Bird Nests

[Jodi Nielson]

In my opinion, nests are architectural wonders. The Eastern Phoebes primarily used moss.  The Blue-gray Gnatcatchers I was watching today used tree lichen.  Mud, spider webs, grasses all woven together to create safe havens for eggs and hatchlings.  After watching the Gnatcatchers, it made me wonder why any given species chooses the materials they use.  

Are there any studies or research projects regarding why they prefer one thing over another?  Ten different species could nest in the same acre and all use different materials, even though the same materials are available to all of them.  Locations are another question.  Ground, trees, eaves, cavities, open, sheltered.  Just curious....