BLOOD HEMATOCRIT MEASUREMENTS OF 4 SPECIES OF NORTH-ATLANTIC SEABIRDSIN RELATION TO LEVELS OF INFESTATION BY THE TICK IXODES URIAE

Data on blood hematocrit levels were collected from free-living indivi duals of 4 species of North Atlantic seabirds. Blood oxygen storage ca pacity was high in relation to published data on other seabird species , with mean (+/-SD) values of 54.8 +/- 6.1%, 55.3 +/- 5.4%, 57.9 +/- 9 .3% and 54.9 +/- 8.3% for Common Murre (Uria aalge), Razorbill (Alca t orda), Atlantic Puffin (Fratercula arctica) and Black-legged Kittiwake (Rissa tridactyla), respectively. Interspecific differences in hemato crit level were not associated with differences in foraging behavior. Ail external body surfaces of birds that were blood sampled were searc hed thoroughly for the tick Ixodes uriae. Levels of infestation varied significantly between the species and for the Black-legged Kittiwake (the most heavily infested species), hematocrit level was negatively a nd significantly related to tick load.