Showing papers in "Journal of Animal Ecology in 1984"

Systems ecology : an introduction

Abstract: An integrated theoretical and applied introduction to systems ecology that uses energy diagrammatic language to explain basic concepts of systems, modelling, and simulation. Teaches energetics while at the same time dealing with the issues of organization, entropy, information, complexity, diversity, frequency, and power and the ways these determine the nature of real systems. Includes analog and digital computer modelling, enabling readers without prior programming experience to create computer models of ecological processes.

The number of species of insects associated with British trees: a re-analysis.

Abstract: An updated list of numbers of phytophagous insects and mites associated with 28 British tree species or genera is presented, together with revised estimates of the abundance of the trees. Difficulties in assessing species-area relationships for insects on trees are discussed and a new relationship calculated. When a number of variables: Log tree abundance, time present in Britain, whether or not trees were evergreen or coniferous, taxonomic relatedness, tree height and leaf length were included in a stepwise multiple regression analysis of insect species richness, all but 'coniferousness' contributed significant F values. These variables accounted for 82% of the variation in insect species richness between British trees. When the regression analysis was repeated, but halted after the entry of the last significant F value, log abundance, time and evergreenness emerged as the best set of predictor variables for the numbers of insect species on British trees and accounted for 74% of the variation. -from Authors

Central place foraging in starlings (Sturnus vulgaris). I: Patch residence time

Abstract: (1) Starlings that were feeding nestlings collected mealworms from an artificial feeder where the cumulative number of prey was a logarithmic function of patch residence time (Tp). The patch was placed at various locations between 8 m and 600 m away from the nests. The number of prey swallowed, Tp, and number delivered to the young was recorded in 1364 round trips. (2) Four models of optimal Tp are discussed: (a) Maximize YIELD: energy collected per total round trip time (including time in the nest); (b) Maximize rate of DELIVERY: YIELD minus parent's metabolism; (c) Maximize FAMILY GAIN: DELIVERY minus brood's metabolism, considering the energy cost of begging by the chicks; (d) Maximize EFFICIENCY :YIELD/parent's metabolism. Relevant when there is a cost in spending energy (for example due to constraints in maximum rate of heat dissipation). (3) The results differ significantly from the YIELD and EFFICIENCY models. The FAMILY GAIN model gives the best fit to the data. (4) The variance in Tp reflects the cost of deviations from the optimum. The frequency distribution of observed Tp resembled the predictions of a descriptive model (PROFITABILITY MATCHING) based on proportional alocation of effort to various behavioural options depending on their relative pay-off. (5) Manipulations in brood size resulted in different allocation of food between parent and young but did not affect overall Tp.

Food distribution and a variable mating system in the dunnock, prunella modularis

Abstract: SUMMARY (1) The mating combinations were very varied and included monogamy (pairs), polyandry (two or three males with one female), polygyny (one male with two females) and polygynandry (two or three males shared two, three or four females). (2) Female ranges were always exclusive. Where two or three males shared one or more females, the ranges of the males overlapped and they cooperated to defend the territory. There was a dominance hierarchy among the males; alpha males were often old birds and beta males often first year birds. There were no known cases of close relatives being involved within any of the mating combinations. (3) It is suggested that the different mating combinations form a continuum in a male's ability to monopolize access to females, varying, in increasing order of mating success, from unpaired, to shared access to one female (polyandry), sole access to one female (monogamy), shared access to more than one female (polygynandry) and finally sole access to more than one female (polygyny). (4) The ability of a male to control access to females depended on female range size, which was influenced by food distribution. Where food patches were dense, female ranges were small and they were then easily monopolized giving rise to mating combinations that reflected high male mating success (polygyny and polygynandry). Where food patches were sparse, female ranges were large and they were difficult for one male to monopolize, thus giving rise to mating combinations with lower male mating success (polyandry). (5) When extra food was provided on some territories, female ranges became smaller

Habitat Quality and the Distribution of Algae-Grazing Catfish in a Panamanian Stream

Abstract: Sont precises: les facteurs controlant la qualite des sites en tant qu'habitat pour Ancistrus, la croissance et la survie des pre-reproducteurs et leur comparaison pour les divers sites, les deplacements des loricariides entre les habitats en reponse a des changements de milieu

Numerical changes and population regulation in young migratory trout Salmo trutta in a Lake District stream, 1966-83

Abstract: (1) This 18-year study of numerical changes in a trout population is part of a general study on the population dynamics, growth and distribution of migratory trout, Salmo trutta L., in Black Brows Beck, a stony stream in the English Lake District. (2) Earliest and latest spawning dates were 3 November and 7 December; larger females spawned earlier than smaller females. Eggs per redd and mean egg weight increased with female size and decreased with time from the start of the spawning period. Migratory trout produced more and larger eggs per unit length of fish than did resident trout in a neighbouring stream. (3) In laboratory and stream experiments, 50% of eggs hatched and 50% of alevins emerged after 444? days and 852? days from fertilization, respectively. Egg weight positively affected alevin size at hatching and emergence from the gravel, but not development times. Survival times of newly-emerged fish kept in the laboratory without food were positively related to weight at emergence. (4) Population densities of eggs and alevins were very similar within but differed between year-classes (range: 12-133 eggs m-2). The dominant factor affecting population densities of young trout was the population density of eggs, and hence alevins, at the start of each year-class. Alevin emergence time, weight of eggs or alevins, water temperature, numbers of older trout and numbers of other fish species (chiefly Cottus gobio L.) had no obvious effect. The number of recruits to each year-class was related to the initial egg density by the Ricker, dome-shaped, stock-recruitment curve. Maximum recruitment was estimated as 7.2 fish m-2 (95% CL = 6.5-8.0) soon after the fry stage ended in May/early June and 2*0 (? 0-5) fish m-2 in late August/September. Optimum egg densities for these values were estimated as 40.0 m-2 (95% CL = 38.5-41-7) and 62.5 m-2 (55.6-71-4) respectively. (5) Mortality was very low for eggs and alevins but high for young trout trying to establish feeding territories. The instantaneous mortality rate was linearly related to egg density and hence was density-dependent. The mortality rate for June to August was also negatively related to, and appeared to compensate for, the high mortality rate in May/early June.

Clutch size variation of birds in relation to nest predation: on the cost of reproduction

Abstract: Etude menee en 1982-83 a Trondheim, Norvege, dans un bois dans lequel ont ete places 440 nichoirs artificiels. Le succes reproducteur de Parus major lors d'une nouvelle tentative de nidification depend du degre d'effort parental deja implique dans une tentative initiale

Interference among Oystercatchers, Haematopus ostralegus, feeding on mussels, Mytilus edulis, on the Exe estuary

Abstract: Observation de kleptoparasitisme chez ces oiseaux et d'une hierarchie de dominance stable et lineaire. Le taux d'ingestion des proies diminue avec l'augmentation de la densite des oiseaux. L'on suggere que la dispersion des huitriers au-dessus du banc de moules peut etre decrite par une modification de la «repartition despotique ideale» proposee par Fretwell

Seasonal trend in the breeding performance of sparrowhawks

Abstract: Etude menee sur plus de 800 nids, dans le sud de l'Ecosse: dates de ponte, succes reproducteur en fonction de ces dates, survie apres l'envol, survie des adultes, taille de la couvee, couvees successives

Population fluctuations in red grouse: analysis of bag records and a simulation model

Abstract: (1) A time-series analysis of numbers of red grouse (Lagopus lagopus) shot per annum was carried out for fifty-two moors in northern England where data were available for at least 20 consecutive years during the period 1870-1977. Correlograms were constructed and auto-correlation coefficients were tested for statistical significance. (2) In the most representative sub-sample of moors, 83% of the series had significant negative coefficients at T + 2 or T + 3 years or both. A mathematical model was fitted to the fluctuations to describe their quasi-cyclic nature and the average 'cycle-length' was found to be 4.84 + 0.086 years. (3) Field observations and data from trials with captive grouse were combined to construct a simulation model of a red grouse population; its main features were:

Differential benefits from ant attendance to two species of homoptera on new york ironweed

Abstract: (1) New York ironweed (Vernonia noveboracensis L.) supports two species of honeydew-producing Homoptera-an aphid (Aphis vernoniae Thomas) and a membracid (Publilia reticulata Van Duzee)-that are tended by Tapinoma sessile Say and two species of Myrmica, M. lobicornisfracticornis Emery and M. americana Weber. (2) The benefits accruing to the honeydew producers from these ant associations are unequal and asymmetric, with aphids benefiting more from association with Tapinoma while membracids benefit more when tended by Myrmica. (3) Survivorship of Homopteran colonies is greatest when attended by the appropriate ant and lowest when ants are excluded. (4) There is no evidence that either ant affects aphid growth or fecundity. However, the size achieved by membracids is increased and the development time is decreased when ants are in attendance. These effects are greatest in Myrmica-tended colonies.

Nutrition, energy and passage time: experiments with fruit preference in European blackbirds (Turdus merula)

Abstract: (1) The patterns of fruit consumption by European Blackbirds (Turdus merula) were examined in relation to in vitro nutritional values, the per cent apparent digestibilities, per cent metabolizable nergies, metabolizable nergies, the pulp and seed passage rates, and intake rates of six fruit species which occur in Wytham Wood, Oxfordshire. (2) The in vitro nutritional values, per cent apparent digestibilities, per cent metabolizable energies, and seed and pulp passage rates of the fruit species differed significantly. Blackbird preferences among winter and spring-ripening fruits were positively related to the in vitro energy, per cent metabolizable nergy, metabolizable nergy, per cent apparent digestibility, and seed passage rates of fruits. Preferences of birds for autumn-ripening fruits were related to seed passage rates only. (3) I propose that seed passage rates play an important role in determining preference, particularly if nutritional and other properties (e.g. accessibility) of fruit species are similar. Calculations how that birds obtain a high rate of energy gain by consuming fruits whose seeds are regurgitated. This is because gut volume may place a constraint on fruit uptake. Seed regurgitation results in a rapid elimination of non-nutritional seed 'ballast' and creates space in the gut for additional food. Fruit species containing seeds which are defecated have lower rates of energy gain because the seeds remain (and take up space) in the gut for much longer periods of time. (4) Fruit intake rates did not appear to constrain energy intake, and did not correspond with blackbird preferences.

Effects of the general predator, notonecta (hemiptera) upon a freshwater community

Abstract: SUMMARY (1) In laboratory experiments we estimated the attack rates and preferences of several instars of the predatory backswimmer, Notonecta hoffmani. The prey included mosquito larvae, surface prey, and three species of zooplankton: Ceriodaphnia reticulata, Daphnia pulex and Moina sp. Notonecta's predatory behaviour was shown to be stereotyped: neither level of hunger nor previous diet significantly influenced preference. Attack rate increased exponentially, and handling time decreased exponentially, with temperature. (2) These laboratory results and others reported elsewhere were used to explain the results of field experiments in which treatment prey populations in stock tanks on ranches in Southern California were exposed to predation by Notonecta populations at natural densities while controls were not. (3) In these field experiments, Notonecta strongly influenced the structure and dynamics of the community. It drove mosquito larvae and D. pulex extinct and reduced the density of Moina sp., C. reticulata, and several other species. Notonecta either destabilized its prey populations, by driving them extinct, or did not affect the degree of temporal variability. (4) We discuss the relationship of these results to prevailing views on the importance of predation by invertebrates in aquatic communities, extinction in natural communities, and the question of whether predators in general act to stabilize or destabilize prey populations. The qualitative results obtained in the field were well-predicted by the information obtained in the laboratory, but caution is needed in extrapolating estimates of absolute attack rates from the laboratory to the field.

Models for the population dynamics of the yellow fever mosquito, Aedes aegypti

Abstract: On note des fluctuations dans la taille des populations adultes et une forte mortalite larvaire

Non-linear interactions of populations and the importance of estimating per capita rates of change

Abstract: On teste la valeur de modeles simples lineaires de productivite de la population (application a Aedes triseriatus)

Food limitation and competition: a field experiment with two Carabus species

Abstract: Etude menee dans une foret des Appalaches sur limbatus et C. sylvosus. Les aliments sont un facteur limitant l'accroissement de la population dans cette foret. L'amelioration du succes d'approvisionnement de C.s. est attribuee a une competition reduite avec C.P. pour les ressources alimentaires dans la nature

Factors affecting reproductive output of the goldeneye duck Bucephala clangula

Abstract: (1) The breeding histories of 172 female goldeneye duck Bucephala clangula were recorded from 1959 to 1980 in a study area in South-central Sweden. (2) The sizes of clutches (x = 8.7 + 0.1 eggs) and broods (x 8.1 + 0.1 young) and the dates of egg-laying and hatching are given. (3) Females breeding for the first time produced smaller clutches, fewer young and bred later in the season than when they were more experienced. There was some evidence of a decline in clutch sizes and later laying dates among older females (> 6 breeding years). (4) Females returning to the same nest site in successive years had earlier egg-laying dates than those that changed nest site between years. (5) There was individual variation among females in reproductive output; some consistently produced larger clutches and broods and bred earlier in the season than others.