The open-mouth gaping is due to the heat. Birds do not have sweat glands and cannot perspire to cool their bodies as do mammals, so they often gape to prevent overheating under very hot conditions.
These sparrows were abundant in all habitats. Males and females are alike. I believe the lower bird is an immature with a less pronounced black ear patch, smaller black bib, and showing a pale base to the bill.
Nine or more subspecies are recognized with P. m. saturatus confined to East Asia. This race is deeper more richly colored and has a slightly larger bill than the widespread nominate form.
Digiscoped with Panasonic DMC-LZ5 | Nikon FieldScope III | 30XWA | hand-held (no adapter)