Emlen funnel
The Emlen funnel (English Emlen funnel ) is an apparatus by which the activity and direction of pull of captured migratory birds during migratory restlessness can be determined. The 1966 developed by Stephen T. Emlen and John T. Emlen cage utilizes a labeling medium ink, in modified versions of typewriter correction paper, so-called Tipp-Ex paper, or thermal paper are used.
Operation
The trapped bird is placed in the Emlen funnel, which is covered up with a net. Here, the funnel should not be made of a ferromagnetic metal, as this interferes with the important for the orientation of the bird geomagnetic field. The birds leave the high hopping in funnel clear traces through which ink or scratch marks on the Tipp-Ex paper. These can be evaluated with respect to the orientation direction and the accumulation of activity.
In contrast to electrical Registration cages of the Emlen funnel is particularly optimized for use in the field.
History
The Emlen funnel was developed by Stephen T. Emlen and John T. Emlen 1966 and first published in the scientific journal The Auk. 1979 J. Rabol described a modified version in which instead of ink, the dirty bird, Tipp-Ex paper was used, on which the bird instead of color stains, leaving scratches. Manuela Zapka et al. 2009 replaced the now hardly available because of the rare typewriters Tipp-Ex paper by a thermal paper to make the tracks visible.