Although several bird species, including sparrows and swallows, nest on or in man-made structures, so far, this has been considered as a strange phenomenon in Japan. However, as it may already be common in urban areas I reviewed cases of the use of man-made structures by birds as nesting sites in Japan and proposed various viewpoints from which to examine the scientific significance the phenomenon. These viewpoints are: (1) nesting on or in artificial structures is an interaction between birds and humans, (2) human culture has led to birds changing their nesting behavior, (3) vice versa of (2), (4) birds adapt to human behavior, (5) man-made structures can be a significant factor determining urban avian communities, (6) man-made structures can serve as a conservation tool to protect certain bird species. Since nesting on artificial structures may cause conflict between humans and birds, it is necessary to comprehensively consider the effect of this phenomenon.
We conducted route censuses of the near threatened Ryukyu Scops Owl's Otus elegans throughout forest areas on Amami-Oshima Island, including mature and secondary broad-leaved forests during the breeding season of 2017. A total of 98 fledglings were detected at 58 points during censuses conducted from 27 June to 25 July; fledglings were detected on more than one day at 13 of these points. We tested a GLMM model with detection/non-detection as a categorical response variable for 53 fledgling detection points and 54 non-detection points randomly located along the individual census routes at approximately the same rate as the detection points. Five explanatory variables were examined: area of forest vegetation (evergreen broad-leaved, secondary evergreen broad-leaved, secondary conifer or secondary deciduous broad-leaved), area of open land, length of forest edge, distance from residential area, and elevation. The model showed a high explanatory power, when it included variables for the area of evergreen broad-leaved forest (positive effect), probably because mature sub-tropical evergreen broad-leaved forest contains more old trees with cavities suitable for nesting in by O. elegans.
At sea behavior of pelagic seabirds can be recorded continuously only by biologging technique. Using the moving speed measured by this technique, on-water/feeding behavior of Procellariiformes that mainly feed on the sea surface can be recorded, but the accuracies have not been determined. To record on-water/feeding behaviour of Black-footed Albatrosses Phoebastria nigripes, we used GPS and acceleration loggers to measure the moving speed, the angle, and the dominant moving cycle of the neck of two individuals that made foraging trips of 213 hr in total from Torishima during their chick brooding period. Accuracies were determined using the still-images taken by the camera loggers at 1–2 min intervals. The proportion of the on-water images (true on-water) categorized as landing on water referring to moving speed was 69–87%, but that referring to acceleration of the neck increased to 100%. Eight of the ten on-water events confirmed with images of potential prey (true feeding), presumably squid, for one bird were categorized also as feeding by referring to acceleration. The accuracy of determination of feeding was unreliable for a second bird, since it indicated only two on-water events with prey images. The duration of on-water bouts with feeding (6.9–16.9 min), determined using acceleration, were longer than those without feeding (3.4–8.0 min). On-water bouts with feeding were often observed during daytime (0.4/h), but some in twilight (0.2/h) and a few during the night (0.1/h). This study shows that landing on water and feeding can be determined using the acceleration of the neck, though the small sample size and the sampling bias of the images (only in daylight) make the conclusions indefinite. Nevertheless, this study indicates that this technique can improve our understanding of the foraging ecology of large surface feeding seabird species.
The use of automobiles to crack open nuts by the Carrion Crow Corvus corone is a remarkable example of tool-use among birds. Previously only studied in Sendai City, during the 1990s, we studied this behavior in Hakodate City, Hokkaido, Japan during autumn and winter 2016, and compared our results with those from Sendai. Certain differences between them were noted. In Sendai, crows were observed to place walnuts in front of cars stationary at traffic signals. This efficient means of breaking walnuts was not observed during our study. Instead, in Hakodate, crows frequently dropped walnuts randomly from electric lines onto roads, which did not seem an effective way of placing the nuts where they were most likely to be broken. Our results suggest that the nut-cracking behavior of Carrion Crows in Hakodate is less sophisticated than that in Sendai. The difference may be a consequnce of several factors such as the length of the cultural learning period history, the learning environment, or features of the walnuts.
Lake Jusan, Northern Honshu, is a major stopover site for geese and swans during spring migration; however, a wind farm is scheduled to be construct in rice fields southeast of the lake. To understand both the habitat use and flight paths of geese and swans in the area before construction of the wind farm, we investigated the number of migratory waterfowl, their migration period, flight direction, flight path and altitude. Our four-year study found that 36, 726–115, 233 geese and 3,415–6,743 swans migrated via the lake every year. The geese began migrating before dawn and most of them flew to the north or northeast; intensive flight paths were observed above the rice fields and the river southeast of the lake. The swans migrated after dawn and most of them flew northeastwards along the river. Migratory geese and swans frequently flew at altitudes corresponding to the heights of wind turbine blades, while birds flying between roosting and foraging sites flew at the same height or lower. Research results suggest that there are three areas of concern: 1) collision risk (the huge number of migrant waterfowl using the area and correspondence between their flight heights and the blades of the wind turbines are cause for great concern after construction of the wind farm); 2) habitat loss and displacement (the wind farm is going to be constructed over rice fields that currently serve as an important foraging site for waterfowl); 3) increased flight costs (the large number of wind turbines to be placed southeast of Lake Jusan will likely lead to increased flight costs for waterfowl while they move between roosting and foraging sites and when migrating as they divert to avoid the turbines). To mitigate these concerns, future study is indispensable after the construction of the wind farm.
The Large-billed Crow is a common and widespread species throughout Japan. However, its life history, behavior and cognition are not well described. In this study, we focused on the species' food storing behavior, specifically whether it exhibits characteristic preferences for food cache sites. We found that the crows preferred to store food in the crowns of tall evergreen conifer trees, perhaps implying that they choose locations that provide good opportunities for hiding food.