STRUCTURE AND FORAGING PATTERNS OF FLOCKS OF TITS AND ASSOCIATED SPECIES IN AN ENGLISH WOODLAND DURING THE WINTER

Blue Tits were the commonest and most frequent members of mixed-species insectivorous flocks during the winter at Wytham Wood, Oxford. Six common flocking species (Blue Tit, Longtailed Tit, Great Tit, Coal Tit, Marsh Tit and Golderest) made up nearly two-thirds of the birds in the study area. A tentative interspecific social dominance hierarehy was constructed: Great Tit > Blue Tit > Marsh Tit > Coal Tit > Long-tailed Tit and Goldcrest. Blue Tits permitted conspecifics to approach them more closely than did other flock members. Blue Tits most frequently led the flocks, but no more than would be predicted by their abundance. Great Tits, and Marsh Tits and Coal Tits to a lesser extent, defended territories during the winter. Two of the six common species frequented the inner parts of branches (Great Tit, Coal Tit), two the outer parts of branches (Blue Tit, Marsh Tit), and two the twigs (Long-tailed Tit, Goldcrest). Members of each of these species-pairs showed marked differences in height of foraging and/or species of tree frequented. Because of their abundance, the impact of Blue Tits outside of their most highly frequented foraging zones may exceed that of species concentrating in these other zones (e. g., twigs high in trees). The Coal Tit foraged most diversely, the Great Tit least diversely. Species that foraged diversely in one of the three foraging categories (species of tree, substrate, height) usually foraged less diversely than most other species in the other dimensions. Species usually overlapped least in the zones exploited (inner parts of branches, etc.). Great Tits overlapped with other species less than did any other common flock member, and Coal Tits were the next lowest in this regard.     

THE SELECTION OF TITS PARUS SPP. BY SPARROWHAWKS ACCIPITER NISUS

Selection of the Wytham Wood population of tits by Sparrowhawks during the tit post-fledging period was studied over three years. Within three weeks of the median date of tit fledging, juvenile Blue Tits were selected more frequently than juvenile Great Tits but thereafter juvenile Great Tits were selected more frequently; it is suggested that the former was due to greater vulnerability of Blue Tits in the two to three weeks after fledging, and the latter due to changes in availability due to immigration/emigration of juvenile tits. When juvenile tits killed by hawks were compared on the basis of brood and physical characteristics with their cohorts in the entire population and in those surviving to the following year, only one factor, fledging date, was found to have affected selection by hawks. It is believed that this was because hawks selected late fledged young still in family parties in preference to early fledged young which had already become independent of their parents and were foraging in the better cover of the forest canopy. When adults killed by hawks were compared with all adults available for selection on the basis of species, sex, timing of nesting and whether or not they had been born in the wood, the only selection trend found was that male Great Tits were taken more often than females due, possibly, to greater risk of exposure for males while foraging or during territorial behaviour. When compared with availability, juveniles were selected more frequently than adults in only one year, possibly a result of yearly differences in the number of prey available per hawk, the rate of non-predator related juvenile mortality or unknown hawk hunting strategies. The overall finding of relative non-selectivity by hawks was attributed to the surprise factor associated with the hunting methods used by Sparrowhawks in woodland.     

BODY SIZE, ITS HERITABILITY AND INFLUENCE ON JUVENILE SURVIVAL AMONG GREAT TITS, PARUS MAJOR

This paper reports on part of a three-year study into the biological significance of variation in body size of individuals from a single population of Great Tits in Wytham Woods near Oxford, from 1973 to 1976. It is a reasonable hypothesis that the body size of an individual is controlled partly by heredity and partly by environmental factors. Genetical factors by themselves are shown to account for nearly three-quarters of the total observed phenotypic variance of body size. Of the likely environmental factors considered, only the date of hatching (in 1973) and an annual difference in body size are shown to have significant effects.
Previous workers have shown that heavier fledglings have a better chance of surviving the immediate post-fledging period than lighter fledglings (e.g., Perrins 1965). It had been postulated that this differential survival rate might be due to variations in the fat reserves of fledglings. However, the data presented here suggest that this hypothesis is unlikely, and that the body size of fledglings has a more significant influence. The aggressive behaviour of fledgling Great Tits towards one another may be the mechanism responsible for this since it is shown that larger fledglings tend to dominate smaller fledglings.     

SEXUAL DIMORPHISM AND DIVERGENCE IN WINTER FORAGING BEHAVIOUR OF THREE-TOED WOODPECKERS PICOIDES TRIDACTYLUS

Measurements of 48 males and 45 females of Three-toed Woodpeckers shot in Norway revealed that the mean lengths of wing, tail, bill and tarsus of males were significantly greater than those of females. Sexual dimorphism was most marked for the bill and tarsus.
Feeding observations of the species from spruce-dominated mixed forests during the October-March period indicated an intersexual partitioning of the foraging niche. The males exhibited a stereotyped foraging pattern of bark scaling low down on the main trunks of dead spruce, whilst females used a more differentiated feeding technique and utilized a greater variety of trunk and branch sizes of dead, decaying and living trees of several different species. Significant intersexual differences were found in tree height preference and in the diameter of trunks and branches. The males foraged almost exclusively on the trunks of trees over 10 m high and over 15 cm in diameter, whilst females often frequented dead spruce, under 5 m high, and foraged on thinner trunks and branches. Foraging height was significantly lower for males than for females.
The relationship between the sexual dimorphism, the intersexual partitioning of the feeding niche and their biological significance, is briefly discussed.     

包囊游仆虫包囊形成和解脱过程中纤毛器的分化

包囊游仆虫(Euplotes encysticus)形成包囊时,各类纤毛器中的纤毛杆被部分地或全部地吸收,毛基体被保留下来。休眠包囊中,背纤毛器的定位无明显变化,但原腹面纤毛器中的口围带和波动膜、额腹棘毛和横棘毛,以及左、右尾棘毛都按序陷入在细胞质内深处,并相互汇聚在一起。脱包囊时,纤毛结构在原毛基体上再分化,新纤毛器按口围带、横棘毛、额腹棘毛和左、右尾棘毛的顺序从细胞内显露出来。     

CHEMICAL DIFFERENTIATION OF NUCLEAR PROTEINS DURING SPERMATOGENESIS IN THE SALMON

By means of qualitative staining experiments the characteristic protein changes which occur during maturation of salmon sperm can be followed. It can be observed that the replacement of histone by protamine takes place after completion of meiosis during an advanced stage of spermiogenesis.     

PROTEIN PROFILES OF RAT EMBRYO CEREBRAL CELLS DURING DIFFERENTIATION IN CULTURE

The protein composition of the particulate fraction of dissociated foetal rat cerebral cells during maturation in culture was investigated. SDS polyacrylamide gel electrophoresis showed a general decrease in the histonal components and significant changes in composition of a group of polypeptides with molecular weights ranging from 42 to 60 K. Two of these polypeptides coelectrophoresed with tubulin and actin whereas a 48 K polypeptide comigrated with the major component of the Wolfgram myelin protein. Its relative quantity appeared to approach a plateau after 8 days in culture. The myelin basic and proteolipid proteins were below detection levels in cultured cells at any time point investigated. A group of polypeptides with estimated molecular weights of 47, 51 and 52 K possibly representing synaptic proteins increased with time in culture. The appearance of a prominent band (60 K) in brain cultures and in other cells of divergent origin was demonstrated. This protein may be related to the process of cell adaptation to culture conditions. The developmental changes in the protein profile are discussed in the context of an in vitro myelinogenesis and synaptogenesis and compared with whole brain particulate and subcellular fractions.     

长春地区冬季流行的轮状病毒核酸电泳型的比较

轮状病毒是婴幼儿腹泻的主要病原,在我国亦广泛流行,根据病毒基因组的电泳分析,可以研究其分子流行病学的规律。文献报道该病毒在流行区往往以一个电泳型感染为主,我们对长春地区1984～1985年和1985～1986年两个冬季流行的婴幼儿腹泻轮状病毒基因组PAGE分析的结果,也表明两个冬季都是以电泳长型感染为主,其中优势株与本室     

烟草茎薄层芽分化过程内源玉米赤霉烯酮含量的变化(简报)

自李季伦等首次发现越冬的冬小麦茎尖中存在玉米赤霉烯酮(zearalenone,以下简称ZEN)的类似物以后,大量的工作证实了高等植物可内源产生ZEN,并发现ZEN与植物的春化作用,光周期(短日)诱导以及花器官的分化、成熟乃至开花都密切相关。薄细胞层(Thin cell layers,以下简称TCL)具有外植体小和组成均匀,易于进行组织培养、对环     

黑龙江省胜山林场冬季驼鹿、马鹿和狍的种间关系

1987—1989年的两个冬季在黑龙江省黑河市胜山林场,对驼鹿、马鹿和狍的食性、采食高度和栖息地进行了研究。驼鹿的主要食物是柳(22.4％)、榛(16.0％)、红松(14.3％)和桦(13.8％);马鹿为杨(36.0％)、桦(22.7％)和红松(17.3％);狍为桦(26.5％)、柳(19.0％)、杨(12.7％)。三种动物采食高度的频次为正态分布。驼鹿的采食高度(标准差)为137.4(±39.0)厘米;马鹿为136.2(±37.0)厘米;狍为84.2(±29.2)厘米。驼鹿和马鹿对红松林的利用程度最高,而狍主要利用沼泽植物和红松林。驼鹿与狍在食物维和栖息地维上的生态位重叠最大,驼鹿与马鹿在采食高度维上的重叠最大。三种动物在食物、采食高度和栖息地三维生态位上的重叠大小的顺序为:驼鹿和马鹿>驼鹿和狍>马鹿和狍。