April 14, 2021 Issue 6
Dating, Mating and Creating: What Nest Behavior to Watch for Now
The happy couple
We have already talked about dinner and a movie, the courtship rituals. The male keeps the female satisfied and close to the nest by feeding her often and warding off any unattached but eager males. Alan Poole’s research shows that Osprey are wedded to the nesting site more than they are to their mate and return to the same site every year. Osprey mate for life and can live to be 25 years old. Generations of Osprey can return to the same nest
Mating almost always happens in the nest probably because that is where the female spends most of her time. My observations of copulation lead me to believe that mating in a tree would be really tricky, due to the lack of open flat space for landing.
If receptive, according to Poole, the female stands up, tips forward with raised tail and drooped wings as the male flies in and lands on her back. She might tip her head down, as they copulate. It happens so quickly; I wonder if she knows what happened. If she is unreceptive, she leans to one side and he slides off her back, so precarious is the whole event.
Although mating is frequent Poole reports, and pairs mate most frequently just prior to egg laying, the act lasts 10 to15 seconds, making it difficult to get a photograph. By the time the Osprey observer realizes what is happening, it is over.
We finally mounted a camera on a tripod in our living room aimed at the nest. As soon as we noticed mating begin, we jumped up, turned on the camera, and took pictures. This went on for weeks until we were moderately successful.
The beginning
Finished
Total elapsed time 10 seconds
Huh?
Our established Osprey are some of the earliest to return from South America to their nest, so they have an advantage. They are equipped with a nest, an experienced mate, and both Osprey have experience with mating and raising a family. Because they are at the nest early, building it up, and mating earlier than later arriving Osprey, they should have the earliest eggs, and therefore, the earliest chicks. These chicks have the most time to get ready for their migration.
The chicks benefit by having a longer time with Mom and Dad to be feed, to practice flying, and to learn to live on their own.
This year’s chicks will not return to Virginia for at least 2 years and may not mate until they are 6 years old. When the juveniles do try to nest and mate for the first time, the results are often unsuccessful and sometimes comical. We watched an Osprey pair bring hundreds of sticks to a site atop a local electrical pole. In order to protect Osprey and provide electrical power, the power company attached two flexible cross members atop the pole. Those cross members would not support an osprey nest.
Are there any eggs yet? Unless you have some fantastic unobstructed overhead view of the nest, you have to rely on the female’s behavior.
Behaviors to watch for in early April happen at the nest. Stick delivery is replaced with offerings of softer material like moss which protects and softens the lining of the nest cup which will hold the eggs. This year April 7 was the first time we saw behavior that would indicate eggs, but Gracie's behavior was inconsistent. We had to keep watching. There is more frequent copulation and, most important, if she is sitting on eggs, the female is hunkered so far down in the nest that she is almost invisible.
Getting comfortable
Almost invisible?
You have to get your binoculars or scope trained on the nest and watch for several minutes. In our early days of Osprey watching, often we could not find the female anywhere. Now we know to look for that little bit of white on the top of her head or the tip of her tail. Keep staring until you see either one of those body parts move.
Invisible?
Osprey usually lay between 2 and 4 eggs. The female does most o the brooding because she has developed a special brood patch (fluffy soft feathers on her abdomen). The brood patch also provides heat.
The Osprey parents look kind of funny when they reposition themselves to sit on the eggs because, as they ease themselves down and flatten out, it might not feel comfortable the first time , so standing up and sitting down again helps.
When eggs are in the nest the female will seldom leave while the male continuously feeds her. The male will sit on the eggs when necessary. Both parents will turn the eggs in the nest. It is exciting and humorous to watch them make the change. They turn their talons under and move carefully but awkwardly around the sides of the nest before the exchange is made. The newcomer wiggles, wriggles, and shakes until the fit on the eggs is just right.
Our Gracie has been on the nest since April 13, and she will remain there until the eggs hatch in about 35-40 days.
This is the rather boring time on the nest. I wonder if that’s why they call it brooding?
Be patient. The waiting wets our appetites for the fantastic show of watching the chicks grow and develop.
A late spring snowstorm Too cold to even think about starting a family
Figuring out the exact date of egg laying depends on the presence of chicks, which are difficult to see shortly after birth.
Determining the date of the birth of chicks also relies on behavioral patterns. After the female has finished eating, if she backs up off the nest and dips her head down repeatedly, she is feeding chicks by ripping bits off of the fish. That hawk beak comes in handy. It takes a while for the chicks' heads to be visible. Watch for movement. Once you see chicks, you count backwards for 34-40 days and make your best guess.
Osprey Nesting Time Frame
First Egg Laid--2-4 eggs (1-3 days a part)
Incubate Eggs—five weeks (34-40 days) eggs hatch 1-5 days a part
Chicks Brooded—10 days
Chicks flap their wings—3-4 weeks
Young start to feed themselves—6 weeks Mom may leave to hunt
Chicks Fledge—8-10 week (another source said 7-8 weeks until their first flight)
The male quickly goes to the nest to sit on the eggs while Mom retires to a pier piling or tree branch to eat. If there are chicks in the nest, the fish is delivered to the nest where Mom eats first and then feeds the chicks last.
Because they are good parents, the Osprey nest is never left unattended for long. If the male is gone, either fishing or chasing off threats, the female is left alone to protect the nest. If she feels threatened, she will leave the nest and her eggs to chase the intruder, but will not be gone for long nor will she travel far. Just about the time you think she has been gone too long; she is back. If something threatens too closely to the nest, she is back in a flash, and the male is right behind her.
Artificial Osprey Eggs in a Created Nest
And now we wait!
Comments or questions pnarney@gmail.com
Poole, Alan F. (1989). Ospreys: A Natural and Unnatural History. ISBN 0 521 30623 X.