摘要:

One‐quarter of Tawny owl nests fail to hatch young, mainly because the eggs are chilled and/or deserted. In 1973–74 automatic photography was employed at four nests near Oxford to relate the incubation behaviour of females to the ration of prey supplied to them by their mates. The eggs did not hatch in two nests and young fledged from only one of the others. Females were less attentive at the nests which failed during incubation and on average received less prey, but even at successful nests there were some nights when the female was supplied with less than her estimated daily food requirement. Female Tawny owls accumulate large reserves of fat and protein before laying. These buffer against any temporary inability of the male to provide sufficient food during incubation, and enable the female to stay on the nest rather than hunt for herself and risk the eggs becoming chilled. When prey are scarce, many females do not lay at all, and the ultimate factor determining whether breeding takes place may be the female's ability to acquire body reserves sufficient to provide a chance of breeding successfu

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb00066.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The effect of territorial behaviour on the density and stability of Tawny owl (Strix aluco(L.)) populations was studied in three habitats during 1971–74: deciduous woodland (Wytham, near Oxford), mixed farmland (south Warwickshire) and conifer plantations (Dumfries). Territory size was determined by plotting the position of territorial challenges (hoots) of males; these were individually recognizable.In all three areas, pairs of owls maintained contiguous territories which changed little in size and configuration from year to year. In Wytham, this was in spite of wide fluctuations in the abundance of rodent prey. Territory size was most variable on farmland (17–74 ha) where it was inversely correlated with the area of closed woodland contained within territories. The mean size of territories was significantly smaller in the deciduous woodland (18.2 ha) than the coniferous woodland (46.1 ha) or farmland (37.4 ha). This variation was probably ultimately related to the availability of prey in different habitats.In Wytham, the annual rate of disappearance of territory‐holding males was around 15% and, except after a poor breeding season, birds which disappeared or were removed from their territories were replaced rapidly. Territory boundaries remained the same after replacement and the number and spatial configuration of territories (around 30) was similar to that found 14 years earlier. There is some evidence that individual pairs would be able to raise more young if they could defend larger territories than is possible at the current population size.Recoveries of birds ringed nationally indicate that owls survive less well without territories, and that young suffer heavy mortality in their first autumn. The proportion of young recovered was highest in years when many were ringed. Examination of 276 corpses (mostly road casualties) suggests that many young starve soon after becoming independent.These observations support the idea that the stability of Tawny owl populations results from the territorial behaviour of residents acting to produce subsequent mortality among birds unable to establish their own territories. This regulation probably applies over wide areas and a variety of hab

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb00067.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Following opercular amputation, stages in opercular regeneration inPomatoceros lamarckiihave been described by light, transmission and scanning electron microscopy. Two to three days after amputation, the rudimentary opercular filament is invested with a delicate cuticle composed of an outer filamentous layer and an inner thicker component composed of orthogonally‐arranged layers of small fibril bundles. The opercular plate is uncalcified and composed of two major components, an outer, thin, electron‐dense layer and an inner, thicker component which structurally resembles that of the opercular filament cuticle. Between five and eight days, opercular plate calcification is initiated as needle‐like crystallites. The structural organization of the organic components of the opercular plate show changes which are related to the onset of calcification. From 13–17 days, the opercular plate becomes heavily calcified and is composed of highly‐ordered, prism‐like crystals. X‐ray diffraction shows these crystals to be aragonite. The structure of the cuticle remains unchanged except that the orthogonally‐arranged fibril bundles aggregate into thicker fibres. Amino acid analysis of the regenerated cuticle and organic components of the opercular plate show that they differ from one another and from the normal cuticle and opercular plate. During opercular regeneration, the differentiation of the cuticle and opercular plate‐secreting cells are described and the mechanisms of cuticle and calcareous opercular plate secret

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb00068.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Following opercular amputation inPomatoceros lamarckiiQuatrefages, wound healing is initiated from a predetermined point on the peduncle. The events of abscission, cell migration and cuticle deposition during wound healing have been studied by light and electron microscopy. Abscission occurs at a predetermined point on the peduncle indicated by specialized epidermal cells, the easy break‐point cells (EBP). Following detachment of tissues distal to the EBP cells, the resultant wound is plugged by a knot of coelomocytes which provide a substratum over which epidermal cells migrate to seal and restore the epidermis. During their migration, the epidermal cells undergo differentiation and deposit a new cuticle. Cuticle formation is initiated by the deposition of a finely filamentous matrix. The fine filaments subsequently coalesce to form thicker fibrils which become aggregated into layers of orthogonally‐arranged fibril bundles. The mechanisms involved in abscission, cell migration and cuticle deposition during wound healing of the opercular filament are discus

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb00069.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The biology of an aberrant saltioid spider,EuryattusThorell sp. indet., is described from observations in a Queensland rain forest and the laboratory. Pronounced morphological and behavioural changes occur during post‐embryological development. Juveniles spin webs, but adult females make ‘suspension nests’ by suspending a curled‐up leaf by heavy guylines from a rock ledge or vegetation. Adult males spin neither webs nor suspension nests. Females oviposit inside their suspension nests, but if denied access to leaves for suspension, they spin and oviposit in webs similar to those spun by juveniles. The flat, papery egg sacs ofEuryattusare atypical for a salticid, being more like the egg sacs of many of the Gnaphosidae. Intraspecific display behaviour has characteristics in common with typical salticids, but also includes unique features. Male courtship includes vibratory displays performed on the surface of the suspended leaf. Mating occurs inside the curled‐up leaf. Males co‐habit with sub‐adult females in suspension nests. Females take over suspension nests of other females and eat each other's eggs. Normal locomotion, intraspecific interactions, and predatory behaviour are characterized by frequent leaping.Euryattusroutinely makes long and accurate leaps on to prey, including flying insects intercepted in mid‐air and spiders and insects located in alien webs. The phylogenetic implications of the unusual characteristics ofEuryattu

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb00070.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The biology of two aberrant species of salticid spiders is described from observations in tropical Queensland and in the laboratory. Typical salticids are cursorial hunting spiders that do not build prey‐catching webs, although they frequently build enclosing, tubular nests.Simaetha paetula(Kerserling) andS. thoracicaThorell, however, are both cursorial predators that build nests and spiders that build large prey‐catching webs. Nests and webs may be built alone or incorporated into the same structure. Adults, more often than juveniles, build isolated tubular nests. Juveniles, more often than adults, build webs without tubes. Nest‐webs are built most often on leaves and stems of plants, and the leaves are sometimes fastened to stems by strong silk clamps. Intraspecific interactions ofS. paetulaoccur both at and away from nest‐webs. Away from nest‐webs, visual displays occur, but both visual and vibratory displays are important at nest‐webs. A repertoire of discrete displays occurs in both contexts. One prevalent display, clawing, is apparently multi‐channel: visual when the spiders are distant from each other and away from nest‐webs; tactile or chemotactic after the spiders come into contact with each other; and vibratory when they are at nest‐webs. During inter‐male interactions, displays occur that are unusually stereotyped for a salticid and require an unusual degree of co‐ordination of the movements of the two spiders. Males co‐habit in nest‐webs with sub‐adult females and mate when the female matures. Two different copulatory postures are routinely adopted, one of which is aberrant for salticids. Cannibalism is frequent, but the hypothesis that cannibalism reduction has been important in the evolution of display behaviour is not supported. Species ofSimaethaThorell often live within the colonies of the social spiderBadumna Candida(L. Koch) as a kleptoparasite, gleaning insects from the edges of the alien webs and incorporating its own nest‐webs within the alien communal web. Although vulnerable to the glue on the social spider webs,Simaethahas behavioural specializations that enable it to avoid becoming prey of the social spiders. The biology ofSimaethais discussed in r

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb00071.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY