Fig. 3: A) The available prey of Eurasian perch vary widely in their DHA content, both within and between habitats. Pelagic perch consume prey with much higher DHA content (e.g. copepods and fish), whereas littoral perch consume large amounts of DHA-poor macroinvertebrates. B) Tree Swallows forage on insects originating from both aquatic and terrestrial habitats, but aquatic prey tend to have higher EPA. Some EPA-poor taxa like Hymenoptera and Thysanoptera are readily available in the environment whereas other high-EPA taxa like Ephemeroptera, Trichoptera, and Odonata are scarce (bars denote habitat availability). All of the rare aquatic prey are preferentially selected by Tree Swallows, relative to the more EPA-poor (points reflect variation in dietary proportions). Perch prey and diet data are from Chaguaceda et al. (2020) and Tree Swallow prey and diet data are from McCarty and Winkler (1999) and Twining et al. (2018).