A LATE SUMMER GOLDFINCH FAMILY & second broods in birds

These images of apparent goldfinch feeding juveniles in late summer might be surprising. Is it nesting, something that birds do in spring? Many common birds may produce multiple broods of offspring in a season if food supplies are abundant, including robins, phoebes, bluebirds, and goldfinches. In warmer southern regions, cardinals are known to produce up to four broods per year, and morning doves up to six. While these images probably depict a second brood at the end of August, goldfinches actually nest later than most birds in spring, and it is possible that this was a first brood that had a late start. To make a second brood, a female might leave her male partner to care for the juveniles of the first brood, while she can start a second nest, often with a different male. Birds in northern regions cannot produce as many broods, since eggs laid later in the season might not produce offspring which have enough time to develop the flight muscles they would need for autumn migration. As climate change makes winters milder and lengthens the time when food might be abundant in spring and autumn, some bird species may be more likely to produce multiple broods. This may be one more factor which puts neotropical migrants at a disadvantage. Their long migrations to wintering grounds in Latin America restrict the time the juveniles would have to grow in late summer. In other words, a warbler species which can only have one brood per year, in part because of its long migrations, might then be at a disadvantage competing with birds which either can stay in an area of the United States or migrate to the southern United States, which now can produce multiple broods and have greater reproductive success.