During the 1970s, the Little Egret Egretta garzetta was a common species in the rice field dominated landscape in and around Higashimatsuyama City, central Japan. Based on field data collected from1970 to 2015, I investigated seasonal and annual variation in the densities of various heron species including the Little Egret, along with the abundance indices of major prey species (fish and shrimp), and the breeding density of the Northern Goshawk Accipiter gentilis (a possible egret predator) in the area. While the Little Egret declined over the study period, both the Great Egret Ardea alba and Grey Heron A. cinerea increased. There was no evidence of a reduction in fish or shrimp, but goshawks increased during the 1980s and 1990s following the first observation of breeding in the area in 1982. The reduction of Little Egrets seems to have coincided with the increase of Northern Goshawks in this area. Some indications were found of goshawks having hunted Little Egrets, and as the egrets forage in open farmland and as goshawks prefer to hunt over the same habitat, I suspect that predation by Northern Goshawks may have been a factor in the local decline of the Little Egret. Further studies are required to eliminate other possible factors that may have contributed to the reduction in Little Egret numbers, such as local variation observed in the abundance indices of fish and shrimp, which may have been caused by increases in the numbers of Great Cormorant Phalacrocorax carbo and/or Largemouth Bass Micropterus salmoides.
Preservation of biological specimens contributes to knowledge of historical variation in morphology and geographical distribution of species. In some cases however, older specimens have no associated information concerning their collection, and thus cannot be effectively used. The present study aims to increase the value of such specimens as resources for research by focusing on a Grey-headed Woodpecker Picus canus specimen (YIO-23324) at the Yamashina Institute for Ornithology, for which the date of collection was not known. I attempted to reconstruct information, such as the year of collection, by inspecting the attached labels and by examining information contained in the collector's field notes. I found that the specimen must have been collected prior to 1885, as evidenced by the attached labels used by the University of Tokyo, to which the specimen previously belonged. Furthermore, the collector's name “Blakiston” was recorded on the label, and by comparing it with the field notes of Thomas Blakiston (a significant contributor to the modernization of Japanese ornithology), it became clear that Blakiston had collected the specimen in May 1881. With reference to this result, I organized corroborating information for the fact that some of the undated specimens in the Yamashina Institute for Ornithology collection, which formerly belonged to the University of Tokyo, were collected in the 19th century. Clarification of a specimen's history and continued data cleansing are necessary for the reliable pursuit of research using old specimens.
Avian diversity in urban areas can be strongly affected by the presence of rivers. However, to date this effect has not been quantitatively assessed. We established 16 observation points along the Kameda River, which flows through Hakodate City, Hokkaido, Japan. Half of these were set alongside the river, whereas the other half were set in residential areas, 200 m from the river. We recorded the number of bird species and individuals of each species at the observation points during summer and winter 2015. During both seasons we observed significantly higher numbers of species and individuals along the river than in the residential areas, indicating that the Kameda River provides habitats for a wide range of bird species and enhances the bird diversity in Hakodate City. We also found that the number of species recorded along the downstream section of the river decreased during summer but increased during winter. This was probably because some species breed only near the upper reaches of the river (near the mountains), during summer, while many waterfowl spend the winter along the lower reaches of the river where the flow is slower. These findings suggest that the effect of the river on the urban bird community changes not only between sections of the river, but also between seasons.
We investigated the nest-site characteristics of Grey-faced Buzzards Butastur indicus in Fukuoka, southwest Japan, and compared them with those described in previous studies in other regions. To compare the species composition of nest-trees across regions, we used data on the nest-trees of buzzards in our study area, comparing the local habitat characteristics of each nest-tree, and using data from 31 nest sites among various data sets. We described the following characteristics of nest sites: tree species, nest tree height, DBH, topography, and height of nest. Previous studies conducted in Tochigi, central east Japan, and Osaka, central west Japan, showed that Grey-faced Buzzards prefer to nest in coniferous trees such as Japanese Cedar Cryptomeria japonica and Japanese Red Pine Pinus densiflora. In Fukuoka, however, buzzards were not confined to nesting in coniferous trees, but also nested broad-leaved trees. The proportion of nests in coniferous trees in this study (52%) was considerably lower than in other areas (100% in Osaka and Tochigi, 90% in all regions other than Fukuoka). These results suggest the possibility that the nest-site characteristics of raptors may differ among regions.
Observations of Okinawa Rail Gallirallus okinawae feeding behavior and of cracked snail shells revealed a correlation between shell-cracking techniques using anvil stones and cracked shell types. Three infrared cameras were used to study rail behavior around stone anvils in the forests surrounding Kunigami Village, northern Okinawa Island. Snail shells were collected for analysis. Four individual rails were recorded smashing shells against fixed stone anvils; the first time this behavior has been described for the Okinawa Rail. Snail shells were classified into four types according to the manner in which they were cracked. It is suggested that rails cracked the majority of the shells (of two types) in order to feed on the snails. The use of anvils by rails to crack snail shells allows them to feed on snails that are too large to be swallowed whole, but which are commonly available on Okinawa Island.
The Cattle Egret is a species known to have undergone recent range expansion at the global scale. We used satellite tracking to follow the long-distance movements of two Cattle Egrets caught in eastern Japan during/after the 2006 breeding season. Both egrets migrated to winter in the central Philippines, but in spring 2007 while one of them returned to the area where it had been first caught, the other migrated to the mouth of the Yangtze River, China, and spent the breeding season there at a location 1,900 km west of where it had been originally captured. This is the first record of long-range breeding dispersal in the Cattle Egret confirmed by satellite tracking.