Why do birds chirp so loudly in the early morning?

Dear Tom,
Why do birds chirp so loudly in the early morning? I like to have my bedroom windows open, but the noisy birds seen determined to cause a harsh clatter.
— Sonya Jarvil, Davenport, Iowa
Dear Sonya,
Ornithologists say the chirping of birds at daybreak is part of their mating ritual. They tell me that increasing daylight, especially in the spring and early summer, triggers the mating instinct in birds, and that the singing, done mostly by males, is a means of communicating the search for a female.
Male birds stake out a “territory” — an area large enough to collect materials for nest building and over which enough food can be collected to support their young. A male’s early-morning chirping effectively indicates a territory is available and that a partner is being sought.
Ornithologists say the chirping of birds at daybreak is part of their mating ritual.