Weaver bird nest

Southern Masked Weaver Bird: http://ibc.lynxeds.com/files/pictures/_MG_3482_Southern_Masked-Weaver_Bontebok_N.P..JPG

First of all, a weaver bird collects the building materials. It will cut long strips from leaves or extract the midrib from a fresh green leaf. There is a reason for its choice of fresh leaves: The veins of dry leaves would be stiff and brittle, too difficult to bend, but fresh ones make the work much easier. The weaver bird begins by tying the leaf fibers around the twig of a tree. With its foot, it holds down one end of the strip against the twig while taking the other end in its beak. To prevent the fibers from falling away, it ties them together with knots. Slowly it forms a circular shape that will become the entrance to the nest. Then it uses its beak to weave the other fibers together. During the weaving process, it must calculate the required tension, because if it's too weak, the nest will collapse. Also it needs to be able to visualize the finished structure, since while building the walls, it must determine where the structure needs to be widened.

Once it finishes weaving the entrance, it proceeds to weave the walls. To do so, it hangs upside down and keeps on working from the inside of the structure. It will push one fiber under another and pull it along with its beak, until it accomplishes a stunning weaving project.

The weaver bird won't just begin building its nest. It proceeds by calculating in advance what it needs to do next—first, collecting the most suitable building materials, then forming the entrance before going on to build the walls. It knows perfectly well where to thin or thicken the structure, and where to form a curve. Its behavior displays intelligence and skill, with no trace of inexperience. With no training, it can do two things at once—holding down one end of the fiber with its feet, while guiding the other end with its beak. None of its movements is coincidental; its every action is conscious and purposeful.

Another member of the weaver bird family builds a solid, rainproof nest. This bird obtains the perfect mortar by gathering plant fibers from the environment and mixing them with its saliva, which gives the plant fibers both elasticity and makes them waterproof. (1)
(1) Harun Yahya

To see a weaver nest under construction go to:http://en.wikipedia.org/wiki/Southern_masked_weaver#mediaviewer/File:Ploceus_velatus_-Johannesburg_-male_making_nest-8.jpg