Here are amazing 10 facts about birds' nests. Not all birds go through the trouble of building a nest, but among those that do some really extraordinary efforts are put forth. Here are 10 facts about birds' nests. Number 10. Some of them are built on water. The Lily Trotter is one type of many that chooses a floating nest over trees or cliffs. Unfortunately, they're not very meticulous when it comes to construction and a lot of them end up sinking. Luckily their eggs are waterproof. Number 9. Not all birds use earth, sticks, and twigs. Take the Elf Owl, for example. This desert dweller has scant resources so it takes shelter in the holes in cacti and canyon trees left by Woodpeckers and Flickers. Number 8. Barn Swallows are particularly committed to the task. They make their abodes out of mud mixed with other materials, and building a single nest can take about 12 hundred trips between the material source and the construction site. Number 7. Sociable Weaver Birds build communes.The giant nests these southern African birds make are meant to house numerous other avian species. That way, the Sociable Weavers get added protection and information about new food sources. Number 6. Edible-nest Swiflets' creations are delicacies. The Southeast Asian birds build their nests on the sides of cliffs, using layers of their own saliva. Even though the structures have no flavor or nutritional value, they are a highly sought after edible and one of the most expensive food items in the world. Number 5. Cigarettes are a key feature in some nests in Mexico. Both house sparrows and house finches living in urban areas there have taken to throwing a few cigarette butts in their homes. It's believed they do it because the nicotine in the filter fibers wards off parasites. Number 4. The world's tiniest bird builds the world's smallest nest. The Bee Hummingbird is only about two inches long and makes a nest the size of a doll's teacup. It's so little, it's secured to branches with threads from spider webs. Number 3. For the Great Crested Flycatcher, texture is everything. These birds prefer crinkly surfaces, so often use snakeskin in their nests. They've also been known to take advantage of onion peels, cellophane and flimsy plastic wrappers they find along their way. Number 2. Gyrfalcons use their nests for millennia. Many birds build a fresh nest every time they lay eggs, but not these falcons. They return to the same one year after year and generation after generation. One such site in Greenland was radiocarbon dated and found to be around 25 hundred years old. Number 1. Tailorbirds sew theirs. They grab some leaves and spider web or cocoon silk and put their needle-like beaks to work punching holes and pulling the threads through them. What's the most interesting bird's nest you've ever seen?.