What does the Northern Mockingbird sound like at night?
Press play. If that is the sound outside, you have your answer — the Northern Mockingbird's "varied medley".
What you're hearing
A long, variable series of phrases, each repeated 2-6 times before changing, often imitating other birds and noises. A single sequence can go on for minutes. For example: "chirp-chirp-chirp ... tweet-tweet-tweet ... clack-clack-clack ..." mixing blue jay calls, car alarm imitations, cardinal whistles, etc., back to back. The overall effect is a loud, rambling musical performance that can be heard day or night.
“varied medley”
Birders often file this one under Song.
What time of night you hear it
All night in spring, and famously on bright moonlit nights.
In spring, males that haven't attracted a mate may sing day and night, with nocturnal singing especially common on bright moonlit nights. Pairs build twiggy nests in bushes or low trees; they may raise 2-3 broods from spring into late summer. Both sexes aggressively defend the nest area, dive-bombing cats, crows, or humans who get too close. Summer is filled with almost nonstop singing and territorial chases. In fall, singing diminishes and the birds focus on fattening up on berries; young of the year disperse to find their own territories. Through winter, mockingbirds remain territorial, often defending berry-laden bushes against others. They usually sing less in winter, but may still practice snippets of their song on warm days. By late winter, the volume and frequency of singing increases again as they court mates and prepare to nest.
Why a Northern Mockingbird calls at night
The single most common answer to "what bird is singing outside my window at 3am". Unmated males sing around the clock in spring, cycling through imitations of other birds, car alarms and phone tones. The night singers are almost always unmated males, and the singing stops once a male pairs up.
What else could it be?
The other voices you are most likely to hear in the dark. Play them and compare.