January 13, 2007
Eagle Mating
In the past week, we've been fortunate to witness several mating sessions by the eagle couple while they were perching on the osprey platform -- the latest on Saturday morning.
This is the first time we've seen this behavior on the Osprey Cam, and these shots also beat out any that we've had of mating behavior on the eagle nest, so we're very excited that our cam watchers were able to capture these photos.
We've had some cam watchers write in with questions about the mating behavior, so I wanted to write a web log entry that discusses this topic.
For a long time it was believed that eagles mated in the air, while they were cartwheeling or sky dancing. But the aerial displays are really a prelude to mating. Once the eagles are ready to mate, they will then take to a tree branch or to their nest and then mate there, using the nest or branch for support.
During the mating session, the male curls his talons up so as not to hurt the female and mounts her back. And the female moves her tail to the side so copulation can occur.
In the book "The Bald Eagle," eagle biologist Mark Stalmaster says, "Copulation takes place in as little as five to fifteen seconds, but can last one to two minutes, and may occur several times a day. Most copulations occur from six days before to three days following the laying of the first egg. Sex is more common in the early morning hours. The sex act, however, has been observed after construction of the nest, and might even happen outside the breeding season."
Stalmaster also relates that "After union, the pair may perch together again, preen their feathers, and they may fly to the nest to arrange nest materials." In our recent mating sequence, we can see the eagles perching and preening after their mating session.
Several cam watchers have asked why the eagles are not mating on the Eagle Cam nest. We have seen at least one photo where it appeared the male was on top of the female while in the nest, but it's important to remember that the eagles seem to look at the osprey platform as a favorite "perching tree," and so they are comfortable mating there as well. The eagle pair have never shown any interest in nesting on the platform for various reasons, such as it is too open to the surrounding environment, it is too close to people, and it is not high enough or deep enough. Some bald eagles have been known to nest in artificial osprey platforms, but it's pretty rare, especially if there are natural nesting trees available in the general vicinity.
White Pine
Before I close this entry, I wanted to mention the white pine sprays that have recently appeared in the Eagle Cam nest. One cam watcher wrote in to ask about their purpose. Mark Stalmaster reports that "Interestingly, bald eagles will bring fresh leafy sprays to the nest, not for use as part of the structure or lining of the nest, but as a sort of decoration on top...In Minnesota, nests almost always contained a sprig of white pine even though red pine was the more common tree species in the area. Why eagles chose white pine is not known." Stalmaster goes on to discuss other odd items that eagles have brought to their nests and speculates that "they serve as an advertisement that the nest and territory are occupied and tell interloping eagles to stay away. The fact that a piece of green and fresh vegetation is kept at the nest indicates recent activity there." So the fresh sprays might be a way of saying "This nest is taken."
We want to thank everyone for their questions and photos. We're feeling very hopeful that our eagle pair will soon produce eggs within the next couple weeks, and we hope to have another exciting opportunity to watch little eaglets come into the world.
Until next time,
Lisa - webmaster
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