Hiroyoshi Higuchi

Age-related variation in foraging behaviour in the wandering albatross at South Georgia: no evidence for senescence.

Age-related variation in demographic rates is now widely documented in wild vertebrate systems, and has significant consequences for population and evolutionary dynamics. However, the mechanisms underpinning such variation, particularly in later life, are less well understood. Foraging efficiency is a key determinant of fitness, with implications for individual life history trade-offs. A variety of faculties known to decline in old age, such as muscular function and visual acuity, are likely to influence foraging performance. We examine age-related variation in the foraging behaviour of a long-lived, wide-ranging oceanic seabird, the wandering albatross Diomedea exulans. Using miniaturised tracking technologies, we compared foraging trip characteristics of birds breeding at Bird Island, South Georgia. Based on movement and immersion data collected during the incubation phase of a single breeding season, and from extensive tracking data collected in previous years from different stages of the breeding cycle, we found limited evidence for age-related variation in commonly reported trip parameters, and failed to detect signs of senescent decline. Our results contrast with the limited number of past studies that have examined foraging behaviour in later life, since these have documented changes in performance consistent with senescence. This highlights the importance of studies across different wild animal populations to gain a broader perspective on the processes driving variation in ageing rates.

Incorporating Color into Integrative Taxonomy: Analysis of the Varied Tit (Sittiparus varius) Complex in East Asia

Species designations are critically important scientific hypotheses that serve as the foundational units in a wide range of biological subdisciplines. A growing realization that some classes of data fail to delimit species under certain conditions has led to increasingly more integrative taxonomies, whereby species discovery and hypothesis testing are based on multiple kinds of data (e.g., morphological, molecular, behavioral, ecological, etc.). However, although most taxonomic descriptions have been based on morphology, some key morphological features, such as color, are rarely quantified and incorporated into integrative taxonomic studies. In this article, we applied a new method of ultraviolet digital photography to measure plumage variation in a color-variable avian species complex, the varied tit (Sittiparus varius). Plumage measurements corroborated species limits defined by morphometric, mitochondrial DNA, and nuclear DNA disjunctions and provided the only evidence for distinguishing two recently evolved species. Importantly, color quantification also provided a justification for lumping putative taxa with no evidence of evolutionary independence. Our revised taxonomy thus refines conservation units for listing and management and clarifies the primary units for evolutionary studies. Species tree analyses, which applied the newly delimited species as operational taxonomic units, revealed a robust phylogenetic hypothesis for the group that establishes a foundation for future biogeographic analyses. This study demonstrates how digital photography can be used to incorporate color character variation into integrative taxonomies, which should lead to more informed, more rigorous, and more accurate assessments of biodiversity. [Color, digital photography, integrative taxonomy, Sittiparus varius, species delimitation, varied tit.].

Modeling daily flowering probabilities: expected impact of climate change on Japanese cherry phenology.

Understanding the drivers of phenological events is vital for forecasting species responses to climate change. We developed flexible Bayesian survival regression models to assess a 29-year, individual-level time series of flowering phenology from four taxa of Japanese cherry trees (Prunus spachiana, Prunusxa0×xa0yedoensis, Prunus jamasakura, and Prunus lannesiana), from the Tama Forest Cherry Preservation Garden in Hachioji, Japan. Our modeling framework used time-varying (chill and heat units) and time-invariant (slope, aspect, and elevation) factors. We found limited differences among taxa in sensitivity to chill, but earlier flowering taxa, such as P. spachiana, were more sensitive to heat than later flowering taxa, such as P. lannesiana. Using an ensemble of three downscaled regional climate models under the A1B emissions scenario, we projected shifts in flowering timing by 2100. Projections suggest that each taxa will flower about 30xa0days earlier on average by 2100 with 2-6xa0days greater uncertainty around the species mean flowering date. Dramatic shifts in the flowering times of cherry trees may have implications for economically important cultural festivals in Japan and East Asia. The survival models used here provide a mechanistic modeling approach and are broadly applicable to any time-to-event phenological data, such as plant leafing, bird arrival time, and insect emergence. The ability to explicitly quantify uncertainty, examine phenological responses on a fine time scale, and incorporate conditions leading up to an event may provide future insight into phenologically driven changes in carbon balance and ecological mismatches of plants and pollinators in natural populations and horticultural crops.

Beyond seasonal climate: statistical estimation of phenological responses to weather

Phenological events, such as the timing of flowering or insect emergence, are influenced by a complex combination of climatic and non-climatic factors. Although temperature is generally considered most important, other weather events such as frosts and precipitation events can also influence many species phenology. Non-climatic variables such as photoperiod and site-specific habitat characteristics can also have important effects on phenology. Forecasting phenological shifts due to climate change requires understanding and quantifying how these multiple factors combine to affect phenology. However, current approaches to analyzing phenological data have a limited ability for quantifying multiple drivers simultaneously. Here, we use a novel statistical approach to estimate the combined effects of multiple variables, including local weather events, on the phenology of several taxa (a tree, an insect, and a fungus). We found that thermal forcing had a significant positive effect on each species, frost events delayed the phenology of the tree and butterfly, and precipitation had a positive effect on fungal fruiting. Using data from sites across latitudinal gradients, we found that these effects are remarkably consistent across sites once latitude and other site effects are accounted for. This consistency suggests an underlying biological response to these variables that is not commonly estimated using data from field observations. This approachs flexibility will be useful for forecasting ongoing phenological responses to changes in climate variability in addition to seasonal trends.

Urbanization and its implications for avian aggression: a case study of urban black kites ( Milvus migrans ) along Sagami Bay in Japan

Urbanization has caused countless changes in the lives, behaviors, and community structures of wild animals. Habitat loss in urban areas has led to the proliferation of certain species over others; in the case of birds, frugivores and certain predators can be found in abundance in cities. These birds, however, occasionally show novel behaviors that can cause stress within human-wildlife interactions. The black kite, Milvus migrans, for example, has displayed a tendency to attack humans for their food in certain urban areas in Japan. In order to determine how habitat availability and land-use types affected these aggressive tendencies, field observations were combined with GIS analysis of five locations along Sagami Bay in Japan. The following locations were assessed according to the amount of each land-use type present and the aggressive tendencies of each location’s black kite population: Enoshima, Fujisawa; Kamakura Beach, Kamakura; Zushi Beach, Zushi; Oiso Beach, Oiso; and Iwa Beach, Manazuru. The aggression of each population, designated by the log of the aggression index, was found to be significantly affected by the amount of forest area per black kite, the amount of non-rice-paddy agricultural area per black kite, and the season. Thus, aggression was higher amongst populations with less forested or agricultural area within their foraging zones, and aggression increased during spring, which is the breeding season.

Function of head-bobbing behavior in diving little grebes.

Most birds show a characteristic head movement that consists of head stabilization and quick displacement. In this movement, which is analogous to saccadic eye movement in mammals, head stabilization plays an important role in stabilizing the retinal image. This head movement, called “head bobbing”, is particularly pronounced during walking. Previous studies focusing on anatomical and behavioral features have pointed out that visual information is also important for diving birds, indicating its significance in the head movements of diving birds. In the present study, the kinematic and behavioral features of head bobbing in diving little grebes were described by motion analysis to identify the head movement in diving birds. The results showed that head-bobbing stroke (HBS) consisted of a thrust phase and a hold phase as is typical for head bobbing during walking birds. This suggests that HBS is related to visual stabilization under water. In HBS, grebes tended to dive with longer stroke length and smaller stroke frequency than in non-bobbing stroke. This suggests that the behavior, which is related to vision, affects the kinematic stroke parameters. This clarification of underwater head movement will help in our understanding not only of vision, but also of the kinematic strategy of diving birds.

Migration and wintering of Chestnut-cheeked Starlings Agropsar philippensis

Abstract n Chestnut-cheeked Starlings are summer visitors that breed in central and northern Japan and then pass the winter in Southeast Asia. Their breeding ecology has been intensively studied, and the effect of climate change on the breeding season has been shown. However, it is not yet known to what extent stopover and wintering conditions influence the advance of their breeding season because the migration areas and migration timing are not well known. In order to obtain such basic migration information, we attached light-level geolocators to Chestnut-cheeked Starlings breeding in Niigata, central Japan. The starlings started their autumn migration in September and after staying in Kyushu for eight days or more, they migrated through the Nansei Islands to the Sakishima Islands, then Taiwan, or Fujian (China) in a relatively short period of time. They arrived on their wintering grounds by late October. Their migration period averaged 33.9±8.3 days. Seven (44%) out of the 16 individuals that we tracked wintered in the central and southern Philippines and nine (56%) on Borneo. They remained in their wintering areas for an average of 166.3±5.9 days before commencing spring migration during late March. After staying for a period of time on Luzon Island in the Philippines and then traveling northwards through the Nansei Islands of Japan, they headed for their breeding grounds in Niigata arriving back there between 10–26 April, after an average of 27.0±5.6 days.

Landscape characteristics derived from satellite-tracking data of wintering habitats used by oriental honey buzzards in Borneo

Knowledge of the spatial distribution of the wintering habitats of migratory raptors is a prerequisite to understanding their wintering ecology and managing their habitats. Oriental honey buzzards (OHBs, Pernis ptilorhynchus) are migratory raptors with wintering grounds in Indonesia. OHBs’ wintering habitats can be divided into core and edge habitats with unique landscape characteristics, which influence wintering-site selection. Twenty-three satellite-tracked OHBs (2006–2010) used Borneo as their wintering grounds. The primary aim of this study was to analyze OHBs’ wintering habitat distributions (core and edge habitats) in Borneo and their landscape characteristics in the province of South Kalimantan. Fixed-kernel density estimation was used to estimate the edge and core habitats of 23 OHBs in Borneo. We used a 95xa0% fixed kernel (FK_95xa0%) and a 50xa0% fixed kernel (FK_50xa0%) to estimate the spatial distribution of edge and core habitats, respectively. Factor analysis was used to analyze landscape characteristics of core and edge habitats. Results showed that edge and core habitats covered about 153,463.4xa0km2 (20.7xa0%) and 27,528.3xa0km2 (3.7xa0%) of the Borneo area, respectively. Habitat selection by OHBs at wintering sites in both core and edge habitats was highly influenced by the availability of thermal winds and food. However, the more frequent presence of OHBs in core habitats indicates that habitat selection is basically influenced by increased thermal winds associated with particular landform characteristics. Identification of these landscape characteristics provides useful baseline information for ecological-based development, particularly for landscape management and biodiversity conservation.

An Eastern Crowned Leaf Warbler Phylloscopus coronatus Nest parasitized by an Oriental Cuckoo Cuculus saturatus with a Reddish Egg in Hokkaido, Japan

Abstract n The distributions of the Little Cuculus poliocephalus and Oriental C. saturatus cuckoos differ throughout Japan. In Honshu, the Little Cuckoo parasitizes mainly the Japanese Bush Warbler Cettia diphone and lays reddish mimetic eggs. The Oriental Cuckoo mainly parasitizes the Eastern Crowned Leaf Warbler Phylloscopus coronatus and lays whitish eggs. However, in central Hokkaido, where no Little Cuckoos breed, Oriental Cuckoos parasitize Japanese Bush Warblers as their main hosts, in whose nests they lay reddish eggs. Anecdotal evidence suggests that they also parasitize Eastern Crowned Leaf Warblers, laying reddish eggs, but this has not been confirmed. Here, we report the first complete evidence in which an Oriental Cuckoo chick, which hatched from a non-mimetic reddish egg, was raised by Eastern Crowned Leaf Warbler hosts in Hokkaido.

Raptor migration in an oceanic flyway: Wind and geography shape the migratory route of grey-faced buzzards in East Asia

Flapping flight is relatively costly for soaring birds such as raptors. To avoid costly flight, migrating raptors generally avoid flying over water. As a result, all but one of the global raptor migration flyways are largely over land. The East Asian oceanic flyway for raptors is the exception. Raptor species using this flyway migrate by island-hopping, flying over open ocean for distances of up to 300u2009km between islands. We used satellite telemetry data for grey-faced buzzards Butastur indicus, a species that dominates the southern part of the flyway, to investigate the geographical and atmospheric factors responsible for the suitability of this flyway for raptor migration. Using a combination of least-cost path analysis and a step selection function, we found that the occurrence of numerous islands and also suitable wind support along the oceanic flyway are responsible for route selection in grey-faced buzzards. These results confirm the role of islands, but also wind, in shaping the East Asian oceanic flyway of long-distance raptor migration.