We studied the pattern of acquisition of breeding positions among helpers in a population of Grey-crowned Babblers Pomatostomus temporalis rubecula in the monsoon tropics of northwestern Australia, using both behavioural and molecular data. In particular, we focused on sex differences, kinship, and their interactions among emigrating helpers. Moreover, we also considered whether intergroup movement and extra-pair mating contributed to incest avoidance in our population. The advantage of this material is that there are previous studies of populations in different regions, and the comparison of the results may provide a better understanding of ecological factors driving helping behaviour in cooperative breeding. Three options for a mature helper to acquire a breeding position were observed: establishing a new territory, emigrating to an existing territory, or waiting in the natal territory for a breeding vacancy. In many cases, male helpers took the third option, while female helpers took the second one. Our population of Grey-crowned Babblers seemed not to be actively avoiding incest. Female helpers tended to disperse from natal groups more than males, but neither intergroup movements nor extra-pair mating were effective in avoiding incestuous breeding. In some groups, dominant breeders were closely related to each other. The frequency of extra-pair mating in our population was similar to that of the New South Wales population previously studied, but dispersal distances were twice as great. The two populations also differ in mean clutch size and group size. Such variation in life history characteristics among different populations of cooperatively breeding species has received little attention, but has the potential to explain how cooperative breeding systems are modified by environmental factors.
One of the consequences of selections acting on body size is the difference in body size between the sexes or sexual size dimorphism. Although many hypotheses have been proposed for reversed sexual size dimorphism (RSD) in raptors, ornithologists have rarely paid attention to temporal aspects of RSD when testing their hypotheses. Because selection pressures may vary temporally, describing temporal variation in RSD is a first step towards understanding evolutionary mechanism which shape and maintain the dimorphism. Here, we describe RSD in the population of Ryukyu Scops Owls Otus elegans on Minami-daito Island using a dataset of the external measurements of 770 individuals obtained during a 17-year long-term population monitoring project. Females were larger than males in body mass, culmen length, bill depth, bill width, tail length and flattened wing length, whereas males were larger than females in tarsus and head lengths. Among these traits, the degree and direction of RSD of body mass, tarsus length, bill depth and flattened wing length varied across years. There were neither increasing nor decreasing trends in RSD. This is a rare study which addressed temporal variation in RSD in a raptor species.
Rice fields provide important inland stopover sites for migratory shorebirds. However, stopover duration and habitat use depend on the environmental conditions in the rice fields, which constantly change due to agricultural activities. This study determined the characteristics of habitat use in two shorebird species, the Wood Sandpiper Tringa glareola and Common Greenshank T. nebularia, in rice fields with different habitat conditions resulting from physical changes (field type: fields flooded after plowing, with high water levels after harrowing, or with low water levels after harrowing) and chemical changes (pesticide use: environmentally friendly or conventional farming) from agricultural activities around the time the migratory shorebirds arrive. The study was conducted during the spring stopover periods of these shorebird species in 2015 (May 2–20, 19 days) and 2016 (May 2–21, 20 days), during which we observed the characteristics of their habitat use and estimated the densities of potential prey. Both Wood Sandpiper and Common Greenshank were observed to use flooded fields with low water levels after harrowing. As for pesticide use, potential prey animals were most densely populated in environmentally friendly fields, for which only the large-bodied Common Greenshanks showed selection. This species-specific habitat use seems to be closely associated with body size-dependent prey availability and prey species selection. The small-bodied Wood Sandpiper was more affected by physical than chemical factors. These findings suggest that rice fields—major inland stopover sites for shorebirds—provide different habitats depending on agricultural activities. The study results also have practical implications for future improvement of inland shorebird habitat through efficient rice field management sensitive to the needs of migratory shorebirds.
In Malaysia, multiple land use by humans has caused substantial losses of wetland ecosystems, and shrinkage of the populations, habitat and food bases of avian species. However, studies of avian populations, especially of waterbirds, is important, allowing us to understand the complexity of the wetland ecosystem structure, and also develop appropriate management techniques with robust monitoring tools to ensure the ecological sustainability of wetlands. This study aimed to determine the eco-climatic factors influencing the occurrence of waterbirds and to develop habitat suitability models for thePaya Indah (PIW) and Putrajaya wetlands (PW), Malaysia. A distance sampling point count technique using stratified random design was employed to survey the wetlands from November 2016 to January 2019. A total of 57 sampling points at 14 lakes at PIW and 54 sampling points at 24 lakes at PW were chosen. An automatic linear modelling algorithm and geographic information systems were employed to compute the importance ratios of 17 eco-climatic factors (hydrology 9; climate 5; waterscape 1 and landscape 2). The results revealed that all individual and estimated indices for observed waterbirds were significant. The automatic linear modelling algorithm results for PIW waterbirds also showed that the maximum and minimum weights of the factors were land cover and water dissolved oxygen, while in PW they were atmospheric pressure and Normalized Difference Water Index (NDWI). The maximum and minimum weights of the factors for waterbirds in PIW were water turbidity and electrical conductivity, while at PW they were atmospheric pressure and six water parameters. Large areas of Putrajaya Wetland were classified as more suitable for waterbirds than Paya Indah Wetland due to the favourable water pH, atmospheric pressure and land cover (forage availability). Thus, the models' adoption as a management tool can help in the maintenance of the wetlands' habitat quality and management effectiveness of waterbird species.
Long-term population monitoring is very important for the conservation of threatened and endangered species. The Black-faced Spoonbill Platalea minor is a globally endangered species and the majority of its population breed on uninhabited islands off the west coast of the Korean Peninsula. The Chilsan Archipelago in the southwest is the southernmost breeding site for this species in Korea and is expected to help buffer the potential dispersal of Black-faced Spoonbills from breeding populations currently concentrated in the Gyeonggi Bay area. As there has been a lack of information regarding the number of Black-faced Spoonbills, their characteristics, and their recent population trends, the present study investigated the population trends of Black-faced Spoonbills breeding in the Chilsan Archipelago. The study, from 2014 to 2018, examined breeding success in 2015 and 2018, and the size and location of nests in 2018. The number of nests ranged from 43 to 163 (2014, 43; 2015, 93; 2016, 84; 2017, 85; 2018, 163). The percentage of birds that attempted breeding between April and May was 84.9% in 2015 and 87.1% in 2018, while the breeding success rate was 69.9% in 2015 and 81.5% in 2018. The average nest size in 2018 was 55.06±6.09 cm long and 53.44±6.56 cm wide, while the average surface slope below the nest was 25.42±6.95˚. In total, nine plant species were used as vegetation for nests. During the present study, the environmental conditions and the presence of anthropogenic disturbances seemed to affect breeding success. Therefore, strictly controlled access to breeding sites and effective management are needed to protect and conserve breeding populations of this endangered species.
Mountains harbour high biodiversity that is facing a crisis due to recent climate change. Bird communities shift along mountain gradients. Some previous studies have suggested that the effect of vegetation is prevalent on temperate mountains. In this study, we investigated the limiting effects of vegetation on the altitudinal distribution of birds on Mount Norikura in central Japan, by comparing bird communities along four gradients of different orientations. We recorded birds using the line-transect method and classified vegetation into six types: montane deciduous broadleaved forest, subalpine coniferous forest, subalpine birch forest, Japanese Stone Pine scrub forest, alpine tundra and bare ground below the alpine area.
We identified the treelines and ecotones between the predominant vegetation types along each gradient. We found that bird species composition changed drastically at the treeline along three gradients. A non-metric multidimensional scaling (NMDS) ordination revealed: 1) the similarity between bird community structures in the subalpine coniferous forest and the Japanese Stone Pine scrub forest differed among the gradients, 2) despite birch being broadleaved, the bird community in the subalpine birch forest was a subset of that in the subalpine coniferous forest and was more similar to that in the subalpine coniferous forest than that in the montane deciduous broadleaved forest, and 3) in upper parts of the subalpine zone, the bird community structures in the subalpine coniferous and birch forests were similar to each other.
Our findings suggest that although the treeline limits the distribution of forest-dwelling bird species, this effect differs among gradients with different orientations, probably depending on the scrub height of the Japanese Stone Pine scrub forests. Furthermore, the heterogeneity of coniferous and birch forests in the upper parts of the subalpine zone may have little effect on the altitudinal distribution of birds.
Research into the breeding ecology of birds is key to understanding the evolution of life-history traits and developing effective species conservation measures. We studied the breeding ecology of the Crested Myna Acridotheres cristatellus on tropical Hainan Island, China, throughout the breeding season from March to August in 2018 and 2019. Parents Crested Myna build disk-shaped nests together and take turns to incubate their eggs and feed their nestlings, with a nestling period of 18–22 days. Eggs were pure blue-green, and the clutch sizes were 3–6 eggs (averaging 4). Egg mass, egg size, and egg volume were 6.78±0.50 g, 28.74±1.20 mm×21.13±0.53 mm, and 6.56±0.50 cm3, respectively (N=274). Egg-laying mainly occurred between 0700 to 1000, and the average time for laying one egg was 172.36±28.29 s (N=11). Feeding frequency during the mid-nestling period was significantly higher than in the early periods (N=55). The Crested Myna population on tropical Hainan nested earlier, laid eggs earlier and had a longer breeding period than populations in the temperate zone.
The Gentoo Penguins Pygoscelis papua has been classified into two subspecies, Northern P. papua papua and Southern P. papua ellsworthi. In Japan, where a breeding program exists for Gentoo Penguins, the Japanese Association of Zoos and Aquariums (JAZA) has recognized three categories of species in its pedigree ledger: Northern (from the islands of South Georgia), Southern (from the South Shetland Islands), and Unknown (when their origins are not clear). Phylogenetic analyses of the mitochondrial DNA (mtDNA) D-loop region of Gentoo Penguins in their natural habitat have differentiated them as belonging to the Kerguelen Islands (Indian Ocean), Falkland Islands (Atlantic Ocean), and South Georgia (Atlantic Ocean), and categorized some as Northern and others as Southern subspecies. However, the identification of a third subspecies has been suggested. Therefore, reclassification of captive Gentoo Penguins using phylogenetic analysis is necessary for domestic subspecies pedigree management. In this study, we determined five mtDNA haplotype sequences using seven Gentoo Penguins (considered morphologically as three Northern, three Southern, and one Unknown) and characterized their phylogenetic relationships among subspecies and among geographical distributions including 56 published mtDNA sequences. The phylogenetic tree showed three major lineages, Kerguelen Islands, Falkland Islands, and Scotia Arc/Antartica. The five haplotype sequences of the seven captive Gentoo Penguins were classified unexpectedly to one lineage, the Scotia Arc/Antartica, which contains the nucleotide sequences derived from Southern P. papua ellsworthi. Therefore, the mtDNA phylogeny of the seven captive penguins suggests that all captive Gentoo Penguins in Japan belong to the Southern subspecies. If so, then more comprehensive genetic testing of Gentoo Penguins in Japanese aquariums and zoos is required for the management of successful breeding programs.
The adaptive mate choice theory is believed to provide a general explanation of sexual selection. Females are thought to choose males based on direct benefits or because they have perceivably good genes based on visual indicators of male quality, involving adaptive qualities acted on by natural selection in the current environment. However, a recent hypothesis, called "Beauty Happens" has been proposed based on Darwin's "Really Dangerous Idea," an idea that has been criticised, to explain sexual selection in animals, including human beings. Accordingly, it has garnered widespread attention and evoked controversial debate. Here, I review the Beauty Happens hypothesis and clarify the arguments that focus on the sexual autonomy and aesthetic perception of females. I found that, in the case of sexually dimorphic birds, unambiguous evidence is absent in support of the adaptive mate choice theory. Although the Beauty Happens hypothesis is logically feasible, aesthetic perception could possibly evolve and develop on the basis of sexual autonomy and resource-independence in females. Therefore, aesthetic radiation among females may lead to beauty radiation in males, and female mate choice as a selection process may act independently of natural selection, favouring good-to-pass-on genes rather than good genes. However, the Beauty Happens hypothesis seems to be more applicable when explaining the behaviour of sexually dimorphic birds than other animal taxa. I suggest that the mechanisms of female mate choice and intrasexual competition in males may lead to biological evolution, depending on the degree of autonomy of females in different animal species.
From December 2018 to December 2019, four nocturnal roosting sites with large aggregations of White Wagtails Motacilla alba were found in Haikou, Hainan, southern China. Three of them were located near road intersections in the city center of Haikou, and one was located at an airport terminal. Numbers of individuals exceeded 1,250 individuals at each roost. Characteristics of the environment and the nocturnal roosting trees were measured to elucidate the nocturnal roost preferences of white wagtails in urban areas, and some assistance was provided to the issues of urban greening and wildlife problems in cities.
The Smooth Newt Lissotriton vulgaris is a hibernating amphibian, whose winter activity in central and eastern Europe is very rarely observed. We found seven Smooth Newts in late November and early December in eastern Poland in larders of the Great Grey Shrike Lanius excubitor. The amphibians had probably been caught by the shrike while it was looking for a suitable overwintering site. Increasing numbers of winter records of Smooth Newts may be expected in eastern Europe in connection with climate warming; analysis of the diets of certain avian species may be helpful in this respect.
We describe a case in which occupation by the European Tree Frog Hyla arborea caused the nest failure of a pair of Eurasian Reed Warblers Acrocephalus scirpaceus. The frog was observed several times sitting on the reed warblers clutch, on the day when the third egg was laid, thereby preventing the parental birds from incubating. Although small frog species have been reported to rest during the day in bird nests (mainly empty ones), to our knowledge this is the first published report providing evidence for avian nest failure due to nest occupation by an amphibian species.