Are yolk thiamine levels associated with stress hormones in arctic seabirds? A comparative approach among populations, species and food webs

Many seabird populations are drastically declining in Norway and internationally. The causes can be complex, but there has been an increasing foucus on disease as a potential causal factor, and especially thiamine deficiency (vitamin B1). Thiamine is essential for all living cells, and function as co-factor for many enzymes in basal cell metabolism. The Norwegian Environmental Agency has initiated a project to investigate the tiamin levels in Norwegian seabirds, in order to assess whether episodic events of timamin deficiency may occur. Eggs will be collected from seabirds breeding in Svalbard, for comparison with eggs from mainland Norway and other countries. In this study we will go one step further and investigate whether yolk thiamine levels are associated with yolk corticosterone levels. This is the avian stress hormone, which is known to be very sensitive to nutritional status. Apriori, we expect a potential indirect link between cort and thiamine, if birds experience food shortage prior to egg laying. This may be expected if food shortage is the reason for low thiamine levels, rather than a specific deficiency of this vitamin in the marine food web. We will assess this using a comparative approach, comparing common eider populations with contrasting environmental conditions and population trends (Svalbard breeding eiders vs mainland Norway breeding eiders) and comparing two species (common eiders and black-legged kittiwakes) feeding in different food webs (bentic vs pelagic) in Kongsfjorden Svalbard.