Fluctuating asymmetry in Sardinian Warblers Sylvia melanocephala inhabiting two shrublands affected by fire

The effects of post-fire changes in vegetation and habitat quality on the developmental stability of individual birds have not been assessed to date. Here we compare fluctuating asymmetry in tail feathers of Sardinian Warblers Sylvia melanocephala inhabiting two shrubby zones, the first burned in both 1982 and 1994 and the second only in 1982. Juveniles with unmoulted rectrices showed significantly higher levels of tail feather asymmetry in the zone burned in 1994. This result is consistent with the hypothesis that recently burned shrublands offer lower quality habitats for this species. Because feather asymmetry was positively and significantly related to the abundance of low shrubs up to 50 cm tall, we suggest that juvenile assessment of habitat quality is primarily based on the structure of the shrub layer.     

Contrasting responses of migration strategies in two European thrushes to climate change

Migration is a widespread strategy that enables animals to escape harsh winter conditions. It has been well documented that migration phenology in birds is changing in response to recent climate warming in the northern hemisphere. Despite the existence of large temporal and geographical scale ringing data on birds in Europe, changes in migration strategies in relation to climate warming have not been well studied, mainly because of a lack of appropriate statistical methods. In this paper, we develop a method that enables us to investigate temporal changes in migration strategies from recoveries of dead ringed birds. We estimated migration probability as the ratio between recovery probabilities of conspecific birds originating from different countries but potentially wintering in the same country. We applied this method to two European thrushes: the entirely migrant redwing Turdus iliacus , and the partially migrant blackbird T. merula . We tested for an immediate and a 1-year lagged relationship between our migration probability and climatic covariates (i.e. mean winter temperature in France and the North Atlantic Oscillation). Using ringing-recovery data collected in Finland, Germany, Switzerland and France from 1970 to 1999, we detected contrasting responses in these two species, likely related to their different migratory behaviours. Both species showed a decline in the probability for northern and eastern birds to winter in France. The entirely migratory redwing exhibited a year-to-year plastic response to climate, whereas the decline in the partially migrant blackbird was smooth, suggesting underlying genetic processes. The proposed method, thus, allows us to identify useful indicators of climatic impacts on migration strategies, as well as highlighting differences between closely related species.     

棕背黑头鸫繁殖习性初步观察

2008年和2009年的4～8月,在四川省雅江县帕姆岭对棕背黑头鸫Turdus kessleri的繁殖生态进行了初步观察.该鸟繁殖期在4月下旬至7月上旬,营树上巢,营巢树种为高山栎Quercus aquifolioides和鳞皮冷杉Abies squamata.窝卵数为2~3枚(n=7),平均卵重(7.96±0.03)g(n=8),卵长径(32.7±0.17)mm,短径(21.9±0.13)mm(n=13),雌雄共同孵卵,以雌性为主,孵化期为15~17 d(n=2),孵化率为83.3%(n=18).雌雄共同育雏,以雄性为主,雏鸟出飞后主要在巢周围的林下或灌从活动,这时亲鸟仍会对幼鸟喂食.在同一繁殖季对巢有重复利用的现象.     

北京发现乌灰鸫

Turdus cardis Discovered in Beijing     

7. ZULU NAMES FOR BIRDS

We report that some 10% of Tristan Thrushes Turdus eremita on the coast at Inaccessible Island feed extensively on marine invertebrates (mainly crustaceans), despite lacking functional salt glands. Such birds regularly drink from freshwater springs that are common along the coast, but thrushes also forage along the coast at nearby Nightingale Island where there is little freshwater. One individual was observed feeding on stranded by-the-wind-sailors Velella velella. This appears to be only the second record of a passerine feeding on a cnidarian. These records further emphasise the resourcefulness of island birds in general, and the Tristan Thrush in particular, to exploit a wide range of food resources.     

贵州省宽阔水发现褐头鸫

正2015年9月30日利用Ltl6210型红外相机(深圳猎科电子有限公司)在贵州省宽阔水国家级自然保护区松林垭口处(28°12′N,107°09′E,海拔1 497m)拍摄到鸫科(Muscicapidae)鸟类1种。照片中的鸟中等体型,具白眉和标志性白色下眼圈,上体、腰及尾上覆羽棕褐色,颏至腹部灰白色,两胁灰色,与白眉鸫(Turdus obscurus)相似,但其胸及两胁灰色而非黄褐色,白色眉纹稍短,经查阅《中     

江西吉安乌鸫的繁殖生态研究

2009～2010年对江西省吉安地区乌鸫Turdus merula的繁殖进行了调查研究,结果表明:当地乌鸫的营巢时间在3月9日至16日,产卵时间是3月18日至26日,平均窝卵数5.14(4～6)枚(n=14),平均卵大小29.71 mm×21.16 mm,平均卵重6.63 g(n=71).孵卵和暖巢主要由雌鸟承担,但雄鸟也有暖巢行为,孵化率为65.83%,育雏期13～15 d,离巢率高达100%.与高海拔的乌鸫相比,当地乌鸫产大窝小卵,这一特征保证了大窝雏数和高离巢率,繁殖对策属于r-选择.     

Function of egg punctures by Shiny Cowbirds in parasitized and nonparasitized Creamy‐bellied Thrush nests

ABSTRACT Avian brood parasites usually remove or puncture host eggs. Several hypotheses have been proposed to explain the function of these behaviors. Removing or puncturing host eggs may enhance the efficiency of incubation of cowbird eggs (incubation‐efficiency hypothesis) or reduce competition for food between cowbird and host chicks in parasitized nests (competition‐reduction hypothesis) and, in nonparasitized nests, may force hosts to renest and provide cowbirds with new opportunities for parasitism when nests are too advanced to be parasitized (nest‐predation hypothesis). Puncturing eggs may also allow cowbirds to assess the development of host eggs and use this information to decide whether to parasitize a nest (test‐incubation hypothesis). From 1999 to 2002, we tested these hypotheses using a population of Creamy‐bellied Thrushes (Turdus amaurochalinus) in Argentina that was heavily parasitized by Shiny Cowbirds (Molothrus bonariensis). We found that 56 of 94 Creamy‐bellied Thrush nests (60%) found during nest building or egg laying were parasitized by Shiny Cowbirds, and the mean number of cowbird eggs per parasitized nest was 1.6 ± 0.1 (N= 54 nests). At least one thrush egg was punctured in 71% (40/56) of parasitized nests, and 42% (16/38) of nonparasitized nests. We found that cowbird hatching success did not differ among nests where zero, one, or two thrush eggs were punctured and that the proportion of egg punctures associated with parasitism decreased as incubation progressed. Thus, our results do not support the incubation‐efficiency, nest‐predation, or test‐incubation hypotheses. However, the survival of cowbird chicks in our study was negatively associated with the number of thrush chicks. Thus, our results support the competition‐reduction hypothesis, with Shiny Cowbirds reducing competition between their young and host chicks by puncturing host eggs in parasitized nests.     

Laying dates and clutch size of open-nesting passerines in the Czech Republic: a comparison of systematically and incidentally collected data

Data are presented on laying date and clutch size (n) of Blackcap Sylvia atricapilla (1434), Song Thrush Turdus philomelos (298), Garden Warbler S. borin (260), Yellowhammer Emberiza citrinella (254), Blackbird T. merula (231), Chaffinch Fringilla coelebs (206), Chiffchaff Phylloscopus collybita (202), Icterine Warbler Hippolais icterina (95) and Dunnock Prunella modularis (89), recorded during an intensive study (since 1993) in woodland habitats of Eastern Bohemia, Czech Republic (49 °54 ′N, 16 °02 ′E). Results are compared with two other data sets (a local study and national nest record scheme) collected by Czech volunteer ornithologists during 1945–85 and with other published data from central Europe. There is no evidence that the laying dates and clutch size of the nine species changed at the regional scale over the past decades, and mean values generally match their known geographical variability. Significant species differences were found among the three Czech data sets in both laying dates and clutch size. Most of the differences could be explained as an artefact of seasonally biased sampling of nests, which in turn influenced mean clutch size. Even a systematic study with a standard searching effort on fixed plots provided biased data for some species.     

Apostatic selection by song thrushes (Turdus philomelos) feeding on the snail Cepaea hortensis

There is no direct evidence that predators exert apostatic selection (the systematic overpredation of commoner forms) on live, naturally polymorphic prey. This study tested whether captive song thrushes ( Turdus philomelos ) select apostatically when presented with dimorphic populations of yellow five-banded and yellow unhanded morphs of the snail Cepaea hortensis. Four thrushes were used. Two were presented with a 9: 1 ratio of five-bandeds to unbandeds and two were presented with 1:9 ratios. Each thrush was given four trials in succession. In each trial 30 snails were presented and the trial was stopped when 15 had been eaten. There were no differences in shell size between morphs or between eaten and uneaten snails of each morph. Three thrushes selected apostatically and one thrush exerted virtually no selection. Overall, there was statistically significant apostatic selection.     

Highly skewed sex ratios in the critically endangered Taita thrush as revealed by CHD genes

The study of sex-ratio patterns in threatened bird species has yielded crucial information with regard to their conservation and management. In the case of sexually monomorphic species, i.e. species that cannot be sexed by their appearance, DNA-based sexing techniques are increasingly applied. We present data on the sexing of adult Taita thrushes, a critically endangered forest endemic from south-east Kenya. In addition to describing a morphometric trait that can be used to sex individuals directly upon capture, we comment on a remarkable skew in sex ratio that might have important consequences for the long-term survival of the species.