An interaction between a juvenile Pied Harrier (Circus melanoleucos) and a Greater Spotted Eagle (Clanga clanga) was observed in Malaysia. This did not appear to be a case of interspecific kleptoparasitism—where one bird steals food from another — but rather the defense of a migratory foraging territory. Photographs of the event can be viewed on the observer’s website.
Greater Spotted Eagle has previously been documented parasitizing other raptors (Wells 1999), including the Eastern Marsh Harrier (Circus spilonotus) in Malaysia and Thailand (Mallalieu 2007). Consequently, this behavior may also extend to the Pied Harrier, though this has not yet been confirmed by a publication.
Mallalieu, M. (2007). Greater Spotted Eagles Aquila clanga in central Thailand. Forktail. 23: 167-170.
Wells, D.R. (1999). The birds of the Thai-Malay Peninsula: Vol. 1 (Non-Passerines). Christopher Helm, London.