Brown Boobies (Sula leucogaster) obtain prey by plunge dives. In order to investigate the foraging behaviour of Brown Boobies underwater, we attached acceleration data loggers to chick-rearing Brown Boobies at Nakanokamishima Island in Japan. We documented, for the first time, Brown Boobies performing many rapid and shallow V-shaped dives and some W-shaped dives during the daylight period. The average and maximum dive depth and duration were 1.03 m and 3.81 m and 1.83 s and 21 s, respectively. Furthermore, Brown Boobies used buoyancy to ascend to the water surface. Our data suggest that Brown Boobies mainly depend on shallow-plunging, contrary to the pursuit divers such as gannets, due to their ecological and/or physiological constraints.
To optimize oxygen usage and foraging, alcids diving by wing-propulsion are expected to regulate body angle, swim speed and wing stroke in relation to the change of buoyancy with the current depth. They may also regulate the diving behaviour in relation to the maximum depth of each dive. We measured body angle, swim speed and wing stroke in vertically diving Common Murres (Uria aalge) and obliquely diving Rhinoceros Auklets (Cerorhinca monocerata) using bird-borne data-loggers that recorded pressure and acceleration. During the descent, the body angle became shallower with increasing current depth in both species. Rhinoceros Auklets kept their swim speed within a range during descent to 40 m. Common Murres slightly increased their swim speed during the descent from the surface to 20 m depth, then they descended with a range of swim speeds in deeper current depths. Both species could make a thrust at each of down- and up-strokes. Possibly to regulate the swim speed during descent, both species decreased the frequency of thrusts by reducing the amplitude of longitudinal acceleration at the up-stroke and the frequency of wing strokes by increasing the duration of up-strokes. During the ascent, both species stopped wing strokes at certain depths and then, ascended passively with increasing swim speed. Both species descended with steeper body angles but with a similar swim speed at depth when they made deeper dives, indicating that the birds would reduce the transit time especially in deep dives. These similarities of the regulation of diving behavior in two species that have different foraging patterns imply a strong biomechanical constraint on flying-diving alcids.
We used miniature light-level/immersion loggers (geolocators) to study the movements and behavior of two Streaked Shearwaters (Calonectris leucomelas) during their travel away from Japan, after the breeding season. During the period from late October until late December, the tracked shearwaters moved south over subtropical pelagic waters with low productivity. The birds traveled to the seas off northern New Guinea and the Gulf of Carpentaria, Australia, 3400–5200 km distant from Mikura Island, their breeding colony in Japan. During the wintering period (December–February), the birds were on the sea surface for 77–85% of their time on average. The migratory and wintering behavior of Streaked Shearwaters are discussed in relation to the physical and biological marine environment of the north-western Pacific.
Alcids are important top predators, consuming substantial amounts of zooplankton and fish in the northern hemisphere. However, studies of their at-sea foraging behaviour are logistically difficult because of their wide foraging range and small body size. We developed a technique to estimate the approximate foraging area for individual birds using water temperature profiles sampled by both diving birds and a research boat. This technique was applied to chick-rearing Rhinoceros Auklets Cerorhinca monocerata breeding on Teuri Island, Hokkaido, which feed primarily on Japanese anchovy Engraulis japonica in the northern coastal Japan Sea. Annual variations of the warm Tsushima Current may influence the distribution of this prey species. Rhinoceros Auklets foraged mainly in waters with 12–15°C sea surface temperatures (SSTs), which formed in waters north of the breeding colony on 17 June 2002 and in waters south of the breeding colony from 30 May to 3 June 2003. Rhinoceros Auklets dove above or around the thermocline in both years. This indicates that foraging locations and dive depths may be influenced by SSTs and the depth of the thermocline, factors that presumably affect the distribution of their prey.
Road Ecology represents a vast area of ecology from local effects, within the road-habitat, to landscape effects that stem from roads and road networks. Australian roads are generally characterised as narrow strips of remnant native vegetation in agricultural areas. However, some extensive reserves of native forests remain and these habitats like all terrestrial habitats have roads that traverse them. Studies of roads passing through such ecosystems can provide baseline data on how these roads are used by birds and have implications for conservation management. This study investigated easily detected bird species on the roads and their immediate verges of a two-lane highway in continuous Jarrah Eucalyptus marginata forest of south-western Australia. Midway during this two year study 14% of the roadside was cleared, which allowed us to measure the immediate responses by birds. Clearing beside roads hugely reduced the abundance and species richness of birds in the road-habitat. The only species to return to the road-habitat adjacent to forest clearings, during the study, was the Australian Raven Corvus coronoides. Australian Ravens and Grey Currawongs Strepera versicolor were the most frequently detected species (37.6 and 25.5%, respectively). Common Bronzewings Phaps chalcoptera and Australian Ringnecks Barnardius zonarius were the most frequently detected granivorous species (12.7 and 12.1% of all observations, respectively). The abundances of birds along roads were positively correlated to road casualties. Australian Raven and Grey Currawong were the most commonly detected road casualties. Road casualties were dominated by juveniles, particularly in the spring and summer months. The Australian Raven and Wedge-tailed Eagle Aquila audax were the only species detected at carrion. The Grey Currawong did not feed from carrion and it undertook a shift away from the road-habitat during its breeding season. The abundances of the granivorous species Common Bronzewing and Australian Ringneck were strongly and positively correlated with the dehiscence of native Jarrah seed. In contrast, the transportation of 116 510 tonnes of grain (over two years) did not correlate with the abundances of granivorous birds. We conclude that food availability on the road most likely correlated with abundance and road casualties of birds, although more detailed studies on insectivorous birds are required to test this hypothesis.
Some woodpecker species select nest trees that have sustained an infectious disease that produces soft, decayed cores and hard sapwood. In the study described in this paper, I measured the wood hardness of nest trees of the Great Spotted Woodpecker Dendrocopos major without destructive sampling to describe the physical characteristics of the wood. The woodpeckers started excavating vertical cavities immediately after digging horizontal holes through the hard sapwood, although the thickness of the sapwood varied widely among nest trees. The depth of the vertical cavities was negatively correlated with the hardness of the cores. The woodpeckers selected heights for nest cavities where the hardness of the core wood and the ratio of core hardness to sapwood hardness were relatively low. They also selected nest trees that had relatively large variations in wood hardness within the stem. These results suggest that the birds can identify variations in wood hardness among trees and among positions within a tree. Thus, wood hardness appears to be an important factor in the selection of nest trees and nest heights within a tree. The woodpeckers do not necessarily excavate their nests in trees with a specific diameter, but instead select trees with specific physical characteristics, irrespective of tree species.
Plasma levels of sex steroid hormones and a stress hormone were monitored in captive male and female Silver Pheasants Lophura nycthemera jonesi once a month for 12 months. The birds were reared in outdoor cages, each containing a male and a female, under natural conditions of temperature and photoperiod. The circulating hormone levels were measured by the radioimmunoassay (RIA) method. Male total testosterone level was clearly bimodal with maxima in February and July. However, male estradiol level remained low throughout the year. Female estradiol level surged significantly in February only and female total testosterone level peaked in February and July at the same time as the bimodal peaks of male total testosterone. Silver Pheasants maintained in captivity had lower corticosterone levels than those restrained in a small enclosure. In February, females in captivity laid 3–6 eggs per clutch. These results suggest that captivity is a valuable route for the better propagation of this species.
Male Bengalese Finches Lonchura striata var. domestica sing syntactically complex songs. A previous study suggested that complex songs elicit more reproductive behavior in female Bengalese Finches than do simple songs. Since the study measured passive reactions to stimulus songs, it is not clear if female birds actively choose complex songs. Here we conducted an active choice experiment using female Bengalese Finches in which selecting a particular perch resulted in the playback of a simple or a complex song. Four out of the eight birds chose complex songs, one chose the simple song, and the remaining three chose both songs randomly. These results suggest that the song preferences of female Bengalese Finches vary individually. A simple population dynamics model confirmed that such a tendency in female preference could lead to the evolution of complex songs in male Bengalese Finches.
The Japanese Wagtail Motacilla grandis has been regarded as a near-endemic species of Japan, but recent evidence indicates the existence of a breeding population in Korea. Based on 270 records, four major breeding groups were found to be widely distributed along three major rivers (the Han, Seomjin and Nakdong Rivers) and eastern coastal areas (the Yeongdong area). Due to its habitat preference for streams with sands and gravels, the Japanese Wagtail is a rare species in general, but a locally common resident in Korea.
The foraging behaviors of the Eastern Great Egret and the Little Egret were studied along a tidal river, the Umi River, Fukuoka City. Interspecific and seasonal differences in the behavior of the two species were derived from a combination of morphological characters and prey availability. Morphological characters were presumed to influence foraging site selection, and each species adopted foraging methods that were best suited to the most abundant prey in their chosen sites. The foraging methods adopted by each egret species were affected by prey characteristics, especially prey mobility. Seasonal differences in egret foraging behavior resulted from seasonal changes in prey availability at each foraging site.
Northern Goshawks Accipiter gentilis are widely distributed in forested areas across the Holarctic Region. To confirm whether the goshawks breeding in Hokkaido are migrants or residents, and to locate migration routes and wintering areas, I satellite tracked two breeding female goshawks in Hokkaido. Both two goshawks moved southward in winter. The distances between nest sites and wintering areas were 540 and 1,046 km, and the two goshawks stayed in the wintering areas for 98 and 148 days, respectively. These results suggest that some goshawks breeding in Hokkaido are migrants.