Context dependent foraging by seed eating birds does not necessarily mean low ecological predictability

MARONE, L.; CAMÍN, S.R.; CUETO, V.R.

CANADIAN JOURNAL OF ZOOLOGY

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Lugar: Otawa; Año: 2015 vol. 93 p. 353 - 359

0008-4301

Flexibility of foraging behavior affects our capacity to predict ecological outputs like population responses to habitat change. Some birds forage following absolute valuation rules, where food options have fixed intrinsic values. Realized diet of these rational foragers is usually predictable since it is strongly correlated to option?s profitability. Consumers, however, do not always follow absolute valuation rules. For example, opportunistic or text-dependent foragers adjust food consumption to option availability in the field. Their diet is still predictable, although more elusive. Another example of irrational choice is relativistic or context-dependent foragers, which change the ranks of food preferences depending on the presence of alternative options in the choice set. Predicting their diet might be particularly difficult since context dependence produces contingent or extremely local ecological outputs. We tested if the context of seed availability affects foraging decisions of three sparrow species by using multiple choice experiments aiming at detecting if seed preferences for two types of target seeds changed when birds faced two different seed availability contexts. Birds showed very similar rankings of preferences for target seed, but preferences for attractive food options were not fixed but often increased in less valuable contexts. Although results imply some degree of context-dependent behavior, predictability of ecological output (diet) may be preserved since (a) the ranking of preferences remained mostly unchanged between contexts (and among bird species), and (b) the higher consumption of target grass seeds in a less attractive context was widely expected from their intrinsic properties.