. mocoa (DeLattre & Bourcier, 1846) – C Andes of S Colombia (E Nariño), Ecuador and N Peru (to Cajamarca).
  • A. k. smaragdinus (Gould, 1846) – E Andes of Peru (S from Amazonas) and WC Bolivia (to Cochabamba).
  • Descriptive notes

    Male 16–19 cm (including outer tail feathers 12 cm), 5–6 g; female 9·7–11·7 cm, c. 4·5–4·7 g. Male has short black bill;... read more


    Presumed song a continuous series of buzzy notes “bzzt...bzzt...bzzt...” at a rate of c. 1 note/... read more


    Variable, depending on location of population and time of year. Pre-montane zones, scrubland and... read more

    Food and feeding

    Nectar and insects. Engages in a variety of forms of feeding behaviour, including trap-lining, territorial defence, and nectar robbing by... read more


    Feb–Oct recorded, but species thought to breed throughout the year. Male engages in ritualized nest building. Bulky, domed nest has a... read more


    Andean populations undergo seasonal altitudinal migrations from pre-montane zone to higher regions... read more

    Status and conservation

    Not globally threatened (Least Concern). Common throughout moderate elevations of E & C Andes and in parts of lowland Venezuela. In Venezuela, abundant in montane forest... read more

    Recommended citation

    Altshuler, D.L. & Boesman, P. (2020). Long-tailed Sylph (Aglaiocercus kingii). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from on 6 April 2020).