Little information is available about the forest bird fauna of Fukushima Prefecture where radioactive fallout has accumulated following the Fukushima Daiichi nuclear power plant accident in March 2011. Here, we describe observations of 103 bird species in a forested area of Fukushima City known as Kotori-no-mori Sanctuary (52ha), from April 2003 to March 2013. These consisted of 35 resident species (34%), 10 summer breeders (9.7%, which remained for an average of 3.7 months), 19 winter visitors (18.4%, which remained for an average of 4.4 months), 5 migratory visitors (4.9%), 12 irregular visitors (11.7%), and 22 accidental visitors (21.4%). The recording ratios of Zosterops japonicus during the breeding and wintering seasons, Ficedula narcissina and Hirundo rustica during the breeding season, and Periparus ater during the wintering season increased annually, whereas the ratio for Passer montanus decreased annually before the nuclear accident. After the accident recording ratios of Cettia diphone, Motacilla alba and Passer montanus increased, whereas Picus awokera, Phylloscopus coronatus, and Motacilla cinerea decreased.
In this paper we present Caesium (134Cs and 137Cs) activity concentrations as measured during two life stages of passerine birds collected in Fukushima prefecture one year after the nuclear accident. We examined various adult specimens (i.e. Varied Tit Poecile varius, Oriental Greenfinch Chloris sinica and Eurasian Tree Sparrow Passer montanus) and un-hatched eggs of Japanese Tit Parus minor, and we subsequently estimated internal and external dose rates (and thus total dose rate) received by these organisms. We showed that the contribution of external dose rate to the total dose rate varied in relation to life stage (i.e., whether adult or egg) and to the contamination of the main surrounding micro-habitats in which the organisms spent most of their time (i.e., nest material for eggs, and air and soil for adults). In the un-hatched eggs, the external dose rate was higher than the internal one and was mostly driven by the nest material, the difference reaching about four orders of magnitude, because nest material was mainly composed of mosses, which are known to retain high quantities of radionuclides. In addition, estimated total dose rates were drastically greater than the ambient dose rates measured in the field. Our study underlined the importance of performing detailed dose analysis and of carefully considering the ecology of the species studied in future field cases when assessing radiation exposure effects on wildlife, in order to better predict potential harmful biological effects on individuals.
We measured the cesium [Cs-134 + Cs-137] concentration of nest material (mainly mosses) used by Japanese Tit Parus minor and Varied Tit Poecile varius (6.6-6,128.9 Bq/g dry weight, n = 14), collected in Tokyo, Nagano, Ibaraki, and Fukushima prefectures (1 m air dose rate: 0.11-21.4 μGy/h) after the Fukushima-Daiichi Nuclear Power Plant accident in 2012. The cesium concentration of nest materials increased significantly with the increment of the air dose rate, suggesting that air dose rate at nest sites provides an available indicator of the relative levels of nest contamination.
To investigate the effect of organic farming on food intake and abundance of three egret and heron species (Great Egret Ardea alba, Intermediate Egret Egretta intermedia, Grey Heron A. cinerea), field surveys were conducted in conventional and organic rice fields in five cities in Ibaraki and Tochigi prefectures, Japan, from May to July 2013 and 2014. Direct observation of prey captures revealed that fish (mainly Oriental Weather Loach Misgurnus anguillicaudatus) and frogs Rana spp. are the primary food sources, although their compositions differed among bird species; proportion of fish biomass was higher in the order of Great Egret, Intermediate Egret and Grey Heron. In addition, for all three species, composition of fish mass in organic fields was higher than that in conventional ones. Generalized linear models showed that organic farming had a positive effect on food intake rates (g/min) although the effect seemed to be clear only for Great Egret. Organic farming also had a positive effect on the abundance of foraging Great Egrets and Grey Herons. Therefore, we concluded that the benefit of organic farming was consistently shown for Great Egret, but not for Intermediate Egret and Grey Heron, possibly due to differential effects of rice pesticides on prey species (e.g., fish and frogs) and the small area of organic rice fields in Japan (only 0.28% of rice fields are managed for organic farming in Japan amounting to 18-68% of census plots in this study).
The Mountain Hawk Eagle Nisaetus nipalensis is listed as threatened under the Endangered Species Preservation Act. Although its recent breeding rate has been considered to be in decline, no broad-based study has been conduced throughout Japan. We studied the breeding rate and related environmental factors from 15 years of data collected by the Ministry of Land and Transport and the Agency of Water Resources from 1994 to 2008. We found that the average breeding rate was 33.2% (N = 512) and that no apparent decline was occurring. Snow depth, beech mast production and breeding success (or failure) of the previous year, were possible environmental factors that affected breeding.
Three species of crows, Carrion Crow Corvus corone, Large-billed Crow C. macrorhynchos and Rook C. frugilegus (a migratory winter visitor) often roost together in Shonai, Yamagata Prefecture, Japan. In order to help understand how these closely related crow species are able to live together in the same locality, we investigated their food habits by DNA analysis of their pellets. Pellets were collected from beneath roosts for analysis of their DNA and species contents. The percentages of three food groups: (a) invertebrates, (b) plants and (c) ‘others’ found in pellets were as follows: Carrion Crow (a) 77.1, (b) 82.1, (c) 10.6; Large-billed Crow (a) 43.9, (b) 73.8, (c) 47.2, and Rook (a) 17.1, (b) 97.6, (c) 0. Carrion Crow pellets contained such organisms as ground wandering arthropods, herbaceous plant fruit seeds, and small herbivorous insects inhabiting paddy fields or wetland edges. These organisms typically occur close to the ground surface. Organisms inhabiting paddy fields were detected in Carrion Crow pellets throughout the year. In addition, they included items such as fruit seeds and insects that occur in tree crowns. In contrast, Large-billed Crow pellets were found to contain items typically found in trees, urban areas and garbage, whereas Rook pellets included mainly residual post-harvest rice grains derived from paddy fields. We conclude that although the diets of these three crow species overlap partially, Carrion and Large-billed Crows segregate based on feeding sites. There was an overlap between the feeding sites of Carrion Crow and Rook, but only when residual post-harvest rice grains in paddy fields were abundant. Such dietary preferences and differences in foraging habitats may allow the co-existence of these three species within the same locality.
The assimilation efficiency and growth of Rhinoceros Auklet Cerorhinca monocerata chicks (30-35 age of days) fed with Japanese Sand Lance Ammodytes personatus and Antarctic Krill Euphausia superba were investigated. Chicks were fed 79.4 ± 3.1 gwet /d (mean ± SD) of sand lance, which included 497.2 ± 14.9 kJ energy, 4.3 ± 0.2 g lipid, and 12.3 ± 0.5 g protein. Chicks were fed 129.3 ± 2.7 gwet /d krill, which include 746.8 ±15.5 kJ energy, 3.1 ±0.1 g lipid, and 23.3 ±0.5 g protein. The assimilation efficiency (corrected with nitrogen retention) of the sand lance-fed chicks (82.8 ±0.5%) was significantly higher than the krill-fed chicks (76.6 ±0.6%). During the experiment, daily mass increments of the sand lance-fed chicks were 11.0 ±4.7 (g/d, n=12) and of the krill-fed chicks 9.7 ±2.7 (g/d, n=14). Sand lance-fed chicks gained body mass significantly faster than did krill-fed chicks after controlling for the significant age effect. Krill may be inadequate for chick growth of the auklets due to the poorer lipid content, compared with sand lance.
The urban biodiversity is a modern concern warranting particular attention. As bioindicators, birds often contribute to the assessment of urban biodiversity; therefore, understanding habitat selection by urban dwelling birds may assist in the maintenance and management of urban biodiversity. However, habitat use by small birds in urban areas on a small scale has been little studied, so far. Here, we aim to reveal where and how the Eurasian Tree Sparrow Passer montanus utilizes a residential area during the winter in Iwate Prefecture, northern Japan. The relationships among sparrow flock size, flock location, nesting site and seasonal changes are the primary focus of our study. Flocks were observed from October 2012 to April 2013. Nests were surveyed during the 2012 and 2013 breeding seasons. Our results revealed that the total number of sparrows and average of flock sizes changed seasonally. In mid-winter, the total number of sparrows was at its lowest, yet the average flock size was greatest. Such changes may have been caused both by severe weather conditions (snow and low-temperatures during mid-winter) as well as by preparation for breeding in early and late winter. Sparrows were not dispersed everywhere, instead they gathered in flocks at particular sites. The average distances between flocks and the nearest nest site were less than 40 m; in fact some old nest sites were used as roost sites. High ranked kernel density areas were located in unpaved areas and/or close to nests, especially in mid-winter. Moreover, new nest sites were commonly constructed within 30 m of old nesting sites. Eurasian Tree Sparrows, it seems, display a level of nest fidelity. Based on such nest-site fidelity it might be possible to control future nesting sites of Eurasian Tree Sparrow through the provision of nest boxes.
Eurasian Coot Fulica atra at Lake Ogawara, Aomori Prefecture, Japan were found to take various aquatic plants, in particular Potamogeton, Najas, Typha, and algae were all important foods for both parents and chicks. Chironomid and Dragonfly (larva and imago) were also fed to chicks. Aquatic invertebrates in general were important food resources for coot chicks. The diet and size of food items fed to chicks were regulated by chick development.
Trios (1♂-2♀) of Carrion Crows were observed in three territories. They occurred when the alpha female had failed to breed for several years. In two cases, the new individuals were fledglings from neighboring territories. One of them laid eggs when two years old. The second females bred successfully after the alpha females had died or disappeared. Temporary bigamy might be involved during the process of mate change. Techniques normally used when studying primates applied to individual identification of Carrion Crows are effective, provided that unchanging characteristics of the individuals concerned are systematically recorded and detailed long-term observations based on such characteristics are possible.
Number of Spectacled Guillemot Cepphus carbo around Teuri Island, Hokkaido, Japan were counted by boat and land-based surveys from 1994 to 2014. The numbers showed marked seasonal differences with the maximum occurring in the pre-laying period. Estimated annual maxima, incorporating this seasonal change, decreased 9.6% ± 1.7% per annum from 1985 to 1995, while counted annual maxima increased 9.7% ± 1.6% per annum from 2004 to 2014, though numbers were fewer than in the 1980s. The number of active nests was 118 in 2013 and 169 in 2014, and was 0.31-0.34 of the maximum number.