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Brood Size

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Joost M Tinbergen – 1st expert on this subject based on the ideXlab platform

  • biased estimates of fitness consequences of Brood Size manipulation through correlated effects on natal dispersal
    Journal of Animal Ecology, 2005
    Co-Authors: Joost M Tinbergen


    Summary 1. Dispersal of parents and offspring in relation to manipulated Brood Size were analysed in the great tit Parus major (L.) to study the potential confusion between dispersal and survival. The study area consisted of eight woodlots interspersed with nonbreeding habitat. The maximum distance between nestboxes was 10 km. 2. The Brood Size of pairs with similar clutch Size and laying date was manipulated in 3 years when chicks were 2 days old (1995, 1997 and 1998). Three nestlings were removed from one and added to another Brood while a third was kept as a control. Offspring were measured, weighed and marked and breeding birds were captured and marked to allow dispersal estimates. 3. For the offspring, dispersal was estimated as the distance between the natal nestbox and the nestbox of first breeding (natal dispersal distance) and, for the parents, as the distance between breeding boxes in two subsequent seasons (breeding dispersal distance). 4. Natal dispersal distance was positively affected by Brood Size manipulation. This effect was more pronounced in males than in females. Breeding dispersal distance was not affected by manipulation. 5. The practical consequence of this finding is that fitness estimates used to measure selection on Brood Size did depend on the spatial scale of the study area. For the Lauwersmeer population measured selection pressure changed from positive to stabilizing when I restricted the spatial scale of recovery. Other Brood Size manipulation experiments may suffer from similar biases in their fitness estimates. 6. The biological consequence of this finding is that, if clutch Size has a heritable component, local adaptation of clutch Size will depend on the spatial heterogeneity of the habitat.

  • strong evidence for selection for larger Brood Size in a great tit population
    Behavioral Ecology, 2004
    Co-Authors: Joost M Tinbergen, Juan Jose Sanz


    We measured the selection pressure on Brood Size in a recently established population of great tits (Parus major L.) in the northern Netherlands by manipulating Brood Size in three years (1995: n e 51, 1997: n e 66, 1998: n e 51), and we estimated fitness consequences in terms of local survival of both offspring and parents. Enlarged Broods had highest fitness; the offspring fitness component was positively affected by manipulation and the parental fitness component was unaffected. Parental survival and the probability that parents produced a second clutch were not affected by the treatment. However, parents that had raised enlarged Broods produced their second clutch later in the season. Clutch Size, Brood Size, and laying date of birds recaptured in the next breeding season were largely independent of the treatment. We conclude that there is strong evidence for selection for larger Brood Size and reject the individual optimization hypothesis for this population because the number of young in the nest predicts fitness independently of the manipulation history. Copyright 2004.

  • energy expenditure nestling age and Brood Size an experimental study of parental behavior in the great tit parus major
    Behavioral Ecology, 1999
    Co-Authors: Juan Jose Sanz, Joost M Tinbergen


    A Brood manipulation experiment on great tits Parus major was performed to study the effects of nestling age and Brood Size on parental care and offspring survival. Daily energy expenditure (DEE) of females feeding nestlings of 6 and 12 days of age was measured using the doubly-labeled water technique. Females adjusted their Brooding behavior to the age of the young. The data are consistent with the idea that Brooding behavior was determined primarily by the thermoregulatory requirements of the Brood. Female DEE did not differ with nestling age; when differences in body mass were controlled for, it was lower during the Brooding period than later. In enlarged Broods, both parents showed significantly higher rates of food provisioning to the Brood. Female DEE was affected by Brood Size manipulation, and it did not level off with Brood Size. There was no significant effect of nestling age on the relation between DEE and manipulation. Birds were able to raise a larger Brood than the natural Brood Size, although larger Broods suffered from increased nestling mortality rates during the peak demand period of the nestlings. Offspring condition at fledging was negatively affected by Brood Size manipulation, but recruitment rate per Brood was positively related to Brood Size, suggesting that the optimal Brood Size exceeds the natural Brood Size in this population. Key words: Brood Size manipulation, doubly-labeled water technique, energy expenditure, great tits, parental care, Parus major. [Behav Ecol 10:598‐606 (1999)]

Heinz Richner – 2nd expert on this subject based on the ideXlab platform

  • physiological responses to increased Brood Size and ectoparasite infestation adult great tits favour self maintenance
    Physiology & Behavior, 2015
    Co-Authors: Michele Wegmann, Beatrice Voegeli, Heinz Richner


    Abstract Different types of stressors trigger responses of different physiological systems, and these responses may contribute differentially to the maintenance of homeostasis, to trade-offs and the evolution of life-history traits. To manipulate two common stressors during reproduction, we infested half of the nests in a naturally breeding great tit population with ectoparasites and simultaneously manipulated Brood Size, using a 2 × 2 experimental design. Parents in this model species commonly compensate for ectoparasites by an increase in food provisioning. We assessed parental responses to these concurrent stressors by measuring several physiological stress parameters such as changes in metabolic rate, oxidative stress and expression of heat-shock proteins (Hsp), and explored how these stressors affect the trade-off between self-maintenance and reproduction. Neither flea infestation nor Brood Size manipulation affected adult metabolic rate, oxidative damage or Hsp levels. Furthermore, we found no interactive effect of the two treatments on adults. However, nestlings in infested nests had lower body mass and lower survival. Nestlings in enlarged Broods were lighter and had lower survival, although parents of enlarged Broods increased food provisioning rate. The findings suggest that adults favour maintenance of cellular homeostasis, and physiological equilibrium over current reproduction, and that the costs induced by both stressors, flea infestation and increased Brood Size, are carried by the offspring. It emphaSizes the importance of self-maintenance over reproduction in life-history decisions, and more generally the need of including physiological traits for understanding the evolution of life-histories.

  • Brood Size sibling competition and the cost of begging in great tits parus major
    Behavioral Ecology, 2003
    Co-Authors: Samuel Neuenschwander, Martin W G Brinkhof, Mathias Kolliker, Heinz Richner


    Evolutionary theory of parent-offspring conflict explains begging displays of nestling birds as selfish attempts to influence parental food allocation. Models predict that this conflict may be resolved by honest signaling of offspring need to parents, or by competition among nestmates, leading to escalated begging scrambles. Although the former type of models has been qualitatively supported by experimental studies, the potential for a begging component driven by scramble competition cannot be excluded by the evidence. In a BroodSize manipulation experiment with great tits, Parus major, we explored the scramble component in the begging activity of great tit nestlings by investigating the mechanisms of sibling competition in relation to Brood Size. While under full parental compensation, the feeding rate per nestling will remain constant over all Brood Sizes for both types of models; the scramble begging models alone predict an increase in begging intensity with Brood Size, if begging costs do not arise exclusively through predation. Great tit parents adjusted feeding rates to Brood Size and fed nestlings at similar rates and with similar prey Sizes in all three BroodSize categories. Despite full parental compensation, the begging and food solicitation activities increased with experimental Brood Size, whereas nestling body condition deteriorated. These findings support a scramble component in begging and suggest that the competition-induced costs of food solicitation behavior play an important role in the evolution of parent-offspring communication. Copyright 2003.

  • are clutch and Brood Size patterns in birds shaped by ectoparasites
    Oikos, 1995
    Co-Authors: Heinz Richner, Philipp Heeb


    Ectoparasites may influence the optimum values of important life history traits such as clutch Size and Brood Size by having different fitness effects for large and for small trait values. We propose here that the life-cycle length of the common ectoparasite species of a host determines whether it is more profitable for the host to raise a large or a small Brood. The hypothesis rests on the following argument: (1) the length of an ectoparasite’s life-cycle relative to the timespan that the host nestlings are available as a resource determines the total parasite load per nest during the nestlings’ growth phase, and therefore (2) also the parasite load per nestling, which in turn (3) determines the parasite impact on the nestlings. Populations of long-cycled ectoparasites (i.e. the life-cycle length of the ectoparasite is similar to the length of time that nestlings take from hatching to fledging) do not build up considerably during the nestling phase and, consequently, parasites become increasingly diluted with an increase in Brood Size. This predicts no correlation between parasite load and Brood Size, but a negative correlation between parasite load per nestling and Brood Size. Larger Broods will be favoured and Brood Size should be reduced only when feeding conditions become increasingly inadequate. In contrast, populations of short-cycled ectoparasites (i.e. the life-cycle length of the ectoparasite is much shorter than the length of time that nestlings take from hatching to fledging) can build up quickly and may reach the carrying capacity given by the number of host nestlings. This predicts a positive correlation between parasite load and Brood Size, but no correlation between parasite load per nestling and Brood Size. Smaller Broods may then be at an advantage because they can be more adequately provisioned with food. Whether females should adjust clutch Size will largely depend on whether they can, when laying their clutch, predict the parasite load after hatching. When future infestation can be predicted, females of species that are commonly infested with short-cycled ectoparasites should lay a smaller clutch, but females commonly infested with long-cycled parasites should lay a larger clutch. When future infestation cannot be predicted at laying, with shortcycled ectoparasites, females should lay a normal clutch and reduce it when the nest becomes infested, but with longcycled ectoparasites, females should lay a larger clutch and maintain Brood Size as long as feeding conditions are adequate. If parasite pressure is constant over many breeding season, we may expect selection for smaller or larger clutches depending on the cycle length of the common ectoparasite. If parasite pressure fluctuates stochastically, a behavioural response will be more appropriate. Patterns from intraand interspecific studies are in agreement with most predictions outlined above. Clutch Size in birds varies widely both among and within species and much of this variation has been attributed proximately to variance in phenotypic quality of the parents, variance in food abundance, nest predation, nestling competition, nest parasitism by other birds, phylogenetic inertia, physiological constraints, and ectoparasites (for recent reviews see e.g. Murphy and Haukioja 1986, Godfray et al. 1991, Poiani 1993a, b). Ultimately much of this variation can be understood in terms of variation in reproductive trade-offs, such as clutch Size with offspring or adult survival and fecundity (for reviews see Linden and M0ller 1989, Dijkstra et al. 1990, Stearns 1992). Ectoparasites can strongly reduce reproductive success (Moss and Camin 1970, M0ller et al. 1990, M0ller 1993, Richner et al. 1993, Clayton and Tompkins 1994) of their hosts, and are therefore most likely to affect reproductive trade-offs. This life-history point of view predicts that hosts may reduce the impact of parasites by altering their own reproductive effort (Forbes 1993, Poulin et al. 1994). In this note we address the question of how ectoparasites are expected to influence Brood Size by considering (1) the relationship between life-cycle length of ectoparasites, host Brood Size and parasite load, (2) the expected relationship between life-cycle length of ectoparasites and the effect of ectoparasites on nestlings of small and large Broods, (3) the expected host response in terms of a change in clutch Size and Brood Size. Empirical evidence supporting the predictions are presented.

Ch Dekogel – 3rd expert on this subject based on the ideXlab platform

  • long term effects of Brood Size manipulation on morphological development and sex specific mortality of offspring
    Journal of Animal Ecology, 1997
    Co-Authors: Ch Dekogel


    1. Little is known about long-term effects of Brood Size on fitness components of offspring. This is unfortunate because such information is needed to predict optimal Brood Size. Furthermore, ontogenetic circumstances are potentially important in explaining the large individual differences in lifetime reproductive success documented in many species. 2. In a laboratory study the long-term effect of Brood Size manipulation on mortality and morphological development of offspring was investigated. Young zebra finches Taeniopygia guttata were reared in small or large Broods. Young were exchanged in such a way that natural siblings from different rearing conditions could be compared. 3. Manipulated Brood Size affected offspring morphology permanently (measurements were taken up to the age of 12 months). Individuals reared in small Broods were heavier, had longer tarsi and wings, higher beaks, were in better condition, and males had redder beaks. The experiment did not affect beak length or female beak redness. Individuals from large Broods had caught up on wing length and males from large Broods on beak redness by 6 months of age, which may reflect priority of investment in traits important to fitness. 4. Mortality of offspring raised in large Broods was higher both before and after independence. After independence the effect of manipulated Brood Size on mortality was sex specific; females were most likely to die. This suggests that the optimal sex ratio of offspring may depend on Brood Size. 5. The effect of Brood Size on mortality after independence was probably partly mediated by Size and condition during the nestling phase and possibly by peer aggression among adult offspring. Sex-linked mortality could not be explained by a sex difference in morphological development. Why females are more vulnerable remains to be discovered.

  • Costs of reproduction in the Zebra Finch Taeniopygia guttata : Manipulation of Brood Size in the laboratory
    Journal of Avian Biology, 1996
    Co-Authors: Ch Dekogel, Gerard Overkamp


    Brood Size of Zebra Finches Taeniopygia guttata was manipulated in an attempt to identify a trade-off between current and subsequent reproduction in a laboratory situation with ad libitum food availability. The birds were able to raise a larger Brood than the most frequent Brood Size under the same conditions. Initiation of the subsequent clutch was advanced after raising a small Brood, and delayed after raising a large Brood. The Size of the subsequent clutch was not affected by the previous, experimental Brood Size. Thus, a cost of reproduction was observed in modification of the reproductive interval. Brood Size also affected the prospects of the current, experimental Brood. Both nestling survival and nestling weight at independence decreased with Brood Size. It has often been suggested that food availability limits reproduction in the field. This study shows that under unrestricted access to food, other factors restrain reproduction. Time allocation, energy expenditure and nutrient reserves of the parents are discussed as potential alternative constraints.

  • effects of Brood Size manipulations on sexual attractiveness of offspring in the zebra finch
    Animal Behaviour, 1996
    Co-Authors: Ch Dekogel, H J Prijs


    Abstract In a laboratory study the effect of Brood Size manipulations on the sexual attractiveness of offspring was investigated. Zebra finches,Taeniopygia guttata, were reared in small or large Broods. Young were exchanged so that natural siblings from different rearing conditions could be compared. Birds of both sexes reared in small Broods were larger and heavier as adults; furthermore, they developed the adult bill colour sooner than birds reared in large Broods. Males reared in small Broods had a redder beak as adults. Males but not females reared in small Broods were more attractive to opposite sex individuals, as measured in choice tests. Males with redder beaks were more attractive to females. No relation was found in females between attractiveness and measured traits. Sexual attractiveness may thus be a potentially important mechanism by which Brood Size affects fitness.