rsg_book_2013

Birdsfledged, with 29 of them still alive at the start of the 2012 breeding season. Theannual survival rate of young after fledging is as high as 81%. With the addition ofa female believed to have immigrated from the continent, the total population sizehas increased to 46. By monitoring an almost fully banded population, it wasshown that this species has territories defended by pairs throughout the year, andimmature birds younger than four years live as floaters. Based on scientificanalysis of monitoring data a grand-design for re-introduction was developed byHPOWS (2011).Although young birds fly long distances and visit various districts of Japan, theyusually return to Tajima centered by Toyo-oka Basin after a short stay in eachdistrict, possibly indicating some difficulty in natal dispersal and suggesting lowfood availability in rural areas where bio-productivity has declined due to achange in the water-supply system for paddy fields all over Japan. Other thanthis, the limited genetic variability of released birds, with highly biased breedingsuccess among pairs, increases the probability of inbreeding in the wild. Geneticanalysis of skins of the past wild birds (Murata et al., 2004) suggests that theywere in the midst of an extinction vortex due to inbreeding (HPOWS, 2011). Inorder to lower the probability of inbreeding in the present population, birdsbelonging to new families were added to the captive population, with some ofthem being released in 2012. In addition, various attempts are conducted toreduce the birds’ use of artificial feeding (Ohsako & Ezaki, 2011).Another problem is the fact that some pairs use nest-towers built at the center ofa paddy field, completely in open space. As the past wild population nested inpine trees on hillsides, pairs were invisible to each other as long as they stayedon the nest. But with introduction of nest-towers just before the extinction of thewild population, birds started to nest in open space and this arrangement isconsidered by local people to be the normal situation. After re-introduction, eggsand chicks in tower nests are sometimes attacked by neighboring pairs while theparents are absent from the nest, indicating that those nest-towers should bemoved to hillside. In orderto solve this problemHPOWS experimentallymoved a nest-tower justbefore 2012 breedingseason. Efforts toestablish other localpopulations also havestarted. A pair of captivestorks were lent fromHPOWS to FukuiPrefecture where the localgovernment is nowengaged in captivebreeding with the aim ofsupporting re-introductionin the future. Lastly, inThird generation wild storks87