The Specialist

Some creatures survive because, like humans, they are generalists. They can do a number of different things quite well. For instance they can catch a variety of prey. This can come in handy when there is a shortage of one prey, they can simple switch to the next item on the menu.

However there are also creatures who are specialists and focus on a single food source, to the exclusion of almost all others. They fill a niche. A predatory niche aimed at a specific type of prey. These specialists usually have unique skills that allow them to procure their prey with a greater success rate than a generalist. One of the following three birds is a specialist. Do you know which one?

 A) A Cooper's Hawk 

B) An Osprey

C) A Bald Eagle

Please make your choice before proceeding.

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This week an Osprey decided to try hunting on the south side of Union Bay. It landed on top of a relatively small snag on Oak Point just north of the mouth of Arboretum Creek. The Osprey is a specialist. Its primary prey is fish. Cornell says Cooper's Hawks will eat many types of birds, and in our area they eat small mammals as well. Bald Eagles will eat birds, mammals, fish and most likely any other creature they can catch (or steal).

One would think that a bird who focuses on fish would not be considered much of a threat by other birds, but this is not the case. In the photo on my masthead you can see an Osprey being chased away from Duck Bay by one of a number of Crows. That photo was taken in April when the Crows were nesting, so they may have been especially nervous. 

Nesting time for Crows has passed, but that did not stop our current Osprey from being harassed. Before the Osprey even landed, this Kingfisher began circling and calling with enough noise to the alert anyone one within earshot. Maybe the Kingfisher was angry because it did not want the competition. 

It makes one wonder why the concern, since Osprey would never catch the small little fish the Kingfishers eat. Basically the Osprey only catches fish that are around the size of the Kingfisher. Maybe the Kingfisher was really more concerned about its reputation.

Nearby, a Robin began a constant strident call for the duration of the Osprey's visit and soon a Stellar's Jay joined in. A Crow flew over, but surprisingly it simply ignored the Osprey. 

The Osprey, however, kept a watchful eye as the Crow passed by.

On the flip side, this modified Mallard kept a close eye on the Osprey as it and its mate passed underneath the Osprey's perch.

The Osprey's focus quickly returned to peering into the water in search of passing fish. The Osprey's special skills include diving feet first into the water, and going as much as three feet below the surface. The Eagle, on the other hand, normally only catches fish that are near the water's surface. Cornell also says the Osprey have a reversible toe which allows them to grasp with two talons on each side of their slippery prey. 

After an hour of patiently waiting and watching, the Osprey finally decides to make its move. By the way, it is interesting to note the color difference between the top of the Osprey and the underside. I suspect that when looking down on an Osprey which is flying over the water or land, the darker color is hard to pick out, while looking up at an Osprey circling against the sky, the lighter color is more difficult to see. This same dark and light pattern can be found on trout and salmon as well, most likely for the same reason.

One exception is the dark portion of the wing that is the furtherest forward in this photo. That area is referred to as the wrist. 

It is fun to try and imagine how the bones of the wings are actually structured in a pattern similar to our arms and hands.

At the last moment, the Osprey threw its feet forward and dived into the water. Sadly this happened behind a branch and out of sight. Much more sadly for the Osprey, it came up empty before heading back to the north side of Union Bay.

The Osprey are migratory birds, and in the next month or two they will be heading south. So if you would like to watch them in action, you should get out on the water as soon as possible. Some Osprey actually winter as far south as Argentina and Chile. In order for them to make a journey of that length, I suspect they must find food all along the way.

In parting, here is a photo, from two years ago, of a nest near the Ballard Locks. When we visited the nest earlier this month, it appeared to be empty. This made me wonder if a lack of fish is to blame.

If you are interested in protecting the Osprey's food sources, as well as our own, you may want to read this story published in the Seattle Times. Reverse decline of marine birds.

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

Larry