DOI: 10.5061/dryad.r4xgxd2bd
title: Omega-3 fatty acids accelerate fledging in an avian marine predator: a potential role of cognition

description: Consuming omega-3 fatty acids (n3-LCPUFAs) during development improves
 cognition in mammals, but the effect remains untested in other taxa. In
 aquatic ecosystems, n3-LCPUFAs are produced by phytoplankton and
 bioaccumulate in the food web. Alarmingly, the warming and acidification
 of aquatic systems caused by climate change impair n3-LCPUFA production,
 with an anticipated decrease of 80% by the year 2100. We tested whether
 n3-LCPUFA consumption affects the physiology, morphology, behaviour, and
 cognition of a top marine predator's chicks, the ring-billed gull.
 Using a colony with little access to n3-LCPUFAs, we supplemented siblings
 from 22 fenced nests with opposite treatments from hatching until
 fledging; one sibling received n3-LCPUFA-rich fish oil and the other, a
 control sucrose solution without n3-LCPUFAs. Halfway through the nestling
 period, half the chicks receiving fish oil were switched to the sucrose
 solution to test whether n3-LCPUFA intake remains crucial past the main
 growth phase (chronic versus transient treatments). Upon fledging,
 n3-LCPUFAs were elevated in the blood and brains of chicks receiving the
 chronic treatment, but were comparable to control levels among transient
 chicks. Across the entire sample, chicks with elevated n3-LCPUFAs in their
 tissues fledged earlier despite their morphology and activity levels being
 unrelated to fledging age. Fledging required chicks to escape fences
 encircling their nest. We therefore interpret fledging age as a possible
 indicator of cognition, with chicks with improved cognition fledging
 earlier. These results provide insight into whether declining dietary
 n3-LCPUFAs will compromise top predators' problem-solving skills,
 thus, their ability to survive in a rapidly changing world.
description: We tested whether supplementing gull chicks with omega-3
 long-chain polyunsaturated fatty acids (n3-LCPUFAs) in a context of
 natural deficiency improved their cognitive development. Using a colony of
 ring-billed gulls (<em>Larus delawarensis</em>) nesting in an
 urban environment with no access to food rich in n3-LCPUFAs, we
 supplemented siblings daily from hatching until fledging with one of
 three supplemental treatments: the control group received a sucrose
 solution daily from hatching until fledging, the chronic group received
 fish oil rich in n3-LCPUFAs daily from hatching until fledging, and the
 transient group received fish oil daily from hatch until 22 days old
 before being switched to the sucrose solution daily until fledging. The
 chicks were otherwise provisioned by their parents at their nest. We
 monitored their weight gain daily from hatch until 22 days old and weekly
 thereafter and we confirmed the incorporation of the supplement in their
 tissues via the fatty acid analysis of blood samples taken at 15 and 36
 days old. We also analyzed the fatty acid profile of their cerebral
 hemispheres at fledging age (42 days old, subsample n=12). We analyzed
 their activity behaviours during cognitive testing through the number of
 steps they took and the time they spent trying to escape the testing
 enclosure. We also recorded their fledging age and interpreted it as a
 measure of the chicks' cognitive development since fledging required
 them to escape the fencing surrounding their nests, with improved
 cognition leading to earlier fledging.  Here we include
 the two datasets used for the analysis described in this paper:
 Lamarre et al. 2021_repeated_measures: Includes the
 concentrations of targetted fatty acids in the chicks' red blood
 cells collected at 15 and 36 days old as well as all mass data points
 (chicks weighed daily from hatch until 22 days old and weekly
 afterwards). Lamarre et al. 2021_non-repeated_measures:
 Includes the concentrations of targetted fatty acids in the red blood
 cells of chicks at 36 days old and in cerebral tissues at 42 days old.
 Also included: chicks' fledging age, hatch and fledging dates,
 behaviours during the string-pull test (activity and escape) recorded at
 35-37days old and averaged, and the mass gained between hatch and 36 days
 old.  Both data detailed the chicks identification,
 treatment group, and hatching order.  We also include
 the R script used to statistically analyze our data and validate the
 resulting models. 
description: Dataset Lamarre et al. 2021_repeated_measures: A few mass data
 points are missing due to bad weather preventing access to the colony
 during a few days. Dataset Lamarre et al.
 2021_non-repeated_measures: Fledging age missing from 2 subjects as they
 died in their nest at 38 days old (attacked) prior to fledging. The
 concentrations of targetted fatty acids in the red blood cells of one
 subject are missing because this individual fledged at 34 days old and
 could not be recaptured prior to the blood sample collected at 36 days
 old. Likewise, the behaviours of two individuals could not be assessed
 during the string-pull tests at 36 days old due to escaping the testing
 enclosure or fledging before the test took place.