| 1. |
- Bruun, Måns, et al.
(författare)
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Polygynous male starlings allocate parental effort according to relative hatching date
- 1997
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Ingår i: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 54, s. 73-79
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Tidskriftsartikel (refereegranskat)abstract
- In many polygynous bird species, males allocate most of their parental effort to their primary females’ broods. There are several hypotheses that may explain this: the relative reproductive value of the brood, the energetic demand of the brood, the genetic quality of the female and the certainty of fatherhood may all be higher for the primary females’ broods. Since these parameters may covary in nature, experiments are necessary to determine their importance. Bigynous male European starlings,Sturnus vulgarispredominantly incubated the eggs and fed the nestlings of their primary females. In an experiment we altered the order in which the clutches hatched by exchanging the primary and secondary females’ eggs before hatching. Even though experimental males mostly incubated their primary females’ clutches, they predominantly fed the nestlings of the secondary female. Experimental males fed secondary females’ nestlings significantly more than control males did. In fact, experimental males invested in their secondary females’ broods to the same extent as control males invested in their primary females’ broods. This result demonstrates that males use relative brood age to decide how to allocate their parental effort between their broods which has important implications for the evolution of the starling mating system.
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| 2. |
- Ottosson, Ulf, et al.
(författare)
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Begging affects parental effort in the pied flycatcher, Ficedula hypoleuca
- 1997
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Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 1432-0762 .- 0340-5443. ; 41:6, s. 381-384
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that nestlings use begging to increase their share of parental resources at the expense of current or future siblings. There is ample evidence that siblings compete over food with nestmates by begging, but only short-term effects of begging on parental provisioning rates have been shown. In this study, we use a new experimental design to demonstrate that pied flycatcher (Ficedula hypoleuca) nestlings that beg more are able to increase parental provisioning rates over the major part of the nestling period, thus potentially competing with future siblings. Parents were marked with microchips so that additional begging sounds could be played back when one of the parents visited the nest. By playing back begging sounds consistently at either male or female visits, a sex difference in provisioning rate that lasted for the major part of the nestling period was induced. If each parent independently adjusts its effort to the begging intensity of nestlings, begging may also be the proximate control mechanism for the sexual division of labour.
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| 3. |
- Sandell, Maria, et al.
(författare)
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Already mated females constrain male mating success in the European starling
- 1996
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Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2954. ; 263, s. 743-747
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Tidskriftsartikel (refereegranskat)abstract
- Most models explaining polygyny in birds have concentrated on variation in male or territorial quality, ignoring the role of females in maintaining monogamy. Although field observations have suggested that already mated females may maintain monogamy by either behaving aggressively toward prospecting females or by interupting male mate attraction behaviour, no experiments have been done to test if already mated females constrain the mating success of their mates. In this study of the European starling (Sturnus vulgaris), the possibility for already settled females to defend their mating status was manipulated by changing the distance between their mates' potential breeding sites. Solitary breeding males were given an extra nest site at different distances from their present one: less than 2 m, 2-5.5 m and 7.5-15 m. The distance between nest sites was the most important determinant of male mating success; few males became polygynous when nest sites were close together whereas most became polygynous when nest sites were further apart. In addition, secondary females were able to lay earlier in relation to the primary females when their nest sites were further away from the primary females' nests. These results support the hypothesis that already mated females constrain the mating success of their mates.
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| 4. |
- Sandell, Maria, et al.
(författare)
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Female aggression in the European Starling during the breeding season
- 1997
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Ingår i: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 53, s. 13-23
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Tidskriftsartikel (refereegranskat)abstract
- Intraspecific female aggression during the breeding season can have several different functions: defence of resources, defence against intraspecific brood parasitism and defence of mating status. The intraspecific aggressive behaviour of breeding female starlings, Sturnus vulgaris, was examined by exposing them to a simulated intrusion of a conspecific bird. A caged male or female starling was placed close to the nest of a breeding pair. Aggressiveness was scored as the proportion of time birds spent near the caged birds after discovery. Caged females elicited stronger responses from females than caged males. Females sang at caged females and sometimes also attacked them. They were most aggressive towards them during the pre-laying period and less so during the egg-laying, incubation and nestling periods. Females were more aggressive towards a caged female when their mate had access to an additional nestbox to which he could attract an additional female, then when he had not. A time-budget study demonstrated that females spent more time near their nest site during the pre-laying period when their mate had access to an additional nestbox than when he had not. These patterns are most consistent with females trying to secure male brood-rearing assistance by preventing or delaying the settlement of secondary females, since early established secondary females may compete for male help in incubating eggs and feeding nestlings.
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| 5. |
- Sandell, Maria, et al.
(författare)
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Paternal care in the European starling, Sturnus vulgaris: nestling provision
- 1996
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Ingår i: Behavioral Ecology. - : Springer Science and Business Media LLC. - 1045-2249. ; 39, s. 301-309
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Tidskriftsartikel (refereegranskat)abstract
- The extent to which male birds in polygynous species with biparental care assist in nestling feeding often varies considerably between nests of different mating status. Both how much polygynous males assist and how they divide their effort between nests may have a profound effect on the evolution of mating systems. In this study we investigated how males in the facultatively polygynous European starling Sturnus vulgaris invested in their different nests. The amount of male assistance affected the quality of the offspring. Polygynous males invested as much as monogamous males, but divided their effort asymmetrically between nests, predominantly feeding nestlings of first-mated (primary) females. Although females partly compensated for loss of male assistance, total feeding frequency was lower at primary females' nests than at monogamous females nests. Secondary females received even less assistance with nestling rearing, and the extent to which males assisted decreased with the length of the interval between the hatching of the primary and secondary clutches. These results are contrasted with those from a Belgian populations of starlings with a much more protracted breeding season and thus greater opportunities for males to attract additional mates during the nestling rearing period. The results show that both the ''defence of male parental investment model'' and the ''asynchronous settlement model'' have explanatory power, but that their validity depends on the potential length of the breeding season.
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| 6. |
- Smith, Henrik G., et al.
(författare)
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Adaptive significance of egg size in the European Starling: experimental tests
- 1995
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Ingår i: Ecology. - : Wiley. - 0012-9658. ; 76, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Reproductive success in relation to egg size was studied in European Starlings (Sturnus vulgaris) by swapping whole clutches between nests at the start of the incubation period. Egg size did not reflect parental quality as no measure of reproductive success was correlated with the foster mothers' mean egg size. There was a significant positive relationship between the mean size of the cross-fostered eggs and the subsequent mean size of hatchlings. The mean size of cross-fostered eggs did not affect hatching success or nestling growth rates, and initial nestling size differences between broods with large and small eggs persisted for <1 wk. No effect of mean egg size on mean nestling survival could be detected. Furthermore, a partial cross-fostering experiment, where nestlings were swapped between nests the day after hatching, failed to demonstrate any lasting effect of egg size on nestling size. It is suggested that mean egg size may only influence reproductive success during particularly inferior environmental conditions
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| 7. |
- Smith, Henrik G.
(författare)
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Experimental demonstration of a trade-off between mate attraction and paternal care
- 1995
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Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2954. ; 260, s. 45-51
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Tidskriftsartikel (refereegranskat)abstract
- Males should invest in mate attraction, mate guarding and paternal care in relation to the marginal fitness value of each of those behaviours. Since time and energy are limited, trade-offs between these activities are expected. This study demonstrates that monogamous male European starlings (Sturnus vulgaris) decrease their paternal effort in response to increased opportunities to attract additional mates and instead invest in mate attraction. Monogamous males' probabilities of attracting additional females were increased by providing them with additional nestboxes. This resulted in both the rate at which males were visited by prospecting females and the probability that they would obtain secondary mates increasing. Males with an additional nestbox sang more than males with only one nestbox, both before laying and during incubation. Males with two nestboxes spent more time at their nest sites when their fertile females were away before, but not during, egg laying. The experiment affected how much males incubated during the early, but not during the late, part of the incubation period. This makes sense, because males can attract additional females mainly during the early part of the incubation period. Male feeding of nestlings was unaffected by the experiment. The fact that the potential to attract mates affects males' investment in parental care suggests that variation in this potential may contribute to the variation in paternal care between bird species.
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| 8. |
- Smith, Henrik G., et al.
(författare)
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Heritability of nestling growth in cross-fostered European Starlings, Sturnus vulgaris
- 1996
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Ingår i: Genetics. - 0016-6731. ; 141, s. 657-665
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Tidskriftsartikel (refereegranskat)abstract
- In altricial birds, growth rates and nestling morphology vary between broods. For natural selection to produce evolutionary change in these variables, there must exist heritable variation. Since nestling traits are not any longer present in parents, traditional offspring-parent regressions cannot estimate heritabilities of these. In this study, a partial cross-fostering experiment was performed, where nestlings of the European Starling (Sturnus vulgaris) were reciprocally exchanged between nests. The experiment demonstrated a significant heritability of nestling tarsus length and body mass, but not of the growth trajectories followed by individual nestlings. The heritability estimate for tarsus length obtained in the cross-fostering experiment using full-sib analysis was lower than those obtained by offspring-parent regressions. This is likely due to a genotype-by-environment effect on tarsus length, with nestlings destined to become large but in poor condition having a low probability of appearing as parents. The main reason for the low heritability of growth was probably the large within-brood variation in growth pattern due to the initial size hierarchy of nestlings. Nestlings demonstrated targeted growth, where small-sized nestlings that initially grew slower than their siblings, managed to catch up.
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| 9. |
- Smith, Henrik G., et al.
(författare)
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Intersexual competition in a polygynous mating system
- 1998
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Ingår i: Oikos. - : JSTOR. - 1600-0706 .- 0030-1299. ; 83:3, s. 484-495
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Tidskriftsartikel (refereegranskat)abstract
- In the facultatively polygynous European starling (Sturnus vulgaris) males attract from one to four mates. Males gain by mating polygynously because they produce more offspring by doing so. This is true also genetically, since polygynous males on average father the same proportion of offspring as monogamous males. However, the marginal benefit of attracting additional mates is negatively affected by extra-pair parentage, which is slightly higher in males' secondary broods. Whereas mating as a secondary female is a better option for floater females than either not reproducing at all or reproducing as a brood parasite, already mated females suffer a cost when their mates attract additional mates. This is because they have to share the parental care provided by the male. Males divide parental investment primarily in relation to the timing of the broods produced by their females, investing mainly in the earliest brood. Male parentage has little effect on male care. Already mated females use aggression to prevent floater females to establish a pair-bond with their mates. The mating system in the starling results from the differing interests of males and females. To be able to construct models predicting when a particular mating system should be expected, more has to be learnt about the costs of male mate attraction and nest defence behaviour and female aggression.
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| 10. |
- Smith, Henrik G., et al.
(författare)
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Paternal care in the European starling, Sturnus vulgaris: incubation
- 1995
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Ingår i: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 50, s. 323-331
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Tidskriftsartikel (refereegranskat)abstract
- In polygynous passerines, males of some species provide food for their nestlings, but male incubation seems to be rare. In the European starling both the mating system and the extent to which males help with incubation vary. This enabled the relationship between mating system and male incubation to be investigated. The extent to which males provided care to a particular nest depended on mating status: monogamous males incubated more than polygynous males did in any of their females' nests. On average, bigynous males incubated as much in their two nests as monogamous males did in their single nest, but polygynous males who invested in only one of their nests incubated less than monogamous males. Females partly compensated for the variation in male incubation, but still nests of polygynously mated females were attended less. Polygynous males invested more in the nests of the first females mated with (primary female) than in the nests of later settling females. Secondary females received less help the later they laid their eggs in relation to the mate's primary female. Bigynous males that incubated in both their nests invested more in the nests of their primary females the earlier these eggs were laid in relation to those of the secondary females. Male help with incubation may affect a female's fitness, both because increased attentiveness resulted in shorter incubation times and because females receiving less help may pay a higher cost in terms of energy expenditure. Hence, there will be a conflict between polygynously mated females over paternal incubation.
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