this specimen is most precisely a simpleDark-blue-opaline female Melopsittacus undulatus (Budgerigar aka Budgie Parakeet) We know that it's a hen Budgie because it displays a brown cere (area above beak where the nostrils are)
While cocks usually display dark-blue (Cobalt) ceres.
Youngsters usually display pink ceres.
We know that this particular female is an opaline mutant because the clear undulations on her mantles are the same colour as her boy colour while it would be white on a non-opaline blue &/or yellow on a non-opaline Green Budgie.
St??phane aka Tintin,
Ruby Eyes Aviary.
"You remain responsible, forever, for what you have tamed."
- Antoine De Saint-Exup??ry