| 1. |
- Lundberg, S., et al.
(författare)
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Parent-offspring conflict over reproductive efforts: Variations upon a theme by Charnov
- 1994
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 1095-8541 .- 0022-5193. ; 170:2, s. 215-218
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Tidskriftsartikel (refereegranskat)abstract
- A novel formulation of the theory of parent-offspring conflict is proposed. The basis of this formulation is an application of traditional life-history theory in combination with simple genetic arguments. The advanatage with this approach is conceptual, and the formulation is not in variance with earlier studies in the area. Parent-offspring conflict is, in our forumlation, not seen as a conflict between individuals, but as a tradeoff-an age-specific selection pressure acting on a trait, which is favourable when an individual is offspring and disadvantageous when it becomes parent. Using an ESS approach we investigate a simple offspring-wins problem: we find that a gene causing assertiveness of offspring will increase when rare, because the advantage thus gained by an assertive individual when young exceeds the cost incurred as adult by that half of its own offspring which belongs to the same assertive genotype.
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| 2. |
- Ohlsson, Thomas, et al.
(författare)
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Development and maintenance of nestling size hierarchies in the European starling (Sturnus vulgaris)
- 1994
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Ingår i: The Wilson Bulletin. - 0043-5643. ; 106, s. 448-455
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we show that nestling mass hierarchies in the European Starling (Sturnus vulgaris) are due to asynchronous hatching. The parents may, by starting to incubate the day the penultimate egg is laid, or earlier, affect the degree of hatching asynchrony and thereby the nestling weight hierarchy. Intra-clutch variation in egg size had no effect on nestling weight hierarchies, explaining only 0.4% of the variation in nestling mass at two days of age. Nestlings kept their relative size to siblings throughout a substantial part of the nestling period. Furthermore, the degree of variation in mass at two days of age affected the variation in mass at least until nine days. This relationship was stronger in larger broods.
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| 3. |
- Sandell, Maria, et al.
(författare)
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Dominance, prior occupancy and Winter residency in the great tit (Parus major)
- 1990
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Ingår i: Behavioral Ecology and Sociobiology. - 1432-0762. ; 29, s. 147-152
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Tidskriftsartikel (refereegranskat)abstract
- This study reports an aviary experiment aimed at determining what affects social dominance in the great tit (Parus major), especially why older birds (adults) in nature normally dominate younger ones (juveniles). When birds were matched with respect to age, prior residency determined dominance. Without a difference in prior residency older birds dominated younger ones. However, when juvenile birds had a prior residency advantage over adult birds, they often became dominant. This was especially so when the juvenile bird was large relative to the adult bird. When a resident juvenile male was also consorted by a female, the became dominant over an adult male on most occasions. An experiment where the dominant bird was removed and later returned to the aviary failed to produce more than one shift in dominance. However, the proportion of reversals in dominance interactions increased with separation time. It is argued that the fact that dominance depends on prior residency selects for winter residency in the great tit.
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| 4. |
- Smith, Henrik G.
(författare)
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Heritability of tarsus length in cross-fostered European Starling broods
- 1993
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 1365-2540 .- 0018-067X. ; 71, s. 318-322
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Tidskriftsartikel (refereegranskat)abstract
- A cross-fostering experiment demonstrated that tarsus length of European starlings (Sturnus vulgaris) was heritable. The tarsus length of the foster-parent had no effect. A full-sib resemblance analysis showed that sibs were much more similar in tarsus length than explained by heritability alone. This was partly due to an effect of female mating status on offspring tarsus length. When nestling growth was retarded in secondary females' nests due to reduced male assistance, the increased environmental variation in tarsus length masked the heritability.
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| 5. |
- Smith, Henrik G., et al.
(författare)
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Interclutch variation in egg size among starlings (Sturnus vulgaris) reflects female condition
- 1993
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Ingår i: Ornis Scandinavica. - : JSTOR. - 0030-5693. ; 24, s. 311-316
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Tidskriftsartikel (refereegranskat)abstract
- Starlings show considerable variation in egg mass among clutches. Mean clutch egg mass was highly repeatable for females, but few characteristics of females were found to relate to egg mass. Egg mass related weakly to female age, but female age only explained a small part of the variation. Hatchling mass was strongly correlated with egg mass, but body mass at 14 d of age was unrelated to egg mass. Nestling tarsus length at the same age was related to mean egg mass in one, but not another, year. Egg mass had no effect on hatchability or fledging success, although there was some evidence that brood reduction was more severe among broods hatching from small eggs. Females that had laid larger eggs were in better condition during incubation thus suggesting that high quality females are able to lay larger eggs and to maintain higher body reserves during incubation. This was supported by the observation that females laying smaller eggs were more likely to abandon their nests during incubation.
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| 6. |
- Smith, Henrik G., et al.
(författare)
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Intrasexual competition among polygynously mated female starlings (Sturnus vulgaris)
- 1994
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 5, s. 57-63
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Tidskriftsartikel (refereegranskat)abstract
- In southern Sweden, the starling (Sturnus vulgaris) has a variable mating system with some males mating monogamously and others attracting several females. Mating status affected the reproductive success of females: monogamous and primary females laid larger clutches and fledged more and heavier young than secondary females. This pattern was explained by female competition for male help, with the male primarily helping the offspring of highest value (i.e., the oldest brood). However, when the nesting attempt of the primary female failed, the success of the secondary female increased to the same level as that for primary and monogamous females. The success of the secondary female in terms of fledging success and fledgling size was higher when the secondary female hatched her eggs soon after the primary female. This was due to the fact that a male divided his effort between his broods when the age difference between broods was small
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| 7. |
- Smith, Henrik G.
(författare)
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Parental age and reproduction in the marsh tit
- 1993
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Ingår i: Ibis. - 0019-1019. ; 135, s. 196-201
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Tidskriftsartikel (refereegranskat)abstract
- In the Marsh Tit Parus palustris, breeding performance improved with the age of both the male and the female parent-older birds produced larger clutches earlier in the season. The effect of male age, however, was mainly due to a positive association with the age of the female. When the effect of laying date was accounted for, there was no additional effect of female age on clutch-size. However, pairs with previous breeding experience laid larger clutches than newly formed pairs of the same age. There was some evidence that young females that laid late in the season were less likely to survive to breed again, leading to an age effect on reproductive performance. There was no evidence that individual birds laid earlier or produced larger clutches when they became older.
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| 8. |
- Smith, Henrik G.
(författare)
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Seasonal Decline in Clutch Size of the Marsh Tit (Parus palustris) in Relation to Date-Specific Survival of Offspring
- 1993
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Ingår i: Auk. - : Oxford University Press (OUP). - 0004-8038. ; 110, s. 889-899
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Tidskriftsartikel (refereegranskat)abstract
- This paper documents and evaluates seasonal trends in reproductive performance in the Marsh Tit (Parus palustris) in southern Sweden. Clutch size decreased for nests started later in the season. This pattern held true both for second-year and older females when analyzed separately. Individual females adjusted clutch size in relation to the relative time of season they produced a clutch a particular year. The seasonal decline in clutch size was also evident for clutches produced in the same territory at different parts of the season in different years. Females breeding for several years demonstrated a high consistency in relative laying date and clutch size. The same was not true for males or for territories. The length of the incubation period normally decreased with season. Nestling mass and survival did not show any systematic seasonal trend. Nest predation was probably more prevalent late in the season. Fledglings that hatched later had poorer survival until autumn. This effect was evident for males, but not for females. Hatching date did not influence fledglings' survival to the next breeding season, but sample sizes were small. I suggest that the Marsh Tit adjusts clutch size to the survival probability of nestlings, this being affected by the probability of nest predation and by fledgling survival. Hence, late-laying females are not prepared to accept as large reproductive costs as early laying females.
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