Mission: To promote the appreciation of wildlife and increase harmony between humanity and nature.

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Saturday, August 13, 2016

Flight Feathers

Flight allows birds to escape danger and easily locate food. For osprey, flight is even more critical. Unlike our local bald eagles--who minimize their hunting effort by sitting in trees, soaring on thermals and stealing from competitors--an osprey actively hunts from the air. 

During the summer, I often see osprey circling Union Bay. They incessantly search the water from a height of about 50 meters. When they see a prospective fish they often stop and hover in place, constantly burning calories. At just the right moment, they dive. I suspect, the osprey are waiting for the fish to surface. 

Their high-energy hunting requires them to catch fish frequently. Their worldwide success and lengthy migrations are proof that this approach works. Their wings are the basis for their active lifestyle.

Does this current photo show one of our young Union Bay osprey in the nest, or one of the parents?

Their growing hunger makes it critical that young osprey learn to fly, and the sooner the better. The parents cannot, and will not, feed them forever. This fall, the adults will head South and the young must be ready to fend for themselves. Until they learn to fly, the young in the nest are sitting ducks. Local bald eagles could raid the nest, in spite of the adult osprey. I have also seen a red-tailed hawk, and a third adult osprey inspecting the nest. These birds are normally escorted away by the adults. 

However, as the young mature, the adults are leaving the nest for longer and longer periods. There may be multiple reasons for the adults' behavior. As the young grow, the adults must hunt more frequently to meet the growing demand for food. They may also be setting an example and encouraging the young to fly. Or maybe they need a little downtime from the constant begging. 

Luckily, for the osprey, I suspect our local bald eagles have left for their annual vacation. The eagles usually leave this area for a few weeks in late summer, just after their eaglets fledge. The absence of bald eagles might also explain the adult osprey leaving the nest for longer periods of time.

Lets review the progress of our young osprey; in particular, the growth of their wings.

Starting with this July 10th photo, we see fuzzy little wing feathers which may provide warmth, but not much lift. In general, the coloring of the nestlings does not yet look like the adults.

A week later, on July 17th, their dark eyestripe is becoming more visible and the white on the head is slightly more pronounced. Can you see the red-orange tint of the young bird's iris, compared to duller, yellow-brown color in Lacey's eye?

Tiny, dark-brown, buds appear in rows on the wings, like young plants in a Spring garden.

A week later, on July 24th, the young birds watch attentively as Chester delivers food to the nest. The size of Chester's wings, compared to his relatively small body, is truly impressive.

The budding feathers do not look a lot longer but the wings have grown. Also, if you look below the wing on your left you can see one of the wing feathers just starting to fan out.

When Chester delivers food he seldom lingers. He immediately leaves to search for more fish. It is interesting to note that his eye color is a brighter yellow than Lacey's.

The fanning of the budding feathers may be slightly more visible in this photo. The two dark spots in the air are meat-eating wasps, attracted by the nearly constant supply of sushi.

As the day heats up, the panting of the young birds increases. Also, as they grow, they spend more and more time focused on the world beyond the nest. I find their mottled coloring makes them harder to see against the broken sticks in the nest. I wonder if this is to confuse predators who might swoop in and remove them from the nest.

Five days later, on July 29th, this young bird's flight feathers are visibly longer and the wings are clearly larger as well.

By August 7th, the feathers have grown so much that it becomes challenging to distinguish the young bird from an adult. Although, there are a few telltale signs: The iris is still a brighter orange in color. The tips of many feathers are edged in white. (The white tips are not as durable as the darker areas, so they will wear away fairly quickly once the birds begin to fly.) Also, their brown feathers are a bit lighter than an adults'.

 Note: This is the same photo you saw at the top of the post. Can you answer the question now?

This young bird's feathers look almost developed, while...

...from a different angle, it or its sibling's feathers, still look ragged.

Exactly one month after the initial wing photo, on August 10th, their wings look nearly fully developed. I find the growth rate astounding.


The young birds are looking more and more like the adults.


While this is not the optimal angle to present the young bird, I do love the windblown crest around Lacey's head.

Here a two more shots of the quickly developing wings.

It will not be long now before the young fledge. The next step will be for them to learn to fish. I wonder how much teaching the parents will need to provide. Is fishing mostly instinctual? Will the young birds leave the nest knowing how to catch fish or will they hang around Union Bay, watching and learning from the parents?

There are still many interesting questions about the development of our young Union Bay osprey.

Have a great day on Union Bay...where osprey nest in the city!

Larry







4 comments:

  1. Was the perch a recent addition? Thank you Larry.

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    1. It was installed last year but the osprey did not choose to use it until this year after their nest on the baseball light pole was dismantled. You can read the complete history at the end of the July 15th post. http://unionbaywatch.blogspot.com/2016/07/something-to-celebrate.html

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