Too Much Disturbance

It is too early to know for sure, but there is a good chance that the great horned owl pair may soon abandon the nest that they have used for the past four years. What is most troubling is the fact that there are already eggs (maybe chicks) in the nest. We were hopeful for a good season of observations.

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There has been a major deforestation effort on the private farm land where the nest is located. This “timber management” (a term used very loosely) has called for hundreds of trees to be taken down. These trees are important to the owls not only to provide coverage while roosting and hunting, but also to provide protection to the chicks from predators (i.e. crows and hawks). By December, we were thinking that the owl pair would probably be forced to find another nest. However, she proved us wrong by returning.

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The deforestation is ongoing, and this past week, they were cutting trees around the nest. We noticed that four trees in close proximity the nest tree had been cut, and the female was not in the nest. After seeing her incubating the past three and a half weeks without moving, this was disturbing. About 20 minutes after arriving, we heard crows mobbing, and knew she was close. We soon spotted her with our scope. For the next two hours we watched as she tried to make her way back to the nest while being chased and harassed by crows. This is encouraging for the simple fact that she was so intent on getting back; obviously, there must be eggs or chicks. She did make it to the nest once, but left after the chainsaws fired up.

Even if the nest tree is not cut, the chances for chick survival have decreased dramatically because of the loss of coverage. At about five weeks of age, the chicks start “branching,”which is basically moving out of the nest onto branches. They do this until they are bold enough to start flying short distances from the nest. This behavior is critical for their long-term survival. However, “branching” and fledging leave the chicks exposed.

There is no way to predict what exactly will happen. We will continue to monitor the nest. There is not much research that analyzes exactly what type of forest cover great horned owls need. Thisabstract indicates that ideal cover would be between 36-65%.

For basic information on great horned owl biology, thisis a good site.

Updates will follow.

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