An Emlen funnel is a

bird cage A birdcage (or bird cage) is a cage designed to house birds as pets. Antique (or antique-style) birdcages are often popular as collectors' items or as household decor but most are not suitable for housing live birds, being too small, improper s ...

shaped like an inverted

cone A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines con ...

, 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 Ink is a gel, sol, or solution that contains at least one colorant, such as a dye or pigment, and is used to color a surface to produce an image, text, or design. Ink is used for drawing or writing with a pen, brush, reed pen, or quill. Thicker ...

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).

References

Ornithology Ornithological equipment and methods {{bird-stub