Katsumi Ushiyama

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...

Methods of Predicting Risks of Wheat Damage by White-Fronted Geese

Abstract Accurately predicting occurrence of wildlife damage is crucial for effective management of problematic wildlife species, because accurate predication allows deterrence efforts to be focused at sites or times where damage is most likely. We explored methods to predict occurrence of white-fronted geese (Anser albifrons) grazing in wheat fields around Lake Miyajimanuma, Japan. Depletion of waste rice grains caused geese to forage on wheat leaves in spring, reducing wheat harvest in grazed fields. The cumulative number of goose-days per hectare of rice-planted area from the beginning of the staging period explained the variation in the proportion of geese foraging in wheat fields. A logistic regression model on the location of vulnerable fields showed that goose grazing was likely to occur in wheat fields far from roads and windbreaks and those close to (within 1,000–2,000 m of) previously grazed fields. Although probability of occurrence of goose grazing was initially low in wheat fields with scaring devices, effectiveness of such devices was lost over the 4 survey years. We recommend farmers in the study area prepare counter-damage measures when the cumulative number of goose-days per rice-planted area approaches a threshold above which some geese are predicted to start foraging on wheat (e.g., 199.46 goose-days/ha rice ± 28.95 for 10% of geese foraging on wheat). Further, farmers should be aware that grazing on wheat is more likely to occur if wheat fields within 1,000–2,000 m have already been exploited during that particular season and should concentrate deterrence efforts to wheat fields that are far from roads and windbreaks. Systematic deployment of scaring devices over the entire habitat has a risk of accelerating the decline in effectiveness. Thus, we need methods to retard goose habituation to scaring devices, such as scaring with guns, providing alternative feeding sites, and preventing diet change by geese.

Creating a potential distribution map for Greater White-fronted Geese wintering in Japan

Abstract For species conservation, identifying factors that affect the distribution of the target species is essential. To provide basic information for the conservation of Greater White-fronted Geese in Japan, this study investigated factors associated with the distribution of the species by using data from the nationwide waterfowl survey. The geese were observed in 88 grid cells (about 10 km×10 km) in 2008–2012. The maximum entropy approach was adopted to model the distribution using presenceonly data. Explanatory variables were the proportion of rice field area, urban area, and lake area; distance to lakes; and maximum snow depth. Spatial filters were also included in the model to account for spatial autocorrelation. Habitat suitability for the geese was high in areas with a high proportion of rice fields, having a certain proportion of urban area and lake area and less snow. Consequently, the suitable habitats tended to be distributed on the plains along the Sea of Japan and Pacific coasts. This study represents the first step towards habitat management and restoration of Greater White-fronted Geese in Japan.

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.

The relationship between abdominal profile index and body condition of Greater White-fronted Geese Anser albifrons

ABSTRACT Abdominal profile index (API) is often used as an index of body condition in studies of anatids. However, few studies have statistically tested the relationship between API and body condition. In this study, we investigated the relationship between API and body condition of Greater White-fronted Geese Anser albifrons, taking into account the structural size effect on body condition. It was found that body mass, excluding the structural size effect, has a positive relationship with API. As API explained only 26% of the variance in body condition, we discuss the limitations of the method and the situations in which it can be used effectively.

Phylogenetic Relationship of the Greater White-Fronted Goose Anser albifrons Subspecies Wintering in the Palaearctic Region

Abstract Greater White-fronted Goose Anser albifrons has a holarctic breeding distribution and is polymorphic. Three subspecies winter in the Palaearctic region, one of which also winters in the Nearctic region: European White-fronted Goose A. a. albifrons breeds in the far north of Europe and Asia and winters in the south and west of Europe; Pacific White-fronted Goose A. a. frontalis breeds in east Siberia and Arctic Canada and winters in East Asia and United States; and Greenland White-fronted Goose A. a. flavirostris breeds in Greenland and winters in Ireland and western Scotland. The phylogenetic relationships among these three subspecies are unclear. We determined the mitochondrial DNA control region sequences of Pacific Whitefronted Goose, using 66 shed feathers collected from wintering sites in Japan, and compared the sequences with those previously published for Greater White-fronted Goose subspecies. Phylogenetic trees and networks revealed that there are three clades within the species. The sequence divergence among the clades corresponds to divergence long before the last glacial maximum (15–25 thousand years ago), which suggests the existence of at least three ancient refugia for the species. However, all three subspecies consist of haplotypes from two of the three clades. This suggests that they originated from individuals that survived in two refugia during the last glacial period.

Evaluating goose-dropping density as an index of food-consumption volume along a depletion gradient

Abstract We evaluated the use of goose-dropping density as an index of food-consumption volume using white-fronted geese (Anser albifrons) foraging on spilled grains in rice fields. It was revealed that even when the dropping densities were similar at 2 sites, the actual rice-consumption volume varied greatly with initial grain density in the field. Also, it was shown that regardless of dropping density, rice-consumption volume was less variable among fields with low initial grain density. Some possible reasons for the weak relationship between dropping density and rice consumption were discussed. Based on our results, we suggest that wildfowls dropping density is likely to have a limited capability as an indicator of food-consumption volume, and we propose some directions for improving its effectiveness.