Maximization of energy or nutrient balancing: the interplay between fruit chemical content and foraging behaviour in fruit-eating birds

BLENDINGER PEDRO GERARDO; BENDER, IRENE MARIA ANTONIETA; MAGRO, JULIETA; LOMÁSCOLO, SILVIA; ORDANO, MARIANO; NÚNEZ MONTELLANO, MARIA GABRIELA; RAIREZ-MEJIA, ANDRES F.; ROJAS, TOBIAS NICOLAS; VALOY, MARIANA; RUGGERA, ROMAN

Ramnagar

Congreso; Seed dispersal in the Anthropocene, 7th Frugivory and Seed Dispersal Symposium; 2020

The fruit diet of frugivores is driven by foraging strategies of energy maximization or nutrient balancing.However, frugivores face a changing fruit market when they make foraging decisions. It is well known thatthe amount of available fruits and phenotypic trait matching impose filters on the fruit diet, but less isknown about the role of foraging decisions of the fruit chemical content. The differences between fruitspecies in pulp quantity and chemical quality can interact with behavioural, morphological andphysiological traits of the consumers, determining the contribution of the fruit species to the provision ofnutrients and energy. We use extensive field and laboratory data and modelling to explore whether afruit-based diet can provide energy and nutrients necessary for frugivores, as well as its variation betweenfunctional types of frugivores. Using the Resource Provisioning Effectiveness (RPE) framework weinvestigate the effectiveness of consumed fruit species to provide daily requirements of energy to Andeanbirds, and compare them with the composition of field diets. Similarly, we use Nutritional Geometry (NG)framework to assess the adjustment of field fruit diets to a theoretical diet balanced in macronutrients.We use diet data of ca. 35 bird species from different sites and seasons, chemical data of ca. 40 species offruits; we model the daily ingestion rate of each fruit species for each frugivore, and estimate their energyassimilation and macronutrient balancing in the diets. Then, we assess how fruit RPEs and balancesdepend on the bird's fruit handling behaviour, body size and specialization, and the adjustment of the dietto energy maximization (in terms of RPE) and nutrient balancing (in terms of NG) strategies. We providevaluable information on how fruit chemical composition interacts with the ability of the frugivores toacquire pulp, determining the foraging decisions and the composition of the fruit diet.