Data for: Fatty acid composition of the red blood cells and cerebral hemispheres of breeding ring-billed gulls (Larus delawarensis) in Newfoundland, Canada.

The Salmonier colony in Newbridge is considered remote with gulls mainly foraging on marine organisms rich in omega-3s. Upon the beginning of each colony's incubation period, active nests were targeted to receive daily supplementation for 21 days. At Long Pond, 30 nests were supplemented with fish oil rich in omega-3s, 30 nests were given coconut oil as a caloric equivalent devoid of omega-3s, and 30 nests were visited daily but not given any supplement (negative control).

At Salmonier, 30 nests were given the coconut supplement and 30 nests were used as negative controls; the fish oil treatment was not implemented at Salmonier since gulls nesting there already consume high levels of omega-3s naturally. At the end of the respective colonies’ incubation period, a cognitive test was deployed at each targeted nest 6 times over 3 days and video-recorded to test the gulls' problem-solving skills.

Once the trials were completed, gulls from targeted nests were captured to collect blood and brain samples. The fatty acid composition of the red blood cell fraction and cerebral hemispheres of gulls sampled was characterized by gas chromatography using the CREAIT Network facilities at Memorial University.