Conservation initiatives for an endangered migratory passerine: field propagation and release

The term 'field propagation and release' refers to the breeding of captive adults in large field enclosures, allowing them to raise their young, and then releasing those young from that location. This technique is currently being implemented in Canada as one of several recovery tools for the endangered eastern loggerhead shrike Lanius ludovicianus migrans. During 2001-2007 a total of 360 shrike fledglings were produced in field propagation enclo- sures and 301 were released from these enclosures. Annual return rates of birds released since 2004 are 2-6.6%. Seventeen released birds have been re-sighted, including 10 birds that have returned to the breeding grounds the following season to produce young with wild mates. The high annual return rate of release birds and the successful integration of these birds into the wild breeding population represent important milestones for the recovery of this population. The management technique we describe here has the potential to be applicable to other species that require natural habitat for breeding and/or are reliant on a suite of parent-learned behaviours that cannot be accom- modated for or adequately replicated within intensive close captive-breeding or hand-rearing conditions.