Nesting Instincts

There are two nests in the front yard oak.  I've never seen this type of nest before and have no idea what kind of bird built them.  They seem to be woven, hanging baskets about the size of a grapefruit, out at the tips of two nearby branches.  I can't get a good angle on them for the camera, and I'm not about to risk climbing on the roof for the sake of art.  Some years back, I knew robins were nesting in this oak because, unfortunately, I found over a dozen of those beautiful blue robin eggs smashed on the driveway.  Discovering the first one, I thought perhaps the wind had shaken it from the nest, but when I found more as days went by, it might have been the work of cowbirds.  Cowbirds are lazy, irresponsible, opportunistic, parasitic interlopers.  Rather than working hard and building a home of their own and then parenting their fledglings, these ne'er-do-wells will find the nest of some industrious couple, push one of their eggs out (to be found in the driveway below), drop in an egg of their own, and fly off with never another thought.  Their chicks are usually larger than the host birds' and demand more food than their nest-mates.  One wonders what the adoptive father thinks the adoptive mother might have been up to, to produce this Baby Huey in their midst.  One also wonders what the chick thinks, a Gulliver abandoned among the Lilliputians.  As the King of Siam said to Anna, "It's a Puzzlement."