We estimated the breeding population of Streaked Shearwaters Calonectris leucomelas, and investigated their nest burrow structures on Nakanokamishima. Streaked Shearwater nest burrows were found throughout the survey area, and at highest densities in flat or gentle sloping areas. The nest burrow density was 0.64±0.22 nest/m2 for the high nest-density area, 0.19±0.15 nest/m2 for the thicket area, and 0.10±0.10 nest/m2 for the low nest-density area. Brooding nest density was 0.13±0.10 nest/m2 for the high nest-density area, 0.01±0.03 nest/m2 for the thicket area, and 0.01±0.03 nest/m2 for the low nest-density area. We multiplied the 3D area by the nest burrow or brooding nest density in each area type, and the total numbers of nest burrow and brooding nest on Nakanokamishima were estimated to be 18,853 and 2,783 nests, respectively, and breeders as 5,566 birds. Entrances of nest burrows of Streaked Shearwater positioned in slope areas tended to be directed to downward of the slope, and entrances of those in flat places tended to be directed to the nearest coast. We found two types of nest structure: straight or curved (or hooked) types. The length of burrows was 75±22 cm for the straight type and 99±20 cm for the curved type.
The Eurasian Magpie Pica pica was first recorded in Muroran City, Iburi District, southern Hokkaido, in 1984. We examined distribution changes of this species in each decade of 1984–2013 based on observations recorded by local birdwatchers. During the first decade (1984～1993) Eurasian Magpies stayed and bred in the original area, before expanding their range from the city eastward along the seaboard and further eastward beyond the study site in the second decade (1994～2003). In the third decade (2004～2013), however, they started to expand westward. It is assumed that the hills extending to the coast to the west of the city had prevented them from westward expansion. Although their breeding rate is not high, the observation of a flock of 10 birds in the third decade suggests that the population density has increased to a level that has triggered the expansion in a new direction.
Mukojima (Muko Island) of the Bonin Islands, Japan, has undergone multiple ecological changes as part of ecological restoration projects, such as the eradication of invasive species. However, the effect of these projects on the resident terrestrial birds of Mukojima are unknown. In this study, we performed censuses in two transects to record quantitative data of resident terrestrial bird species of Mukojima. In addition, all bird species observed from February to May 2008–2012 were also recorded. Only two species, the Blue Rock Thrush Monticola solitarius and the introduced Japanese White-eye Zosterops japonicus were regularly observed. There were no changes in abundance of either species between 2007 and the present study, except for an increase in the Blue Rock Thrush along one transect. We observed a total of 74 bird species, 32 of them newly recorded on Mukojima. Although preliminary, our results contribute to an understanding of the effects of ecological restoration on the avifauna of Mukojima.
On Honshu Island, Japan, the Black-faced Bunting Emberiza spodocephala generally breeds in open forests and forest edges at an elevation of 700 m – 1,600 m. However, in recent years, this bunting species has started to breed in coastal Japanese Black Pine Pinus thunbergii forest in lowland areas, such as Niigata Prefecture. Previous studies have shown that this bunting usually nests at ground level or in low shrub vegetation. In order to elucidate the tendency of habitat selection of this species in Niigata area, we compared the distribution density of territorial males between two study sites, the well-managed forest with a poor shrub layer vs the poorly-managed one with a dense shrub layer. The present data in the breeding season clearly demonstrated that this species occurred at higher density in the poorly-managed forest with a dense shrub layer habitat.
The Brown Booby Sula leucogaster is divided into four subspecies and is distributed throughout the tropical and subtropical seas of the world. This species was believed to show little movement and low or no gene flow among populations, however, there exist several records of dispersal and breeding across the East Pacific Basin, both by S. l. plotus and S. l. brewsteri inhabiting the western and eastern sides, respectively. We observed a male of S. l. brewsteri visiting Nakanokamishima, Japan, which is one of the breeding sites of S. l. plotus in the West Pacific. Presumably, it was this same individual that was observed intermittently until 2014 and bred and produced offspring with a S. l. plotus female, adapting to the breeding schedule of the Nakanokamishima population from 2012 to 2014. Another male having a white head and neck was recorded at another location on the island since 2011. Although this male often courted a female, they have not yet formed a pair. These are the first records of S. l. brewsteri breeding behaviour in Japan and provide important ecological information regarding the process of pair formation and breeding at the breeding sites of other S. leucogaster subspecies.
In the lowland deciduous broad-leaved forests of western Hokkaido, reddish-brown egg parasitism by the Oriental Cuckoo Cuculus optatus has been recorded for three species: the Eastern Crowned Leaf Warbler Phylloscopus coronatus, the Japanese White-eye Zosterops japonicus and the Asian Stubtail Urosphena squameiceps. We here describe for the first time in this area reddish-brown egg parasitism by the Oriental Cuckoo on a fourth species, the Black-faced Bunting Emberiza spodocephala, and document the incubation and feeding of a nestling by the host. The nest was built in a low bamboo clump, but was initially vacant. A single egg was laid by the parasite three days later. The incubation period was 12–13 days and the nestling period was 18 days. This case was remarkable in that the bunting accepted only one, differently colored, egg from the parasite, and fed the nestling.
Between 14th–16th July 2013, 11 species of birds were observed on Kita-daito Island, Daito Islands. Of these, six species included juveniles. In this survey, the Mallard Anas platyrhynchos which had bred there in the past, was not observed, and it may no longer be present on this island.
During the breeding seasons from 2005 to 2014, 12 females of the Mandarin Duck Aix galericulata which used three nests were observed in Hokkaido, Japan. During the incubation period, females leaving their nests to forage in the early morning and the evening were often accompanied by males when returning to their nests. The male attendance finished from mid-May to mid-June, whereas the fledging dates fluctuated from late May to late June.