Update On Marsha And Monty, Marsh Island Eagles

 Here is a recent post from the Union Bay Watch Blog published by Larry Hubbell, long-time local photographer and birder.

Eagles Overhead

Marsha and Monty keeping an eye on their nest site, which is just south of Montlake Cut. 

(This perspective provides a nice example of a female being larger than her mate.)

During the last year, they have added this branch to their set of preferred perches. Not only do they sit in and around the nest tree, in the tallest cottonwood on Marsh Island and to the north of the Waterfront Activities Center (WAC), they also perch near the top of this tall sequoia tree - which is located immediately southwest of the WAC.

In addition to providing a nice view of their nest, it also allows them to absorb the rays of the setting sun and gives them a serious height advantage. They can descend rapidly to begin hunting on Union Bay (which is to their left) or they can plunge forward and chase intruders away from the nest site or they can turn and dive to the north when defending that portion of their territory.

This time of year Monty and Marsha probably have a lot on their minds. They have to find food, make nest improvements, defend their territory and there is also construction happening below their nest. The pump station is being replaced. Hopefully, the noise and activity do not impact their willingness to lay eggs. We should know by the end of March. Marsha ought to be totally committed by then.

This January photo was taken when Monty and Marsha had an interaction with Russ and Talia, their Bald Eagle neighbors to the north. No one got hurt, there was a lot of vocalizing, chasing, and flying in circles, and then everybody returned to their respective sides of the border. 

This interaction was preceded by Monty vocalizing loudly and...

...Marsha responding in kind.

They must have seen some activity by Russ and Talia that felt like territorial encroachment. I am not sure if their vocalizing serves to "egg-each-other-on" but it sure seemed like a call to action. Ironically, from what I can see Marsha and Monty seem to be the ones who are encroaching. Until last year, this cottonwood used to be Russ and Talia's favorite perch at the southern end of their territory. Now, it clearly belongs to Monty and Marsha.

Portage Bay is a more distant part of Monty and Marsha's territory. From their normal Union Bay perches, I do not believe Monty and Marsha have a line of sight to see what is happening there. On Friday, I spotted this young Bald Eagle perched in a cottonwood tree on the south side of Portage Bay. 

Monty and Marsha will often chase visiting Bald Eagles away, if they see them hunting in their territory, and if they are not out-numbered. I once did a post explaining the Bald Eagles must do math because they clearly know when the odds are in their favor.

People often ask if immature eagles, like this one, are the offspring of our local adult eagles. Honestly, without a unique identifying band or tag we cannot know for sure, but in general, I doubt it. My understanding is, that by their first Winter, the young are on their own. The implication is they disperse and roam freely, primarily searching for food, until they around 5 years of age. At which point, they develop a white head and tail, take a mate, begin defending a territory and prepare to raise young. 

However, our three resident Union Bay pairs are not representative of all Bald Eagles. Many are migratory. This dynamic eBird map of weekly Bald Eagle sightings tells the story of migration far more eloquently than I can. 

It shows large numbers of Bald Eagles migrating north during warm weather and then heading south for the Winter. In Western Washington, Western Canada, and Southern Alaska their movement seems to focus primarily on coastal areas, especially during the winter. Birds of the World (BOW) explains, "Adults and immatures from Alaska and the Pacific Northwest follow the salmon runs south down the coast; Adults arrive on Pacific Northwest wintering grounds Nov-Dec; immatures arrive later in Jan." (see citation below)

BOW goes on to say, "Northern birds return to the breeding grounds as soon as weather and food availability permit, generally Jan-Mar." The text also implies that mature birds migrate more directly when headed north, presumably this is because of competition for mating opportunities and territories. Apparently, the early bird gets the territory. Immature birds still tend to migrate north, but they take a bit more time since they are not yet competing for mates or territories. I wonder if their northern migration is related primarily to food availability or if they also feel a slowly-intensifying instinct to head north. I suspect that most of the non-resident Bald Eagles we see in Winter are migrants.

The young Bald Eagle in the prior photo was watching this second immature Bald Eagle as it circled over Portage Bay. The second Bald Eagle was also being watched by the Red-tailed Hawk circling above it. Soaring, circling, and rising up on thermals, takes very little energy. Once a bird has gained enough height it can simply glide north until it finds another thermal and repeat the process. I believe this is the key to Bald Eagle migration. Since thermals are caused by heat differentials their migration is most likely a daytime activity and probably most effective on bright sunny days. 

I believe our resident Bald Eagles also use the thermals to circle up and hunt from a height particularly on sunny days. (This may be one reason why on cloudy days Bald Eagles are often seen hanging out at lower levels.) From what I have seen, Bald Eagles are often soaring carnivores who also have a very healthy taste for fish e.g. piscivores. 

When we look more closely at the second young Eagle we see the trailing edge of its wings are scalloped. This is because in their first year Bald Eagles have their longest-ever set of flight feathers. The feathers that replace their first set are shorter and it takes two years to complete the process. So during their second year, they have half long and half short flight feathers.

After a few more moments the first immature Bald Eagle took off from the tree. Its secondary feathers also looked long but less scalloped than the second bird. I suspect this may mean it is even younger and may not have grown as many replacement feathers yet. Although the short  outer tail feathers are interesting. It is as if each bird we see is a mystery that we can only partially resolve, still each piece of information we learn helps expand our understanding of life on earth. 

Earlier this week, I spotted this Bald Eagle circling above the south end of the Arboretum. 

Due to its white head and tail, my first impression was that it was a fully mature bird.

However, when looking closer I noticed the dark tips on its outer tail feathers, a faint darkness in its central tail feathers, and a small dark spot on its cheek. I suspect this bird is very close and will probably reach full maturity, e.g. ~5 years of age, this year. 

I am surprised by the slight scalloping on this bird's wing feathers. It is obviously beyond its second year and its shorter feathers do not look like a just few new feathers just growing in - as I have seen in mature birds.

For comparison here is a photo of Monty from 2018. Since he and Marsha had what appeared to be their first two young that year I presume he was at least 5 or 6 years old. His feathers are not in perfect condition but they do appear to be of a more uniform length. On his upper wing, the equivalent of his "middle-finger" of his outer five primaries is an example of a new feather halfway grown in. While on his lower wing the equivalent of his "pointer-finger" is also not fully regrown. Luckily, this slow incremental process of feather replacement never causes Bald Eagles to lose their ability to fly - unlike ducks. Without the ability to fly, and hunt, they would probably starve.

Mysteries, like the slightly scalloped flight feathers on this nearly mature Bald Eagle, demonstrate the richness and depth of nature. I find the attraction irresistible and the process of observing and hoping to learn more deeply satisfying. I suspect we will not see this eagle again this Spring. Given that it is close to maturity it may be all the way to Canada by now. No doubt it is hurrying north to stake out its very first breeding territory.

On the other hand, on Sunday I visited Portage Bay again. I found an immature Bald Eagle in the same cottonwood tree where one had been sitting on Friday. It also had some shorter than normal outer tail feathers. It might even be the same bird. Perhaps this demonstrates the case that immature Bald Eagles are not yet driven by their reproductive urges. If they are finding food, particularly at a location hidden from the resident adults, they have no need to hurry north.

Did you notice how this young bird's bill is starting to turn yellow? It takes time before they get the bright yellow bill of an adult.

What species of plant is this? Is it native to Union Bay?

Flowering Red Currant: Yes! This early-bloomer is native and beautiful. Although, some might say the fragrance may be a little to be desired. Click Here to learn more.