The female Common Kingfisher is identical in appearance to the male except that her lower mandible is orange-red (in stead of black) with a black tip.

1st, 2nd & 3rd photo: A female. Lagoa de São Lourenço, Algarve, Portugal, 19 November 2017
4th photo: A male. Choupal National Forest, Coimbra, Portugal, 9 June 2023