An Emlen funnel is a bird cage shaped like an inverted

cone In geometry, a cone is a three-dimensional figure that tapers smoothly from a flat base (typically a circle) to a point not contained in the base, called the '' apex'' or '' vertex''. A cone is formed by a set of line segments, half-lines ...

, used to study bird behaviour, in particular birds' migratory instincts. It is named after S T and J T Emlen who introduced the technique in 1966. An ink pad is placed on the bottom, so when the bird hops or flutters onto the sloping walls it leaves a track before slipping back down again. The bird's view through the top of the cage can be manipulated to show how it responds to different apparent "star patterns" (actually generated in a

planetarium A planetarium (: planetariums or planetaria) is a theatre built primarily for presenting educational and entertaining shows about astronomy and the night sky, or for training in celestial navigation. A dominant feature of most planetariums is ...

References

Ornithology Ornithological equipment and methods {{Ornithology-stub