Great Horned Owls are one of the earliest nesting birds in North America, typically laying eggs in late winter or early spring. The exact timing of egg laying can vary across their range, but generally occurs between January and April.
When do Great Horned Owls lay eggs?
Great Horned Owls begin nesting very early in the year while it is still winter in most of their range. Egg laying typically takes place between late January and early April.
In northern regions of their range, Great Horned Owls may begin laying eggs as early as late January. For example, in Alaska and Canada, eggs are often laid in February.
Farther south, the nesting season starts a bit later, often in February or March. In the southernmost parts of their range in the United States and Mexico, Great Horned Owls may not begin laying eggs until March or even early April.
The exact timing can vary slightly from year to year depending on environmental conditions. During years with milder winter weather, Great Horned Owls may begin nesting earlier. When winters are severe, they may delay nesting by a few weeks. On average though, February and March are the peak months for egg laying across most of their range.
Why do Great Horned Owls nest so early?
Nesting in late winter is unusual timing for owls and most other North American birds. So why do Great Horned Owls start so early?
There are a few key reasons:
- Food availability – By nesting early, they can take advantage of abundant food sources like winter-weakened prey and waterfowl that are migrating north.
- Less competition – Other predatory birds are not yet nesting, so early nesting gives Great Horned Owls first access to the best nest sites and prey.
- Longer breeding season – Nesting early allows for a longer breeding season and potentially raising more than one brood.
- Synchronized hatching – Hatching in early spring aligns food demand with increasing food supplies.
Overall, their flexible nesting chronology allows Great Horned Owls to take advantage of seasonal food resources and get a head start over potential competitors. This early season strategy has clearly been effective, as Great Horned Owls have one of the broadest distributions of any owl in the Americas.
What factors influence exactly when eggs are laid?
Several factors can influence the precise timing of egg laying for individual Great Horned Owl pairs:
Weather
Colder winters or late winter storms may delay nesting by a few weeks. Unusually warm and early springs may trigger earlier egg laying. Great Horned Owls are sensitive to temperature and weather changes.
Prey availability
Access to abundant food sources is critical for successful breeding. Great Horned Owls time egg production to match peaks in prey populations. If a major food source crashes or migrates late, owls may delay laying.
Age
Younger birds often nest later. First-time breeders may lay eggs several weeks after mature adults start. Experience helps pairs get a head start each year.
Courtship
Pairs that complete courtship quickly can begin egg laying sooner. Delayed pairing up pushes the process back. Great Horned Owls that keep the same mate year after year tend to lay earlier.
Latitude
More northern owls nest earlier to take advantage of short summers. Farther south, they can afford to lay eggs later in the year.
So in general, food availability and weather are the most important external factors controlling egg laying timing. But the circumstances of individual pairs also play a role in determining the precise nesting chronology each year.
How many eggs do Great Horned Owls lay?
A typical Great Horned Owl clutch contains 2-3 eggs, though clutch size can range from 1 to 5 eggs.
Here are some more details on Great Horned Owl clutch size:
- The average clutch size is 2 eggs
- 3 egg clutches are also common
- Only 1 egg may be laid by a young female
- Up to 5 eggs may be laid by an older, experienced female
- Eggs are laid at 1-3 day intervals
- Incubation starts after the 1st egg is laid
- Therefore, chicks hatch asynchronously over several days
Having asynchronous hatching gives the first hatchling a size and strength advantage over its nest mates when competing for food. This hierarchy helps ensure at least one chick survives in lean times.
The massive stick nests built by Great Horned Owls can easily accommodate multiple eggs and chicks. By using existing nests or tree cavities, they avoid the energy costs of new nest construction each year. Their flexible clutch size enables Great Horned Owls to take advantage of seasonal food abundances when they arise. More food means more eggs!
How long is the incubation period?
Once a full clutch has been laid, the incubation period lasts about 30-37 days. The female Great Horned Owl does the majority of incubating, only leaving the nest for short periods to eat prey brought by her mate.
Here are some more details on Great Horned Owl incubation:
- Incubation lasts 30-37 days on average
- It begins after the 1st egg is laid
- Only the female incubates
- The male provides food for her throughout incubation
- The female may leave the nest briefly to eat and defecate
- Frequent egg turning is critical during incubation
- The eggs hatch asynchronously over several days
The extended incubation period gives the embryos time to fully develop before hatching. Towards the end, the female owl spends more time on the nest to provide warmth needed for embryos to finish growing. Once most eggs have hatched, the true work of raising owlets begins!
How long before the young owls can fly?
Great Horned Owlets remain in the nest for about 6-7 weeks before fledging and learning to fly. They grow from small fluffy hatchlings to almost adult size in less than two months!
Here’s an overview of the owlets’ development:
- Eyes open at 4-5 days old
- Down begins growing around 2 weeks old
- The owlets start walking around the nest at 4 weeks
- Wing flapping and hopping starts around 5 weeks
- Fledging occurs between 40-49 days old
- First short flights happen by 6 weeks old
- The owlets become strong fliers and leave the parents’ territory by about 7-8 weeks old
The owlets grow incredibly fast, increasing their body weight 15 times or more before fledging! This rapid growth requires lots of food provided by the parents. Fledging any young is an immense investment for Great Horned Owls each breeding season.
How many broods do Great Horned Owls raise per year?
Great Horned Owls are capable of raising one or sometimes two broods per breeding season. Here are more details:
- Most pairs raise just one brood per year
- Some may raise two broods, especially farther south
- Second broods are usually smaller (just 1-2 owlets)
- There is typically 4-5 months between first and second broods
- Double brooding is more common when food is abundant
- Only very experienced parents can successfully fledge two broods
Raising one brood each winter-spring is energy intensive enough for most Great Horned Owl pairs. But when hunting is good, some accomplish the impressive feat of two successful broods in a single year.
Summary of Great Horned Owl Breeding Season Timeline
Here is an overview of the Great Horned Owl breeding and nesting timeline throughout the year:
January to February | Courtship and pairing |
Late January to April | Egg laying |
February to May | Incubation |
March to June | Hatching and owlet development |
April to July | Fledging and independence |
February to April | Potential second brood |
As this summary shows, the Great Horned Owl’s breeding season is long, beginning up to 4 months before most other birds! Their unique winter and spring nesting strategy has served the species well. This adaptive approach has allowed Great Horned Owls to thrive across an incredibly wide diversity of habitats in the Americas.
Conclusion
To recap, Great Horned Owls are one of the earliest nesting birds, laying eggs from January through April depending on latitude. They often begin incubating in February, with eggs hatching in March or April after about a one month period.
Owlets take their first flights 6-7 weeks after hatching. Some pairs may even raise a second brood later in spring if food is plentiful. Their early breeding gives Great Horned Owls a head start to raise young before summer heat and competition from other raptors.
This unique winter and spring nesting schedule is just one of the many fascinating adaptations that have made the Great Horned Owl one of the most successful and widespread avian predators across the Americas. Their flexible breeding chronology and double brooding ability reflect the species’ resourcefulness and adaptability.