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| 2. |
- Nilsson, Jan-Åke, et al.
(författare)
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Early fledging mortality and the timing of juvenile dispersal in the marsch tit Parus palustris
- 1985
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Ingår i: Ornis Scandinavica. - : JSTOR. - 0030-5693. ; 16, s. 293-298
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Tidskriftsartikel (refereegranskat)abstract
- Family flocks of Marsh Tits Parus palustris in southern Sweden kept together until 11-15 d after fledging and stayed within the former territory of the parents. Mortality in the family flocks was low in one year (1.2-3.6%) but higher in another (18.6%). This level of mortality is compared with post-dispersal mortality in other species of tits. The occurrence of a parent-offspring conflict with regard to when juveniles should disperse is called in question. The level of aggression from parents towards their young was very low. Experimental broods of increased and reduced size stayed equally long within the parental territory, thus refuting the hypothesis that parents force their young to emigrate to avoid local competition for food or the harassment from the begging young. Dispersal of young from a family flock took place over more than one day. Late dis- persers were significantly smalller than their nestmates. This supports the hypothesis that dominant individuals disperse first, while subdominants stay longer in the safety of the parental territory to increase their self-feeding ability,
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| 3. |
- Nilsson, Jan-Åke, et al.
(författare)
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Effects of Dispersal Date on Winter Flock Establishment and Social Dominance in Marsh Tits Parus palustris
- 1988
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Ingår i: Journal of Animal Ecology. - : JSTOR. - 1365-2656 .- 0021-8790. ; 57:3, s. 917-928
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Tidskriftsartikel (refereegranskat)abstract
- (1) We studied the effect of sex, size, age and prior occupancy on social dominance winter flock establishment in a population of marsh tits Parus palustris L. (2) When sex was accounted for, time of establishment in the winter flock-prior occupancy, was critical for the outcome of later aggressive interactions juveniles within flocks. Residents won all interactions with intruders irrespective controlling for sex. (3) Success in, and timing of, establishment were closely linked with hatching lower proportion of late-hatched than early-hatched juveniles became established winter flocks; they also became established later. Even small differences in hatching greatly influenced dominance and the probability of becoming established flock. (4) Since early establishment depends on early hatching, dominance and survival juveniles are determined by how early their parents start breeding. Furthermore, will be strong selection for quick establishment after
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| 4. |
- Nilsson, Jan-Åke, et al.
(författare)
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Incubation feeding as a male tactic for early hatching
- 1988
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Ingår i: Animal Behaviour. - 1095-8282. ; 36:3, s. 641-647
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Tidskriftsartikel (refereegranskat)abstract
- Male marsh tits, Parus palustris, regularly feed their mates from the beginning of nest building until hatching. Over three periods (the 15 days preceding egg formation, egg formation/laying and incubation) the number of food passes by the male to the female increased significantly. There was a significant negative relationship between the frequency with which the male fed the female in the nest during incubation and the length of the incubation period. Female blue tits, Parus caeruleus, experimentally supplied with food in the nestbox during incubation had a significantly shorter incubation period than control females. Clutches of experimentally fed females also tended to hatch more successfully. It is concluded that feeding of the female by the male is a nutritional contribution and that the shorter incubation period and increased hatching success enhance the fitness of both parents. However, the male should balance the benefits against the costs in time and energy and therefore not necessarily work at a maximal level. In accordance with this is the finding that the male's provisioning rate increased when ambient temperatures decreased. Adverse weather may jeopardize the whole or large proportions of the clutch, thereby significantly reducing the benefit from the current breeding attempt.
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| 5. |
- Smith, Henrik G., et al.
(författare)
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Effect of experimentally altered brood size on frequency and timing of second clutches in the great tit
- 1987
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Ingår i: Auk. - 0004-8038. ; 104, s. 700-706
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Tidskriftsartikel (refereegranskat)abstract
- Brood size in the Great Tit (Parus major) was manipulated (increased, decreased, or unchanged) when nestlings were 5 days old. Both the frequency of second clutches and the interbrood interval were affected. The number of nestlings and hatching date, but not nestling and female mass, differed between first broods followed and not followed by second clutches. Hatching date and the number of nestlings in the first brood explained most of the variation in interbrood interval, whereas female mass did not contribute. Feeding first-brood nestlings and fledglings is an energy-demanding process, and the female may have to allocate resources to brood-feeding at the expense of reproductive de- velopment. Furthermore, a larger brood requires a longer period of feeding than a smaller brood. These circumstances probably explain why the size of the first brood affects the timing of the second clutch. Female condition and food depletion of the territory do not seem to be important. Because late second clutches have a lower probability of fledgling survival than do earlier ones-and consequently are of lower value from the female's standpoint-a large first clutch may delay laying to the point that a second clutch is not worthwhile. We conclude that a female's decision whether to lay a second clutch is a strategic one based on the value of the second clutch; a female that "decides" to lay a second clutch starts as quickly as possible.
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| 6. |
- Smith, Henrik G., et al.
(författare)
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Feeding freqency and parental division of Labour in the double-brooded great tit Parus major
- 1988
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Ingår i: Behavioral Ecology and Sociobiology. - 1432-0762. ; 22, s. 447-453
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Tidskriftsartikel (refereegranskat)abstract
- We studied the relative contribution of each sex and total effort expended in feeding nestlings in the great tit Parus major in relation to artificially altered brood size. A recent model suggests that feeding frequency should reflect the optimal trade-off between parental and fledgling survival, the former being negatively, the latter positively, influenced by high feeding frequencies. In both sexes weight loss was linearly related to feeding frequency. Since fledgling survival increases with nestling weight, the conditions of this model are fulfilled. However, in contrast to the predictions of the model, the total feeding frequency for both sexes combined did not differ between control and enlarged broods, but was lower for reduced ones. This outcome was not the result of a physiologically related inability of the parents to increase their delivery rate. Instead, we suggest that parents with enlarged broods could not find sufficient amounts of prey large enough to be economically worth transporting to the nest. Differences in brood-provisioning rates between the sexes may arise because costs and benefits of feeding nestlings may differ. Females lost more weight than males during the nesting period, but maintained a relatively higher weight during the incubation period. The relationship between weight loss and feeding frequency was similar for both sexes. Male and female brood-feeding frequency was related to brood size in a similar way. This is discussed in light of the great tit's mating system and the fact that the great tit is facultatively double-brooded.
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| 7. |
- Smith, Henrik G., et al.
(författare)
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Intraspecific variation in migratory pattern of a partial migrant, the Blue Tit (Parus caeruleus) : An evaluation of different hypotheses
- 1987
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Ingår i: The Auk. - : Oxford University Press (OUP). - 0004-8038 .- 1938-4254. ; 104:1, s. 109-115
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate hypotheses explaining intraspecific variation in migratory behavior in partial migrants, a local population of Blue Tits (Parus caeruleus) was studied in southern Sweden. Birds born in the study area and recaptured there in winter were compared with birds recaptured at a nearby bird station where a large number of migrant Blue Tits were passing. By comparing sex ratios among migrants and residents, we concluded that, among juveniles, more than 40% of the females and a significant proportion of the males migrated, while considerably fewer adult females and virtually no adult males did so. Migrant and resident Blue Tits did not differ in size as nestlings, but more late- than early-hatched males migrated. No differences in hatching date were determined for females, presumably because most of them migrated. Our findings are consistent with the "dominance hypothesis" as an explanation of partial migration, i.e. that the individuals lowest in rank migrate. The fitness gain that leads dominants to stay as residents may be lower winter mortality or a higher probability of establishing a territory in spring. In either case, keener competition for breeding territories among males than among females as a cause tor higher residency cannot be excluded.
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| 8. |
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| 9. |
- Smith, Henrik G., et al.
(författare)
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The significance of cluch overlap in the great tit Parus major
- 1989
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Ingår i: Ibis. - 0019-1019. ; 131:4, s. 589-600
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Tidskriftsartikel (refereegranskat)abstract
- We studied the effects of manipulation of the size of first broods in the Great Tit Parus major on the size and breeding success of second clutches and its relation to the degree of clutch overlap. The rearing of first brood fledglings always overlapped with the laying of the second clutch and in most cases also with the incubation period of the latter. The degree of clutch overlap depended on the size of the first brood, being less when the first brood was large. Clutch overlap also increased with season. Mechanisms affecting the timing of laying of second clutches are discussed. A large first brood imposed reproductive costs. It affected the size of the second clutch by causing it to be delayed; second clutch size decreases with season. It affected the post-fledging survival of second brood young as, in this population, this decreases with fledging date. The breeding success of second clutches was, however, not affected by the size of the first brood, but instead by the weight of the female when rearing the first brood.
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| 10. |
- Smith, Henrik G., et al.
(författare)
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The trade-off between offspring number and quality in the great tit Parus major
- 1989
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Ingår i: Journal of Animal Ecology. - : JSTOR. - 1365-2656 .- 0021-8790. ; 58, s. 383-401
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Tidskriftsartikel (refereegranskat)abstract
- (1) Trade-offs between brood size and offspring growth and survival were manipulating the size of 221 great tit Parus major L. broods between 1983 (2) Nestling mass, wing length and tarsus length were inversely related to Hatching date also affected nestling growth, but its effect differed between Intrabrood variability in nestling size increased with brood size. (3) Nestling survival was inversely related to brood size. Small nestlings suffered mortality than large ones. The difference in nestling survival rate between categories was too small to equalize their productivity. (4) Fledgling survival to the autumn and to the following breeding season inversely related to brood size; fledglings from reduced broods survived better from control broods, which in turn survived better than fledglings from enlarged This resulted in the most productive category being the control broods. The fledglings increased with their size as nestlings and decreased with their hatching (5) The sex-ratio among independent fledglings was affected by brood size tion; proportionally more males survived in enlarged than in reduced broods. (6) Dispersal distance of juveniles was not affected by brood size, size hatching date, whereas it was affected by sex. The effects of starvation competition on fledgling survival and dispersal
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