Fig. 2

Common structural features of the upper eyelid and lower eyelid on the Strigiformes (a, d, g, j, m, p, t, x), Accipitriformes (b, e, h, k, n, r, u, y), and Falconiformes (c, f, i, l, o, s, w, z). (a) – Western Barn Owl; (b) and (k) – Eurasian Sparrowhawk; (c), (f), (s) and (w) – Peregrine Falcon; (d) – Ural owl; (e) – Eurasian Goshawk; (g) – Boreal Owl; (h) – Steppe Eagle; (i), (l), (o) and (z) – Eurasian Kestrel; (j) – Philippine Scops-Owl; (m) – Eurasian Eagle-Owl; (n) and (y) – European Honey-buzzard; (r) – Hen Harrier; (p) – Little Owl; (u) – White-tailed Eagle; (t) – Northern Hawk Owl; (x) – Tawny Owl. aps – anterior palpebral surface, bv – blood vessels, bv + m – blood vessels and melanocytes, cf – conjunctival folds, dct – dense connective tissue, e – epithelium, et – elastic tendon, fs – folds of skin, gc – goblet cells, hf – „hair feathers”, lp – lamina propria, mmp – mm. pennarum, mz – marginal zone, pps – posterior palpebral surface, pz – plate zone, swg + sbg – sweat glands and sebaceous glands, tp – tarsal plate. a – c, e, f, h, i, m – o = Mayer’s H&E stain; j, u = Masson Goldner trichrome stain; d, g, l, p – t, w, y, z = Movat pentachrome (modified Russell-Movat) stain; k, x = picro-Mallory trichrome stain. Scale bars: d, g, h, i = 200 μm; e, f, p = 100 μm; j, k, l, m, r, s = 50 μm; a, c, n, o, t, u, w, x, y = 20 μm; b, z = 10 μm