171,720 research outputs found
A fixed energetic ceiling to parental effort in the great tit?
No full text1. To elucidate the links between avian brood size, parental effort and parental investment, we measured daily energy expenditure (DEEfem), condition (residuals of mass on tarsus) and feeding rate in female great tits Parus major L. rearing broods in which the number of young was either reduced, unmanipulated or enlarged. 2. Female condition was negatively correlated with manipulation when measured at the nestling age of 8 days (measured during the day), which suggests a shift in allocation from self-feeding to chick-feeding. However, there was no detectable manipulation effect on condition measured at the nestling age of 12 days (measured during the night). Either female condition was only affected by manipulation in the early nestling phase or the females adjusted their diurnal mass trajectory in response to brood size manipulation. More detailed data are required to verify this point. There were no indications of a fitness cost associated with the condition during the day, but condition at night was positively related to winter survival. Since manipulation only affected condition during the day, there was no link between manipulation and winter survival. 3. The duration of the working day was not affected by manipulation and female feeding rate tended to flatten off with manipulated brood size. Similarly, brood reduction resulted in a lower DEEfem, whilst brood enlargement had no effect. This suggests that females worked at an energetic ceiling when rearing an unmanipulated brood. However, the level of this 'ceiling' in DEEfem was not fixed: it differed between years. This leads us to conclude that the observed ceiling was imposed by extrinsic factors (e.g. available foraging time) and not by an intrinsic factor such as maximum energy assimilation rate. We hypothesize that time limitation was the cause for the observed ceiling in energy expenditure and that the annual variation in the level of this ceiling was due to annual variation in ambient temperature. 4. A cost of reproduction was previously demonstrated in this population: brood enlargement caused a reduction in the incidence of second clutches. However, since DEEfem did not differ between control and enlarged broods, we judge it unlikely that daily energy expenditure is a general predictor for parental investment. [KEYWORDS: clutch size; condition; energy expenditure; cost of reproduction; parental effort; Parus major L. Starlings sturnus-vulgaris; kestrel falco-tinnunculus; parus-major; brood size; clutch size; blue tits; food availability; feeding frequency; field metabolism; trade-offs]
Darby (H. C.) en Campbell (E. M. J.). The Domesday Geography of South-East England Darby (H. C.) en Maxwell (I. S.). The Domesday Geography of Northern England
No full textVerhulst Adriaan. Darby (H. C.) en Campbell (E. M. J.). The Domesday Geography of South-East England Darby (H. C.) en Maxwell (I. S.). The Domesday Geography of Northern England. In: Revue belge de philologie et d'histoire, tome 44, fasc. 2, 1966. Histoire (depuis la fin de l'Antiquité) - Geschiedenis (sedert de Oudheid) pp. 616-618
Studies in Econometric Method, by Cowles Commission for Research Staff members, Edited by W.M.C. Hood and Tjalling C. Koopmans.
No full textVerhulst Michel. Studies in Econometric Method, by Cowles Commission for Research Staff members, Edited by W.M.C. Hood and Tjalling C. Koopmans.. In: Revue économique, volume 5, n°3, 1954. pp. 481-482
Studies in Econometric Method, by Cowles Commission for Research Staff members, Edited by W.M.C. Hood and Tjalling C. Koopmans.
No full textVerhulst Michel. Studies in Econometric Method, by Cowles Commission for Research Staff members, Edited by W.M.C. Hood and Tjalling C. Koopmans.. In: Revue économique, volume 5, n°3, 1954. pp. 481-482
A. Verhulst, C. Vandenbroeke, Landbouwproduktiviteit in Vlaanderen en Brabant (XIVde-XVIIIde eeuw), offset, Gand, 1979
No full textSivéry Gérard. A. Verhulst, C. Vandenbroeke, Landbouwproduktiviteit in Vlaanderen en Brabant (XIVde-XVIIIde eeuw), offset, Gand, 1979. In: Revue du Nord, tome 63, n°251, Octobre-décembre 1981. p. 1103
A. Verhulst, C. Vandenbroeke, Landbouwproduktiviteit in Vlaanderen en Brabant (XIVde-XVIIIde eeuw), offset, Gand, 1979
No full textSivéry Gérard. A. Verhulst, C. Vandenbroeke, Landbouwproduktiviteit in Vlaanderen en Brabant (XIVde-XVIIIde eeuw), offset, Gand, 1979. In: Revue du Nord, tome 63, n°251, Octobre-décembre 1981. p. 1103
Why fight?: Socially dominant jackdaws, Corvus monedula, have low fitness
No full textSocial dominance is intuitively assumed to be associated with higher fitness, because social dominance implies better access to resources. We found that, in a colony of jackdaws, the dominant males consistently produced fewer fledglings, which had lower chances of survival to 1 year of age. Laying date and clutch size were independent of dominance, but females that mated with dominant males were in poorer condition and laid smaller eggs. Parental survival was independent of social dominance, and the frequency of extrapair fertilizations in jackdaws is negligible. Dominance was a stable trait of individuals, and not a state that all individuals eventually attained. We conclude that, in this colony, dominant jackdaws had lower fitness. To our knowledge, this is the first example of such a pattern in a free-living species. We hypothesize that the high density of our colony resulted in high testosterone titres, which suppressed paternal care of mate and offspring to the extent that it outweighed the benefits of higher resource access. (C) 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved
High heritability of telomere length and low heritability of telomere shortening in wild birds
No full textBauch C, Boonekamp JJ, Korsten P, Mulder E, Verhulst S. High heritability of telomere length and low heritability of telomere shortening in wild birds. Molecular ecology. 2021.Telomere length and telomere shortening predict survival in many organisms. This raises the question of the contribution of genetic and environmental effects to variation in these traits, which is still poorly known, particularly for telomere shortening. We used experimental (cross-fostering) and statistical (quantitative genetic 'animal' models) means to disentangle and estimate genetic and environmental contributions to telomere length variation in pedigreed free-living jackdaws (Corvus monedula). Telomere length was measured twice in nestlings, at ages 4 (n=715) and 29 days (n=474), using TRF-analysis, adapted to exclude interstitial telomeric sequences. Telomere length shortened significantly over the nestling period (10.4±0.3 bp/day) and was highly phenotypically (rP =0.95±0.01) and genetically (rG >0.99±0.01) correlated within individuals. Additive genetic effects explained a major part of telomere length variation among individuals, with its heritability estimated at h2 =0.74 on average. We note that TRF-based studies reported higher heritabilities than qPCR-based studies, and we discuss possible explanations. Parent-offspring regressions yielded similar heritability estimates for mothers and fathers when accounting for changes in paternal telomere length over life. Year effects explained a small but significant part of telomere length variation. Heritable variation for telomere shortening was low (h2 =0.09±0.11). The difference in heritability between telomere length (high) and telomere shortening (low) agrees with evolutionary theory, in that telomere shortening has stronger fitness consequences in this population. Despite the high heritability of telomere length, its evolvability, which scales the additive genetic variance by mean telomere length, was on average 0.48%. Hence evolutionary change of telomere length due to selection is likely to be slow. This article is protected by copyright. All rights reserved
Post-natal exposure to corticosterone affects standard metabolic rate in the zebra finch (Taeniopygia guttata)
No full textPost-natal stress has been shown to have important short and long term effects on many adult traits in birds. During stress, metabolic alterations often result in the mobilization of energy away from energy-sensitive functions such as growth, which could have significant implications for developing animals. However, little is known about the implications of stress hormones for energy consumption in growing individuals. We experimentally increased corticosterone (CORT) levels in nestling zebra finches via oral administration, between the ages of 7 and 18 days. The standard metabolic rate (SMR) of birds was measured twice overnight when birds were between 11-13 and 55-65 days of age. Developmental CORT administration significantly elevated overnight variability in SMR (sd) in nestling birds (during the treatment period), but not at 55-65 days (5-6 weeks after the treatment period). The effect on variability was seen more prominently in birds from larger brood sizes and in females. We found no effects of our treatments on mean SMR overnight. However, brood size and sex had interactive effects, with males from larger brood sizes having higher SIVIR at 55-65 days of age. These results suggest that stress hormones can have significant effects on energy metabolism and possibly nocturnal arousal and sleep fragmentation. However, there were no detectable long term effects of our treatments on SIVIR, suggesting that these effects are only short-lived, in order to maintain homeostasis in the short term. (c) 2008 Elsevier Inc. All rights reserve
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