what is up with all the April birthdays?

always popular in my family growing up we would celebrate my brother, father, grandmother, grandfather & an uncle's birthday all on one day of course with all those names to fit a large cake was required. With the advent of facebook and the tab that let's me know when folks have a birthday I am amazed at the amount of people I know with April birthdays which would make conception what in the summer months? Would have thought more babies would be conceived during colder months.