Differential begging and locomotory behaviour by early and late hatched nestlings affecting the distribution of food in asynchronously hatched broods of altricial birds

• 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.

Subject headings

SAMHÄLLSVETENSKAP  -- Psykologi (hsv//swe)

SOCIAL SCIENCES  -- Psychology (hsv//eng)

Keyword

parent-young interaction

behavioral ecology

sibling rivalry

Publication and Content Type

art (subject category)

ref (subject category)