Fig. 5

Distinctive structural features of the third eyelid in Strigiformes species. (a) and (j) – Boreal Owl; (b) and (k) – Northern Hawk Owl; (c) and (l) – Eurasian Eagle-Owl; (d) and (m) – Ural Owl; (e) and (n) – Little Owl; (f) and (o) – Tawny Owl; (g) and (p) – Snowy Owl; (h) and (r) – Philippine Scops-Owl; (i) and (s) – Western Barn Owl. bfs – bulbar folds, bv – blood vessels, bv + m – blood vessels and melanocytes, le – leading edge, mp – marginal plait, mz – marginal zone, pfs – palpebral folds. a, c, f – l, n – s = Mayer’s H&E stain; b, e, m = Movat pentachrome (modified Russell-Movat) stain; d = picro-Mallory trichrome stain. Scale bars: a, c, d, f, g – i = 200 μm; b, e, k, l, m, r = 100 μm; j, n, o, p, s = 50 μm