She is wearing “Kapppougi” (割烹着, かっぽうぎ). “Kappougi” is a kind of apron. It was invented in Japan and is designed to be worn on top of a kimono.
Browsing: Strike Witches
Yes, it’s well know as the bird that tells the arrival of spring in Japan, but the bird in the picture is a Japanese white-eye (Mejiro). Bush warblers are really cautious, so you can rarely see them even when you can hear them.
“肝油” (かんゆ, Kan yu) is cod liver oil. This is a nutritional supplement derived from the livers of cod fish.
There are two reasons for this. One reason is to make the gift easy to carry by wrapping it in a cloth, and the other reason is to use the purple color to show his gratitude.