Owls of the Estes Valley and RMNP

Northern Saw-whet Owl

by Scott Rashid
Colorado Avian Research and Rehabilitation Institute
All Photos by Scott Rashid

Few people are aware that there are six species of owls that inhabit the Estes Valley and Rocky Mountain National Park (RMNP). They range in size from the diminutive Flammulated and Northern Pygmy-Owls reaching a maximum length of about seven-and-a-half inches and weighing about two ounces, to the 24-inch, four-pound Great Horned Owls.
 
The other owls found here are the Northern Saw-whet Owls, Boreal Owls, and the Long-eared Owls. All but the Flammulated Owls feed upon animals and birds.   The Great Horned and Long-eared Owls use nests constructed by other birds such as Red-tailed Hawks, Cooper’s Hawks and even American Crows and Black-billed Magpies.

Flammulated Owl in her nest

The Great Horned Owls are the earliest nesting owl and most often seen owl in the area. These birds frequently begin their courtship in January, if not before, and begin nesting in March. The female lays between one and four eggs two to three days apart. But has been known to lay eggs more than a week apart. She begins incubating with the first egg. Incubation lasts about 35 days and is done exclusively by the female. Her owlets remain on the nest for about a month before they begin exploring their surroundings.

Long-eared Owls are one of the more difficult birds to find nesting, as they are experts at remaining still and their cryptic coloration blends perfectly with their surroundings.  Both male Great Horned and Long-eared hoot to attract females. These birds can be heard in the spring after dark.

A very surprised looking Boreal Owl in RMNP.

The Boreal Owl nests specifically in the high spruce-fir forests above 9000 feet. In that habitat they are the top avian predator. They are also the largest of the cavity nesting owls in valley and RMNP. Many of these owls remain on their territories year-round and feed upon the voles and birds in the area. Due to their larger size and strength, they can pre upon animals as large as red squirrels, small hares, birds large as Canada Jays, and Pine Grosbeaks. Due to their large size, they need to nest in a cavity constructed by a Northern flicker or a larger natural cavity. 

Once a female is attracted by the male, and she has accepted the cavity, the male is no longer allowed into the cavity. He spends his time hunting for the incubating female and later for the female and young. The young remain in the nest for about a month and frequently fledge in May or June.

Northern Saw-whet owl

The Northern Saw-whet, Flammulated and Northern Pygmy-Owls all prefer the same habitat, as they have been found nesting in the same tree in different years. Their preferred habitat is a combination of Douglas fir, aspen, ponderosa, junipers, downed logs, openings in the forest and a water source.

Northern Pygmy Owl

As for nesting, the Northern Saw-whet Owl begins nesting in March, the Northern Pygmy-Owls begin nesting in late April, early May and the Flammulated Owls begin nesting in May and June. All these owls have about a 30-day incubation period and their chicks remain in their nests for about 30 days before they fledge.

Flammulated owlet

The Flammulated Owls usually raise two owlets, the Northern Pygmy-Owls raise between two and five owlets and the Northern Saw-whet Owls if in a natural cavity have two owlets, but if they are using one of our nest boxes, they can raise as many as five or six owlets. This is because the nest boxes are much larger than a natural cavity, enabling more owlets to fit in the box and survive.

With the exception of the Flammulated Owls, the other species prefer to nest near water, as they often get dirty when capturing prey and need to bathe to clean their feathers.
 
Being insectivores, the Flammulated Owls migrate to Mexico in the fall, remaining there until spring and returning in late April to mid-May. Flammulated Owls prefer moths, larvae and caterpillars.