A really lovely picture. The bird is beautifully painted with the yellow and green tones, which fade into each other. I think you've made a wonderful effect with the background - not painting it so it stands out, but just so that the viewer can faintly see it. This really brings the picture depth - a detail but not unimportant, because your foreground consists of very few elements.
Your style is very elegant and the use of colors matches the picture perfectly, so that they don't stand out, but instead fit with the brownish background. Your picture reminds me of some chinese illustrations I once saw - I think it's the way you've painted the leaves.
A last thing: The star is a very sweet element, and it gives the picture a touch of childishness.
Oh my gosh it's so cute! D8 The little bird is beautifully constructed and is absolutely adorable! The shading and coloring of the overall image is fantastic! Everything is so smooth! It has a wonderful look to it, that it does! Your mother should feel very thankful to have a child that can draw such wonderful work! I know if I had been on the receiving end of the greeting cards, this would be be the only one I would ever keep. It's so unique and beautifully done! :3