Grey Squirrels (Sciurus Carolinensis) are seasonal pests that are highly activity through the spring and summer periods also birthing litters roughly within the same seasonal period. In terms of an infestation within the premises, twigs and leaves (though insulation is more common) are gathered to construct nests and are used for shelter and breeding. The gestation period is roughly 6 -7 weeks to which the young are birthed spending the next 4 -5 weeks developing senses and physical traits. A number of weeks after the development stage, exploration and experimenting solid foods takes place until they become mature enough to lose their infantile coat gaining a thicker seasonal coat and begin to venture outside the premises which is when excessive activity and noise will occur...
Activity can last for hours after dawn being one of the main reasons their known for being a pest. Squirrels are capable of birthing twice a year with up to 7 young in a litter and it's common for them to begin breeding as early as 6 - 7 months of age meaning an infestation can become an outbreak within a year depending on the available resources.