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

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Sunday, August 1, 2021

A Learning Curve

I was lucky enough to find this male Cooper's Hawk searching the ground, e.g.hunting for prey, in the middle of the Arboretum on April 15th.
A couple of weeks earlier I had noticed a Cooper's Hawk building a nest high overhead in the same area. Most likely, it was this bird or its mate.

Later in the day, I found the female. She was less than 100 yards to the northwest. She stopped to survey the world before she headed towards the nest. 

It is perfectly fair to ask how I determined their gender. The two genders look quite similar. It helps that males are generally smaller. 

My intuition was probably based on their size. Later, looking more closely at the photos, I compared their heads to the width of their bodies. The female's head looks like it is only half as wide as her body. She may very well have been carrying a partially-developed egg at this point. The male's head looks larger - relative to the size of his much smaller body. 

Experts can also see a difference in the size of their legs. The males have relatively tiny little legs. Personally, I still struggle to see this difference, especially when I have only one bird in front of me. 


Martin let me know he measures this size difference between the two Cooper's Hawk genders with a leg gauge, not visually. Although he can see the size difference between Cooper's and Sharp-shinned legs.

In any case, while researching this post I stumbled across some additional information.

A month earlier in mid-March, I photographed two Cooper's Hawks mating in the Arboretum. In this case, there was no doubt about their gender.

When the male dismounted he moved to our left.

Even without a clear view of the legs, the male was obviously smaller. When bent over, the female's shoulders were still higher and her tail looked longer - especially when you consider that she was holding it at an angle. She was simply bigger.

What I found most interesting about this photo was the dark and light bands on their tails. Particularly their right outer tail feathers - the tail feathers to our left. The dark bands on the male's outer tail feather looked taller and darker than the female's.

If you look back at the very first photo in this post, his tail stripes are nearly a perfect match. I wondered if the female's stripes in the second photo would be a match as well. However, her stripes in this current photo, are faint and difficult to see.

Here is an enlarged photo of the female's tail, from just before their mating. Her tail stripes on her right outer tail feather, look like a pretty good match for the second photo in this post.

I do not have enough evidence to suggest there is a gender-related difference in the tails of all male and female Cooper's Hawks. I am only suggesting that the differences in the tail feathers of these two birds demonstrate individual variations. 

Although, gender differences in Cooper's Hawk tail feathers might make an interesting study.  

A week later, I found the male resting on a snag above the Lower Woodland Garden pond. I documented that set of observations in the post labeled, "Surprised". Once again, the stripes on his outer tail feather look like a match.

Over a month passed, with occasional activity in the nest. Given the height, distance, and obscuring branches, the photos were not exceptional.

On May 9th, I watched a Cooper's Hawk harass a Red-tailed Hawk to the southwest of the nest. After the Common Ravens joined the battle, along with the ever-present American Crows, the Red-tailed Hawk quickly evacuated the area. I believe all three species had nests and young in the area this year.

I could not see the tail feathers well enough to deduce this Cooper's Hawk's identity. Although, I would guess the male might have more defensive duties given his smaller size and greater expected agility.

By May 17th, not only had one of the young hatched, it was large enough to be flexing its wings in the nest. Although its flight feathers were just beginning to open up.

The following weekend, one of the young decided to do a little sunbathing. 

The primarily white feathering is a stage they pass through rather quickly. 
Did you notice the adult?

Ed Deal from the Urban Raptor Conservancy (URC) says it takes about four weeks from egg-laying to hatching and approximately six weeks from hatching to fledging. Two weeks later, the experts from the URC like to begin applying identifying bands to the legs of the young birds.

On Wednesday, this young female was within a stone's throw of the nest. During their first year, Cooper's Hawks have vertical stripes on their chests, unlike the adults in the earlier photos.

Martin Muller and Jeff Graham watched the bird closely to see if it would approach the trap. Martin is one of the founding members of the Urban Raptor Conservancy (URC) - along with Ed Deal and Patti Loesche. During the last couple of Springs, Jeff has become a very active and helpful URC volunteer. 

Actually, Martin, Ed, and Patti, the URC Founders, are also volunteers. Their Cooper's Hawks program is the only totally volunteer study of its type in the country. They have freely invested thousands of hours in documenting the ever-changing story of Cooper's Hawks, and other raptors in Seattle. A growing army of volunteers assists them by locating and monitoring the nests, the parents, and their offspring. 

When I was young, Cooper's Hawks were considered primarily birds of the forest. However, they are now successfully adapting to life in the city and their numbers (and the number of nests) in the city continue to increase. You can read more about URC's labor of love by clicking on The history of the Cooper's Hawk Project.

On Wednesday, Martin was hoping to band the young (and if possible the adults too) from the nest in the Arboretum. The three of us spent about 45 minutes following the begging sounds, of the generally hidden young, while they moved about in the treetops. 

You may need to turn up your volume to hear their cries. To me, their food begging sounds like a descending high-pitched whistle. Some people think it sounds like a squeeze toy. The sound is repeated just twice in this short recording. I am sure the parents can hear the begging from quite a distance.

This photo is courtesy of Jeff Graham. Thank you, Jeff!

Finally, the young bird from the photo above became curious enough to get caught. Martin determined she was a female due to her size. He measured her weight, the length of her wing, and attaching a Federal, aluminum-colored, band to her left leg. He also attached the uniquely coded colored band labeled "H3" on her right leg.

The next bird he banded was a young male. Females can weigh nearly a pound while the males are normally much smaller. Nonetheless, the larger talon shown on this male bird is roughly the size of the curve at the end of Martin's thumbnail.

The codes for male birds are imprinted on purple bands, instead of orange, and secured to their left legs. For females in the current URC study, their orange bands are always placed on their right legs. This young male now carries the code "S7".

Being present during the banding is a unique opportunity for observation. For example, look how the tongue abruptly changes from flesh-colored inside the bird's mouth, to brown around the tip. I wonder if the outer part of the tongue might be harder and less flexible than the inner portion. If true, that might make the tongue more durable which could be important for a predatory bird. 

Also, as Martin pointed out, the irises of the young birds are very light in color. As they age they will turn orange and, if they live long enough, red.

Here is an example of a red eye in a mature bird, from 2015.

The closer I look the more the mysteries of nature mesmerize me.

The final young bird Martin captured and released was also a female. Her code is "K3". The next day she was still in the same area waiting for her parents to bring food.

A fellow observer asked, "What is she carrying?" It turned out to be a pine cone. Apparently, starting with stationary objects is just one of the steps in learning to hunt.

The following photo is also courtesy of Jeff Graham!

Earlier, when it came time to release "H3", Martin asked for a volunteer. I was lucky to serve as a comparatively soft, artificial branch. I held my hand perfectly still and when Martin slowly released the bird it simply laid in my palm. I could feel its heart beating. It was a calm and peaceful moment that I will never forget. After a time, I very slowly began to lift my hand. Immediately, the young bird took to the air and flew to a nearby tree.

With the ongoing expansion of their Cooper's Hawk Project, Martin and the URC will be needing more volunteers in the Spring of 2022. You can learn even more about their project by:

Once you reach the page, if you scroll down you will find a way to send an email to URC just in case the idea of volunteering becomes irresistible. This same page can also be used to report sightings if you see one of these young birds (i.e. H3, S7, K3) in the Arboretum, 

This morning I saw and heard one of the young as it mantled its food. Mantling means widely spreading its wings and tail to hide something. In this case, it was trying to protect the lower half of a rat from its sibling who was sitting on the other side of the tree. The food was most likely caught and supplied by one of the parents.

After about ten minutes of vocalizing, the young bird decided to move further away to eat.

It landed on an abnormally large, high, and horizontal branch of a nearby Douglas Fir. When a Cooper's Hawk finds a prime feeding location they will often reuse it. The young bird fed very slowly, taking nearly 45 minutes. During the process, it turned sideways and I was able to identify it as H3

When it finished feeding it had a huge crop. The crop is a temporary storage location in the upper chest. In this case, it almost hides the bird's head. The crop enables mature, predatory birds to quickly swallow their food, so they can move to a less exposed location, and let the meat slowly descend into their digestive tract. 

During the next few months, these young birds will face a huge learning curve. They must stop begging, learn to hunt, fly with precision, attack with accuracy, and in H3's case learn to in-take her food far more quickly. They do not have long, by winter they must be totally self-sufficient. 

Have a great day on Union Bay...where nature lives in the city and Black Birders are welcome!


Going Native:

Each of us, who breathe the air and drink the local water, needs to watch and protect our local environment. 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. 

(By the way, my friend Tom Brown pointed out that the application named 'Wildflower Search' is extremely helpful. Click on the highlighted link to see for yourself.

Also, Jane Lundin has created a small package, with a lot of critical information that looks quite handy, and light, for backpacking in the mountains in Springtime. It is titled, Mountain Wildflowers of Washington.)

Another idea that integrates perfectly with living in harmony with nature is the concept of Forest Gardening. Apparently, Native Americans collected and nurtured dense multi-layered gardens of native herbs, plants, shrubs, and trees that produced food and herbal medicines. Even after 150 years of no maintenance, the gardens are essentially intact and the diversity of life remains significantly higher than in the surrounding forests. Click Here to learn more.

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

Scroll down for the answer.


This photo created a tricky situation. The foliage and the trunk are from two different species, both of which are native to our area.

The foliage is from a Western Red Cedar, who's trunk is hidden behind the larger tree.

The rope-like trunk belongs to a Big-leaf Maple.


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. Google never responded to my requests for help with this issue. Now, in 2021,
 the service is being discontinued.

In response, I have set up my own email list. With each post, I will manually send out an announcement. If you would like to be added to my personal email list please send me an email requesting to be added. Something like:

                Larry, I want to see more of nature. Please add me to your personal email list. 

Thank you for your patience and interest!

My email address is: LDHubbell@Comcast.Net


A final photo:
Have a great day!



  1. What a wonderful story post of Cooper's Hawks, dear Larry! This makes me homesick for Seattle again. Still lingering in my ears, the juveniles' calling in Aurora Washellii at dusk where I found their nest and reported to the URC.

    1. It is great to hear from you. I certainly hope you get to return to Seattle, one of these days, and visit our nesting Cooper's Hawks. :-)

  2. How did Martin get the birds? Does he climb up the trees?

    1. From what I have seen Martin's magic does not include climbing trees. To protect the birds I was asked not to reveal how they are encouraged to wear the bands. I will say, if you spend time helping URC many mysteries will be revealed.

  3. Could you describe the "trap"? Was it baited? How does it work?

    1. I certainly understand your curiosity. However, to protect the birds I was asked not to reveal how they are encouraged to wear the bands. I will say, if you spend time helping URC many mysteries will be revealed.