Wednesday, January 21 2009 @ 04:31 PM EST
Contributed by: davidh
Bald eagles mate from the time of returning to the nest territory in early fall through egg laying, and sometimes a few months after. Like all raptors that I know, the mating takes place when the female is securely standing on a perch, usually a high tree limb, and the males gently lands upon her back, using both his wings to carefully balance, and then curling his tail and cloaca under the female’s tail, which she has simultaneously moved to the side as she turned her cloaca upwards so the two cloaca touch face to face. The sperm passes from his cloaca to hers and then travels up the oviduct to meet the downward flowing ova for the ‘meeting’, the fertilization.
What great moments of trust. These great predators who can instantly kill prey with the sharp and powerful talons are now, so gently and trustfully, coming in direct contact. The trust that allows the female to accept the male's killing talons onto her vulnerable back is quite extraordinary – but it is an essential and ultimate act of the bonding that has been developed between them. No bonding, no trust, no mating, no young, no species!
Lets go back: The Pre-nuptials!!
On October 9, 2002 1030: I was at our Blaine, WA warehouse and heard an adult bald eagle scream – I immediately ran outside as this was the first record of the eagles return since their departure in mid-July when they left the nearby nest with the young. But the intensity and pitch of the call was most unusual. It was the male's higher pitch but the intensity and constancy of the calling was unusual. But I could see no other birds around or direction to his intentions. This was their favorite hunting perch overlooking Semiahmoo Bay so I was used to them being here.
The male continued his calls almost non-stop for over an hour when all of a sudden he changed the pitch and intensity – something was up and I darted outside to see what. He was now standing horizontally on the branch, his head stretched outward to the southern shore of the Bay and his calls were quick and loud. Within a few seconds later and I could focus on the source of his calls – another approaching adult eagle – headed straight at us. The approaching bird stared to scream and it was obviously a female by the deeper call, she circled the calling male and landed on the adjacent tree about 80 feet away. Both birds kept up the calling, and within a few seconds it developed into a “unison” call, with both birds doing the same thing at the same time. Each bird arched its head forward and then upward and backwards over it's shoulders so the head followed about a 180 degree arch – all the time calling in unison. .
I was mesmerized. I had seen this intense behavior before but always later in the year and as a prelude to mating. Within a minute of these unison calls the male took off, flew directly to the female's tree and lighted beside her. Here they continued, even increased the intensity of the calls and head throwing, always in absolute unison. Then it happened. The male jumped up on the female's back and they mated. This was October 9. This was approximately 5 months from her first egg. What was the explanation?
I believe I just witnessed the return of the pair to their nesting territory from the short ten week fall northern migration. But what a reunion, what a reaffirmation with incredible vocal intensity, all taking place on their two favorite hunting perches, and then the ultimate, mating. What a climax to the event.
We know that eagles build and intensify the mutual bond between the pair through aerial displays, and particularly through the described mutual vocalizations and displays. But what I think I witnessed that day was the actual moment of their arrival back at the nesting territory after their separate northern sojourns at the end of the last breeding season, their re-confirmation of the bond, their reconfirmation of each other. In 55 years of eagle watching I have seen a lot of eagle courtship, all the aerial flights, the mutual calling and many matings. But never have I seen it done so intensely, and never so early in the year.
Just 40 miles south of Blaine WA, on the Skagit River, the USF&WS had banded a pair of adult eagles with solar powered satellite tracking devices. Sadly their two young were not tagged. But the story of the adults northern migration was quite astounding. The normal pattern of fledging occurred. The adults quit feeding the eaglets in the nest, after about 3 - 5 days they get hungry and make their first flight with the concerned parents watching. After another week of flying around the nest territory, sometimes picking up food that the adults have been eating nearby, the adults simply fly off and leave the youngsters to their own fate. Harsh but obviously successful.
But this story is about what happened next to the adults. The male, now being tracked by his satellite .....