Omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), in particular docosahexaenoic acid (DHA; 22:6n-3), are essential for optimal functioning of metabolism and neural development of most vertebrate consumers (Pilecky et al. 2021; Twining et al. 2021). DHA is highly retained by vertebrates (Pilecky et al. 2021) and it has been shown to be a dominant building block of brain of fishes (Ebm et al. 2021), birds (Speake & Wood 2005), and mammals (Innis 2007). Laboratory feeding studies have shown that increased dietary intake of n-3 LC-PUFA facilitates brain growth and neuron proliferation in rodents (Kawakita et al. 2006), passerine birds (Hall et al. 2014), and freshwater (Lund et al. 2012) and marine fishes (Ishizaki et al. 2001). These dietary induced changes in brain development have also been shown to influence cognitive skills of vertebrate consumers (Lund et al. 2012; Sugasini et al. 2017; Pilecky et al. 2021) and could thus potentially have a direct impact on their fitness in the wild (Boogert et al., 2018). Yet, little is known about how n-3 LC-PUFA content in natural diets influences the development of vertebrate brain in the wild.