Busard St Martin, circus cyaneus, hen harrier, blauwe kiekendief, kornweihe, blâkärrhök, albanella reale, aguilucho palido.
Male pale grey, with black wing-tips, differing from smaller male Montagu's Harrier in its prominent white rump (instead of white bar at base of tail) and no dark bars on the secondaries or rufous streaks on flanks and underwing.
Female brown, with conspicuously barred tail, hard to tell from slenderer female Montagu's except by size, more conspicuous white rump and ruff extending across throat as blackish line.
Immature as female, without deep buff underparts of immature Montagu's.
Alarm or display call a chattering 'ke-ke-ke' or 'kek-kek-kek'.17 - 20 in.