An Assessment of Two Methods used to Release Red Kites ( Milvus Milvus )

Abstract

Between 2003 and 2005, we released 12 red kites (Milvus milvus) to the wild in Hampshire, England. Four kites were captive-bred and released as fledglings in artificial nests (‘hacking’). The remaining birds were mature and released from a large aviary. Interaction with electricity power-lines killed two of the captive-bred birds three weeks post-release and a third captive-bred kite died as a result of head injuries six months post-release. One mature kite died 10 days post-release. We suggest that the different release methods of the two groups amplified the behavioural variation between individuals and exposed them to different risk factors. We concluded that releasing mature flight-fit kites from aviaries is likely to be a superior method to hacking pre-fledged kites in artificial nests. The flight skills of the mature kites, developed prior to release, enabled them to avoid potentially lethal interactions with power-lines and aggressive inter-specific encounters. Modifying or adapting release methods to incorporate behavioural variation between individuals within a release population should be a consideration for reintroduction practitioners, particularly where release numbers are small.