Sibling Rivalry pnarney@gmail.com
Staying cool
June at the nest began auspiciously with confirmation of three Osprey chicks and considerable food from George.
As they mature, the two oldest chicks, who are probably female because they have grown so large, are identified by their black heads and the beginning colors of feathers. Females at 20-35 days old are heavier and larger than males (Poole). Tentatively, barring any more definite sex characteristics, the two oldest are Thelma and Louise.
All the chicks fed until they were exhausted. When they are resting, they look like three chicken breasts in a row.
Babies in a row.
Life at the nest settled into a rhythm alternating feedings with naps.
Then things changed.
The two oldest and largest chicks, Thelma and Louise, who had hatched within days of one another, began to monopolize Gracie’s attention at feedings. They were demanding and greedy.
The latest arrival, covered in his grey down with no other colors, looked like a ghost. He was the runt. According to multiple sources, he could be as much as five days younger than the oldest chick.
The runt being feed. Thelma and Louise are just behind and to the left of him.
Based on size alone, he is very small. The runt is probably a male because males in the nest gain less weight than females but mature faster. Males usually leave the nest first and fish independently first (Poole).
The runt, because he hatched significantly later, was disadvantaged. He did not have the experience of fighting for Gracie’s attention and was not strong enough to force his way into the mix. When he tried, Thelma attacked, pecking on the runt’s head.
A peck on the head
That dominant chick, Thelma, was so pushy that before Gracie moved on to feed the next chick, Thelma dropped the food Gracie had just given her and grabbed the next bit that Gracie offered. Thelma did not even want her sister to get fed. This helped the runt who grabbed the fallen food.
Thelma stands tall and proclaims, "Mom loves me best!"
Resolutely, the runt, tried over and over again to make it to the front of the food line. He was rebuffed, pushed out, and pecked on. Bullied and beaten back, Resolute assumed a submissive posture. He moved as far away from the rest of his family as he could, frequently to the other side of the nest. He crouched, slumped his shoulders, and kept his head down. His flattened body disappeared into the nest.
And he waited.
Late in the feedings, when hunger must have forced him to move, he inched toward Mom, raising his head tentatively as he approached her. Only to be pecked again.
Resolve waiting his turn.
In previous years, we had observed the pecking behavior only once when there were four chicks in the nest and competition for food was intense.
But this year, there was more going on than just another mouth to feed. Searching for an answer, I went to Poole. Poole reports that a decrease in food to the nest is the only reason chicks will peck on each other.
I had been so focused on the chicks and their behavior that I had failed to notice that George’s food deliveries were farther apart. The large fish he had been bringing earlier were reduced to small bits and ends of fish. Was the availability of fish declining? Was something wrong with George? Was he injured, unable to fish productively or were there other reasons for the limited amount of food?
And, was lack of food the problem?
I didn’t have a clear reason for the pecking behavior. George did not usually fish in view of the nest. Using a tracker, I might have located his fishing grounds and gauged the size and frequency of his catches to see if food deliver was the problem. I could not count the number of times he brought food because I was not home all day every day. Not many eagles were around, so they weren’t stealing food. One of the frustrating things about being a Citizen Scientist is that too much of Osprey behavior is unobservable and/or unknowable.
Gracie was now using her begging call to get more food from George. She hadn’t begged previously. She also brought more sticks and moss. She began arranging the sticks in the nest. Was she contributing what she could to the family situation? Gracie could not go out and catch fish because she could not leave the nest unprotected for long. The entire family depended on George.
By Wednesday, June 9th, I was distraught. Watching Resolute being picked on, being submissive, being the last to feed, and sitting on one side of the nest flattened down with his head protected, was a sorrowful sight. Would he weaken and starve?
Don't poop on me!!
Interference was not an option. I wanted to borrow Joyce Reimherr’s full body Osprey costume, mount a ladder, and throw fish into the nest. Absurd. More harm than good would come from interfering.
I began selectively viewing the nest, waiting until the end of the feeding, and then screaming, feed him, Mom!!
The evolutionary development of Osprey promotes feeding two offspring, so the species survives. “Nature red in tooth and claw”, nature’s sometime brutality, is the impersonal reality of survival of the fittest.
I did not think Resolute would survive on the little bit of food he managed to get, but his crop was always full, indicating that he had fed.
As the temperatures rose feeding noticeably declined.
And so, it continued.
Every morning I steeled myself to look into the telescope and count, fearing that there would only be two chicks, or that Resolute, in his submissive posture, would not be moving at all. Ever again.
As an observer, this Osprey season has been grueling.
Time passed. Resolute grew. He is in the reptilian stage now, well behind his siblings in development but maturing.
Growing.
As he approaches the size of his siblings, Thelma and Louise, he asserts himself more. He moved in front of Gracie earlier on and stayed, demanding food. He even pecked on his tormentor, Thelma. Progress!
When is it my turn?
Resolute making his move.
Getting closer.
Success.
Resolute, I am as big as them now!
Gracie is now more aware of Resolute and is feeding him along with the others. Although he prefers to spend non feeding time on his own, crouched at the other side of the nest, he is intermingling with his siblings more often. And resembling them too in developmental stages: coloring, size and wing span.
George is bringing bigger fish.
The chicks are beginning to feed themselves, when Gracie drops food. Soon, they will be ripping into fish as soon as they arrive, not just picking up bits of dropped food.
Just one of the guys.
The chicks are discovering that they have large appendages that move, seemingly, without their control. Wing development is well on its way. They whack each other and their parents often.
Resolute and the others need to stay in the nest until they are ready to fly. Will Resolute be the first to leave the nest?
Time will tell.
*From the Tennyson poem “In Memoriam LVI”
Poole, Alan F. (1989) Ospreys: A Natural and Unnatural History. Cambridge University Press.