A large number of Large-billed Crows Corvus macrorhynchos and Carrion Crows C. corone are culled annually either by shooting or trapping in Japan, but the effects of such culling on crow behaviour have never been evaluated. I hypothesized that in an area where crows are shot they would become more sensitive to human disturbance than those in an area where they are trapped. I compared alert and flight initiation distances of crows in two nearby, but separate, areas in Iwate Prefecture, Japan, in March 2004. In 2003 all 1,025 crows culled in the Daito area were shot, whereas 95.3% of 1,586 crows culled in the Tono area were trapped. Topography, land use, and human population densities were similar in the two areas. Analyses using generalized linear models showed that the area (and hence the method of culling) was the sole explanatory variable in the best model and included in each of the top five models for both distance measures. The median alert distance and flight initiation distance were greater where crows were shot than where they were trapped (60.0 m vs. 20.5 m and 46.0 m vs. 18.0 m, respectively). Other factors, such as species, flock size, behaviour, and habitat type, were far less important. These results show that shooting has a greater non-lethal effect on crows than trapping. While trapping may be a more efficient way of removing crows than shooting, shooting not only reduces the number of nuisance animals directly, but also affects their behaviour and habitat use so that damage is reduced indirectly. Shooting is thus the more effective choice for culling in order to reduce damage caused by crows.
Detecting different bird species requires different and appropriate surveying methods. We tested a new detection method for the Tataka Area in Yushan National Park, Taiwan, which is an important alpine stopover site for migratory landbirds. Numerous migrant species have previously been reported from this area during bird counts and banding operations. However, these traditional survey methods are incapable of detecting nocturnal migrants. Therefore, we applied acoustic monitoring devices to survey the flight calls of nocturnal migrants in the Tataka Area in order to identify the species and estimate their detection rate. We set up acoustic recorders at five recording stations twice a month during September, October and November, and once in December 2014. We identified 18 nocturnal migrant taxa from 801 hours of recordings. The Black-crowned Night Heron Nycticorax nycticorax was the most frequently recorded species, followed by thrushes (Turdus spp.) and the Brown Shrike Lanius cristatus. Passages of nocturnal migrants occurred during every hour of the night, but with a significantly higher detection rate during the period from 2000 to 2300. Detection rates also varied significantly among months and recording stations. Significantly higher detection rates were recorded in September and October than in November and December. The recording station on a ridge detected significantly fewer birds than the other four recording stations situated in or near valleys. This suggests that nocturnal migrants use lower-lying stream valleys in order to pass over mountain ridges at the lowest possible point. This study provides the first evidence to demonstrate that, besides landbird migrants, many shorebird species and even kingfishers migrate through alpine areas at night when they pass over Taiwan Island during autumn migration.
Much literature exists on the comparative oral morphology of birds in relation to dietary niche, but little research has been done on the nightjars, (Caprimulgidae, Caprimulgiformes). Herein, we describe the oropharyngeal cavity of the Egyptian nightjar, Caprimulgus aegyptius, using gross anatomical analysis and scanning electron microscopy. The tongue of C. aegyptius is short with a blunt apex carrying numerous scale-like structures. The body of the tongue has both small and large conical papillae for capturing and retrieving insects, and is separated from the root by a distinct papillary crest. The laryngeal mound is bounded by a laryngeal groove with a median glottic fissure that bears two laryngeal folds rostrally and two conical papillary rows caudally. Salivary glands are scattered on the lingual body and root, the floor of the oropharyngeal cavity, and the anterior maxillary and posterior palatine regions. The palate is divided into papillary and non-papillary regions. Furthermore, the median portion of the papillary region has two main clefts: the choanal and infundibular clefts. At the rear edge of the palate, a single transverse row of large caudally-directed conical papillae is present. Our findings reveal multiple structural and functional adaptations of the lingual papillae, salivary gland distribution, and palatal architecture in C. aegypitus that reflect the species' insectivorous dietary habits.
Long-distance bird migration is often characterized by a number of flight bouts interspersed with intermittent stopover periods for re-fuelling. However, little is known about the stopover ecology of songbirds migrating along the East Asian flyway. The aim of this study was to estimate the minimum stopover duration and body mass change during stopover of Red-flanked Bluetail Tarsiger cyanurus and Yellow-browed Warbler Phylloscopus inornatus based on 6,073 ringed and 502 re-captured birds during spring and autumn migration in the Russian Far East. For Red-flanked Bluetail the minimum stopover duration averaged 3.4 days in autumn and 1.7 days in spring, while for Yellow-browed Warbler it was 3.2 days in autumn and 2.1 days in spring. Significant differences in stopover duration were found between seasons, but not between the two species. The body mass of Red-flanked Bluetails significantly increased during stopover in spring and autumn, but no significant body mass changes were detected in Yellow-browed Warblers. The shorter minimum stopover duration of both species in spring may indicate a faster migration than in autumn, suggesting a time-minimizing strategy in spring to reach the breeding grounds as fast as possible.
The Eurasian Skylark, Alauda arvensis, is a passerine bird that mainly breeds in open habitats, such as lowland grasslands and farmlands. However, recent studies have shown that they form breeding territories on volcanic and alpine slopes in central/northern Japan. During the 2018 breeding season, we investigated the density and habitat selection of Skylarks on the volcanic slopes above timber line, of Mt. Tarumae, Hokkaido. Our results showed that there were 27 Skylark territories in the study area, with a density of 7.26 territories per square kilometer. This spatial arrangement was dense around the eastern slope. Skylarks favored habitats with a low vegetation height. The quantity of short plant species, i.e. Carex oxyandra and Arcterica nana was larger in territories than in randomly selected points. C. oxyandra plays important roles not only in forming low vegetation, but also in available and limited nest material in their breeding territories on the volcanic slopes. These results suggest that Skylarks occupy areas of low vegetation with C. oxyandra, as there are limited resources available for nest materials within the breeding territories that are on the volcanic slope above a timber line.
The syntactical organization of the avian song is of particular interest in light of recently discussed analogies between the songs of birds and human speech. We present here a description of the song structure of the Siberian Rubythroat Calliope calliope, a small insectivorous bird, widespread in Siberia and the Russian Far East. This species sings predominantly discontinuously, but the duration of individual songs varies significantly. Each individual song is composed of a number of song units, a stereotypical set of different notes and syllables that are always presented together and in a strictly fixed order. Although the variety of song units in an individual's repertoire is significant, the diversity of units presented in the very beginning of individual songs was found to be much more limited. The song of the Siberian Rubythroat is not only extremely complex and variable, but it is also organized as a set of clusters rooted in strictly defined initial song units. Each cluster in turn contains several branching points with a limited number of branches. Despite its impressive variety, the rubythroat's song nevertheless contains numerous fixed sequences of song units.
For the long-term survival of bird populations in urban areas, it is necessary to protect both bird habitats fragmented by urbanization and potential pathways for movement between them. However, urban pathways for waterbirds have rarely been studied. Suspecting that certain waterbird species that visit inland waters would tend to move along rivers, as movement pathways, we surveyed waterbird movement along the Kanda River in Tokyo, Japan in the winter of 2017/2018. We defined those species that very frequently (more than 95% of all flights) flew along the river as "river travelers". Three species, Great Cormorant Phalacrocorax carbo, Black-headed Gull Larus ridibundus, and Herring Gull L. argentatus proved to be river-dependent movers that frequently used the Kanda River as a pathway. The gulls relied more heavily on the river as a movement pathway than the cormorant. In this sense, urban rivers may play a role for these species that is analogous to that of linear vegetated spaces for terrestrial birds. In addition, the distribution of river travelers (especially Black-headed Gull) may have been affected by the extent of riverside vegetation alongside, and highways covering, the river. To protect movement pathways for gulls and cormorants in urban areas, it is necessary to consider the differences among bird species in terms of their relative dependence on urban rivers as movement pathways and their comparative susceptibilities to the impact of manmade structures covering the rivers.
We examined brood patch development, sex ratios, and morphological traits of 30 Ancient Murrelets Synthliboramphus antiquus captured from the nocturnal at-sea congregation off Teuri Island, Hokkaido, Japan during late May to early June 2016. Molecular sexing determined that 12 of the murrelets were males and 18 were females. The proportions of murrelets with brood patches (an indicator of breeding status) were similar for males (58%) and females (56%). Breeding murrelets were heavier than non-breeding murrelets. Males had deeper bills and longer heads than females, but their weights, wings, culmens, tarsi, bill widths, and skull widths were similar.
The Brent Goose Branta bernicla population of East Asia is the least studied. We banded 24 Brent Geese at Notsuke Bay, east Hokkaido, Japan, in autumn, and collected six opportunistic sightings of these birds during winter, contributing to an understanding of their migratory movements to wintering sites in Japan. Birds were resighted at five widely distributed wintering sites in west Hokkaido and northeast Honshu. While this study showed that birds moved between Notsuke Bay and wintering sites elsewhere in Japan, further studies are needed to understand the migration patterns and routes used during autumn and spring in East Asia.
The provision of nest boxes to supplement naturally available nest sites can be an effective means of conserving cavity nesters. The White-throated Needletailed Swift Hirundapus caudacutus is a large, cavity-nesting swift. With reference to their natural nesting cavities in trees, we developed nest boxes for the species. Fourteen out of 20 nest boxes were used by needletails in 2017 and 2018 and monitored using nest cameras inside the boxes. Nest boxes were as successful as natural tree cavities in terms of the number of young reared.
The Red-crowned Crane Grus japonensis population of Hokkaido, Japan, has increased to over 1,600 individuals since near extinction in the late 19th and early 20th centuries. Adults and subadults can be distinguished by visible characteristics of their remiges; adults have pure white primaries whereas subadult birds have black primary tips and upper primary wing coverts. Banded individuals hatched during 2015–2017 were examined in detail using photographs and videos and it was found that the subadult characteristics of the remiges disappeared in individuals older than two years.