We have monitored the status of Black-tailed Gulls Larus crassirostris breeding on Tobishima Island since 2004. On Yurijima Islet, we estimated 2,034 nests in 1 June 2014 and observed a single cat Felis catus in the breeding colony and the carcasses of 14 adult Black-tailed gulls that probably were killed by a cat. We also found feathers of adult Black-tailed Gulls in a single cat feces collected on the mainland of Tobishima. Approximately 1,500 nests were estimated on Tateiwa Islet in 2009, but no nests were found in May 2014. To conserve the breeding sites of Black-tailed Gulls at Tobishima, immediate control management of the feral cat population is essential.
We monitored the breeding performance of Black-tailed Gulls Larus crassirostris on Kabushima Island from 2012 to 2015. During this period mean clutch size and productivity ranged from 1.57 to 2.14, and 0.03 to 0.29, respectively. The mean clutch size in 2014 and 2015 was higher than in 2012 and 2013, but the productivity in 2014 and 2015 was lower than in 2012 and 2013.
From 2012–2015 we conducted a Monitoring Avian Productivity and Survivorship (MAPS) program in Fukushima, Japan, using constant-effort mist netting and banding. Analysis of preliminary results, including adult abundance index, productivity index, and estimated adult survival rate, from four years of data showed no trend of increase or decrease. Continuous research for five to ten or more consecutive years is necessary in order to obtain reliable trends of productivity indices and estimated survival rates. Our results suggest that it is important to consider anthropogenic disturbances when study sites are chosen. To more-accurately analyze bird populations and dynamic parameters it is necessary to revise the JP MAPS protocol to include data from more study sites.
In 2015, a nest of the Okinawa Rail Gallirallus okinawae was observed using a video camera between 7 : 00 and around 12 : 00 from 1 June to 4 June, which was the day before all chicks hatched. The parents spent 95%, 93%, 94% and 83% of observation time incubating eggs on each day, respectively. The closer to the hatching day, the higher was the frequency of egg turning. Parents were present at the nest after 10 : 00 on all observation days.