Georgia songbirds produce as many as four broods per season

Many of our year-round birds — Northern mockingbirds, Eastern bluebirds, Northern cardinals, American robins and such — already are raising their second broods of the season and may produce a third or fourth before their seasons end around September.

Other songbirds, though, may be limited to only one brood — or two at the most — per season. (That doesn’t include the fact that most songbirds will attempt to renest if their first nest is destroyed by predators or natural calamities.)

It is advantageous, of course, for creatures to produce as many healthy offspring as possible to help ensure survival of the species.

But there are several reasons why some songbirds raise multiple broods per year while others produce only one or two.

For one thing, Southern-nesting birds, as compared with those up North, usually have more favorable conditions — better weather, abundant insects — that allow them to extend their nesting seasons by at least a month or more.

Georgia’s bluebirds, for instance, may raise three to four broods per year while those in North Dakota may produce only one or two. Interestingly, however, the Southern birds tend to lay fewer eggs per nest than those in the North.

Neotropical songbirds — tanagers, orioles, flycatchers, purple martins, several species of warblers and vireos — which migrate to Central and South America for the winter, usually raise only one brood per season because they have little time for more. Some of them begin migrating south as early as July.

Georgia’s resident birds, such as the cardinal, can raise three to four broods per season largely because they remain on or near their breeding grounds year-round. They get a head start on courtship and establishing territories and don’t have to prepare for long journeys to wintering grounds.

For the American goldfinch, the nesting season hasn’t even started yet. It usually begins in July. Because they nest so late, a pair of goldfinches usually produces only one brood per season.

In the sky: From David Dundee, Tellus Science Museum astronomer: Summer officially begins Sunday at 12:38 p.m. — the longest day of the year. The moon will be first-quarter Wednesday. Mercury is low in the east just before dawn. Venus is in the west at dusk and sets about three hours later. Jupiter is low in the west at dusk and sets a few hours later. It will appear near the moon on the night of June 26. Saturn is in the southeast just after dark.