The game is promising, but there are some things that could be improved:
1. It seems like the hitbox for hit detection is much bigger than the box for catching a power up, many times an egg just flies through me, but I do not pick it;
2. The power ups you get by reaching higher scores should improve your combat abilities rather than decreasing them. After unlocking the lance the game became worse, because in comparison to the rings of fire the lance is pretty useless.
3. Lots of times the game places the birds in the places where there is no possibility you can reach them, for example right inside the cloud or just next to the jet fighter;
4. The birds themselves should appear in more regular time periods. Sometimes I fly a really big distance without meeting any of them while last time I met 2 in a row, the second one just seconds after I hit the first one.
Think about expanding the game, maybe with a story. Check Sky Quest here on Newgrounds for inspirations ;-)