Dietary wariness influences the response of foraging birds to competitors

Abstract

Foraging animals must choose between familiar prey and novel prey of uncertain profitability and potential toxicity. Owing to a healthy aversion to potentially dangerous prey, foragers show an initial transient wariness of novel food (neophobia). In addition, some individuals display a much longer period of avoidance before incorporating the novel food into their diet (termed dietary conservatism). There are two stable foraging strategies found within forager populations: (1) adventurous consumers (AC) which rapidly accept novel foods and (2) foragers showing dietary conservatism (DC). The expression of these two strategies may also vary with environmental conditions. We measured the effect of competition on the plasticity of foraging strategies when domestic chicks, Gallus gallus domesticus, foraged for familiar and novel coloured crumbs with or without competitor chicks. In addition we investigated the effect of prey detectability on the response of foragers to a competitor, by making the familiar food cryptic or conspicuous. AC birds responded to competition by accepting the novel prey more quickly than when foraging alone, regardless of how hard familiar food was to find. In contrast, DC birds failed to reduce their wariness in response to competition when the competitor's food choice was obscured. The foraging strategies of the birds were thus found to be plastic in their expression, but this plasticity differed between inherently AC and DC individuals. The implications of these results are discussed in relation to the foraging strategies of wild and domestic birds.