How do the abilities of parent Pokemon affect that of the offspring in HG/SS?

Question

So I have two questions. First, if I breed a female Skarmory with Sturdy, what are the chances the progeny will have Sturdy and the chances of it having Keen Eye (I would rather have Keen Eye because this is Gen IV and no Sturdy buff yet.)? Second, if I am breeding two Pokémon and they share a common ability (I am breeding a Keen Eye Spearow with it, and the other ability for Skarmory is Keen Eye.), so is there a chance at all that the Spearow can influence the baby to have Keen Eye? Or is it dependent only on the mother?

Comments

Heartgold/soulsilver is the gen he seems to be using and is generation iv (4)

Answer 1

Before Generation V, the Ability slot that a Pokémon Egg would have when it hatched was left to random chance, resulting in a 50% chance of having either slot.

source
Also why are you trying to breed a drill peck Skarmory when fly is stronger?

Comments

Fly could miss, or the opponent could switch out to an Electric type or anything that can resist Flying type moves. Drill Peck is the opposite, sure it only has 80 attack power but that’s still pretty good, and it has 100 accuracy unlike Fly.

---

In-game opponents almost never switch in HGSS. Drill peck is more likely to miss the OHKO or 2HKO than fly is to miss completely. Also fly lets him fly to places.

---

If they did, then Drill Peck is better (that's just my opinion).

---

Thank you! Also, I would rather have a quicker paced 100 percent move than a two turn move like fly