Reference article
Skill Seed (Duck Life 1)
A blue seed whose effects differ between original Flash and later Unity editions.
Original Flash effect
Skill Seeds improve 
Energy and all three racing skills in original Flash. Each bite raises energy, running, flying and swimming by 1 level.
Later-edition effect
In 
Retro Pack and The Flock, the blue seed adds energy only. It gives 3 energy levels and does not increase running, flying or swimming. The shop still calls it “Skill seed”.
Buying and value
A Skill Seed costs 10 
Coins. For energy alone in the later editions, five normal Seed cost half as much for the same increase.
Across the games
Compare games and editions on the 
Skill Seed page.