Eagles and owls get an early start on nesting

For most of our birds, nesting season commences in spring.

But for some of our largest birds, namely bald eagles and great horned owls, the nesting season is in full swing by mid-January, usually the coldest part of winter. Even on the most frigid of days, when icicles are hanging from tree limbs, the birds will be incubating eggs in their bulky nests.

Last week, for instance, the folks at Berry College in Rome notified us that, for the third winter in a row, a pair of bald eagles was sitting on two eggs in a nest atop a 100-foot tall pine tree on campus. (Video cameras focused on the nest provide live online streaming of the eagles as they tend the nest.)

The first egg was laid Jan. 6. On that day, a front page story in The Atlanta Journal-Constitution warned that Georgia was facing its coldest temperatures of the season — in the low teens in Atlanta and even lower in North Georgia.

The bitter cold, though, did not faze Berry’s eagles, which produced a second egg three days later.

So, why would some birds begin nesting in the dead of winter, when the weather is at its coldest and harshest?

“Obviously there are benefits, or the birds wouldn’t do it,” said Jim Ozier, head of the Nongame Conservation Section of the Georgia Department of Natural Resources.

One reason, said Ozier, a leading eagle expert, is that it takes several months to raise an eaglet or a great horned owlet. The parents must begin nesting early so that, by the time the offspring leave the nest in spring, there will be ample food for them and they can fend for themselves.

Bald eagles, for instance, incubate their eggs for 34 to 36 days. After the babies hatch, it may be another 70 to 95 days before they leave the nest. Great horned owlets also stay with their parents for several months.

In contrast, northern cardinals, which begin nesting in late March, incubate eggs for 12 to 13 days; the young fledge nine to 10 days after hatching. The offspring, however, may still be dependent on adults two to four weeks after they leave the nest.

In the sky: The moon will be new Tuesday, said David Dundee, Tellus Science Museum astronomer. Mercury and Venus are very low in the west at dusk. Mercury will appear near the moon Wednesday and Venus will appear near it Thursday. Mars sets in the west a few hours after sunset and will appear near the moon Friday. Jupiter rises out of the east at around 8 p.m. Saturn rises out of the east around 3 a.m.