Seed selection by the trumpeter finch, Bucanetes githagineus. What currency does this arid-land species value?

Abstract

We tested the hypothesis that in harsh environments seed contents, specifically water, and handling time will determine food preferences in an arid bird species, the trumpeter finch. Rape (69.9%) and canary (23.9%) were the most commonly consumed seeds. Mean handling time differed among the tested seed types. There existed a non-linear inverse relationship between mean handling time of different seeds and their selectiveness by individuals. Data estimated from five hypothetical diets and their respective nutritional intakes indicate that this arid land passerine selects a balanced diet optimizing energy and total water intake (energy and water gain per unit of time), rather than a diet that maximizes just energy intake. For birds inhabiting arid and semiarid habitats, food selection should be highly adaptive as selected food items must maximize energy intake rate, but also must contain or produce adequate water to satisfy metabolic requirements.