Mom and the Subadult: As The Nest Turns

Prepare for another edition of ‘As The Nest Turns’, an episode that opens with the subadult eagle delivering a stick to N1 (! Where is DM2? Is the subadult interested in Mom? Is Mom interested in the sub-adult? And why is nest work – if it is nest work – occurring so early? We went to our eagle council with the following questions about DM2. Could he have migrated? Did his ‘shyness’ around Mom indicate a weaker pair bond (followers might recall that she topped him in most of their encounters)? Could blackflies drive a territorial eagle away and would it return once the blackflies died down?

Eagle researcher and expert Jim Grier replied that the traditional idea about bald eagles mating for life is not correct. Research indicates that eagle ‘marital’ life can be much more complicated, depending on the eagles. He said “I’ve considered bald eagle mating to be more like humans, where some pairs stay together throughout life but others don’t. Partnerships last variable lengths of time, from mated for life to promiscuity at the other end of the spectrum.”

How about fidelity to nest sites? Again, from Jim: “Some individuals stay at the same nest sites for long periods and others don’t. Moves might result from competition, fighting, or even variation in individual personalities. Eagles can be aggressive, timid or submissive (as we saw with DM2), or unwilling to form partnerships.” He added that some eagles just leave, although we rarely have complete enough data to know for sure what happened in any particular case.

Did Dad just leave back in 2018? It seems extremely unlikely, since he had held the territory since the early 2000’s and was a devoted companion to his first mate and to Mom. But DM2 was a new arrival. He (shyly) mated with Mom, produced children, and helped care for them, but the last time he was seen was June 27. We didn’t see the sub-adult until July 12, which, while we don’t see everything that goes on in the eagle world, makes it less likely that he drove DM2 off. No one in Decorah reported an injured or dead eagle to us after DM2 disappeared and a few searches, a hundreds of eagle fans, and people fishing along Trout Creek didn’t turn up anything. Could he have taken off? Did the blackflies play a role? Did he have a relatively weak bond with Mom and the territory? Given what we know about eagles, he may simply have left. We’ll see if he returns.

Where do we go from here? Please feel welcome to join us on the confusion couch as we wait for all of this to play out! Eagles instinctively build nests and engage in stick play, but it seems unlikely that the sub-adult is bringing sticks in only for himself. In addition to programmed behavior (I must build a nest!) he may be seeking to impress Mom and deepen their bond with his commitment to nest building. Whatever happens, we’ll be watching and learning. Go eagles!