If another male dares to approach, the singing male will pause and fly directly at the intruder, taking its perch. If the intruder does not leave immediately, he will be chased and driven away. If the singing and chasing behavior of the male does not alert you to any nests in your area, you may notice another territorial signal which involves high, looping flights of the male above the boundary of the nesting territory. During this display the bird appears to ride an invisible aerial roller-coaster as it alternately tucks its wings and dives steeply, then spreads its wings while gliding smoothly upward. Territorial displays of the male cease when incubation begins, usually after the second or third egg is laid.
Incubation continues for twelve to fourteen days, and is performed exclusively by the female.
While incubating, the female rarely leaves the nest, and is frequently fed by the male. The male makes regular flights above the nest, and if called by the female will drop down to a branch near the nest and feed the female a meal of partly digested seeds. The male then leaves and the female returns to the nest. Both parents feed the young a diet of regurgitated seeds. When the birds fledge, the male will continue to feed them while the female begins construction of a second nest.