Hsiao-Wei Yuan

Antiphonal duetting in Steere’s liocichla (Liocichla steerii): male song individuality and correlation between habitat and duetting behavior

We studied duet song and vocal duetting behavior in an endemic Taiwanese passerine, Steere’s liocichla (Liocichla steerii). We found that the leading male song in duets was highly individualistic. Also, we found duetting behavior varied significantly across different habitat types. Females were more likely to answer male songs in densely vegetated, steep forest habitat compared to open agricultural habitat. These findings provide quantitative evidence for vocal individuality for a duet song and provide tentative support for the idea that females are duetting to reveal their location to their mates.

Using stable isotopes to unravel and predict the origins of great cormorants (Phalacrocorax carbo sinensis) overwintering at Kinmen

The Food and Agricultural Organization of the United Nations and the World Organization for Animal Health have called for a better understanding of the role that migrating birds may play in spreading H5N1 highly pathogenic avian influenza (HPAI). Bird banding, traditionally used in studies of migration, is limited by low recapture rates. Telemetry can only be applied to larger species and a limited number of birds. We show that analyses of multiple stable isotopes (delta(13)C, delta(15)N, delta(18)O and deltaD) can provide an understanding of the number of breeding populations represented at large congregations of wintering birds, probable locations of these breeding populations, and which breeding populations do not contribute migrants to a wintering site. As Asia is thought to be the origin of many HPAI strains and the center of their evolution, and as bird migration is poorly understood in this part of the world, we recommend that, in addition to banding, satellite, and VHF telemetry, the stable isotope analysis of migration patterns should become a part of long-term surveillance studies.

Group provisioning limits sharing conflict among nestlings in joint-nesting Taiwan yuhinas

Offspring often compete over limited available resources. Such sibling competition may be detrimental to parents both because it entails wasted expenditure and because it allows stronger offspring to obtain a disproportionate share of resources. We studied nestling conflict over food and its resolution in a joint-nesting species of bird, the Taiwan yuhina (Yuhina brunneiceps). We show that adult yuhinas coordinate their feeding visits, and that this coordination limits competition among nestlings, leading to a ‘fairer’ division of resources. Transponder identification and video-recording systems were used to observe adult feeding and nestling begging behaviours. We found that: (i) yuhinas feed nestlings more often in large parties than in small parties; (ii) feeding events occurred non-randomly in bouts of very short intervals; and (iii) food distribution among nestlings was more evenly distributed, and fewer nestlings begged, during large-party feeding bouts compared with small-party feeding bouts. To our knowledge, this is the first study in a cooperative breeding species showing that adults can influence food allocation and competition among nestlings by coordinating their feeding visits. Our results confirm the hypothesis that the monopolizability of food affects the intensity of sibling competition, and highlight the importance of understanding the temporal strategies of food delivery.

JOINT NESTING IN TAIWAN YUHINAS: A RARE PASSERINE CASE

Abstract Joint nesting, in which more than one pair contributes eggs to a group nest, is rare among cooperatively breeding birds. Early reports of the breeding biology of Taiwan Yuhinas (Yuhina brunneiceps) described them as joint nesters; however, these studies were preliminary and did not involve color-banded individuals. We conducted a 7-year study on the breeding biology of yuhinas. We found that the frequency of joint nesting was extremely high (90% of groups). Breeding groups were composed of two to seven adults (mode = 4). Most of the juveniles (78%) disappeared from our study site the year after they hatched. Only 6% remained in their natal groups; therefore, our study groups appeared to be composed primarily of non-kin. Within each group, there was a linear hierarchy of socially monogamous pairs. Mean reproductive skew index, as determined by microsatellite markers, was low (0.19). Alpha males had longer wings than beta males, whereas females did not show any differences in body size. Breeding group size had no significant effect on nest survival rate. Overall clutch size of the group increased while the average number of eggs laid by each pair decreased with group size. However, average number of fledged young per pair per season was similar for all group sizes. Alpha females were the major contributors during both diurnal (65% of groups) and nocturnal (77%) incubation, although beta females and males also contributed substantially toward incubation. Nidificación Grupal en Yuhina brunneiceps: un Caso Raro en Aves Paserinas Resumen. La nidificación grupal, en la cual más de una pareja contribuye con huevos a un nido grupal, es muy rara entre las aves que presentan cría cooperativa. Estudios anteriores sobre la biología reproductiva de Yuhina brunneiceps describían a esta especie como con nidificación grupal; sin embargo, esos estudios eran preliminares y no involucraron individuos marcados con anillos coloreados. Realizamos un estudio de 7 años de duración sobre la biología reproductiva de Y. brunneiceps. Encontramos que la frecuencia de nidificación grupal fue extremadamente alta (90% de los grupos). Los grupos reproductivos estuvieron compuestos por dos a siete adultos (moda = 4). La mayoría de los juveniles (78%) desaparecieron del área de estudio luego de que eclosionaron. Sólo el 6% permaneció en sus grupos natales, por lo tanto los grupos estudiados parecen haber estado compuestos principalmente por individuos no emparentados. Dentro de cada grupo hubo una jerarquía lineal de parejas socialmente monógamas. La desviación reproductiva promedio, determinada por marcadores micro-satelitales, fue baja (0.19). Los machos alfa presentaron alas más largas que los machos beta, mientras que las hembras no presentaron diferencias en el tamaño corporal. El tamaño del grupo reproductivo no tuvo un efecto significativo sobre la tasa de supervivencia de los nidos. En general, el tamaño de la nidada del grupo aumentó mientras que el número promedio de huevos puestos por cada pareja disminuyó con el tamaño del grupo. Sin embargo, el número promedio de polluelos emplumados por pareja por época reproductiva fue similar para todos los tamaños de grupo. Las hembras alfa fueron las que más contribuyeron durante la incubación diurna (65% de los grupos) y la nocturna (77%), aunque las hembras y los machos beta también contribuyeron substancialmente a la incubación.

Colony site choice of blue-tailed bee-eaters: influences of soil, vegetation, and water quality

All bee‐eaters (Family Meropidae) are cavity nesters, excavating terrestrial burrows in sites ranging from flat ground, to small mounds of soil, steep earthen banks seen in road clearings, eroded cliff faces, and river gorges. However, very little is known concerning the environmental factors that influence nest site selection in bee‐eaters. We addressed abiotic and biotic issues associated with colony site choice in blue‐tailed bee‐eaters (Merops philippinus) nesting on Kinmen Island, off mainland China, from 2000 to 2002. About 89% of the colonies were located on slopes with soils of sandy loam and the other 11% on sandy clay loam. No colony was found on clay loam, which covered 20% of the island. The sandy loam and sandy clay loam had lower soil pressure, density and moisture, which, presumably, were easier for bee‐eaters to excavate and provided better drainage and ventilation for nest cavities. Bee‐eaters avoided placing nest cavities in areas with dense vegetation and abandoned colony sites when they became overgrown. Vegetation would impede excavation and decrease the detectability of predators. Bee‐eaters may prefer colony sites near water bodies showing water chemistries indicative of more biological productivity, especially in relation to the diversity and abundance of their major prey, dragonflies.

Unfavourable environment limits social conflict in Yuhina brunneiceps

Identifying the factors that modulate cooperative and competitive behaviours is the key to understanding social evolution. However, how ecological factors affect social conflict and their fitness consequences remain relatively unexplored. Here, using both a game-theoretical model and empirical data, we show that Taiwan yuhinas (Yuhina brunneiceps)--a joint-nesting species in which group members are unrelated--employ more cooperative strategies in unfavourable environmental conditions. Fighting duration was lower, fewer total eggs were laid and incubation was more likely to start after all females completed egg laying (which causes more synchronous egg hatching). Surprisingly, as a consequence, there were more surviving offspring in unfavourable conditions because the cooperative strategies resulted in fewer dead nestlings. To our knowledge, this study is the first theoretical analysis and empirical study demonstrating that an unfavourable environment reduces social conflict and results in better fitness consequences in social vertebrates.

Recent range-wide demographic expansion in a Taiwan endemic montane bird, Steere's Liocichla (Liocichla steerii)

BackgroundThe subtropical island of Taiwan is an area of high endemism and a complex topographic environment. Phylogeographic studies indicate that vicariance caused by Taiwans mountains has subdivided many taxa into genetic phylogroups. We used mitochondrial DNA sequences and nuclear microsatellites to test whether the evolutionary history of an endemic montane bird, Steeres Liocichla (Liocichla steerii), fit the general vicariant paradigm for a montane organism.ResultsWe found that while mountains appear to channel gene flow they are not a significant barrier for Steeres Liocichla. Recent demographic expansion was evident, and genetic diversity was relatively high across the island, suggesting expansion from multiple areas rather than a few isolated refugia. Ecological niche modeling corroborated the molecular results and suggested that populations of Steeres Liocichla are connected by climatically suitable habitat and that there was less suitable habitat during the Last Glacial Maximum.ConclusionsGenetic and ecological niche modeling data corroborate a single history--Steeres Liocichla was at lower density during the Last Glacial Maximum and has subsequently expanded in population density. We suggest that such a range-wide density expansion might be an overlooked cause for the genetic patterns of demographic expansion that are regularly reported. We find significant differences among some populations in FSTindices and an admixture analysis. Though both of these results are often used to suggest conservation action, we affirm that statistically significant results are not necessarily biologically meaningful and we urge caution when interpreting highly polymorphic data such as microsatellites.

SEXUAL DICHROMATISM, DIMORPHISM, AND CONDITION-DEPENDENT COLORATION IN BLUE-TAILED BEE-EATERS

Abstract Abstract. The Blue-tailed Bee-eater (Merops philippinus) is a cooperatively breeding and socially monogamous member of the Coraciiformes that displays conspicuous coloration and elongated central rectrices (“streamers”). Humans cannot distinguish males from females; both sexes are brightly colored with a chestnut throat patch, a yellow chin, and green body coloration fading into a turquoise-blue rump and tail. We quantified coloration with ultraviolet- (UV) visible spectrometry and measured morphology to determine the extent of sexual dichromatism and dimorphism. Males displayed more exaggerated coloration, longer tail streamers, and were larger than females. Multiple plumage ornaments (measures of plumage coloration and streamer length) were positively correlated in both sexes. Males in better body condition expressed darker chestnut throats and more chromatic green body plumage. Females in better body condition, however, exhibited more chromatic blue rumps and yellow chins. This study represents the first objective description of plumage ornamentation in the order Coraciiformes.

GROUP-SIZE EFFECTS AND PARENTAL INVESTMENT STRATEGIES DURING INCUBATION IN JOINT-NESTING TAIWAN YUHINAS (YUHINA BRUNNEICEPS)

Abstract We investigated the effect of group size on incubation effort in Taiwan Yuhinas (Yuhina brunneiceps) at the Highlands Experimental Farm of National Taiwan University at Meifeng, Nantou County, central Taiwan, during 2000 and 2001. The Taiwan Yuhina is a joint-nesting, cooperatively breeding species endemic to Taiwan. We compared differences in parental investment among individuals of different sexes and status, explored the effect of group size on group incubation effort, and investigated whether individuals show compensatory reductions in care with respect to the number of females laying. Constancy of incubation increased as group size increased. Alpha females exhibited a significantly greater incubation effort than other individuals, but effort was similar among other group members. Both alpha males and females decreased their relative and absolute incubation effort as group size increased (i.e., there was a compensatory reduction in parental effort). However, beta pairs maintained a consistent but low incubation effort when either gamma pairs or an extra individual joined the group. Our study also demonstrated a new potential group-size benefit for cooperatively breeding birds—an increase in the constancy of incubation.

Effects of weather variation on the timing and success of breeding in two cavity-nesting species in a subtropical montane forest in Taiwan

ABSTRACT Biological processes at low latitudes are often associated with seasonal rainfall, while those at high altitudes are also influenced by low temperature and high humidity. Thus, the breeding phenology of montane species at low latitudes requires clarification. We monitored the timing of nesting for two species of secondary cavity-nesting passerine, the Green-backed Tit (Parus monticolus) and the Rufous-faced Warbler (Abroscopus albogularis), in a montane cloud forest in subtropical Taiwan between 2010 and 2014. To determine the effects of weather and extreme events on nesting success, we used program MARK to model daily nest survival rate as a function of weather variables. The results showed that March temperatures, but not spring (February–March) rainfall, affected the mean laying date of Green-backed Tits. Females shifted their laying dates to lay earlier in response to earlier warm spring weather. The Rufous-faced Warbler exhibited a similar but weaker relationship between March temperature and mean laying date. Spring temperature and rainfall did not affect the length of the laying season of either species. The reduction in the limiting effect of spring rainfall on biological processes may be attributable to the perhumid climate of the study area. Both species were negatively affected by heavy seasonal rainfall during the nesting period. Nest survival declined under extremely heavy rainfall (daily precipitation >20 mm), but did not vary linearly or nonlinearly with daily precipitation levels. The daily survival rate of Green-backed Tits was further reduced by cold weather combined with heavy rain. Our results show that the breeding densities of both species declined across the 5-yr study period, indicating that the negative effects of adverse weather may contribute to further decreases in annual productivity, which would accelerate population declines at the current rate of climate change.