Long- term effects of previous experience determine nutrient discrimination abilities in birds

H Martin Schaefer¹ , Kathrin Spitzer¹ and Franz Bairlein²

¹Faculty of Biology, University of Freiburg, Department of Ecology and Evolutionary Biology, Hauptstr. 1, 79104 Freiburg, Germany

²Institute of Avian Research, 'Vogelwarte Helgoland', An der Vogelwarte 21, 26286 Wilhelmshaven, Germany

author email corresponding author email

Frontiers in Zoology 2008, 5:4doi:10.1186/1742-9994-5-4


Published:	22 February 2008

Abstract

Background

Foraging behaviour is an essential ecological process linking different trophic levels. A central assumption of foraging theory is that food selection maximises the fitness of the consumer. It remains unknown, however, whether animals use innate or learned behaviour to discriminate food rewards. While many studies demonstrated that previous experience is a strong determinant of complex food choices such as diet mixing, the response to simple nutritional stimuli, such as sugar concentrations, is often believed to be innate.

Results

Here we show that previous experience determines the ability to track changes in sugar composition in same-aged individuals of a short-lived migratory songbird, the garden warbler (Sylvia borin). Although birds received identical foods for seven months prior to the experiment, wild-caught birds achieved higher sugar intake rates than hand-raised birds when confronted with alternative, differently coloured, novel food types. Hand-raised and wild birds did not differ in their initial colour selection or overall food intake, but wild birds were quicker to adjust food choice to varying sugar intake.

Conclusion

Over a period of at least seven months, broader previous experience translates into a higher plasticity of food choice leading to higher nutrient intake. Our results thus highlight the need to address previous long-term experience in foraging experiments. Furthermore, they show that hand-raised animals are often poor surrogates for testing the foraging behaviour of wild animals.