Primary producers drive the availability of dietary n-3 LC-PUFA in prey communities, which is generally lowest in terrestrial, intermediate in freshwater, and highest in marine food webs (Hixson et al. 2015; Brett et al. 2017; Colombo et al. 2017). Vascular plants dominating primary production in terrestrial ecosystems can synthesize only short chain n-3 PUFA alpha-linoleic acid (ALA, 18:3n-3), while multiple aquatic primary producers, especially microalgae, can synthesize long-chain n-3 PUFA de novo, mainly eicosapentaenoic acid (EPA; 20:5n-3), but also DHA (Arts et al. 2009; Brett et al. 2017; Twining et al. 2016). The dominant determinant of n-3 LC-PUFA synthesis by primary producers appears to be their phylogeny (Twining et al. 2016; Marzetz et al. 2017). Therefore, the structure of the primary producer community is determinant of the n-3 LC-PUFA availability to herbivores (Marzetz et al. 2017; Guo et al. 2018) and to consumers at higher trophic levels (Guo et al. 2021). Observational studies on wild European perch Perca fluviatilis(Scharnweber et a. 2021) and Eastern Phoebe Sayornis phoebe (Twining et al. 2019) have shown that diet of individuals from the same species can differ substantially in the content of n-3 LC-PUFA due to intra-specific niche partitioning (Araújo et al. 2011). Therefore, differences in diet quality in wild vertebrate consumers can potentially be large enough to cause intra-specific divergence in brain development, but this hypothesis remains to be tested.