January 23, 2006
Adult Relationships
Nest Update: First, an egg update. At this point we have two eggs, and it's probably best if another is not laid at this late date, as it will put the eaglet at a major disadvantage in the nest, so we kind of hope we hold at two from here.
The interesting thing about the second egg was that it was the first one that was not laid in the early morning. Based on the photos we’ve seen, the female laid it sometime in the later morning or early afternoon. All her other eggs have come in the early morning hours, which is typical for a raptor.
For those keeping track, here is where we stand, assuming a 35-day incubation period:
1st egg laid: 1/17
Hatch date: 2/21
2nd egg laid: 1/19
Hatch date: 2/23
Previously in the web log I mentioned that in these early stages -- when there are just eggs in the nest -- the eagle parents share the incubating duties, with the female spending the most time at the nest. This arrangement gets more equitable for the female when the chicks are a few weeks old, and she can get off the nest more and share in the hunting duties along with the male. But in the beginning, the weight of the egg-sitting chores falls to the female.
In the book The Bald Eagle: Haunts and Habits of a Wilderness Monarch, the authors state that since the male eagles are smaller, they are the subordinate sex. And this size difference ultimately affects the dynamics of the couple's relationship, as they go about their duties of incubating the eggs and raising the young.
According to the authors of the book, "If Bald Eagle partners do not exchange roles frequently enough, the bird on the nest may call to its mate for a relief of duties. At one nest I watched in 1976, the female had been caring for the chicks for several hours and had repeatedly called to her mate; she would look in the direction where he was perched not far away. Finally, as if tired of waiting, she took off, circled around, and dived at the male, almost knocking him off the perch; she landed on a tree nearby while he went straight to the nest without a sound."
Female dominance can also be seen at mealtime. The authors relay that "It is common for males to have their prey taken from them by their mates, while on the nest or away from it...A female's response to a male bringing food to the nest is quite variable. Depending on her motivational state, she may either ignore him or be aggressive...Given the female's dominant role, there are times when the male is not allowed to eat on the nest. The male adjusts by feeding immediately after catching prey."
But not all encounters between the couple are ruled by domination. During courtship, the couples stroke each others back and neck, rub beaks, share meals at the nest, and perform aerial displays to cement their bond (click on the thumbnail image above). And this bond continues after the eggs arrive.
An observation of this type was sent in by Alice, one of our cam watchers, who wrote "Two years ago, while watching the eagle pair on the Northeast Utilities eagle cam, I witnessed the female eagle make a call and within a couple minutes her mate arrived. She stepped off the egg she had been sitting on for a couple days and showed him she had laid another egg (I had seen only one a couple hours earlier). Then she sat back down...they didn't change positions. My thought at the time was 'Wow, she called him just to show him they had another eaglet on the way. What a close couple they are!' I felt I had been lucky enough to be in the right place at the right time to witness other species communicating with each other!"
Each of these eagle stories reminds us that humans aren't the only species to have complex relationships; eagles also have their own unique relations that are a mix of genetics and personality. And knowing this just makes it more fun to watch each season unfold.
In our next post we'll talk about the newly laid eggs and the changes that are happening inside the shells as the eaglets slowly develop into baby raptors.
Until next time,
Lisa – webmaster
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