In the video below is a Blyth’s Hawk-Eaglet seemingly trying to learn how to fly in its nest. Blyth’s Hawk-Eagle, Spizaetus alboniger (IUCN, 2010) is a medium size bird-of-prey at about 51-58cm in length with thick white band on its uppertail and undertail and long erect crest (Wikipedia, 2010; Poh, 2001). They can mainly be found in South-East Asia (SEA) countries such as Singapore, Malaysia and Indonesia. Due to its large range and estimated population, it is considered the least concern under IUCN’s Red List Category and Criteria (IUCN, 2010).
The behavioural combination that resembles a dance exhibited in the video appears to be part of eaglet’s wing exercises as they practice and strengthen their wings in preparation for adulthood. To take note of in the video, the eaglet engages in the following behaviour concurrently:
1. Spread its wings widely
2. Flapping its spread wings with great amplitude
3. Spreading its tail
4. Holding its body almost horizontally
5. Feet holding itself to its nest
6. Occasion jump
However, as there are limited researches done on Blyth’s Hawk Eagles, it is difficult to find credible explanations for these behaviours. Not to be daunted, researches on Golden Eagles, Aquila chrysaetos (IUCN, 2010), showed behaviour traits identical to the ones described above. Though both species are different in their Genus and Species type, they share the same Order (Falconiformes) and Family (Accipitridae) in their scientific classification (IUCN, 2010; IUCN, 2010). And as this particular behavioural trait fits exactly what was described for Golden Eagles, it is reasonable to extrapolate it to Blyth’s Hawk-Eagle in this particular situation in order to provide plausible explanations given the lack of researches done on them.
Accordingly, behaviours 1 to 5 are part of an eagle’s locomotive behaviour exclusively practiced by their young called the ‘Flap and Spread-Hold’ (Ellis, 1979). Such behaviour helps to “strengthen their wings, develop wing coordination, and provides experience with the forces at play as the wings pass through a moving air stream” (Ellis, 1979). Thus, in this regard, behaviour 6, occasion jump, can be interpreted as the eaglet trying to get a better feel of how its wings interplay with the surrounding air or wind forces. Eaglets would engage in this wing practicing behaviour at about eight to nine weeks of its development (Hoechlin, 1976; BBC, 2008).
When these behaviours are carried out concurrently, it would seem to an outsider that the eaglet is carrying out a dance as both its widely spread wings and legs are seemingly moving in concert with one another.
Second Source:
Rettig, N. L. (1978). Breeding Behavior of the Harpy Eagle (Harpia harpyja). The Auk, ii+629-643.
Video:
“Young Blyth’s Hawk Eagle.flv” by BorneoProduction, YouTube Channel, 31 March 2010. URL: http://www.youtube.com/watch?v=KsZK1D3RsA8 (accessed on 1 April 2010)
References:
BirdLife International 2009. Aquila chrysaetos. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.1. <www.iucnredlist.org>. Downloaded on 03 April 2010.
BirdLife International 2009. Spizaetus alboniger. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.1. <www.iucnredlist.org>. Downloaded on 03 April 2010.
Ellis, D. H. (1979). Development of Behavior in the Golden Eagle. Wildlife Monographs, 3-94.