In a certain bird species, clutch size (the number of eggs laid by a female in one breeding season) ranges from four to eight and the most frequent clutch size is six. This phenomenon is an example of:

The correct answer is - Stabilizing selection

Explanation:

In stabilizing selection nature favor the average value over the extreme value in a population. Therefore in stabilizing selection non-extreme traits are selected by nature. Stabilization selection can be seen in human birth weight, number of eggs laid by birds, etc.

Here the extreme value of trait is 4 and 8 but the most frequent clutch size is 6 therefore average is selected here over the extreme values which show that stabilizing selection is favored here. Therefore the phenomenon is an example of stabilizing selection.