Here is a recent post from the Union Bay Watch Blog published by Larry Hubbell, long-time local photographer and birder.
On Nesting
This is the Broadmoor Bald Eagle nest as seen in 2018. It is probably one of the largest nests in Seattle. Having watched the eagles spread their six-foot wings while they were sitting on the nest, I would estimate the nest is more than seven feet in diameter. It is probably six feet deep and may weigh more than a small car.
Sadly, so far this year, I have not seen these eagles incubating eggs. I believe this may be their first failure to nest, in ten years. The reason for this change is a bit of a mystery. Maybe they are simply exhausted. Parenting is hard work and they may just need a year to recharge their batteries.
Also in 2018, a new Eagle pair, Monty and Marsha, built their first nest in a Cottonwood tree on the southeast corner of Montlake Cut, just west of Marsh Island. This year they appear to be on eggs for the fourth year in a row.
A consistent theme with Bald Eagles is nesting near water where Cottonwood trees naturally grow. Most Bald Eagle nests that I have seen have been in Cottonwood trees. Plus, all but one of the sticks I have seen Bald Eagles take to their nests have come from Cottonwood trees.
Luckily, for the Eagles, Cottonwood branches do not need to die to be weak. They are naturally easy to break. This may be related to the fact that Cottonwoods grow along riverbanks where they are often toppled during floods. Easily broken branches float off and become embedded downstream, take root, and create Cottonwood "clones" which may be spread by the same flood that brought down the original tree or broke off the branch.
With most birds nesting happens in the Spring when the days are getting longer and warmer. Plants and trees are beginning to grow leaves, flowers, seeds, fruits, or nuts that will help feed a wide variety of new life. We might even say that nesting, and raising young, is the essence of Spring. I suspect this incredible explosion of life is the reason Earth Day happens in the Spring.
To be safe from predators it helps if nests are somewhat hidden. Sadly, this means we often overlook where birds are nesting. As a result, it is easy to accidentally disturb their nests. Knowing what various nests look like and where we might find them should help us to avoid accidental interference. So, let's take a closer look at the variety of nests which we can find in the city.
Since they eat primarily fish Ospreys like to nest not far from water. Given their size they do not worry about hiding their nests. Tall, leafless manmade structures are fine for Ospreys. Their main problem seems to be the parasitic behavior of Bald Eagles. If an Osprey nest is too close to a Bald Eagles' nest, the Eagles will steal their fish and make it difficult for the Ospreys to feed their young.
This particular nest is south of N.E. 45th St. and directly across from the University Village QFC. Unlike Bald Eagles, Ospreys do not seem to care what species of tree they get their sticks from - although they do seem to prefer the upper, most brittle branches of dead trees.
This week I saw an Osprey eating a fish on this light pole but it did not look like either of the pair that built the nest. I am hoping they are on their way north, return shortly and raise another brood of young this year.
Most of the Great Blue Heron nests I have seen have been in the upper areas of Big-leaf Maple trees. This Great Blue Heron secured this small stick by breaking off a dry, inner twig from a Douglas Fir tree.
Both the twigs and their nests are smaller than what Bald Eagles and Osprey use. This may be because Heron's carry their nesting material in the bills - since their legs and feet are thin and built for wading unlike the heavier talons and thicker legs of Eagles and Osprey.
Obvious Nests:
The nests of these three species we just reviewed are the most easily seen nests around Union Bay. Bald Eagle and Osprey nests are large, solitaire nests that often stand out. Great Blue Heron nests are smaller and normally more hidden, but since they nest in colonies their activity is concentrated which can make the collection of nests fairly obvious. These nests are high enough that your presence is unlikely to disturb the birds.
This map displays many obvious, but distant, nest sites around Union Bay. Binoculars are suggested.
Some Less Obvious Nests:
Unlike the previous species, Barred Owls do not build their own nests. they tend to look for a cavity in a dead tree or an abandoned nest. I believe this tree was originally a Big-leaf Maple but I have also seen them nesting in Cottonwood trees. In their case, I suspect a well-shaded site, in the midst of a wooded area, might be their most critical requirement.
Cooper's Hawks break off twigs and...
...build their nests in a wide variety of tree species. By the time their eggs hatch their nests are generally hidden near the tops of conifers or by the thick foliage of deciduous trees.
Even though American Crows are similar in size to Cooper's Hawks their nests appear to be smaller and are often located in smaller trees. This may have to do with the overall density of American Crows in the city. With smaller territories and more intra-species competition, they may simply have fewer nesting options. I have heard of Crows aggressively defending their nest sites and even attacking people who venture too close. Being aware of the location of Crow's nests is in everyone's best interest.
Green Herons are very shy. Nonetheless, they gather nesting materials in a manner similar to Cooper's Hawks.
Since they are smaller than the Cooper's Hawks, it is logical for their nests to also be smaller. Given their aquatic hunting style their nests are usually close to water.
Excavated Nests:
Pileated Woodpeckers are our largest woodpecker species. Their large bills enable them to carve out spacious nest sites inside trunks of mature trees. While nest building, a pile of chips will often accumulate. To get the chips out of the way a Pileated Woodpecker will reach in and grab a bill-full and flick them over his or her shoulder with amazing quickness.
During the last decade, the local pair of Pileated Woodpeckers, have excavated and used a new nest each year. All ten nests have been in dead or dying Red Alder trees. I have seen roosting holes and potential nest sites in other trees, like Cottonwoods, but when it comes time for the female to lay her eggs she has consistently chosen a Red Alder.
Each nest we have reviewed so far is dependent on trees. While there are nests built in other places, and with other materials, in general trees are critical to many birds and creatures - including us.
Trees supply us the oxygen we breathe, our primary sustainable building material, fruits and nuts that we eat, erosion control, shade and temperature balancing, water filtering, flood moderation, visual beauty, and in the Pacific Northwest the structural framework for a functional ecosystem.
After trees die, but before totally decomposing and providing nutrients to the next round of flora, they provide nest sites to many additional species. Click Here to read about a study that found more than 38 species that reused Pileated Woodpecker nest sites. Pileated Woodpeckers are a keystone species. They are critical to a functional forest ecosystem. In our area apparently, the Red Alder trees could be considered critical as well.
The post Housing Crisis gives a great example. The story focuses on a female Wood Duck in need of a nest site. Sadly, the one she found was still in use. Click Here to read the story. Click Here to read about our response.
Many current studies have shown there are mental and physical benefits from viewing nature. I believe these benefits are greatly enhanced by the variety of lifeforms we encounter. Safely leaving dead trees standing in the city is a challenge - but obviously worth the effort.
Northern Flicker's weigh about half as much as Pileated Woodpeckers and are far more common in the city. (They are also woodpeckers even though the word is not included in their name.) They build their somewhat smaller nests in the same fashion as the Pileated Woodpeckers and can also be considered a keystone species.
Last year, this tiny male Downy Woodpecker built a nest in a dead branch of a Pacific Madrone tree. The wood of a Pacific Madrone is one of the hardest of our native trees. Given the Downy Woodpecker's small bill nest building in a Pacific Madrone seems almost as impressive as the excavating effort of a Pileated Woodpecker.
This year will be the sixth year in a row that Red-breasted Nuthatches have excavated or reused a nest site in this same dead branch on the Pacific Madrone that the Downy Woodpecker used last year. Their bills are even smaller. The chips they remove are so fine they are very difficult to see. Given the effort involved, it is not surprising that Nuthatches occasionally reuse their prior year's nests.
Chickadees, both Black-capped and Chestnut-backed, are similar in size to Red-breasted Nuthatches. They are all around one-third of an ounce, e.g. ~10 grams. However, the Chickadees have even smaller bills. This may be why they tend to excavate nests in older snags or knot holes where the deadwood has had some time to soften up and start to decompose.
Chickadees will also nest in very small dead branches, just a few inches in diameter. To keep from disturbing their nests you might want to refrain from trimming dead branches in the Spring. Plus, if a dead branch is not currently used and if it can be safely left intact, then leaving it could provide potential nest sites in coming years.
Classic Nests:
This American Robin's nest was made primarily of grass and mud. Their nests may be the most common and classic conception of a bird's nest. Depending on availability and need they may mix in many other materials. I would not be surprised by moss, twigs, leaves, rootlets, or feathers.
American Robin nests are often in trees but occasionally they also nest in the undergrowth or, as in the previous photo, under an outdoor light just above our backdoor.
Song Sparrows make similar, but smaller, nests. They are also often hidden in dense foliage, like a blackberry thicket, and can be just a few feet from the ground.
Before beginning the removal of invasive plants in the Spring it would be wise to spend a few minutes checking to see if there are active bird nests in the area. In addition to actually seeing a nest, seeing a bird, or birds, consistently coming and going from a specific area is often a good hint.
Dark-eyed Juncos will even build their nests on the ground with nothing but leaves for cover. Spotted Towhees are another local bird species that will often build nests on the ground or close to it. Taking time to quietly observe your yard before beginning Spring weeding may be your only chance of observing the parents and avoiding the nest.
Optimally, leaving leaves undisturbed in a flower bed provides nesting habitat for birds during Spring, the warmth of decomposition in the Fall and Winter, and nutrients for the soil thereafter.
Some Unique Nests:
This Anna's Hummingbird nest was only three feet above the ground in a small tree along the edge of Foster Island. Their nests can be less than three inches in diameter. They are often very hard to see - even when they are right in front of you. This is a case where watching the behavior of the bird, as it comes and goes, maybe the best way to find a nearby nest.
Sadly, after a beaver decided to start gnawing on the trunk of this little tree the mother abandoned the nest.
This photo shows a female Anna's Hummingbird carry a strand of spider silk she found under a park bench in the Arboretum. The major components of an Anna's Hummingbird nest are moss, lichen, and spider silk. The spider silk is what holds the nest together. In our society removing spider webs seems like a normal part of maintaining your yard. However, leaving the webs for the small birds to reuse is actually a much more thoughtful approach.
Bushtit nests are often built of the same major components as Hummingbird nests. However, the result is dramatically different.
Bushtit nests can be nearly a foot long and shaped like a sock. Although, since the top is closed the entry hole is usually on the side "above the ankle".
I spotted one yesterday in a Douglas Fir tree. It was so completely surrounded by needles that it was impossible to get a photo that gave the slightest hint of the nest's existence. It was only the consistent activity of the birds that gave away the location.
On the positive side, being well-hidden may help the nest to survive until the young fledge. On the negative side, it would be very easy for someone to not notice the nest, trim the branch, and accidentally cause the demise of the whole brood.
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