Who’s There: How Many Chicks in the Nest?
Volume 2: Issue 7
Pam Narney firstname.lastname@example.org
Four days of rain and fog prove that bad weather equals poor fishing.
It rained on May 12th, the 35th day Gracie has sat on the nest incubating eggs. Once laid Osprey eggs should hatch between days 35-42. The eggs should hatch soon.
The clutch size for Northern Osprey is 3-4 eggs. Our pair had four eggs once in twelve years. All four fledged. The average is three.
Gracie knew something was about to happen. She was off the nest a lot, calling to George. But to no avail. Researchers say that the male does not respond to the begging call. He has his own timeline for hunting.
While waiting, Gracie turned her talons under, minced carefully around the upper edges of the nest, and kept looking for George’s arrival or for any changes to the eggs.
After half an hour waiting, Gracie flew off the nest, back into the nest, sat down in the nest cup in brooding position, flew off again, sat down again, and repeated the sequence in a short period of time.
Gracie walked around the edges of the nest and looked down. Gracie must have heard something.
Two days later on May 15th, Gracie was agitated. However, she was dropping her head into the nest, which is basic feeding behavior, indicating she was feeding a chick.
Our nest is located even with our deck, so we can’t see down into it. We have to rely on George and Gracie’s behavior. We think that at least one chick hatched; later behavior showed possibly two.
Gracie repeated her begging call, over and over. Not much food arrived. Torrential rains made fishing difficult. Dense morning fog did not help. Osprey have to see fish to catch them.
Once Gracie flew off the nest and tried to catch a fish. This is not normal behavior for a nesting female. Her job is to stay in the nest and feed the chicks. George’s job is to supply fish.
Later she stopped her begging call and flew over to George in the loafing tree. One routed, George delivered his half-eaten fish to the nest.
Chicks triple their body weight in the first eight days of life. From the ninth to the 13th day of life, the chicks double their weight. To survive, Osprey need sustained food deliveries after birth. These first two weeks are their most critical growth periods, and the food supply was reduced.
Averages for Osprey Growth and Development Periods
Osprey Body Weight
Darker body feathers appear
30 days old
Achieved 70-80% of their total body weight
By Monday, May 21, food delivery was regular. Gracie had a system to feed herself and the chicks. She ate a bit of fish, then bobbed her head into the nest cup: one for you, one for me, and repeated the movements. She bobbed her head in two different places, so we think she had two chicks.
George doesn’t feed the chicks. In between hunts, he sits on a piling, close to the nest, watching. George has been more attentive than in past years when he dropped off the fish and disappeared.
A male Osprey usually brings four to five fish to the nest a day. On average, it takes him thirty minutes for one hunt. He spends 20 to 30 percent of his day fishing, which exhausts his energy for the day. Fish delivery doubles and triples in the first 20 days after a chick is born.
The male does not lose much of his body weight during feedings. Average weight loss for the female is 10-15 percent of her body weight. If the female loses 30-40 percent of her body weight she will abandon the chicks and save herself.
When not fishing, George is on his loafing tree.
When everyone was fed, a huge hunk of fish remained uneaten in the nest.
And baby makes three?
Gracie spent a lot of time rearranging sticks to make the nest cup bigger and deeper.
Are there three chicks?
By Saturday, May 21th, we can almost see, or believe we see, heads. I believe I‘ve seen three, but my husband John has only seen one. That makes a definite two.
If there are three, the timing of this year’s egg hatching--three chicks withing five days--is more typical of Osprey.
Last year, the runt was nine days behind the first hatchling, which caused sibling rivalry and the runt‘s hard road to survival.
Ninety degree days arrive. Too hot for chicks.
Time will tell as life at the nest continues.
Poole, A.F. 1989. Ospreys: A natural and unnatural history. Cambridge: Cambridge University Press.
Poole, A. F., R. O. Bierregaard, and M. S. Martell. 2002. Osprey (Pandion haliaetus). In The Birds of North America, No. 683 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.