Nature Discovery

This bird's nest was found by a 4D student's dad. He was working with a tree in the front yard one day, and he found this perfect, circular nest.  (Mrs. Alaniz says: Perfect and circular are adjectives!) The student's mom thought the tiny nest would be perfect to take to school to show our class.  This tiny nest is interesting!

Mrs. Alaniz asks:  What type of bird builds a nest like this?