Can you use a claw attack while wearing a light shield? You can't hold a weapon, but your hand is available. Presumably, you'd lose the AC bonus doing it, but can you do it?
Same question for buckler. The phrasing specifies weapons, how does it interact with a claw attack?
For sake of completion, heavy shields. I presume you can't claw while holding one, but am I wrong? I'd love to hear.
I would say "No" for a light shield, "Yes" for a buckler (with drawbacks). And definitely not with a heavy shield.
Natural Attacks: Attacks made with natural weapons, such as claws and bites, are melee attacks that can be made against any creature within your reach (usually 5 feet). These attacks are made using your full attack bonus and deal an amount of damage that depends on their type (plus your Strength modifier, as normal). You do not receive additional natural attacks for a high base attack bonus. Instead, you receive additional attack rolls for multiple limb and body parts capable of making the attack (as noted by the race or ability that grants the attacks). If you possess only one natural attack (such as a bite—two claw attacks do not qualify), you add 1–1/2 times your Strength bonus on damage rolls made with that attack.
Buckler: This small metal shield is worn strapped to your forearm. You can use a bow or crossbow without penalty while carrying it. You can also use your shield arm to wield a weapon (whether you are using an off-hand weapon or using your off hand to help wield a two-handed weapon), but you take a –1 penalty on attack rolls while doing so. This penalty stacks with those that may apply for fighting with your off hand and for fighting with two weapons. In any case, if you use a weapon in your off hand, you lose the buckler's AC bonus until your next turn. You can cast a spell with somatic components using your shield arm, but you lose the buckler's AC bonus until your next turn. You can't make a shield bash with a buckler.
Shield, Light; Wooden or Steel: You strap a shield to your forearm and grip it with your hand. A light shield's weight lets you carry other items in that hand, although you cannot use weapons with it.
Shield, Heavy; Wooden or Steel: You strap a shield to your forearm and grip it with your hand. A heavy shield is so heavy that you can't use your shield hand for anything else.