Atmospheric currents influence the choice of migratory routes and flight characteristics of birds as well as their decisions regarding migration onset and stopovers. Among long distance avian migrants, soaring birds are particularly dependent on wind and updrafts to help them complete their journeys. This review focuses on the behavioral adaptations of migratory soaring birds at various scales with regard to these atmospheric phenomena. Soaring landbirds and soaring seabirds have evolved morphological characteristics that make them specialists in soaring flight, thus enabling them to reduce the costs of migration significantly. We introduce the flight strategies of each group and discuss how migratory routes, flight characteristics, and onset and stopover decisions are all adjusted in relation to atmospheric conditions best suited for soaring. In addition, we discuss briefly how this strong dependence on atmospheric conditions makes soaring birds vulnerable to anthropogenic threats, such as wind energy development and climate change.
There is increasing evidence showing that wind velocity affects the flight and foraging behavior of seabirds; however, few studies have examined these effects on seabirds inhabiting tropical oceans where lighter wind conditions usually prevail. The Brown Booby Sula leucogaster is an example of a tropical seabird with relatively low wing loading; strong wind conditions may be expected to impede the stability of their flight. We examined how different wind conditions affected the duration and flying behavior of Brown Booby fledglings during foraging trips by means of direct observation of nest attendance and by attaching video loggers to birds. The duration of foraging trips by fledglings decreased with increasing wind speed, and during flight, the body rotation of fledglings became greater with increasing wind speed. As expected, fledglings were buffeted by strong winds due to their relative inexperience in flight combined with their low wing loading. Fledglings were probably forced to flap against strong winds in order to adjust the stability of their bodies, offsetting the efficient use of wind for gliding. Furthermore, the height at which fledglings flew fluctuated more at higher wind velocities, which may have constrained their detection and capture of prey. In conclusion, our results indicate that the aerodynamic performance of Brown Booby fledglings is impaired by strong wind conditions, leading to poor flight stability and potentially reduced prey detection.
Sex-related differences in foraging habitat are common among seabirds. Streaked Shearwaters Calonectris leucomelas breeding on Awashima Island in the Sea of Japan are considered to exhibit gender differences in foraging habitat: only males cross the windy Tsugaru Strait into the Pacific Ocean. Since males are larger, with greater wing loading than females, winds are expected to increase the effect of sexual size dimorphism on their flight performance, which may determine accessibility to foraging habitats. To assess the sex-related differences in foraging movements among years in which environmental and wind conditions differed, we analyzed foraging trips of male (N=243) and female (N=241) Streaked Shearwaters during the chick-rearing period by using GPS loggers in 2011, 2012, and 2013. Both males and females were found to travel through the Tsugaru Strait into the Pacific Ocean, but the frequency was higher for males than for females. Nevertheless, we found that wind velocities had no effect on the probability of transiting the Tsugaru Strait. Greater wing loading requires higher energy demands for flight; therefore, males possibly needed to travel into the Pacific Ocean to feed on the energy-rich Pacific Saury Cololabis saira. In 2012, when the sea surface temperature (SST) in the Sea of Japan was the highest among the three study years, the frequency of foraging in the Pacific Ocean was similar for males and females. Shearwaters are considered to forage in association with predatory fish, the distribution of which is largely influenced by the Tsushima Warm Current migrating partially into the Tsugaru Strait. Hence, both males and females were more likely to travel into the Pacific Ocean when the Sea of Japan SST was high, generating conditional sex-related differences in foraging habitat.
The Rough-legged Buzzard Buteo lagopus is a Holarctic species that breeds in the Arctic and subarctic regions and winters in a broad range from 40° to 55°N. In Japan, this species is typically a rare winter visitor, but in January 2008 there was an unprecedented influx and 350-400 individuals were observed in western and central Japan. Winter irruptions of this species are considered to be caused by low temperatures and increased snow cover. Here, we describe the distribution of snow cover in mainland Asia leading up to the irruption into Japan. We predicted that movement patterns during spring migration would also be influenced by snow cover. We satellite-tracked four Rough-legged Buzzards from Japan, to show their spring migration routes, and examined the relationship between their spring movement patterns and changes in snow cover along their route. There were two spring migration routes from Japan, which varied with wintering sites. One route led up to the Amur River basin bordering China and Russia. The other extended northwards, reaching the lowlands of the western Chukotka Autonomous Okrug in North-eastern Russia. The bird following the latter route was tracked for two consecutive years and was found using the same summering site in 2009. Shortly before the irruptive movements into Japan, most of north-eastern China and eastern Russia were covered with snow, suggesting that unusually severe weather conditions caused the irruptive movements. The northward movements of one bird tracked to Russia generally matched the northward progression of snowmelt.
This paper introduces user-friendly atmospheric data, so-called objective analysis data, for ornithological studies. The data have been interpolated onto grid points distributed at a regular interval in space and time, and are suitable for analyzing using computer data analysis software. Data assimilation techniques, which are basically the application of optimization and control theories, are utilized for producing objective analysis data in order to reduce errors as much as possible and obtain the most reliable dataset. Some examples of objective analysis data are shown and their features are described. Some cautionary notes are also given in order to avoid misinterpretation of the data.
Daily records of bird observations were obtained from the Wild Bird Society of Japan bird sanctuary at Lake Utonai, Hokkaido, from 1982 to 2002. We analysed the daily records of four species thought to be experiencing declines: Brown Shrike Lanius cristatus, Black-browed Reed Warbler Acrocephalus bistrigiceps, Chestnut-eared Bunting Emberiza fucata and Yellow-breasted Bunting E. aureola. The detection rates of Brown Shrike and Yellow-breasted Bunting declined drastically during the two decades, whereas the detection rates of Black-browed Reed Warbler and Chestnut-eared Bunting remained stable. In 2002 and 2003 we conducted line transect censuses, and detected very few Yellow-breasted Buntings and no Brown Shrikes, both of which had been abundant as recently as 1977. The accumulated data from annual bird watching surveys showed similar declines in the same two species. These observations suggest that whereas the Brown Shrike had been common prior to the early 1980s, it declined drastically in 1986. The Yellow-breasted Bunting remained common until 1997, but declined seriously thereafter. There were no clear trends for Black-browed Reed Warbler or Chestnut-eared Bunting from 1982 to 2002, although the latter appeared to decline from 2011 onwards. Large-scale habitat destruction is unlikely in the study area, since the lake and its surrounding area have been a designated a wildlife protection area since before the study began. We discuss potential causes, together with previous studies.
We summarize records of courtship and offspring feeding for 16 resident passerine birds based on long-term observations made by amateur ornithologists in Kanagawa Prefecture, Japan. Courtship feeding was detected in nine passerine species, including two that had not been previously reported to perform this behavior in Japan. Fledgling feeding and food transport to nests were detected in almost all of the species. Courtship feeding was detected mainly in early spring, but in some species it also occurred in winter. We discuss briefly the implications of the results, as well as possible biases and limitations of citizen-based research.
Nesting success of Mallard Anas platyrhynchos was evaluated at Haigam, Hokarsar and Shalabug lakes in Kashmir in 2012 and 2013. Nests were located, tagged and monitored until the clutch hatched. Nest location, nest volume and height above water/ground measured, and threats were all noted. A total of 95 nests with 556 eggs within tree holes, willow root mats or reed beds were monitored. Nests in which at least one egg hatched were deemed successful. A logistic regression was used to identify variables associated with nesting success over two years. Nesting success was 53% and hatching success 64%. Nesting success was significantly higher within tree holes due to lower risk from flooding and human disturbance. About 27% of nests were affected by human harvesting and 16% by flooding.
We studied the song syntax of the Siberian Blue Robin Luscinia cyane, a small insectivorous passerine of the taiga forests of Siberia and the Far East. Males have repertoires of 7 to 14 (mean 10.9±2.3) song types. A single song typically consists of a short trill comprised of from three to six identical syllables, each of two to three notes; sometimes the trill is preceded by a short single note. The most complex songs contain as many as five or six different trills and single notes. The song of the Siberian Blue Robin most closely resembles that of the Indian Blue Robin L. brunnea. The individual repertoires of Siberian Blue Robin, Common Nightingale L. megarhynchos and Thrush Nightingale L. luscinia contain groups of mutually associated song types that are sung usually one after another. The Siberian Blue Robin and the Common Nightingale perform them in a varying sequence, while Thrush Nightingale predominantly uses a fixed sequence of song types. The distinctions between the song syntax of Larvivora spp. and Luscinia spp. are discussed. The individual songs of Luscinia spp. are much more complex and are performed with less prolonged pauses than those of Larvivora spp.
Since the 1970s the Bull-headed Shrike Lanius bucephalus has established a breeding population on the Daito Islands. The islands represent the southwestern limit of the species' breeding range. We investigated the habitat selection of this isolated population during the 2003 breeding season in the agricultural landscape of Minami-daito Island. A comparison of habitat types around shrike nests and randomly selected points, showed that shrikes largely foraged in sugarcane fields and utilized fences and utility wires as suitable perch sites. Our results suggest that it is the open, cultivated areas (sugarcane has been grown on the island since 1900) that have provided suitable habitat for the Bull-headed Shrike allowing it to establish a breeding population on the Daito Islands.
We investigated whether the badge size of the Eurasian Tree Sparrow Passer montanus is correlated with morphological traits and hematocrit during the breeding season in order to elucidate the function of badge size as a potential signal of body size and physiological condition. We found a positive correlation in males between badge size and hematocrit, but not in females. As individuals with larger hematocrit values can transport more oxygen to their tissues or organs, male badge size may be linked with oxygen transport ability. We suggest that male badge size may be a signal of physiological status.
We analysed space use strategies in two populations of Alpine Rock Ptarmigan Lagopus muta helvetica considering three topographical variables (elevation, slope and aspect) to investigate whether populations living at range margins can adapt to suboptimal conditions by exploiting the available habitat differently. Selection for topographic features differed between populations, suggesting that Rock Ptarmigan adapt their habitat selection to local availability. Therefore, we suggest considering a wide range of habitat parameters when planning conservation strategies for species living at the margins of their range.
The editor-in-chief and authors sincerely apologize for the mistake in “Dual foraging strategy and chick growth of Streaked Shearwater Calonectris leucomelas at two colonies in different oceanographic environments” by Daisuke Ochi, Kei Matsumoto, Nariko Oka, Tomohiro Deguchi, Katsufumi Sato, Takashi P. Satoh, Fumihito Muto, and Yutaka Watanuki, pages 213-225, Volume 15, Number 2 (2016).
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