Thanks to te valuable help of experienced phlatobyz here in the forum, I have been able to complete this free flying bird for the kids. The idea is to rely on a KFM4 airfoil to achieve good gliding performance. The smoother leading edge the better gliding. Material is 3mm depron/like sheet. The outline is a true one from a bird guide book, modified to allow cutting with a 3mm bit. Upper and lower profile differ as the upper covers the front feathers to avoid breaks. Hole in the body shapes is for one euro cent. Folding a bit outer feathers and the tail improves stability and gliding.
profile update: it works fine even with a KFM2 wing profile, i.e. only top half wing. Just add weight to keep CG at right point, I have added one euro cent. So much easier for the kids to get a good shape leading edge