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Sonora Desert Museum Hummer feeding baby, April 2014
© 2014 by Jeff Young |
Caliology
by Lauretta Young
How many types of bird nests can you name? Many of us think first of the American Robin’s cup-like nest. In Cedar Mill we are fortunate to have many Robins, and these birds are quite comfortable nesting on top of our lamp posts, on beams over our porches, or in trees close to the house—offering us a great view of the nest building and baby fledging activity. After the eggs hatch we may find pieces of broken shell, which has its very own color description, “robin’s egg blue”.
There are many diverse types of nests, even in one geographic area. If we look at other habitats, the number of nest options increases greatly. The scientific study of nests is called caliology, and there are many related scholarly articles in the ornithology literature. One can even find some birds who don’t “nest” in the ways we might imagine—some ocean birds don’t build a nest per se, but instead, simply lay their eggs on ledges near the ocean. These eggs are shaped in such a way that when they roll, they roll toward the slightest depression in the rock or dirt, allowing them to stay in one spot, but I imagine some get accidentally bumped off.
At this time in our local area, yard birds are building nests to secure their eggs. Ducks and geese build their nests on the ground, which pose risks, given the marauding wildlife such as coyotes or skunks that raid ground nests for eggs or helpless hatchlings.
Then there are the nests built in trees by perching birds. One of the most interesting to me is the nest of the Great Blue Heron. These nests always look incredibly flimsy to me with a few sticks lying together. I wonder how they survive windy days or hold an egg, but apparently the engineering skills are more solid than they appear. A group of these birds nesting together is referred to as a rookery. Local rookeries can be found on Ross Island, along the shoreline of the Willamette River, at Fernhill Wetlands in Washington County, or on Sauvie Island.
Other platform-type nests are incredibly sturdy—such as those built by Bald Eagles. Over a period of years, as the birds reuse these nests and add materials to remodel these nests, they can grow so large and heavy that they weigh thousands of pounds, enough to bring down trees at times.
Bushtits are our only local examples of birds that “weave” their nests. They gather long dried grasses and cattail fluff into a sock-like structure similar to that of orioles in other locations. If you have them in your yard, you might see them gathering spiderwebs to line the nests.
A more common type of local nest is the cavity nest, and we have several yard birds that build these. Several species of woodpeckers create a hole in a tree for their nest. Other birds, such as Wrens, Nuthatches, Swallows and the uncommon Blue birds, use abandoned woodpecker holes. In early spring you may hear woodpeckers working on building their houses. I recently enjoyed listening to a couple different species of woodpeckers each pecking away with their distinctive drumming sound, which can be used to identify the species.
My most unusual “nest spotting” was done on the island of Lanai, where on an early morning walk to see the sun rising over Maui, I heard “moaning” sounds and saw ghostlike small figures emerging out of sand burrows and flying off to sea. As the light increased it was clear these were birds flying out to fish, and as I looked into the burrows I could see eggs at the bottom. This turned out to be a type of Petrel found only in the Polynesian island chains. These pelagic birds only come to land to make burrows in sandy ledges on a few islands, and then spend the other 11 months at sea.
Many of us enjoy supporting our local birds by providing houses or nest-building materials. Perhaps you have built or purchased a birdhouse –these only attract cavity nesters. I often leave out bits of dryer lint, cotton, shredded paper and other assorted options and then enjoy watching my nesting pair of Bewick’s wrens looking over the offerings before picking up a shred of yarn to take inside the bird house.
Another way of enjoying nesting birds is through use of nest cameras, which transmit images to a desktop computer or website. Edgefield Golf Course had a nest camera in a Tree Swallow nest, which allowed a very intimate view of the young developing over the days before they left the nest. Other cameras watch nesting Peregrine falcons on local bridges—you can google “nest cams” and find some interesting ones.
While the science is fascinating, the sheer beauty of various nests makes me smile in wonder. To me hummingbirds are tiny jewels, which inspire my delight as they hover over my blueberry flowers to eat the bits of nectar in each blossom. These birds gather spider web to add to their incredibly small nests. They also add whatever plant materials are available in the local area. When we observed nests recently in Arizona, we noted use of some desert plant materials such as creosote leaves.
As you go outside, see how many nests you can find before the leaves fully hide them from our view. Scan the trees, the ground, look in holes in trees, and notice the ways our birds use natural materials to build their homes. Many are camouflaged so it takes some effort to spot. When I take people on bird tours, I encourage them to identify what they see, notice the songs, and understand the behaviors, from territorial singing, to displays, to nesting, to molting, and related feather pattern changes over seasons. Enjoy and be delighted as you notice what is outside your door.
Lauretta Young MD is the OHSU Medical Student Resiliency Project Director and a prior chief of mental health at Kaiser. Now she teaches at PSU and OHSU and takes clients out on bird watching tours. Her web site is portlandbirdwatching.com. See more photos her husband took of adventures outside at flickr.com/photos/youngbirders.
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