Nest-site characteristics may affect the daily survival rate of avian nests. We monitored the nests of Chestnut Thrush Turdus rubrocanus breeding in an agricultural landscape near the Lianhuashan Natural Reserve (central China) during the breeding seasons of 2013 and 2014. We describe the Chestnut Thrush’s breeding ecology and used logistic-exposure methods and an information theoretic approach to assess the factors influencing daily survival rates of nests. Results from model averaging indicated that daily survival rates of nests consistently decreased from habitat edge to interior, contradicting the classic edge effect hypothesis describing predation of avian nests. Concealment of nests from below was positively correlated with nest daily survival rates, whereas concealment from the side and from above were not. These results suggest that determining the various effects of vertical and/or horizontal concealment on nest survival rates may help us assess the variation in the ability of local predators to detect nests.
Puffinus lherminieri bannermani is a small black-and-white shearwater, which is endemic to the Ogasawara Islands, Japan. The taxonomic position of this shearwater is contentious. It is treated as a subspecies of Audubon’s Shearwater P. lherminieri or the Tropical Shearwater P. bailloni in some checklists, while it is as considered monotypic, as Bannerman’s Shearwater P. bannermani, in others. We examined the mitochondrial cytochrome b region to determine the taxon’s phylogenetic position. While on the one hand the results showed that it was not genetically related to either P. lherminieri or P. bailloni, but formed a clade with P. myrtae, P. newelli, and P. auricularis, on the other hand, bannermani has diverged substantially from the other three taxa in both genetic and morphological features. This shearwater was first described as Bannerman’s Shearwater, and our results confirm that P. lherminieri bannermani should be split from Audubon’s Shearwater, and the monotypic Bannerman’s Shearwater is recommended to be restored as a distinct species.
Many species of flightless rail are endemic to small islands and endangered, or have become extinct during historical times. However, our understanding of their basic ecological knowledge remains limited. The Okinawa Rail Hypotaenidia okinawae is a flightless species of rail endemic to Okinawajima Island in the Ryukyu Archipelago, Japan. In this study we have quantified the dietary components of the Okinawa Rail using gizzard contents classified by the frequency of occurrence and wet weight. The Okinawa Rail feeds on a wide variety of animals and plants throughout the year, but the frequency of occurrence and wet weight of animal matter significantly exceeds those of plant matter. The number of items present in the gizzard did not differ among seasons, ages and between sexes. Grit was present in almost all individuals and the wet weight did not differ between sexes or among age groups. Although the diet was observed to be diverse, the primary dietary component of both sexes, all ages, and throughout the year appears to be land snails, indicating their great significance as a source of food.
The Canary Islands hold an exceptional number of endemic taxa including six endemic bird species. Over the last few decades, a plethora of information has emerged about colonisation, diversification and extinction of birds in the Canary Islands demonstrating certain evolutionary processes occurring on this oceanic archipelago. However, advances in studies of the biology and ecology of these taxa have been very limited. To discriminate male and female individuals is an important issue in many studies of avian ecology such as dispersal and parental care. Here I provide a rapid, low-cost and robust method for sex determination in the endemic Canary Island Chiffchaff Phylloscopus canariensis. This method was built using eight morphological traits, and sex determination is based on molecular markers from 207 individuals. Discriminant Function Analysis (DFA) correctly classified 98.1% of the grouped cases. The most explanatory variables obtained in the DFA were the tarsus, wing, and tail lengths. In addition, a MANOVA analysis showed that males were significantly larger than females in all measured traits. Overall, the method proposed is highly efficient and accurate for sexing this endemic bird species in the hand.
Morphological differentiation of island-dwelling organisms provides model systems for studying evolution. Computed tomography (CT) scanning is an entirely non-destructive technique that provides detailed three-dimensional (3D) images of physical structures. Geometric morphometrics has been increasingly used in avian morphology studies by analyzing 3D data obtained from CT scans. We used geometric morphometrics to evaluate the morphological details of the skulls of three, genetically distinct, island populations of the Ryukyu Scops Owl Otus elegans: O. e. elegans from the northern part of the Ryukyu Archipelago, O. e. elegans from the southern part of the Ryukyu Archipelago, and O. e. interpositus from Minami-daito Island. Skulls were scanned using an X-ray CT system and the digitized 3D coordinates of 16 landmarks for each skull were analyzed in order to describe geometric morphometric features. O. e. interpositus was found to have a significantly smaller skull than either population of O. e. elegans. From principle component analysis of shape variation, we also found that the skull shape of O. e. interpositus differed significantly from both the northern and southern groups of O. e. elegans. This difference was in terms of PC1, which mainly represented relative anteroposterior length, and angle of the orbit. We inferred that the small skull of O. e. interpositus is partly a consequence of the particular founders of the population, or evolutionary selection that has taken place on Minami-daito Island and that the distinctive shape of the skull of O. e. interpositus is partly a consequence of adaptations for foraging efficiency, or of morphological integration.
The populations of many waterbird species along the East Asian-Australasian Flyway (EAAF) are declining, mainly due to the loss of natural wetland. Meanwhile, artificial wetlands, such as aquaculture ponds, saltpans and rice paddies, have increased in area. Artificial wetlands typically host fewer species and fewer individuals of waterbirds compared to natural ones, thus the conservation importance of artificial wetlands in general appears secondary. However, over large areas of densely populated East and Southeast Asia, few coastal lands above the high tide line remain natural. Waterbirds may utilize the natural intertidal zone at low tide, but are forced to feed or roost in artificial environments when tidal flats are submerged. In such landscapes, coastal artificial wetlands are not only supplementary or alternative to natural ones, but provide crucial habitats for waterbirds at high tide. To investigate the use of artificial wetlands by waterbirds in such a landscape, we studied supratidal waterbird communities in Changhua, Taiwan, an important stop over and wintering site on the East Asian-Australasian Flyway. We found very high species richness and abundance of waterbirds in the area compared to other studies conducted in artificial wetlands. This might have been partly due to the fact that we censused waterbirds at high tide, when artificial wetlands were the only habitat available. Waterbird abundance and species richness were higher at sites with intensive clam aquaculture and less fragmentation, reflecting the preference of shorebirds. Despite the fact that past transformation of natural coastal wetlands into artificial ones has had negative impacts on waterbirds, these artificial wetlands nowadays may provide exclusive supratidal habitats for waterbirds in many regions. Suitable artificial supratidal habitats for waterbirds need to be managed along with natural tidal flats as part of the same system.
As more and more species become threatened, the need to assess population sizes accurately in order to facilitate effective management actions increases. There is an extensive literature on counting birds, but no consensus on the most appropriate units in which to record the results. To stimulate discussion on the use of “number of pairs” for estimating bird population size we review some of the main problems and difficulties. Some counts, especially of seabirds, give total numbers, whereas breeding season counts of songbirds often record territories or, less frequently, numbers of nests. The use of different units complicates comparisons, for example between non-breeding and breeding populations. In many populations there are non-breeding individuals (including immatures, helpers or those who have failed to secure a mate or a territory) that may be hard to distinguish from those that are breeding. Some of the last may even be more conspicuous than paired birds. The proportion of such, for most species, is unknown. In some species, males may attract more than one female. But detailed knowledge of demography is lacking for many species, especially in the tropics. Nest counts can also present problems as some species may make more than one nest. On the other hand, all individuals alive in the breeding season may potentially contribute to future generations and thus, for most purposes, it is preferable to record the number of all individual birds. Wherever known, estimation of the proportion of birds breeding could be added, and we suggest that a global database of such information would be valuable.
Generalist predators are able to exploit diverse prey depending on its spatial and temporal availability. Here, we examined how the diet of a generalist fish-eating predator, the Common Kingfisher Alcedo atthis, varied at the small spatial scale and throughout the breeding season. Analysis of debris collected from six nests showed that the diet composition of five breeding pairs significantly differed, although they bred in close proximity. Prey choice also differed between birds that reared their young at the beginning and at the end of the breeding season. Overall, kingfishers consumed seven fish species, with Roach Rutilus rutilus as the most frequent prey taken both at the beginning and at the end of the breeding season.
We studied the breeding phenology of the Brown Booby Sula leucogaster on Nakanokamishima, southern Ryukyu Islands, Japan. During the breeding season (April-November) of 1989 we observed the presence and absence of 18 chicks and measured their growth on a total of 17 days. Egg hatching was observed during April and May. The estimated minimum pre-fledging period ranged from 60 to 100 days and the maximum pre-fledging period ranged from 86 to 122 days, whereas the minimum post-fledging dependence period ranged from 24 to 105 days and the maximum post-fledging dependence lasted from 74 to 124 days. All of the monitored fledglings left the colony by early-November, and the total period over which parents cared for their chicks was 119-197 days (minimum) and 146-208 days (maximum). Body weight and culmen length attained 95% of asymptotic values in 65 and 69 days of age and wing length in 91 days. Six out of 18 fledglings were seen again in the colony, three to seven years after initial independence.
Little is known about Eurasian Sparrowhawk Accipiter nisus feeding habits outside the breeding season in its wide geographical range. The present study concerns the autumn-winter and spring-summer diet of this raptor species in Northwest Spain in a hedgerow habitat. A total of 23 avian prey species were recorded, only six of which occurred in both periods of the year. However, Eurasian Sparrowhawks fed mainly on medium-sized birds that often forage on the ground at some distance from shrubs and trees, mostly the Song Thrush Turdus philomelos and the Common Blackbird Turdus merula, both species together accounting for approximately half of the prey in any season of the year. The contribution of larger birds, i.e., pigeons, was considerable in terms of ingested biomass. In spring-summer, the mean body weight of avian prey was over 15 g less than in autumn-winter.
We compared the number of individuals and juvenile-to-adult ratio of Rustic Bunting Emberiza rustica, Black-faced Bunting E. spodocephala, and Reed Bunting E. schoeniclus captured in sound-lured and unlured mist nets at an autumn stopover site during October and November 2004-2011. The numbers of all three buntings captured and the proportion of juveniles of Black-faced and Reed buntings increased with sound luring. Use of sound luring could help further our understanding of migration ecology and conservation of the globally vulnerable Rustic Bunting and its congeners through increasing the number of individuals captured and banded.
We found five Ruddy-breasted Crake Porzana fusca nests in a swamp among emergent vegetation, and one in a dry sugarcane field more than 500 m (radius) from any swamp or pond, on Minami-daito Island. Nests were saucer-shaped. All of the nests in the swamp fledged chicks. It is assumed that nesting in such habitat renders nests safe from ground predators such as introduced weasels and feral cats. Roosts were similar in structure to nests, but lacked lining. It is inferred from one observation that males and females roost together at night before the egg-laying period.
To study total mercury concentration ([Hg]) in organ tissues and feathers, 13 carcasses of adult Black-tailed Gull Larus crassirostris were collected at the breeding colony on Kabushima (Kabu Island), western Pacific Ocean, at the northernmost point of Japan’s Sanriku Coast. [Hg] in liver (10.7±6.5 μg/g dry weight±S.D. and 3.2±2.1 μg/g wet weight±S.D.), kidney (6.7±4.8 and 1.8±1.3), breast muscle (3.3±2.3 and 1.0±0.3), heart (4.5±3.0 and 1.1±0.7) and brain (2.8±2.3 and 0.7±0.6) were 2.6-12.5 times higher than in previous studies of the same species. The order of [Hg] concentrations in Black-tailed Gull feather tracts was: inner primaries (P1-P5, 11.2±4.9 μg/g dry weight±S.D)>breast feathers (6.5±2.0)>secondaries (S1-S15, 2.8±1.9)>outer primaries (P6-P10, 2.5±1.9)>rectrices (R1-R6, 1.6±1.4).