Peacocks are one of 31 Rare Resources in the game and, if present on a map, available from the beginning. They appears as a small flock of green-blueish-black peacocks. Like most rare resources, they can be gathered by sending a Merchant from the Market to the resource location. Peacocks provide the following benefits:Military Research level: With Military 1 the regular limit is 50 and Peacocks would add another 5 for a total maximum of 55. The bonus is also allowed to exceed the maximum population (by default it is 200, with Peacocks 220). The bonus from Peacocks is cumulative with the 100% population bonus of the Bantu. However, population limit increases from other sources, like the +50 from the Colossus wonder, are not affected by this resource.
Peacocks should typically be seized as soon as possible, as building a large army is difficult without population boosts. However, one should not become too enraptured with seizing rare resources, as an enemy army may choose to assault one's cities while the player is otherwise occupied.
Note that in normal gameplay, there is normally only one of these resources avaliable in a map. Basically, even if you put more than one Peacocks in a custom made map, a nation that obtains two or more Peacocks will not experience a significant increase in the population limit.