A comparison of the Emlen funnel and Busse's flat cage for orientation studies
The Emlen funnel cage was introduced in 1966. Since then it has been used in numerous studies on bird orientation. In 1995, Busse proposed another technique - in the form of flat, round cylindrical cage. Busse also tested nocturnal migrants in the daytime. He, and Nowakowski and Malecka (1999), proved that birds tested in daylight and at night displayed similar distributions of their preferred directions. This study also supports their findings. Zehtindijev et al. (2003) found that results in the Emlen funnel and Busse's flat cage were coherent, despite the tests were performed in different conditions (night-day) and in different years. This study is the first one that compares results of the same individuals tested in the two types of orientation cages during the day (N = 75) and night (N = 17). Results of both methods did not differ (Watson-Williams test of mean angles, Mann-Whitney U-test of angular dispersion) both during the day and at night. Multiheading bird behaviour is common in both types of cages and seems to be a normal feature of orientation data. The only difference was found in bird activity (i.e. number of scratches during 10 minutes of testing) that was higher for Busse's flat cage in daytime tests.
Quantitative estimates of average geomagnetic axial dipole dominance in deep geological time
