A mortality event at the Christiansø colony in the Baltic proper killed 115 common eiders (Somateria mollissima) in mid-May 2016. To
complement previous studies of incubating females, 39 males were necropsied and from a subsample of these a biochemical and haematological profile was obtained. The birds were emaciated and cachexic having a 50% reduction in body mass. Twenty-nine eiders were diagnosed with hydropericardium, 15 had hunger
edema, three birds had
enteritis and a single air sac
infection. All birds were infested with intestinal Polymorphus minutus and 32 of these with the intestinal Trematoda spp. Microscopic parasitic investigations identified endoparasitic trematodes of the families Bucephhalidae, Echinostomidae, Notocotyluridae and Levinsiniella. White blood cell count showed slight heterophilia and
lymphopenia while the
albumin:
globulin ratio (0.28) indicated stress, immune supression and inflammatory reactions supported by a high heterophil:lymphocyte index (13). Declined plasma concentration of
glucose,
fructosamine,
amylase,
albumin and
protein likewise indicated long-term
starvation prior to mortality indicating phase III
starvation (catabolism of
protein). The dramatic increase in
aspartate transaminase,
glutamate-dehydrogenase,
lactate-dehydrogenase and
bile acids indicate liver disorders while
dehydration, renal, heart and bone disorders was reflected in the increased
uric acid,
urea, phosphor and
potassium values. These findings show that male eiders undergo long-term
starvation and multi organ failure similar to that of incubating females previously reported from the same colony. It increases our knowledge of the physiology of starving eiders and add to our understanding of the recurrent mortality events in the colony that seems to be linked to changes in food availability being an important factor together with a warmer climate in a declining Baltic eider population. We recommend future studies to focus on food composition, migration patterns and environmental changes including
parasitic infections and global warming.