Bukkit

Spawn limits can also be set in this file. it consists of default, global and world-specific restrictions. If a world is not found in this file, it will use the default. The global limits are set around those.

IMPORTANT: if animal (or mob) limits are set, it will remove existing animals if the total count rises due to chunks with animals loading.

spawnlimits:
  default:
    creeper: 1
    cow: 1
    itemwood: 64
    fallingblock: 20
    fallingsand: 10
    tnt: 50
  global:
    mob: 30
    animal: 40
    monster: 260
  worlds:
    lowgrass:
      cow: 1
      creeper: 2
      wood: 10
      slime: 2
    world2:
      enderman: 10
      itemstone: 6

Items are the mobile droppings, not the blocks. You can use this to set creature ranges too. If, for example, all pigs are disabled the pig slots will be used for other creatures, such as sheep. By disabling all animals you would end up with lots of monsters. :)

You can use mob, animal, monster and item as shared types. For example, if you set the 'mob' limit to 50 then 20 animals and 30 monsters can spawn. The default nodes are applied to all worlds automatically, unless this world already has a default limit set. Then the world limit specified is used. For example, lowgrass has a limit of 2 creepers and 50 tnt.

Global limits are, as the name, global. It is a total limit of certain types on the entire server. If you set a global mob limit of 200 and world1 already has 140 mobs spawned, then world2 and all other worlds can only spawn 60 more.

Falling block limits work slightly differently; it will cancel those blocks from falling if the limit is reached. Since I am unable to track and trace the falling blocks, the limit is an estimate per update interval.

Grouped limits:

• animal
• monster
• mob
• item
• fallingblock

Individual limits:

Items

• itemwood
• itemstone
• itemcobblestone
• itemnetherrack
• itemtnt
• itemredstone_torch_on (etc.)

Misc

• experienceorb
• arrow
• egg
• snowball
• fireball
• tnt
• fallingsand
• fallinggravel
• boat
• minecart
• poweredminecart
• storageminecart
• fish (no idea what'll happen)
• painting

Monsters

• creeper
• enderman
• cavespider
• spider
• ghast
• pigzombie
• skeleton
• giant
• silverfish
• slime
• zombie
• ender_dragon

Animals

• chicken
• cow
• sheep
• pig
• squid
• wolf