Living on Osprey Time
2022 Volume 2 Issue 8
Pam Narney email@example.com
After twenty years of watching Osprey, from casual observer to fanatic, I have seen aggressive sibling behavior in only three mating seasons. Once in the distant past, last year, Nature Red in Tooth and Claw and again, this year.
In 2021, George and Gracie had three chicks. Even though Resolute hatched last, was picked on, and got the last scraps of every feeding, he fledged. Often the first-born chick’s aggression was so gruesome, I stopped watching before the feeding periods ended. Apparently, when I wasn’t watching closely, Resolute ate enough to survive.
I did not see any reasons for the aggression.
Do two years in a row signal a trend? Something wrong with our Osprey pair or in the waters of the Chesapeake Bay? Are fish scarce this year? Has the weather been too cold too long? I have no specific answers. I can only describe Osprey behavior this spring on Placid Bay.
This year, after the eggs hatched, I conducted dawn-to-dusk observations of the actions at the nest for two weeks from May 26 to June 8, 2022. I had over 200 hours of minute-by-minute observation notes and over 800 pictures.
With only two chicks to feed, sibling rivalry should have been reduced or eliminated entirely. That was not the case.
Will an in-depth look at this Osprey family reveal the reasons?
What follows is an intimate view of Osprey and the behaviors I observed.
Some behaviors point to food insufficiency.
Feeding patterns changed
About half the time when a fish is delivered, Gracie feeds herself first. Not so unusual, she has to keep herself alive. In past years she generally fed the chicks first and herself last. Now she regularly feeds herself first, stops in between feeding the chicks to feed herself again, and frequently ignores their open beaks.
Begging calls changed
Begging calls increased this year in intensity and frequency. They were hard to ignore.
Gracie usually started begging immediately after she and the chicks finished feeding. Usually begging calls end when everyone has fed. I was listening from dawn to dusk, and the sound grated on my nerves. Begging call https://www.youtube.com/watch?v=4eRUsTgU4lk
Even the chicks made begging calls. This was the first year I noticed chicks begging so early in their lives.
Naturalists assume the purpose of begging calls is to attract the male’s attention and urge him to deliver more food. What else can a hungry mom do?
These calls did not have a recognizable cause-and-effect pattern, they happened before food delivery, after food delivery, or just because.
Begging calls did not affect George. He did not fly over the nest or immediately leave his perch to go fishing. According to Poole, this is typical male Osprey behavior.
If begging calls don’t elicit food, then, why do them? Begging calls reveal more about the degree of motivation of the caller and less about the effect as a signal to a listener (Bierregaard).
George ate a fish right in front of the nest, ignoring begging calls and eating until he was full. My neighbor texted: “Why doesn’t he feed her first?”
Gracie is off the nest more
Osprey have a gender-based division of labor. The male supplies all of the fish: the female stays on the nest feeding the nestlings. Generally, she does not leave the nest often, and almost never to fish. Her usual absences lasted one to two minutes.
Twice in two weeks she left to fish, leaving the chicks unprotected. She stayed in the bay, close to the nest, head and eyes focused down, flying in circles and then hovering. She attempted one dive, but aborted the dive before she hit the water.
If there was enough food, why would Gracie try to fish, when it is a rare action for a female with chicks in her nest?
In the past two years George quickly guarded the nest and chased threats away. Now Gracie often protected the nest alone. Twice she flew off the nest chasing eagles.
Once, a lonely male tried to take George’s place by hovering over Gracie and lowering himself, attempting to mate? George was not around to help her.
Gracie also flew off, after periods of extreme begging calls, toward George’s known perch. Once she flushed him out, forcing him to the nest with his fish.
She spent an inordinate amount of time bringing sticks to the nest and rearranging them. Normally, Osprey continue adding nesting material to the nest all during the nesting period, but Gracie does it more often.
She brings sticks big enough to bop the chicks on the head. She once moved one very large stick and placed it in four different locations making a complete circle around the nest until she was back where she started.
Giving her human traits, she seems to be redecorating the house because she has no power to do anything else. She is doing something to contribute to the welfare of the family.
Where is George?
George is mostly absent during the two-week observation period.
He is not hanging out on his usual perch. Early in the nesting season, during incubation, he caught fish on the first attempt several times close to the nest. One catch was about a 14-inch catfish. Lately he has not been fishing in Placid Bay. This might mean that fish are less abundant than usual, and he has to travel farther away to find fish.
Once the eggs hatched, and my minute-by-minute observation began, George was more absent.
Toward the end of the two weeks, George was seen more frequently while fish deliveries remained steady.
Fish deliveries were:
· two days with 6 deliveries,
· eight days with three deliveries and
· four days with four deliveries for an average of 3.7 fish deliveries.
· the number of fish delivered (some very small pieces),
· duration of feeding sessions (some very short), and
· length of time between deliveries (erratic).
That’s data for another blog.
Placid Bay on Mattox Creek, off the Potomac River near the Chesapeake Bay, had many storms this spring. Some days had zero visibility.
Were fish scarce or were fishing conditions poor?
“This has been a cool spring and a slower migration of fish has followed. (causing) a slight delay in arrival of many species…” (Pipkin).
Was food scarce? Do these behaviors point to food shortages?
The story continues with the chick’s behavior. Read “The Chicks Are At it Again” in the next issue.
Bierregaard, R. O., A. F. Poole, M. S. Martell, P. Pyle, and M. A. Patten (2020). Osprey (Pandion haliaetus), version 1.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.osprey.01
Pipkin, Billy. The Fishing Line. Rivah. June 2022 p. 30.
Poole, A.F. 1989. Ospreys: A natural and unnatural history. Cambridge: Cambridge University Press.
Osprey-watch.org Nest 168