The Eurasian Tree Sparrow Passer montanus is one of the most common urban avian species in Japan; it predominantly nests in artificial structures. Humans act as ecosystem engineers, unintentionally providing nest sites for these birds. Birds nesting on utility poles can cause electrical power failure in the surrounding area; thus, such nesting behavior may impose risks and losses on the human community. While it is necessary to prevent sparrows from causing power failure through nesting on utility poles, this is in conflict with the global trend of promoting biodiversity in cities. Our aim was to obtain basic information concerning nest site selection on utility poles by Eurasian Tree Sparrows, in order to find ways for humans to coexist with this species. Our main results were as follows: (1) sparrows built nests in arms, the most common material of power poles; (2) the number of nests per utility pole differed between regions because different power companies use distinct arms; and (3) even within the same region, the number of nests on utility poles differed between urban and suburban areas. For humans to coexist with Eurasian Tree Sparrow, while supporting their population, it may be necessary to provide the birds with alternative nest-sites and to preclude them from nesting on power poles.
Amami Woodcock Scolopax mira is endemic to the islands of Amami-oshima (and its surrounding islands) and Tokunoshima, in the Nansei Shoto archipelago of southwestern Japan. The species is designated as vulnerable in the IUCN Red List and is under conservation management. Knowledge of behavioural sexual differences is essential to design an effective conservation plan for this species. However, because neither morphological sexual differences nor field criteria for sex determination are known for the Amami Woodcock, behavioural sexual differences remain mostly unknown. In the hope of revealing behavioural and morphological sexual differences, we banded and measured Amami Woodcock and determined the gender of banded birds using molecular sexing of sampled feathers. On Amami-oshima, adult females were found to be larger than adult males in six of nine external parameters (exposed culmen length, nalospi, bill width, bill height, total head length and weight), whereas males had longer tails than females. Using these data, a linear discriminant formula for sex determination was derived and it correctly designated approximately 86% of the birds banded on Amami-oshima. The formula was similarly valid for adults on Tokunoshima, but invalid for juveniles. During the mating period and in the early breeding season (March/April), adult males were more frequently captured than adult females. This difference in capture rate was considered to be associated with behavioural differences, in particular because males frequently display during this period, whereas females are incubating. This result suggests a likely male-biased risk of mortality on roads during March and April, the period when such mortality is most abundant. Among juveniles, a female bias in trapping was found during the late breeding season (May/June) and during the dispersal period of juvenile birds (November/December). The latter is likely to be associated with female-biased long-range dispersion, although the reason for the former is unknown.
To evaluate the effect of mass stocking of fish on the distribution of communal roosts or breeding colonies of Great Cormorants Phalacrocorax carbo, we examined the relationship between the size of cormorant roosts or colonies and the amount of Ayu Plecoglossus altivelis released within 20 km of each cormorant aggregation site in the Kanto region of Japan for three years (2006-2008). Approximately 14,000 Great Cormorant occur in the Kanto region and about 120,000 kg of Ayu are released in the region each year. This quantity of fish represents a substantial potential food resource for cormorants. Assuming that a cormorant consumes 500 g of fish per day, the Ayu stock is equivalent to the food requirements of all the Cormorants in the Kanto region for 17 days. Two hypotheses were examined by using generalized linear mixed models: first we tested whether the size of cormorant roosts or colonies in March was affected by the amount of Ayu released within their foraging range (20 km); and second we tested whether changes in the size of cormorant roosts or colonies from March to July were affected by the amount of Ayu released per cormorant. No relationship was observed between the size of cormorant roosts or colonies and the amount of Ayu released, suggesting that cormorants do not select the location of their roosts or colonies according to the amount of Ayu released. The rate of increase in cormorant roost or colony size from March to July was significantly greater in areas with larger quantities of Ayu per cormorant, suggesting that cormorants may increase their roost or colony sizes during the breeding season either through enhanced reproductive success or immigration.
In order to conserve the threatened Japanese Night Heron Gorsachius goisagi, a habitat model was established based on surveys in the West Mikawa area of Aichi Prefecture. Using presence or absence data as an objective variable, we generated a logistic regression model with seven environmental variables as explanatory variables. The best model revealed that precipitation and the number of abandoned rice fields were positively related with occurrence. Such habitat was considered to provide large amount of food resources such as crabs and earthworms, and preferable nesting trees such as broad-leaf trees. The same model showed that forestry plantations were negatively related with occurrence.
To establish a simple and strict method for molecular sexing of Grey-headed Lapwing chicks, we attempted to extract DNA from natal down. Sex-linked CHD genes were successfully amplified with the DNA samples as templates in PCR. DNA extracted from natal down was shown to be sufficient for this purpose. Using this method, of 30 chicks from 17 nests, each of 14 females and 16 males were clearly sexed. Obtaining DNA from natal down is not only easy for researchers, but also one of the least invasive methods for the study of chicks.