Now that all of the Thanksgiving feasts and a fraction of the leftovers have been consumed, the holiday season is in full swing. For many, this time of year often brings much needed time away from the office, more time with family and friends, travel and preparing for the colder temperatures that December usually brings. While we’re gearing up for the holidays, some of our feathered friends are gearing up for an entirely different season.
Culturally, we as humans have always seen the shorter and colder days of winter as a time to lower our activity levels and rely on the food we’ve harvested to help get us through until the warmth and brightness of spring brings the new life of another year. For large birds, such as Bald Eagles and Great Horned Owls, they must get a very early start on nesting. Pair bonding and nest construction for these massive birds of prey begins as early as late October, depending upon location. Though these species don’t usually begin until late November or December in South Carolina, I encountered a pair of Great Horned Owls dueting and setting up their territory the week before Halloween in Schulle Canyon here in Texas. Whether in SC or TX, it isn't at all uncommon for the eggs to be laid in middle of December.
You may be wondering why birds would ever think of starting their nesting season with the coldest days of December, January and February ahead of them. I’ve certainly marveled while watching eagles and owls sitting in a nest with snow falling around them. Well, the necessities and pressures of reproduction in nature sometimes overrule our human sense of logic. These very large birds have three particular needs that require them to begin courtship and mating rather early.
Needing a large and sturdy nest to raise large chicks means they must set up territories and begin nest construction early. When I say large, I do mean large! Bald Eagles add to their nests each year, causing the nests to grow and grow each successive year. I have been fortunate enough to monitor a number of Bald Eagle nests and they are quite a few feet wide and several feet high. But, the nests I’ve monitored are nothing compared to the largest recorded eagle nest. It was found in Florida in 1963, was 9 ½ feet wide, a little over 20 feet high and weighed in at an astonishing 4000 pounds!
For Bald Eagles, nest building may mean anything from starting a new nest from scratch or simply adding to and tidying up the previous year’s nest. For Great Horned Owls, this may be nothing more than finding a suitable nest previously constructed by another bird and stealing it. Being one of the strongest and toughest birds on the block, Great Horned Owls will take over nests built by Red-tailed Hawks, Red-shouldered Hawks, Ospreys and even Bald Eagles. There aren’t many birds that have the consistent ability to fend off a pair of Great Horned Owls wishing to usurp a nest. Before you get angry with my nocturnal feathered friends, remember the owls are taking over the nests at a time when most other species aren’t looking to nest.
Bald Eagle on nest in SC. The adults at this nest made a very good living taking wintering gulls from nearby lakes and ponds (and even a landfill). Photo taken 12/31/13
The second and third requirements both deal with time; time for incubation and time for raising their chicks. Their eggs require a considerable incubation time, usually around 30-35 days. This long incubation time is followed by a long period of time feeding and rearing young, with the chicks not leaving the nest for at least 10-12 weeks. This isn’t all that uncommon for larger birds of prey, but getting an early start allows them to successfully begin rearing their chicks long before other birds of prey even begin nesting. This is an effective way of reducing competition and it is an extremely successful way to have their fledglings begin learning the art of the hunt without the pressures of other newbies flooding the prey market.
Adult Bald Eagle sits alert out on a limb, while two nestlings (one sits on the rim of the nest and one sits down inside the nest) wait for the other adult to bring the next meal. I watched the nestlings exercising their wings before the photo was taken. They fledged four weeks later, taking to the sky with the adults. Photo taken 4/12/12
These large birds of prey approach nesting in a very similar way some of us approach shopping. Just as it is easier to get your holiday shopping done early and not wait until the night of December 24th to race out to find gifts for your friends and family, it is better for them to start their breeding season early. Evolutionarily, these birds have benefitted greatly from getting a jump on their shopping lists!