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

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Sunday, February 9, 2020

An Eagle's IQ

Marsha and Monty are the newest pair of Bald Eagles that nest on Union Bay. Marsha, on the left, is slightly larger and her white head feathers never seem as clean as Monty's. 

They often sit on top of the old world cedars just north of the Waterfront Activities Center (WAC). This location, on the southwestern shore of Union Bay, is obviously their favorite hunting roost. By clicking on this Union Bay Map you can get a more precise idea of the location.

(Roosting locations for all three pairs of Union Bay Bald Eagles are indicated by white diamonds. Clicking on the diamonds will bring up clarifying descriptions. By the way, a significant number of other updates have been added to the map.)

This is Monty struggling to break a branch off a cottonwood tree near their nest on Sunday.

Marsha, being larger, has less of an issue procuring a branch from a cottonwood tree on the north side of The Cut.

Currently, the Montlake Cut nest is not too impressive. Last years nest, as well as their original 2018 nest, fell apart as the eaglets grew. The resulting struggles of last year's young can be read about in these posts:



Once again, the parents are rebuilding the nest on the southeast corner of the Montlake Cut. By the end of March, the nest should once again be at least large enough to hold Marsha and this year's eggs. Marsha and Monty get credit for their tenacity, but their engineering and construction skills are still a bit suspect.

By the way, do you know why their nesting location may be the best nest site in King County? 

This October photo shows their nearest neighbors, Talia and Russ. This pair nests on the north side of Union Bay, in the old Talaris property. However, they commonly roost in the first cottonwood immediately north of the WAC. This roost is quite close to where Monty and Marsha prefer to sit. Both locations are shown on the Union Bay Map.

By mid-winter, the leafless tree looks pretty bare, but it is almost always the same pair in the same spot. Even the winter wind does not disturb their hunting focus.

A couple of years ago, I watched Russ pulled grass from an offshore island. He then carried it directly back towards their Talaris nest, which certainly helped to validate which pair I was watching.

The next week, when the sun broke through they landed on the nearby log. Both of them called out their greetings. Clearly, this little island and log are in the southern part of their territory.

Commonly, when an eagle from either pair heads directly out over the water, all four of these eagles take to the air. There is lots of circling, diving and calling as they enforce the invisible boundary between their territories.

Lately, I have occasionally seen Monty or Marsha wander over the line apparently looking for food, whenever Talia and Russ were not nearby. Often, the northern pair will notice the incursion and the two of them will come streaking across the bay to chase the invader away. As apex predators, eagles tend to take whatever they can easily get. I have never seen them actually fighting. Apparently, intimidation is less risky.

During the last few weeks, there have been as many as five Bald Eagles in the cottonwood tree on the north end of Foster Island. Most of them appear to be immature, like this one, which is most likely a second-year eagle. From the second through the fourth year immature eagles are generally as large as adults, but size does not translate to skill. Mature eagles must learn to be capable hunters in order to feed themselves and their hungry offspring.

This secondary hunting roost on Foster Island typically belongs to Eva and Albert. It is also shown on the Union Bay Map.

Eva and Albert are the local Bald Eagles that nest in Broadmoor on the south side of Union Bay. They generally defend Foster Island, the 520 light posts, Duck Bay and the Arboretum. 

I suspect the five eagles are hungry transient eagles stopping by to hunt for food. Last Saturday, as we watched, one of the young flew out over the bay and dived at American Coots. Finally, it wore itself out and gave up. I have seen adults fly out over the bay, pick off some food and return with no visible delay.

The young are not all the same age. This one looks like it may have an eyestripe indicating it is most likely a third-year Bald Eagle.

Last Saturday, I believe I saw Eva and Albert circling overhead high above the transient eagles. I suspect the reason they did not attempt to drive them out of their territory is simply a matter of numbers. 

This week's best example of an eagle exerting its influence, when the odds were in its favor, was sent in by Jeff Graham.

A male Common Merganser, on the left, approaching a female.

Jeff sent in the following photos and reported, "...A common merganser came up with a fairly large fish. Just then a gull aggressively flew at it and the merganser dropped the fish. 

The gull plucked it out of the water. It flew over to the dock just off the boat rental building. 

A mature eagle flew right at the gull and the gull dropped the fish on the dock.

The eagle came down and ate the fish. So interesting to watch....The eagle flew off to the nest tree across the Cut when it was done eating."

Thank you, Jeff!

The Bald Eagle in Jeff's photos was operating in Monty and Marsha's territory. It flew to their nesting tree and sure looks like Marsha to me.

By the way, Marsha and Monty's nest site is optimally placed because the complete Lake Washington watershed drains through Montlake Cut. This means all seagoing fish that enter or exit the watershed must pass below Monty and Marsha's nest. Looking down from a hundred feet in the air, with the sun behind you must make the migrates quite easy to see.

When it comes to nest building Monty and Marsha may not be engineering geniuses but in regards to site selection, they are certainly sitting on the upper side of the bell curve. Mature Bald Eagles often catch prey on the first pass, consistently extort fish from smaller birds and carefully choose when to defend their territories. It may be impossible to accurately estimate an eagle's IQ, but it is obvious they calculate optimal odds with ease.

Have a great day on Union Bay...where nature lives in the city!

Larry

Going Native:

Without a well-funded Environmental Protection Agency, it falls to each of us to be ever more vigilant in protecting our local environments. Native plants and trees encourage the largest diversity of lifeforms because of their long intertwined history with our local environment and native creatures. I have been told that even the microbes in the soil are native to each local landscape. I hope we can inspire ourselves, our neighbors and local businesses to respect native flora and to support native wildlife at every opportunity. I have learned that our most logical approach to native trees and plants (in order of priority) should be to:

1) Learn and leave established native flora undisturbed.
2) Remove invasive species and then wait to see if native plants begin to grow without assistance. (If natives plants start on their own, then these plants or trees are likely the most appropriate flora for the habitat.)
3) Scatter seeds from nearby native plants in a similar habitat.
4) If you feel you must add a new plant then select a native plant while considering how the plant fits with the specific habitat and understanding the plant's logical place in the normal succession of native plants.

My intention in my weekly post is to include at least one photo each week and visually challenge us to know the difference between native and non-native lifeforms. 




What species of duck is this? Is it native to our area?













Scroll down for the answer.














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Ruddy Duck: This is the more subtly-colored female of the species. The shape of the female is virtually the same as that of the male. Both, have a relatively large head and bill with a fairly long and stiff tail. They are native to Washington and most common in our area in the Winter.














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The Email Challenge:

Over the years I have had many readers tell me that Google is no longer sending them email announcements regarding my posts. Even more frustrating when they go to 're-sign-up', hoping that will enable them to once again start receiving the announcements, they get a message which says 'Sorry, you are already signed up.' Google has not responded to my requests for help with this issue. 

My functional workaround is to set up my own email list and each week I manually send out a new post announcement. If you are experiencing the issue and would like to be added to my personal email list please send me an email requesting to be added. Thank you for your patience!

My email address is: LDHubbell@Comcast.Net



One more photo as a reward for reading this far.

This is Marsha, in 2018, feeding a fishtail to one of her young in the nest.

4 comments:

  1. Last week, we saw a mature bald eagle and a juvenile flying and perching together near the crew boathouse. From the close association, we assume it must have been a parent/child from this past year.

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    Replies
    1. Thank you for the observation. The Urban Raptor Conservancy is now banding young eagles that fall from the nests. Hopefully, in the future we may be able to ID and know the relationship between some adults and their young.

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