The main pollinating agent in the case of a maize plant is wind. This means that the transfer of pollen in maize plants primarily occurs through the action of wind.

Option 1: Birds are not the main pollinating agent for maize plants. While birds may play a role in the pollination of certain plants, they are not known to be significant pollinators for maize plants.

Option 2: Insects, such as bees, are important pollinators for many plants, but they are not the primary pollinating agent for maize plants. Maize plants do have flowers, but they primarily rely on wind to transfer pollen.

Option 3: Rodents are not known to be pollinators for maize plants. They do not typically visit flowers and therefore do not contribute significantly to pollination in maize plants.

Option 4: Wind is the correct answer. Maize plants have male flowers (tassels) that release pollen into the air. The pollen is then carried by the wind to the female flowers (ears) where pollination takes place. Wind pollination is a common mechanism in many cereal crops, including maize.