Nesting Behavior

by Prevost and Rogers
The Great horned owl is by far the most common owl in the Americas; they derive their name from the plumicorns on their head that resemble horns. We have been studying a family of great horns. We have never seen the two (male and female) together but we know they are a nesting pair. We can tell the difference between the sizes of the birds, the male great horned is much smaller then the female.  Another way we can tell the difference is the male’s call is far deeper. We have heard him calling to the female as well as to the bothersome crows that flock to the female.
Since these two are nesting pairs I felt some basic nesting information was in order.
·         Usually breeds late Jan-early Feb.- we heard mating calls from this pair in late December
·         Has an average of 2-5 eggs (30-37 days to hatch)- this particular pair had two chicks in 2011
·         The young hang around nest 2.5 months after they have left mothers protection.
The female currently has eggs in the nest. They should be hatching any day now. Just to get an idea of daily activities, we set up some cameras. The following show some of our data:
            05 Feb 2012
·         18:03- female leaves nest
·         18:15- female returns to nest
            06 Feb 2012
·         6:03- owl leaves nest
·         6:04- owl returns
·         8:14- crows disturb nest
·         4 crows arrive at nest at 9:03, stayed until 9:32
·         Crows return at 9:49, leave at 9:50
·         Crows return at 10:38, leave at 10:41
·         Crows return at 12:45, leave at 12:48
·         Multiple crows at 14:14, video ends at 14:38
17 Feb 2012
·         Owl leaves nest at 18:10
·         Returns at 18:13
18 Feb 2012
·         Movement at 7:48, too foggy to tell what exactly
·         Crow activity at 10:1, settles down at 10:20
·         Owl leaves at 18:05pm
·         Returns at 18:12pm
24 Feb 2012- We took a scope out to actually see what the owl was doing and where she was going when she leaves the nest.
·         18:22- female left nest and flew across creek into another section of woods
·         18:35- she returned to nest
·         Crow disturbs nest at 8:14am
These movements cause us to ask several questions. First of all, where is she going? Is she going to get food from the male? Where exactly is the male hanging out? With great-horns, the males will sometimes take turns sitting on the eggs. We have not observed this behavior. We will continue to gather data after the eggs hatch. Hopefully, we will be able to answer some of these questions. We would like to eventually be able to better understand the nesting habits of these owls. Perhaps if we can better understand their needs and behaviors, then we may be able to protect them.
Female peering over the edge of the nest.
One of the chicks from 2011.
Two chicks from 2011 with the mother behind them.
Check out the following two cameras:

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