Go Fujita

Forest edge creates small-scale variation in reproductive rate of sika deer

Habitat edges are considered to have an important role in determining the abundance of deer in forest landscapes, but to our knowledge there are few lines of evidence indicating that forest edge enhances the vital rate of deer. We examined pregnancy of female sika deer in Boso peninsula, central Japan, and explored how forest edges, food availability in forests, and local population density influence the pregnancy rate of sika deer. Local deer density was estimated by the number of fecal pellets, and food availability in forests was estimated by combining GIS data of vegetation distribution and the relationship between vegetation biomass and local deer density. Forest edge length was also determined by GIS data. Model selection was performed with multiple logistic regression analyses using the AIC to find the best model for accounting for the observed variation in pregnancy rates of the deer. Multiple logistic regression analysis showed that the length of forest edge had a positive effect on the pregnancy rate of females, whereas food availability in forests and local deer density had little effect. This forest edge effect was detected in a 100–200-m radius from deer captured locations, indicating that deer pregnancy is primarily determined by habitat quality within a 10-ha area. This result was confirmed by tracking females with GPS telemetry, which found that the core areas of the home range were less than 12 ha. The positive effect of edges and the lack of density dependence could be a result of high plant productivity in open environments that produces forages not depleted by high deer densities. Our results support the view that land management is the cause of the current problem of deer overabundance.

DECISION-MAKING IN GROUP FORAGERS WITH INCOMPLETE INFORMATION: TEST OF INDIVIDUAL-BASED MODEL IN GEESE

One important challenge of spatial ecology is to generate models linking individual behavior to population-level phenomena. Although animals often face great uncertainty regarding foraging patch quality, earlier models explaining the aggregation of animals have rarely specified how stable outcomes are achieved through individual decisions, especially under realistic assumptions for incompletely informed foragers. We developed a new foraging model that assumed a realistic decision-making rule for incompletely informed group foragers, and we tested its performance against existing models with different assumptions by comparing how well they reproduce the patterns observed in foraging White-fronted Geese (Anser albifrons). The assumptions in each of the four compared models were: (1) incompletely informed foraging with benefits of group foraging, which uses the expected gain rates for making decisions on diet choice, patch departure, and flock joining; (2) incompletely informed foraging without benefits of g...

Satellite tracking of the migration of the red‐crowned crane Grus japonensis

Autumn migration routes of red-crowned cranes, Grus japonensis, from two continental east Asian sites were documented in detail by satellite tracking. Two routes were identified: a 2200 km western route from Russia’s Khingansky Nature Reserve to coastal Jiangsu Province, China; and a 900 km eastern route from Lake Khanka (Russia) to the Korean Peninsula and the Demilitarized Zone. The most important rest-sites were identified as Panjin Marsh (China), coastal mudflats south-east of Tangshan City (China), the Yellow River mouth (China), Tumen River mouth (North Korea/China/Russia), Kumya (North Korea) and Cholwon (Korean DMZ). Movements within the wintering range were also recorded, including complex commuting between sites by individual cranes and patterns of daily movements within sites. These data should prove useful for conservation of the flyway.

Spring Migration Routes of Mallards (Anas platyrhynchos) that Winter in Japan, Determined from Satellite Telemetry

Abstract Wild birds, in particular waterfowl, are common reservoirs of low pathogenic avian influenza viruses, and infected individuals could spread the viruses during migrations. We used satellite telemetry to track the spring migration of the mallard ducks (Anas platyrhynchos) that winter in Japan. We studied their migration routes, distribution of stopover and breeding sites, and timing of migration movements. We tracked 23 mallards from four different wintering sites. Nine of the 23 mallards reached presumable breeding sites, where migration terminated. The migration routes of the birds greatly differed not only among the wintering sites but also within the same wintering site, although the general feature of the routes was shared among birds within the same wintering site. The mallards used several stopover sites, and they typically stayed for a long period (about one to four weeks) at a site between migration intervals of two to three days. Stopover sites were located in northeast Japan, the eastern coastline of South Korea and North Korea, and the interior of Far Eastern Russia. Mallards from three different wintering sites used a stopover area near the middle part of the Ussuri river in Russia. The terminal sites, which were presumably also breeding sites, were distributed widely over northeast Asia and Far Eastern Russia. These results suggest that mallards that winter in Japan originate from breeding areas widely distributed across eastern Asia. Mallards could potentially transmit avian influenza viruses between Japan and a broad region of northeastern Asia.

Low Level of Extra-Pair Paternity in a Population of the Barn Swallow Hirundo Rustica Gutturalis

Abstract On average, male birds other than social father sire more than 10% of all offspring. Levels of extra-pair paternity below 5% of offspring are rarely found and are now considered worthy of explanation in monogamous birds. We recorded the lowest levels of paternity loss ever reported in a population of Barn Swallows Hirundo rustica. The levels of extra-pair paternity were below 5% of offspring (7/243 in 2005 and 1/53 in 2006). We discuss our results in relation to the density-dependence of extra-pair paternity.

Evidence for intercontinental parasite exchange through molecular detection and characterization of haematozoa in northern pintails (Anas acuta) sampled throughout the North Pacific Basin

Graphical Abstract

Barn swallows prefer to nest at sites hidden from neighboring nests within a loose colony

Some loosely colonial species scatter their nests within a colony. Most studies on mechanisms that generate such scattered nests within a colony have primarily focused on the measurement of distance related to the intensity of interactions among conspecific neighbors. However, these interactions can change not only with distance between nests but also with other factors. In particular, whether the nest is hidden from neighbors can strongly affect the intensity of interaction for birds that usually use sight for communication. To show the possible benefit of nesting at sites hidden from neighboring nests, we studied the nest arrangements and settlement patterns within a barn swallow colony. We tested whether the swallows prefer nesting at sites hidden from neighboring nests in cattle barns that are often used as colony sites by the swallows in Japan. We found that the sides of ceiling beams hidden from neighbors were preferred as nesting sites. A randomization test suggested that the rectangular sections occupied by swallows were not spaced out within a colony. The results suggested that the swallows preferred nesting sites hidden from their neighbors and did not space out their nests within a colony. This paper also refutes intraspecific brood parasitism as a plausible function of this behavior.

Satellite tracking of migrating Whooper Swans Cygnus cygnus wintering in Japan.

Abstract We satellite-tracked Whooper Swans Cygnus cygnus wintering in northern Japan to document their migration routes and timing, and to identify breeding areas. From 47 swans that we marked at Lake Izunuma-Uchinuma, Miyagi Prefecture, northeast Honshu, and at Lake Kussharo, east Hokkaido, we observed 57 spring and 33 autumn migrations from 2009–2012. In spring, swans migrated north along Sakhalin Island from eastern Hokkaido using stopovers in Sakhalin, at the mouth of the Amur River and in northern coastal areas of the Sea of Okhotsk. They ultimately reached molting/breedmg areas along the Indigirka River and the lower Kolyma River in northern Russia. In autumn, the swans basically reversed the spring migration routes. We identified northern Honshu, eastern Hokkaido, coastal areas in Sakhalin, the lower Amur River and northern coastal areas of the Sea of Okhotsk as the most frequent stopover sites, and the middle reaches of the Indigirka and the lower Kolyma River as presumed breeding sites. Our results are helpful in understanding the distribution of the breeding and stopover sites of Whooper Swans wintering in Japan and in identifying their major migration habitats. Our findings contribute to understanding the potential transmission process of avian influenza viruses potentially carried by swans, and provide information necessary to conserve Whooper Swans in East Asia.

What landscape elements are correlated with the distribution of wintering Grey-faced Buzzards Butastur indicus in the Sakishima Islands, southwestern Japan?

ABSTRACT The Grey-faced Buzzard (Butastur indicus) is a typical migratory raptor species in East Asia, and has suffered a population decline recently. In southern Japan, the wintering buzzards are widely distributed to the Sakishima Islands. The mainly human activity on these islands is agriculture, and the natural environments are fragmented by such exploitative land-use that produces a characteristic landscape pattern. In this study, we describe the distribution pattern and habitat selection of the buzzards wintering in the Sakishima Islands, and focus on landscape elements in order to give a basic reference for further conservation study. Ten islands were investigated during January to March 2005. We used the generalized linear mixed model (GLMM) on a set of landscape elements to model buzzard distribution in the 1×1 km grid cell within each island, and studied the relationships between the numbers of buzzard and landscape elements among islands by using the generalized linear model (GLM). The results were similar on two spatial scales, and they both suggested that the area of farmlands (sugar cane, pasture, and rice paddy), and the perimeter of forests have significant correlation with the distribution and the numbers of the wintering buzzards. Different from breeding sites where distribution was limited by critical nest resource, distribution of Grey-faced Buzzards in wintering sites was simply related to foraging habitats. We suggest that further study should focus on measuring quantitatively the relationships of different farmland types with buzzard distributions in order to make more realistic predictions about distribution when habitat is lost or shifted from one category to another.

Seasonal and Sexual Differences in Migration Timing and Fat Deposition in the Greater White-Fronted Goose

Abstract We investigated fat deposition and the timing of departure of Greater White-fronted Goose Anser albifrons at Lake Miyajimanuma, Hokkaido, which is the largest stopover site in northern Japan, focusing on the differences between seasons and between sexes. We assessed the fat mass of neck-banded geese by observing their abdominal profiles. In spring, the variation in departure dates among individuals was smaller than that in arrival dates, and there was a positive correlation between arrival dates and departure dates in the fall. The factors affecting decision-making relating to the timing of departure are assumed to be the time constraints of migration before breeding in the spring and on the duration of stay in the fall. The spring fat increase in females was larger than in the fall, and had a tendency to be larger than in males in the spring, The seasonal and sexual difference in fat mass increase seems to be explained by the requirement of fat for breeding after departing from the stopover site. This study supports the possibility that migratory birds adjust their fat mass and the timing of departure at stopover sites according to seasonal differences in events occurring after migration, such as breeding.