The Amami jay Garrulus lidthi, a species of forest bird endemic to the Amami Islands, Japan, breeds between February and early June. The early start of breeding may give the species some advantages, such as the possibility of increased reproductive success due to breeding in a season when potential predators are inactive. However, to benefit from this potential seasonal advantage, adults must obtain enough food to successfully raise chicks throughout the breeding period. We investigated the availability food resources and the diet for Amami jay during the early breeding season. We conducted the study by observing and collecting available prey items between February and May 2012, including arthropods, with methods such as visual encounter along line transects, beating and netting from the vegetation, and pit-fall traps. We also recorded the food provisioned to chicks by identifying prey from video recordings at nest sites, and by fecal analyses of chicks.
We found that the most frequent food item provisioned to chicks were arthropods such as Blattodea, Orthoptera, Coleoptera, Mecoptera, Lepidoptera, Hymenoptera, Araneae, and Opiliones. Those results suggest that the Amami jay captures ground cursorial species during the early spring (February and March) breeding period. The availability of these arthropods varied during the season, but those arthropods were the most available prey species in terms of both population and biomass throughout the breeding season. These findings suggest that the Amami jay has a broad prey base of ground-dwelling arthropods that it utilizes, and that according to changing prey availability during the breeding season, it can vary the food items that it provisions to its young.
We have engaged in acoustic monitoring inside and outside of the evacuation zone suffered the impact of the Fukushima Daiichi nuclear power plant accident since 2014. Not only to promote communication between researchers and local community but also to improve transparency of the research processes, we held an event, “Bird Data Challenge in Fukushima”, in 2015. In the event, we listened to the audio data and made the identified species list of birds with participants using a newly-developed web-based interface for acoustic identification, “SONO-TORI”, and a semi-real-time visualization system, “SONO-TORI VIS”. In the event, 30 participants were divided into five small groups, and listened to the audio data of 63 minutes and succeeded to identify 23 bird species in total. The results of questionnaires on the participants showed that the level of satisfaction and willingness to revisit was substantially high. We also found that mutual communication between participants and improvement of identification skill had significant effects on the level of satisfaction. Although there are several things to be improved in the way to share the result with participants and to assign the appropriate tasks, our attempt showed a potential of identification of birds from recorded birdsongs as an event format of citizen-participating survey.
We observed the flight behavior of white-tailed sea eagles Haliaeetus albicilla at the town of Tomamae in northern Hokkaido from 2009 to 2016, to determine how the eagles’ flight behavior was affected by updrafts created by the topography of coastal cliffs. The frequency, location, direction and speed of eagle flights were recorded by theodolite, along with weather conditions and topographic variables. Based on those variables, a statistical model of flight behavior was created. The eagles flew in the study area most frequently when the wind blew in the west-northwesterly direction (29.5%), and in the westerly direction (23.5%). The statistical model, based on the flight frequency of the eagles and the terrain variables in the 10m grid, indicated that slope degree, slope direction (east-northeast and west-northwest), number of cliffs, and presence of coastline had a positive effect on the flight frequency. Based on this model, we performed a numerical simulation of airflow in the survey area. As a result, it was determined that as the wind velocity increased, the resulting updraft generated by the coastal cliff developed farther away from the cliff. The eagles were observed flying farther out to sea when the wind blew stronger, apparently to make use of the updraft located further from the shore. The observed flight speed of eagles flying along the cliffs was less than the minimum flight speed required to maintain their altitude, as estimated by the general lift model. In this case, eagles would be expected to lose altitude and descend. However, the result of the simulation showed that the updraft at the particular position of the eagles’ flights were stronger than the estimated subsidence force. We conclude that updrafts occurring in the vicinity of the cliffs overcome the subsidence.
We recorded the first breeding record of black-tailed gulls Larus crassirostris in TokyoBay in 2015, and again in 2016. On 18 June 2015, chicks were observed in a nest constructed on a collision-barrier protecting the pier support of a railroad bridge in Tokyo Bay. In 10 May 2016, two nests with 3 eggs were observed at the same site and an additional 10 to 20 nests were estimated around the original site. Chicks were observed on 18 May 2016, and 16 juveniles were counted on 24 June 2016. Based on the previous breeding records in Tokyo, black-tailed gulls have moved their breeding site from inland areas to more seaside areas, and have now started to breed in Tokyo Bay.
Use of foraging habitat by the Whooper Swan Cygnus cygnus was observed to determine habitat selection in relation to water level of Lake Izunuma-Uchinuma, a shallow lake in northern Japan. During the wintering season of 2008/2009, the abundance of swans was recorded at a variety of suitable foraging habitats in the vicinity of the lake. During 21 counts, the mean abundance of swans was 645 birds (range 186 to 1,239). As the water level in the lake increased, the percentage of swans foraging in the areas of lotus and wild rice significantly decreased, while swans increased in rice fields. As the aquatic plants became unavailable due to deepening of the lake, it appears that swans shifted their feeding habitats to those that remained shallow or exposed.
We report nest site characteristics and seasonality of breeding behaviors observed in a Common Crossbill Loxia curvirostra population of Shimokita Peninsula, Northern Japan. Twenty nests were observed during the six breeding seasons from 2010/2011 to 2015/2016. Observation of banded birds confirmed that at least some crossbills were residential breeders in the study site. During the winter of 2012/2013 season, when ripe pine cones were scarce, we were unable to find any nests. The crossbills of this population, therefore, seem to opportunistic breeders, as reported for populations in other countries. Most of the nests were placed at the edge of black pine Pinus thunbergii forests. The nest height ranged from 8 to 18.4 m. The main breeding season was from November to April, which seems adapted to the timing of ripening pine cones
A wind farm was constructed 3.1km offshore of Choshi city, in east-central Japan, The facility was established as a test-case, to allow studies of various related factors, including mechanical, meteorological, and environmental. To assess the risk of offshore wind turbines to seabirds, we studied the tracks of seabirds by using a marine radar in 2013 and 2016. The radar showed that the tracks of seabirds were concentrated in areas more distant from the wind turbine, and were scarcer near the turbine. The seabird tracks that did pass nearby the turbine appeared to follow routes to avoid the turbine. These observations suggest that seabirds altered flight patterns to detour around the wind turbine. On the other hand, seabirds flew significantly closer to the wind turbine in 2016 than in 2013, which may show habituation. Further study is needed to clarify the risk of offshore wind farms on seabirds, and to illustrate in detail the behavioral reactions of seabirds.
We observed the occurrence of Large Hawk-Cuckoos Hierococcyx sparverioides and Asian Koels Eudynamys scolopaceus from 2015-2017 at the Oono Forest in Miyako Island, Okinawa Prefecture, Japan. Two Asian Koels (a male and a female) were present for more than two months during the breeding season of 2015, and this suggests that they may have attempted breeding, although there was no confirmed observation of reproductive behavior. These two species are increasingly recorded in Japan, which suggests that these species are expanding their distribution northward.
We observed the inter-island movements of Japanese Wood Pigeons Columba janthina between Hachijo-jima and Hachijo-kojima in the Izu Islands on July 1, 2017. In total, about 2000 birds moved between the two islands during the 8 hours of observation. Average population density of C. janthina per 1 km of census line was much higher in Hachijo-kojima (69.93) than that in Hachijo-jima (1.54). Breeding behavior of C. janthina was also observed frequently in Hachijo-kojima, an uninhabited islet adjacent to Hachijo-jima, which seemed to be suitable breeding habitat for C. janthina because of its low degree of anthropogenic disturbance. On the other hand, due to the islet’s small size, it may be hard for C. janthina to obtain enough food resources on Hachjo-kojima. To augment the low food resources available on the smaller island, C. janthina may frequently move between Hachijo-jima and Hachijo-kojima.