Learning the ecological niche

Abstract

A cornerstone of ecological theory is the ecological niche. Yet little is known about how individuals come to adopt it: whether it is innate or learned. Here, we report a cross-fostering experiment in the wild where we transferred eggs of blue tits, Cyanistes caeruleus, to nests of great tits, Parus major, and vice versa, to quantify the consequences of being reared in a different social context, but in an environment otherwise natural to the birds. We show that early learning causes a shift in the feeding niche in the direction of the foster species and that this shift lasts for life (foraging conservatism). Both species changed their feeding niches, but the change was greater in the great tit with its less specialized feeding behaviour. The study shows that cultural transmission through early learning is fundamental to the realization of ecological niches, and suggests a mechanism to explain learned habitat preference and sympatric speciation in animals.

Figure 1

Foraging height (mean+s.e.m.) for blue tits and great tits: (a) in August–September, and (b) in April. Open bars, juveniles; filled bars, older birds. Cross-fostered birds were reared by the other species. Sample sizes are shown above bars. The p-values refer to t-tests between cross-fostered birds and controls. Age of focal bird had no significant effect in these comparisons.

Figure 2

Percentage of time foraging in twigs (mean+s.e.m.) for blue tits and great tits: (a) in August–September and (b) in April. Sample sizes and symbols as in figure 1, except that p-values refer to logistic regression for great tits where age of focal bird had a significant effect (p-value refers to the model with both treatment and age included), and to U-tests in the other comparisons where age did not have any significant effect.