Current methods and future directions in avian diet analysis

Abstract

Identifying the composition of avian diets is a critical step in characterizing the roles of birds within ecosystems. However, because birds are a diverse taxonomic group with equally diverse dietary habits, gaining an accurate and thorough understanding of avian diet can be difficult. In addition to overcoming the inherent difficulties of studying birds, the field is advancing rapidly, and researchers are challenged with a myriad of methods to study avian diet, a task that has only become more difficult with the introduction of laboratory techniques to dietary studies. Because methodology drives inference, it is important that researchers are aware of the capabilities and limitations of each method to ensure the results of their study are interpreted correctly. However, few reviews exist which detail each of the traditional and laboratory techniques used in dietary studies, with even fewer framing these methods through a bird-specific lens. Here, we discuss the strengths and limitations of morphological prey identification, DNA-based techniques, stable isotope analysis, and the tracing of dietary biomolecules throughout food webs. We identify areas of improvement for each method, provide instances in which the combination of techniques can yield the most comprehensive findings, introduce potential avenues for combining results from each technique within a unified framework, and present recommendations for the future focus of avian dietary research.

The influence of seabirds on their breeding, roosting and nesting grounds: A systematic review and meta‐analysis

“…Stable isotope analyses were a popular method for tracing MDN in recipient terrestrial environments in many of the studies (Table 2). Stable isotopes of a variety of elements (C, N, O, H and S) have been used extensively in seabird ecology for inferring foraging locations and providing insights into diet (Bond & Jones, 2009; Callaham et al, 2012; Hoenig et al, 2022) and their application as tracers of nutrient flows is well established (Hebert et al, 2006; Michener & Schell, 1994). They can easily trace seabird‐derived nutrients in coastal and island food webs because of the distinction in marine δ 15 N and δ 13 C values compared to terrestrial N and C isotopes (Harding et al, 2004).…”

“…have been used extensively in seabird ecology for inferring foraging locations and providing insights into diet (Bond & Jones, 2009;Hoenig et al, 2022) and their application as tracers of nutrient flows is well established (Hebert et al, 2006;Michener & Schell, 1994). They can easily trace seabird-derived nutrients in coastal and island food webs because of the distinction in marine δ 15 N and δ 13 C values compared to terrestrial N and C isotopes .…”

Grand challenges at the frontiers of bird science

“…Like so many scientific topics, encouraging collaborations among experts, such as ornithologists and entomologists co-creating a database of avian diet information, should be a priority to ensure rapid and reliable progress. Perhaps the increasing improvements in eDNA technology will revitalize the level of respect practitioners of dietary studies enjoy (Ruppert et al, 2019;Hoenig et al, 2022).…”

Using stable isotope (δ13C, δ15N) values from feces and breath to infer shorebird diets

“…Knowledge of diet is key to understanding species interactions, food web structure, nutrient physiology, and biogeochemical cycling (Martínez del Rio et al 2009 ; Estes et al 2011 ; Atwood et al 2015 ; Hoenig et al 2021 ). Dietary needs have been investigated using various conventional approaches, including the identification of dietary items ingested, their digestion and assimilation (Nielsen et al 2018 ).…”