Editor’s Note: Osprey Cam has been a popular feature for five years on The Nature Conservancy’s web site. Viewers enjoy a 24/7 look at the life of nesting ospreys. This year, though, a surprise occurred. A bird was nesting, but it wasn’t an osprey! What’s going on?
David Mehlman, Director of the Conservancy’s Migratory Bird Program, shares more information on why there’s an owl on Osprey Cam.
You’re seeing things correctly. This year’s Osprey Cam nest is occupied by an owl! A Great Horned Owl has occupied the Osprey’s nest, which I personally find fascinating.
As someone who studies the geographic ranges of birds, the Great Horned Owl has always intrigued me because of its enormous range. It is found throughout the Americas, all the way from far northern Canada and Alaska, through Mexico and Central America, to very southern South America in Patagonia. And, it is found from sea level to well over 4300 meters (over 14,000 feet)!
That distribution is one of the most widespread of any native species that we have. It also has an equally large diet, eating everything from insects to medium sized mammals and large birds; having said that, about 90% of its diet is mammals. In many parts of North America, they are famed for having an inordinate fondness for skunks. To top that all off, although the Great Horned Owl, like most owls, is primarily a nocturnal predator, it is known to forage in the daytime. Nothing is safe!
One unique feature of the Great Horned Owl, though, is that it does not build its own nest. This is the primary reason that we are seeing it in the Osprey’s nest – it has taken that nest over from its true owner. Most commonly, Great Horned Owls nest in nests that were actually built by other tree-nesting birds, such as hawks, crows, and ravens. If there are no trees, the Great Horned will nest on rock ledges, snags, buildings, artificial platforms, and even on the ground.
Since the Great Horned Owl is so widespread and found in so many habitats, they are somewhat nest site limited so are forced into using whatever is available to them where they are.
But, lest you think that the owls are nest thieves, there is one aspect of the Great Horned Owl’s biology that makes it likely that the owl did not “steal” the nest or displace another occupant. Great Horned Owls generally begin nesting very early in the year, often in the middle of winter.
At that time, most of the species which build the nests are many months from beginning to nest. So, Great Horned Owls are almost always either using an abandoned nest from prior years or an old nest from the previous season.
In the latter case, if the rightful owner comes back and finds an owl in its place, the nest builder can go off and easily build another nest in a nearby tree. I suspect that is what happened in this case, that the owl began to nest early, before the Osprey had returned, and that’s why the Osprey nest turned into a Great Horned Owl nest. We’ll have to wait until next year to see if the Osprey comes back or whether the owl renews its “lease.”