Tidewater glaciers as feeding spots for the Black-legged Kittiwake (Rissa tridactyla): A citizen science approach

Thirty-one tidewater glacier bays in Spitsbergen Island were visited by yachts in August 2011, 2015, 2016 and 2017. Surface water samples were taken by volunteers, the members of the yacht crews, to measure concentrations of suspended matter, salinity, and temperature. Secchi disc measurements were used to measure water transparency. A series of photographs along the glacier fronts were taken and used to count seabirds that were present near the glacier cliff. Basic topographic features (depth, presence of a sill, exposure, glacier width) were obtained from sea charts and analysed. The number of preying Black-legged Kittiwakes (Rissa tridactyla; a target species) ranged from zero to over 2000 birds during 89 visits. High concentrations of individuals (above 100) were observed in 20% of the visits, while no birds were recorded in 42% of the visits. There was no statistical correlation between the topographic features of the glacier and bird concentrations. To our present knowledge, Black-legged Kittiwake feeding spots are random and temporary in time in which (or soon after) the juveniles are leaving the colony. They are a recurrent phenomenon related to krill abundance and simultaneous jet-like meltwater discharges.