| 1. |
- Bengtsson, Hans, et al.
(författare)
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Development of Parent‐Young Interaction in Asynchronously Hatched Broods of Altricial Birds
- 1981
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Ingår i: Zeitschrift fuer Tierpsychologie / Journal of Comparative ethology. ; 56:3, s. 255-272
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Tidskriftsartikel (refereegranskat)abstract
- In bird species which have developed a brood reduction strategy, initial inequality among siblings is established through asynchronous hatching. After hatching, the maintenance of a weight hierarchy within the brood and its spread is governed by the allocation of feeds to the chicks and by the rate of parental feeding. In the present study, the initiation of parental feeding and subsequent changes in the feeding procedure were studied in asynchronously hatched broods of the great tit Parus major and the blackbird Turdus merula. During the period of hatching the brood was roused by a parental feeding call on most visits to the nest which made feeding niore effective. Late-hatched young initially increased their chances to receive feeding offers by showing a high rate of spontaneous begging. In addition, they were more dependent than the older young on a high rate of mobility in order to be fed and they showed increasing mobility with age. Crucial changes in the feeding procedure took place at the end of the hatching period when the parents ceased to emit feeding calls and in the last few days before the abandonment of the nest when the biggest young started to jump towards the parents at feeding. These periods were identified as critical for late-hatched young. We argue that parental feeding rate is a feature of parent-young interaction that develops in order to adapt parental investment in individual nestlings to changes in food conditions when the brood is being raised.
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| 2. |
- Bengtsson, Hans, et al.
(författare)
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Parental feeding rate in relation to begging behavior in asynchronously hatched broods of the great tit Parus major: An experimental study.
- 1983
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Ingår i: Behavioral Ecology and Sociobiology. - 1432-0762. ; 12:3, s. 243-251
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Tidskriftsartikel (refereegranskat)abstract
- Four experiments manipulated the stimulus situation encountered by great tits on their feeding visits to the brood in order to explore its effect on feeding rate. Three broods containing 8, 8, and 10 nestlings were studied. A higher feeding rate was observed under the following conditions: (1) after a period of food deprivation, as compared with normal conditions and satiation through artifical feeding; (2) in periods when recorded begging calls were played during feeding visits, as compared with control periods; and (3) after temporary removal from the nest of heavier, as compared with lighter, siblings. The lighter nestlings benefitted more (in terms of weight gain) from the increase in parental feeding rate following the playing of begging calls than did the heavier nestlings. Differences in weight within broods did not affect the amount of food the parents brought. It is concluded that parental feeding rate is affected not simply by the begging of the hungriest nestling but rather by the behavior of all the nestlings, which makes possible an adjustment of the feeding rate to the average hunger level of the brood.
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| 3. |
- Rydén, Olof, et al.
(författare)
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Differential begging and locomotory behaviour by early and late hatched nestlings affecting the distribution of food in asynchronously hatched broods of altricial birds
- 1980
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Ingår i: Zeitschrift fuer Tierpsychologie / Journal of Comparative ethology. ; 53, s. 209-224
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Tidskriftsartikel (refereegranskat)abstract
- Distribution of food to early and late hatchcd nestlings was studied in asynchronously hatched broods of the grr,it tit P~rcrs major, the blackbird Turdus mcrula, and the fieldfare T. pilaris. Food distribution is related to the locomotory and begging behaviour and positions in the nest of these nestlings. Late hatched (small) nestlings were found to beg more often per feed than bigger nectlings and move more towards favoured positions in the nest to counteract selective feeding of bigger young. The functional significance of these differences in the behaviour of early and late hatched nestlings are discussed. It is argued that they are adaptive by 1) ensuring that each nestling survives when food supplies are ample, and 2) by mediating an optimal brood reduction when food is insufficient to raise the entire brood. The roles of asynchronous hatching, and selective feeding which follows from differential behaviour of early and late hatchcd young are discussed in relation to food conditions during the breeding season.
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