A. Kacelnik et al., FOOD ALLOCATION AMONG NESTLING STARLINGS - SIBLING COMPETITION AND THE SCOPE OF PARENTAL CHOICE, Proceedings - Royal Society. Biological Sciences, 259(1356), 1995, pp. 259-263
Parental provisioning for nestling birds is generally considered to be
an interactive, conflictive process because the optimal provisioning
rate differs between parents and young and because nestlings are engag
ed in intersibling competition. Understanding the evolution of communi
cation in such a situation presents unusual problems because the scope
for parental strategies may be limited by competitive behaviour of th
e chicks. We substantiate this view by studying parent-offspring feedi
ng interactions between chicks and provisioning adults in the European
starling Sturnus vulgaris in relation to chick state and intersibling
competition. The state of one target chick in each nest was manipulat
ed in the field by temporarily placing it in enlarged, reduced or norm
al-sized broods before returning it to its original nest. Conditions i
n the original nests were standardized during manipulation by using su
bstitute chicks. Once returned to its original brood, the probability
of the target chick being fed increased if it increased its begging in
tensity and/or it positioned itself closer to the entrance of the nest
. Both begging intensity and position were functions of the treatment
previously experienced, with target chicks begging more and attaining
positions closer to the nest entrance after they had spent time in lar
ger broods. We postulate that these factors must be included in theore
tical analyses of the evolution of food-solicitation signalling becaus
e, although the effect of begging on feeding probability may be mediat
ed by parental choice, the effect of position depends on between-chick
dynamics, and the parents apparently accept the outcome of these inte
ractions.