Twice in the last week a large owl has made nighttime attacks on the incubating Great Blue Heron at the nest outside our office. The female heron does not seem to have been injured by the attacks, which included strikes by the owl very close to the bird’s head.
The attacks were caught by our live-streaming nest camera, and we’ve put together the clips into a short video. The nest camera is very sensitive to low light levels, but even so the views of the attacking bird are brief and blurry. The large bird appears out of the blackness, approaching from below the nest and flying at full speed. It aims at the heron’s head and its momentum carries it almost into the camera. At about 1:35 in the video you can briefly see the owl perch on a branch beyond the nest.
We’re drawn to nest cameras for the intimate views they give us into the activities of the parents and the fragile new lives of their young. The uninterrupted observation is also a source of new data, particularly in the case of hard-to-study species such as Great Blue Herons. But these owl attacks are also a reminder that life as a bird is fraught with uncertainty and danger. Even North America’s largest heron is not entirely safe from predators.
What’s even more interesting than the owl’s brief appearance is the female heron’s defense. Before the attack, she rests quietly over her eggs, feathers sleeked down, her head resting against her body with her long neck folded underneath her. As soon as the owl appears she jumps to her full height, spreads her wings, and lets out a long series of grating screeches. As the seconds tick by, she settles back over the eggs in an entirely different posture—feathers fluffed, plumes erected, her neck extended, fully alert with her heavy bill at the ready. With her wings she forms a tent over the nest and makes herself look as large as possible.
Based on the size of the attacker, the habitat, and the time of night, we believe this was a Great Horned Owl. The diet of these large owls is typically about 90 percent mammals, according to Birds of North America Online. Although they hunt birds relatively rarely, the tactic of taking incubating birds from their nests at night is a fairly common one—Great Horned Owls have been recorded taking coots, ducks, loons, mergansers, and grebes in this way.
Great Horned Owls also sometimes take nestlings at night, meaning that there may be some danger of an owl attack later in the nesting season. For now, the attacks seem to have subsided—the last one was on Monday night. We will continue to watch the herons and hope for the best.
8 Comments
A couple of years ago in Prospect Park, Brooklyn, NY, I and other birders noted the remains of a Great Blue heron, mostly wing and those 14″ long primaries. Wondered what might have killed it. This attack presents a possibility. GHO where then nesting in neighboring Green-Wood Cemetery. GBH forage in both the park and cemetery, but none are known to nest in these parts of NYC.
Very intriguing. Was the owl actually hoping to get the heron? If so, that seems like a rather desperate move on the owl’s part; herons can be deadly wicked with those beaks. Of course, lots of Great Horneds have chicks they’re feeding now, so he/she might have been driven by that. Maybe they’ve been attacks of opportunity where the owl figures its worth a shot. Or, was it just checking for chicks that it could grab?
Whatever the case, it will be extremely interesting to see what develops!
Sad and scary, but common – I know of two instances where a GHO had taken over a GBH nest. Here are some pictures from Rhode Island: http://www.providenceraptors.com/?p=1951
I can’t Imagin the Owl missing. Is it possible that the Owl is protesting the Herons choice of nesting site close to it’s own?
Way to protect your nest, sister! Awesome job!
interesting. I didn’t know those type of attacks happened. I’ve also been watching the eagle cam at Decorah, Iowa, and a the female eagle was also attacked at night by a GHO. Does anyone know if this is a territorial thing or is it a predatory move?
We have several yellow crowned night herons nesting around our home. This morning we watched as a huge owl landed on one of the nests and sat there ignoring several herons screaming at it. I’m assuming it is eating the hatchlings? Not all though, because I can still hear some up there…
I believe the owl is slightly smaller, or that is what an ornithologist I know said as we have both species present in Golden Gate Park (she specializes in herons, and found the first colony of them in our city) Nevertheless, I suppose it is to be expected since great horned owls will indeed go after larger animals then themselves.