BIRD TALK: NESTS - HOMES FOR BIRDS

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By Greg Dunne

July 24, 2013 (San Diego’s East County) – Bird nests can be hard to observe. We usually just stumble across them out in nature. One place you can always see a large variety of Egret and Heron nests is in the Eucalyptus trees at Lindo Lake.

“Large” fledgling Egrets and Herons are leaving the nest at this time of the year. I say large because the Snowy and Great Egret babies getting ready to leave the nest are as big as their parents. It always looks a little odd to see Mother Egret feeding a bird nearly her own size in a very crowded nest.

Bird nests come in a variety of shapes and sizes: from some of the largest ones made by Bald Eagles weighing up to a ton, to the smallest ones made by the smallest bird in the world, the Cuban Bee Hummingbird, whose nest is only 2.25 inches in length, or sometimes smaller.

A knothole in a tree makes a fine nest for Woodpeckers, Bluebirds, and even Wood Ducks. Birds nest in burrows in the ground as well as shallow depressions in the sand and some waterbirds such as Grebes build floating platform nests. The different nesting sites and construction materials seems endless.

Some of our East County examples are shown here of the Egret nests at Lindo Lake and the nest of the tiny Bushtit taken at Mission Trails Regional Park. The photo of the Osprey platform high on top of the pole at Lake Murray is my favorite nest.

Nesting birds lay eggs in a variety of ways. For instance, the Thick-Billed Murre, a Northern Hemisphere sea bird, and the Razorbill lay their eggs directly onto the narrow rocky ledges they use for breeding sites. In most species, the female does all the work building a nest, but in some polygynous species, the male does most or all of the work.

Our common East County resident Cowbird does not build a nest at all. The Cowbird uses other birds’ nests to lay its eggs and depends on the host to raise its young.

Protection is usually key for most birds when building a nest. They may try to conceal it or make it inaccessible to predators. The Kingbird will attack other birds that come too close to their nest.

Both male and female Bushtits help build remarkable hanging nests, a process that may go on for a month or more. The nest hangs up to a foot below its anchor point and has a hole in the side near the top that leads down into the nest bowl. The adults make a stretchy sac using spider webs and plant material, sometimes stretching the nest downward by sitting in it while it is still under construction. A Bushtit pair often gets help building their nest from other Bushtits, a rare behavior made more unusual by the fact that most of the helpers are adult male Bushtits - a commune of sorts in the bird world.

Lastly, a short comment on the Osprey nest at Lake Murray. This nest has been there for approximately eight years and this is the first year a nesting pair has raised their young at this site. I walk the entire six-mile Lake Murray path three times a week and never get tired of viewing the large Osprey nest approximately two miles out from the parking lot at the fishing license store.

Birds and walking at parks or lakes is a great combination for exercise and observing nature. Stay fit and enjoy our wonderful diverse nature.