The male House Sparrow has a black bill in the breeding season and in summer.
In winter the male's bill is lighter in color.
Young males have a yellowish bill.
Females have a yellowish bill all year round.

House Sparrows look similar to Eurasian Tree Sparrows.
If you want to tell them apart, remember that Eurasian Tree Sparrows have a brown cap and House Sparrows have a grey cap.
Male and female House Sparrows look different while male and female Eurasian Tree Sparrows look similar.
In Europe you may find the Eurasian Tree Sparrow in wooded open countryside, while the House Sparrow breeds in the more urban areas.

First photo: A male
Last 4 photos: A female

1st, 2nd & 3rd photo: At Hotel Vila Galé Albacora, Tavira area, Algarve, Portugal, 20 November 2017
4th & 5th photo: Ferragudo, Algarve, Portugal, 1 June 2023