“Fœtificant bruma, qui dies halcyonides vocantur, placido mari per eos et navigabili, Siculo maxime.  Plin. x. 47.  cf. Arist., H.A. v. 8, 9, and Ælian, H. N. i. 36.  So Theoc. vii. 57: Χ᾽ ἁλκυόνες στορεσεῦντι τὰ κύματα, τάν τε θάλασσαν Τόν τε νότον τόντ᾽ εὖρον ὃς ἔσχατα φυκία κινεῖ Sir Thomas Browne (Vulgar Errors) denies the use of a kingfisher as a weather-gauge, but says nothing as to the “halcyon days.”  Kingfishers are rarely seen in the open sea, but haunt estuaries which are calm without any special miracle.  Possibly the halcyon was a tern or sea-swallow, which resembles a kingfisher, but they brood on land.