Distribution of parental effort between nestlings of European starlings: Runting and a spoilt‐brat strategy

Abstract

Many birds and other animals face conflicting priorities on leaving the nest—to be lean and active so as to avoid predation, or to remain fat to withstand starvation in bad weather. Parents of such animals could hedge their bets by adopting a spoilt‐brat strategy. This involves feeding the whole brood to some adequate but minimal level, and using any excess food to spoil one (or more) selected individuals. The corollary, runting, is already well established, but it has been widely assumed that the heaviest remaining chicks would be the fattest. Analysis of fat content in 372 European starling (Sturnus vulgaris) chicks at fledging showed great variation within broods, and the heaviest chicks were often not the fattest ones. This is evidence that the parents may be selectively spoiling an individual chick, not feeding at random or allowing the largest chick to dominate. The spoilt‐brat strategy should be looked for in larger species which could carry more useful quantities of fat.

Key words:

• European starling
• Sturnus vulgaris
• body weight
• fat
• parental effort
• runting
• predation
• feeding