 Its call has been described as a high-pitched "kik"; the sound of a large flock has been called "deafening".Hybridisation between this species and white-winged black tern has been recorded from Sweden and the Netherlands.Two juvenile birds at Chew Valley Lake, England, in September 1978 and September 1981, were also believed to be hybrids; they showed mixed characters of the two species, specifically a combination of a dark mantle (a feature of white-winged black) with dark patches on the breast-side (a feature of black tern, not shown by white-winged black).