Sexing adult Northern Shrikes using DNA, morphometrics, and plumage

ABSTRACT.   Northern Shrikes ( Lanius excubitor ) are predatory songbirds found primarily in taiga regions throughout their Holarctic breeding range. The species is poorly known, especially in North America, and is generally thought to be sexually monomorphic. From 2004 to 2007, we captured 50 adults in northern Wisconsin during the nonbreeding season (December–March) and determined sex using DNA extracted from feather samples. Males had significantly longer wings, longer tails, and less black in the outer rectrix than females, but body mass did not differ between the sexes. A discriminant function equation using tail length and extent of black on the outer rectrix correctly assigned the sex of 97.4% of captured adults. Plumage dimorphism was also evident, with males having paler gray heads and backs without brown tones, whiter underparts with lighter barring, and a more distinct and horizontal border at the base of the sixth primary feather. The ability to accurately determine sex will provide opportunities to examine possible inter- and intrasexual differences in the behavior and ecology of adult Northern Shrikes.     

Trophic ecology of the Southern Grey Shrike (Lanius meridionalis) in insular environments: the influence of altitude and seasonality

The seasonal diet and prey selection of the Southern Grey Shrike (Lanius meridionalis) was studied in two different insular habitats: shrub environments of the Canary Islands in coastal and high mountain zones. We measured, in each season, food availability and prey size in order to determine prey size selection of shrikes along an altitudinal gradient. Moreover, we compared the diet patterns observed with those documented on the continent, to determine if Southern Grey Shrikes in the islands’ high mountain zone (which has a continental climate) showed seasonal diet variation similar to those in northern continental areas. We analysed a total of 1,139 shrike pellets collected in 1 year and identified 10,179 prey items. Numerically arthropods (91%), and in terms of biomass lizards (70%) were the main prey consumed by the shrikes. The proportions of the main prey items differed significantly between seasons and habitats. Diet in the coastal areas was less variable than in the high mountain zone. The greater seasonal climatic variation in the high mountain zone was associated with diet patterns similar to those found in some northern continental areas, such as the Iberian Peninsula and southern France. Finally, shrikes selected the largest prey in the high mountain habitat. This suggests that foraging behaviour in this species is related to climatic conditions, as the biggest and most profitable prey were consumed in the most harsh habitats.     

Different effects of age on reproductive performance in relation to breeding stage in Bull-headed Shrikes

The difference in the reproductive performance of males and females of the Bull-headed Shrike (Lanius bucephalus) according to age class, i.e. yearling and adult, was studied, and the age-related difference was examined according to parental feeding behavior. The clutch initiation date was not affected by the age class. Females that paired with an adult male laid more eggs per clutch than those paired with a yearling male. The age class of males affected the mass of nestlings at 6 days old, and the age class of females affected the mass of nestlings at 12 days old. The effects of the age of either parent independently were observed at different breeding stages. A change in the degree of nestling feeding peformed by the male and female parents occurred at some point between when the broods were 6 days and 12 days old. It is likely that this caused an effect of age at different stages of the breeding cycle. The effects of the age of the male parent are consistent with accounts of age-related reproduction in raptors where males provide resources to offspring. Individual improvements in foraging skills and/or courtship feeding rate are suggested to be possible explanations. Electronic Publication     

Change in body mass in relation to breeding phase in bull-headed shrikes

Changes in body mass of both sexes of the bull-headed shrike, Lanius bucephalus, were investigated over the six breeding phases of this species. Standardized body mass (SBM), which was defined as body mass divided by the length of the tarsus, of the males was relatively constant over the phrases, while the SBM of the females changed drastically. In the females, the SBM during egg-laying was higher than the SBM in all the other breeding phases. The SBM of the females did not differ between the incubation and early-nestling phases, and was lowest during the fledgling phase. Mass loss in bull-headed shrikes did not correspond to an adaptive adjustment of body mass to permit a reduction in the power required for flight in the nestling period. It is likely that incubating females constantly maintain their body mass to invest in parental efforts from the incubating to nestling periods.     

甘肃安西荒漠伯劳的繁殖生态

2010年4～8月在甘肃安西极旱荒漠国家级自然保护区,采用样点法对荒漠伯劳(Lanius isabellinus isabellinus)的繁殖生态进行了研究,采用单因素方差分析(ANVON)对荒漠伯劳卵体积与卵序之间的关系进行了研究,用二元Logistic回归对雏鸟生长曲线进行拟合。结果表明,荒漠伯劳的繁殖时间为4月底至8月初,每巢产卵3～6枚,平均窝卵数为4.67±0.57(n=21),卵体积为(3.14±0.32)cm3(n=95),卵鲜重(3.48±0.20)g(n=20),卵体积随着产卵顺序显著减小(R=-0.427,P=0.021,n=29),其采取的是"窝雏减少"的繁殖策略。雌鸟产首枚卵后即开始孵卵,雄鸟负责情饲及警戒。温度自动记录仪测量平均孵卵温度为(38.19±0.77)℃(n=2),雌鸟在巢率为93.95%。平均孵卵时间为(15.33±0.52)d(n=6)。荒漠伯劳雏鸟留巢期12～15 d,幼鸟离巢后亲鸟继续饲喂幼鸟,整个育雏期最长达31 d。研究地区荒漠伯劳种群的孵卵率为82.50%(n=80),卵成功率为46.25%(n=80),雏鸟离巢率为56.06%(n=66),巢成功率58.62%(n=29)。在2010年环志标记的12对繁殖鸟中只有1对繁殖了第二窝。     

五种雀形目鸟类核型的比较研究

染色体核型的比较研究,对于了解物种的特性,探索物种的遗传、进化、系统发育及分类地位都有一定的意义。有关鸟类的核型研究,国外已有不少报道(Castrovicja,1969; Hammar,1966,1975; Ray-Chaudhuri et al.,1969;Shidds,1982;Ta—kagi,1972等)国内在这方面的工作开展较迟,已作过核型分析的鸟类为数不多,仅见王应祥等(1982)的报道。迄今,作过核型研究的鸟类已达500多种,其中雀形目有200种。本文比较分析了五种野生雀形目鸟类的核型,它们是黑头蜡嘴雀,斑鸫,黄腹山雀,红尾伯劳和灰背椋鸟。     

虎纹伯劳的巢生境选择与繁殖行为

2005年3~7月通过焦点动物取样法(focal animal sampling)和完全记录法(all-occur rencerecording)对四川南充地区虎纹伯劳的繁殖行为进行了研究。结果表明,虎纹伯劳喜在5~12m的高大阔叶乔木的冠部分叉处营巢。对15个巢址主成分分析表明,前5个主成分特征值均大于1,累积贡献率高达83.15%,说明前5个主成分已经基本包含了所有参数的总信息量。4月下旬开始陆续有虎纹伯劳迁到,初到时并未配对。5月上旬开始出现求偶行为,并伴有递食行为。5月中旬首次见到营巢,两性参与营巢,营巢期5~7d。营巢结束一两天后开始产卵,一天一枚,窝卵数4~6枚。营巢期和产卵期都有求偶和交配行为。产完最后1枚卵后即开始由雌鸟单独孵卵,孵卵期13~14d。两性育雏,育雏期13~15d。     

Diet of the nominate Southern Grey Shrike Lanius meridionalis meridionalis in the north of its range (Mediterranean France)

Capsule In this region the diet is mainly cold-blooded prey, mostly insects such as beetles.

Aims To describe the diet of this newly separated, poorly documented and endangered species.

Method Diet was inferred from pellet analysis, collected during a single breeding and winter period in the steppe of the Crau.

Results A total of 5409 prey were identified from 257 pellets. Vertebrates were seldom taken, except by adults (small passerines) during the fledgling period. High seasonal differences were found. Hymenoptera were largely consumed in autumn, Arachnida in autumn and winter, Orthoptera in summer and autumn and Lepidoptera larvae in winter and spring and by fledglings. Nevertheless, Coleoptera were ingested in large proportions all year round. Carabidae were the main prey in winter and Melolonthidae were especially important for adults during the nestling period, as were Cetoniidae for the fledglings.

Conclusion Small mammals and small birds were less exploited in France and Spain (L. m. meridionalis) than in Israel (L. m. elegans or L. m. aucheri), whereas the opposite might be expected, following a north–south climatic gradient. Thus, the nominate subspecies L. m. meridionalis differed in diet from L. m. elegans or L. m. aucheri.     

Are predatory birds effective secondary seed dispersers?

We have studied the unusual phenomenon of secondary seed dispersal of Lycium intricatum seeds on a small oceanic Atlantic island (Alegranza, Canarian Archipelago) in which a small frugivorous lizard ( Gallotia atlantica ) and two different predatory birds participate, a shrike ( Lanius excubitor ) and a kestrel ( Falco tinnunculus ). Endemic lizards that are common prey of both bird species consume Lycium fruits. Lizard remains were significantly matched with the presence of Lycium fruits in the regurgitation pellets of the two predatory birds. Seeds were found in 7.3% of the lizard droppings, 31.0% of kestrel pellets and 55.7% of shrike regurgitations. The mean number of seeds per dropping or pellet was 4.8 ±4 in lizard, 20.2 ±34.5 in shrike and 6.7 ±8.1 in kestrel. The percentage of viable seeds showed significant differences among all four treatments, decreasing in the following direction: seeds collected directly from plants (98.0%), shrikes (88.0%), lizards (72.3%), and kestrels (31.7%). Seeds from Lycium fresh fruits and shrike pellets showed significantly higher germination rates than those from lizard droppings and kestrel pellets. While lizards and shrikes are effective seed dispersers, kestrel gut treatment decreases seed viability. Seed viability is always higher than seed germination in each of the four treatments. In this island environment, Lycium seeds are under an important random influence during the seed dispersal process. Secondary seed dispersal seems to acquire a relevant dimension in small and remote insular environments or isolated continental systems where interactions among the different elements involved are intense, all of them are abundant native residents, and they have been coexisting for a long time. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 345–352.