人工巢箱条件下白眉姬鹟的繁殖参数

2005～2006年,在吉林省左家自然保护区的次生林中,对人工巢箱条件下白眉姬鹟(Ficedulazanthopygia)的繁殖参数开展了初步研究.结果表明,人工巢箱中自眉姬鹟的窝卵数为5～7枚,平均6.0枚;卵重平均为1.6 g.卵大小平均为17.0 mm×13.1 mm.孵化期平均为13.1 d,每巢平均出雏5.4只,育雏期平均为12.8 d,每巢平均出飞雏鸟5.3只.白眉姬鹟的营巢成功率为70.0%,繁殖成功率为81.3%.     

灰蓝姬鹟暂时弃卵的低温耐受性

鸟类的亲鸟有时会暂时放弃孵卵的义务,使正在发育的胚胎连续数小时甚至几天处于较低的环境温度条件下。在甘肃莲花山自然保护区采用温度数据自动记录仪对一只灰蓝姬鹟(Ficedulatricolor)雌鸟的孵卵节律进行了监测,记录到雌鸟3次长时间的异常离巢,离巢时间分别为4·45h、1·17h和5·32h。雌鸟离巢期间,巢温最低降至7·7℃,并且在2次较长时间的异常离巢时,巢温低于10℃的时间分别达到了3·83h和4·60h。此后,雌鸟恢复了正常孵卵直至雏鸟出壳。     

Variation in climate warming along the migration route uncouples arrival and breeding dates

Migratory species are of special concern in the face of global climate change, since they may be affected by changes in the wintering area, along the migration route and at the breeding grounds. Here we show that migration and breeding times of a trans‐Saharan migrant, the pied flycatcher Ficedula hypoleuca, closely follow local temperatures along the migration route and at the breeding grounds. Because of differences in long‐term temperature trends of short within‐spring periods, the migration period and the time interval between migration and breeding dates of this species have extended in SW Finland. Temperatures in northern parts of Central Europe have risen at the time when the first migrants arrive there, facilitating their migration northward. Temperatures later in the spring have not changed, and the last individuals arrive at the same time as before. The timing of breeding has not advanced because temperatures at the breeding site after arrival have not changed. These results show that the pied flycatchers can speed up their migration in response to rising temperatures along the migration route. Our results strongly indicate that the effects of climate change have to be studied at the appropriate time and geographical scales for each species and population concerned.     

Reduced breeding success of Pied Flycatchers Ficedula hypoleuca along regulated rivers

Most large rivers in northern Sweden are regulated to produce hydropower, with subsequent effects on flow dynamics and aquatic insect communities. Several studies have shown that aquatic and terrestrial systems are intimately connected via the export of emergent aquatic insects, but few have assessed how human modifications of aquatic habitats may influence this connection. We compared breeding success of the insectivorous Pied Flycatcher Ficedula hypoleuca in near‐riparian upland forests along two regulated and two free‐flowing large rivers in northern Sweden over 3 years. The regulated rivers showed lower aquatic insect export to the surroundings, as a consequence of regulation‐induced loss of suitable aquatic insect habitats. Survival of Pied Flycatcher nestlings was 10–15% greater along the free‐flowing rivers. Females breeding near the free‐flowing rivers also started egg‐laying earlier and with greater synchrony than those at the regulated rivers, and showed a smaller decrease in weight during breeding than did females along the regulated rivers. However, there were no differences in occupation rate, clutch size or number of successfully hatched juveniles between regulated and free‐flowing rivers. As regulated rivers showed lower abundance of flying aquatic insects, which may also reduce the abundance of terrestrial invertebrate prey, regulation‐induced changes in the export of emergent aquatic insects may explain both directly and indirectly the observed reduction in Pied Flycatcher breeding success along regulated rivers. Large‐scale river regulation may therefore impair the breeding success of insectivorous birds through impacts on prey availability.     

Long-lasting mobbing of the pied flycatcher increases the risk of nest predation

Mobbing behavior may provide real benefits because mobbing preyindividuals often cause a predator to leave the vicinity. However,mobbing calls of prey can attract acoustically oriented predatorsthus increasing nest predation. Therefore, a real value of mobbingas a type of adaptive behavior may depend on its duration. Inthis experimental study, we tested whether mobbing durationby the pied flycatcher Ficedula hypoleuca, a small hole-nestingpasserine, increases the risk of nest predation. From the topof one nest-box within each of 78 experimental plots, we playedback long calls of pied flycatchers, whereas recordings of shortmobbing calls were played back from the top of another nearbynest-box. The nest-boxes were arranged in pairs, and each ofthem contained a quail Coturnix coturnix egg. Long-call nest-boxeswere depredated by martens Martes martes significantly moreoften than short-call nest-boxes. This predator usually huntsby night and may eavesdrop on the calls of their mobbing preywhile resting nearby during the day. The results of the presentstudy show that long-lasting conspicuous mobbing calls may carrya significant cost for the breeding birds.     

Seasonal decline in cell-mediated immunity of collared flycatcher Ficedula albicollis nestlings: does the sex of offspring matter?

The seasonal decline in offspring performance is a frequently reported phenomenon in species breeding in a temperate zone, but the potential effect of brood sex ratio on such declines has not been studied. Here, we predicted that this decline may occur if the sex that exhibits the lower immune response or lower survival rate tends to be more frequent among late broods. The seasonal patterns of four performance parameters of collared flycatcher Ficedula albicollis nestlings have been examined during 4 years. Sex was assigned to all studied individuals using molecular techniques. We found significant seasonal decline in cell-mediated immune response, tarsus length and survival of the chicks. The lack of interactions between gender and hatching date revealed that both sexes contributed equally to the observed decline. The brood sex ratio did not vary with the laying date. On the basis of available data, we suggest that the breeding date may only exceptionally induce female-driven sex allocation in species with only slight sexual size dimorphism. In consequence, we suggest that seasonal sex ratio shifts do not account for seasonally declining fitness of nestlings in passerines.     

Climate change can alter competitive relationships between resident and migratory birds

Climate change could affect resource competition between resident and migratory bird species by changing the interval between their onsets of breeding or by altering their population densities. We studied interspecific nest-hole competition between resident great tits and migrant pied flycatchers in South-Western Finland over the past five decades (1953-2005). We found that appearance of fatal take-over trials, the cases where a pied flycatcher tried to take over a great tit nest but was killed by the tit, increased with a reduced interspecific laying date interval and with increasing densities of both tits and flycatchers. The probability of pied flycatchers taking over great tit nests increased with the density of pied flycatchers. Laying dates of the great tit and pied flycatcher are affected by the temperatures of different time periods, and divergent changes in these temperatures could consequently modify their competitive interactions. Densities are a result of reproductive success and survival, which can be affected by separate climatic factors in the resident great tit and trans-Saharan migrant pied flycatcher. On these bases we conclude that climate change has a great potential to alter the competitive balance between these two species.     

Footprints of adaptive evolution revealed by whole Z chromosomes haplotypes in flycatchers

Detecting positive selection using genomic data is critical to understanding the role of adaptive evolution. Of particular interest in this context is sex chromosomes since they are thought to play a special role in local adaptation and speciation. We sought to circumvent the challenges associated with statistical phasing when using haplotype‐based statistics in sweep scans by benefitting from that whole chromosome haplotypes of the sex chromosomes can be obtained by resequencing of individuals of the hemizygous sex. We analyzed whole Z chromosome haplotypes from 100 females from several populations of four black and white flycatcher species (in birds, females are ZW and males ZZ). Based on integrated haplotype score (iHS) and number of segregating sites by length (nSL) statistics, we found strong and frequent haplotype structure in several regions of the Z chromosome in each species. Most of these sweep signals were population‐specific, with essentially no evidence for regions under selection shared among species. Some completed sweeps were revealed by the cross‐population extended haplotype homozygosity (XP‐EHH) statistic. Importantly, by using statistically phased Z chromosome data from resequencing of males, we failed to recover the signals of selection detected in analyses based on whole chromosome haplotypes from females; instead, what likely represent false signals of selection were frequently seen. This highlights the power issues in statistical phasing and cautions against conclusions from selection scans using such data. The detection of frequent selective sweeps on the avian Z chromosome supports a large role of sex chromosomes in adaptive evolution.     

Development of stress response in nestling pied flycatchers

Birds respond to unpredictable events by secreting corticosterone, which induces various responses to cope with stressful situations. However, the evidence is still elusive whether altricial nestlings perceive and respond to external stressors. We investigated the development of adrenocortical stress response to handling-related stressor in nestlings of a small passerine bird, the pied flycatcher (Ficedula hypoleuca). Nestlings were held in isolation from their parents during the experiment to ensure that they indeed respond to handling, not to parental alarm calls. We found that both 9- and 13-day-old nestlings were able to elicit hormonal stress response. Although baseline as well as stress-induced corticosterone levels rose slightly with age, the magnitude of difference between the control and stress-induced levels remained similar in both age groups. However, comparison with adults showed that the stress response of nestlings prior to fledging was still incomplete and significantly lower than in adults. Overall, our results indicate that altricial nestlings do respond to acute stressors, but on the contrary to previous predictions the development of corticosterone stress response during growth period is not gradual and varies remarkably between different passerine species.