When Do Great Horned Owls Nest? Winter Nesting Explained

When does the great horned owl nesting season start?

The breeding cycle starts in fall. From October to December, males hoot loudly at dusk to defend their territories and attract or reunite with a mate, and pairs hoot back and forth in duets. By midwinter the pair has chosen a nest site, and the female starts laying soon afterward.

Timing shifts with latitude and climate. In warm southern regions the owls start earliest; in the far north they wait until late winter or spring.

In years when food is plentiful, owls in the same area may lay a few weeks earlier than usual. In very poor years, when prey is scarce, some pairs do not nest at all.

Where do great horned owls nest?

Great horned owls nest in a wider variety of places than almost any other North American bird, but they never build a nest of their own. Their favorite sites are large stick nests left by other birds, especially those of the red-tailed hawk, as well as crows, ravens, herons and even eagles. Squirrel nests (dreys), broken treetops and large tree cavities are used too.

Where trees are scarce, they nest on cliff ledges, in small caves, in desert cacti, on rock outcrops and occasionally on the ground. In towns they sometimes nest in barns, on building ledges or on artificial platforms. They add little or no nesting material, perhaps a few of their own feathers.

Because they start so early, great horned owls often occupy a hawk’s nest before the hawks return to breed. The hawks then have to build elsewhere.

Laying and incubating eggs in winter

The female usually lays 2 eggs, though clutches range from 1 to about 4 and rarely more. The eggs are round, dull white and roughly the size of a large chicken egg, about 55 mm (2.2 in) long. They are laid a day or more apart.

Incubation begins with the first egg and lasts about 30–37 days, around 33 days on average. The female does almost all of it, and she rarely leaves the nest; the male hunts for both of them and brings food to her, usually soon after dark. Because incubation starts early, the owlets hatch on different days and the first chick is a little larger than the others.

Keeping eggs warm in freezing weather is possible because of the female’s thick plumage and a brood patch, an area of bare, well-supplied skin on her belly that presses against the eggs. Nesting females have been photographed sitting tight with snow piled on their backs.

Owlets, branching and fledging

Newly hatched owlets weigh only about 35 g (1.2 oz) and are covered in whitish down. They grow fast, gaining around 30 g (1 oz) a day in their first weeks. The female broods them closely at first, and both parents bring food: rabbits, rats, mice, voles, birds and other prey.

At about 6 weeks old, the young begin to leave the nest and clamber onto nearby branches, a stage called branching. They make their first short flights about a week later, but they are not skilled fliers until 10–12 weeks. During this period young owls are often seen sitting on low branches or even on the ground, which is normal; the parents are nearby and still feeding them.

Parents are very protective at this stage and may swoop at people or dogs who come too close (see do owls attack people?). The young keep begging for food through summer and into fall, sometimes as late as October, before dispersing to find territories of their own.

Why do great horned owls nest so early?

Biologists think several factors favor winter nesting:

• A long upbringing. Great horned owls need several months to raise their young to independence. Starting in winter gives the owlets time to learn to fly and hunt before the next winter arrives.
• Food when chicks need it most. By the time the owlets are large and hungry, in spring, many prey animals are breeding, and young rabbits, rodents and birds are abundant and easy to catch.
• First pick of nest sites. Nesting early lets the owls claim large stick nests before hawks and other raptors return to use them.
• Long nights. Winter nights give owls more hours of darkness to hunt for themselves and the incubating female.

Large raptors in general take a long time to raise young, and the great horned owl’s early start is one solution to that problem.

How can you tell if great horned owls are nesting nearby?

Listen for hooting duets on winter evenings, a sign that a pair holds a territory. Later, look for a large stick nest with the tips of two feather tufts or a tail showing over the rim, or for crows loudly mobbing a spot in the trees. In spring, fluffy owlets peering from the nest are often noticed by walkers.

If you find a nest, watch from a distance with binoculars, keep visits short and never climb toward the nest or handle owlets. More about the species is in our profile of the great horned owl, and other North American owls are covered in owls of North America.