A classification scheme for avian diet types

Abstract

Descriptions of avian diets currently lack consistent terminology and standardized methods. As a consequence, most available classifications, especially for tropical birds, are inconsistent and often misleading. We identified 23 food categories most commonly eaten by birds (e.g., seeds, fruits, and insects) and proposed standard names that accurately describe the diet type associated with each food category (e.g., granivore, frugivore, and insectivore). We also propose a classification scheme for avian diet types that takes into account the number of food categories consumed and the volumetric proportion (based on stomach content analysis) of each category eaten to indicate the diet type of a species, using a binomial terminology. Given that bird diets encompass a continuum between some extremes commonly treated as distinct categories, we adopted arbitrary breaking points to delimit distinct diet types. For example, species with different proportions of insects and fruits in their diets can be classified as insectivores (IN), insectivores secondarily frugivores (INFR), frugivores‐insectivores (FR‐IN), frugivore secondarily insectivores (FRIN), and frugivores (FR). Because many factors can influence avian diets, the diet types of species can also be classified based on age‐related, sexual, seasonal, and/or geographic variation, e.g., young are insectivores and adults are frugivores, we believe that our classification scheme provides a standardized terminology that can contribute to a more consistent and effective exchange of information about avian diets.

Insectivorous birds consume an estimated 400–500 million tons of prey annually

“…Most bird species are insectivores that depend for the most part on insects as prey (Losey and Vaughan 2006 ; Şekercioğlu 2006a ). In this paper, “insectivorous birds” are defined in a wider sense as the total of all bird groups that include, at least temporarily, a considerable percentage of arthropods (in particular insects and spiders) in their diets (Lopes et al 2016 ). Included in this definition are also omnivorous birds such as starlings (Sturnidae) and thrushes (Turdidae) that consume large amounts of arthropods in addition to other types of food (Del Hoyo et al 2016 ).…”

Food availability and breeding season as predictors of geophagy in Amazonian parrots

“…Here, hundreds of psittacines of up to 18 species congregate daily on exposed riverbanks at sites called clay licks to consume soils rich in sodium and clay minerals (Munn 1994, Brightsmith 2004, Brightsmith & Villalobos 2011. Findings from this system have helped shape the global dialogue on geophagy across a wide range of vertebrate taxa (Diamond 1999, Panichev et al 2013, Lopes et al 2016, Mahandran et al 2016, Adams et al 2017, making detailed understanding of this system vital to the overall study of geophagy.…”

Seasonality determines bird abundance, richness, and diversity among contrasting forest environments in the Northern Pantanal

“…Species foraging a greater variation of food resources (e.g., fruits and insects) show a high ability of survival and adaptation to spatially and/or temporally variable environments. Conversely, bird species specialized in a particular resource (e.g., fruits or insects) can limit their reproductive output and survival due to food shortage during annual periods (Poulin et al 1994;Ducatez et al 2015;Lopes et al 2016;O'Hanlon et al 2017). Therefore, determining spatial (among environments) and temporal (across seasons) variations in bird abundance, richness, and diversity is especially relevant in seasonal flooding environments, given the potentially high environment heterogeneity, fluctuation in habitat availability, and subsequent niche diversity-dependent food resource.…”