This paper focuses on field practice using different types of orientation cages. The two orientation cage designs most commonly used in field work, i.e. Emlen’s funnel and Busse’s flat orientation cage, are described in detail and compared for compatibility of results, simplicity of use and time effectiveness. Apart from cage designs and field procedures (60-min nocturnal tests in Emlen’s funnel vs. 10-min diurnal tests according to Busse’s procedure), the standard data evaluation procedures are compared and discussed. The data used in the discussion were collected for four species of nocturnal migrants (the Reed Warbler, the Sedge Warbler, the Willow Warbler and the Whitethroat) at the Kalimok Bird Station (Bulgaria): altogether 141 individuals were tested in Emlen’s funnel in 2001 and 788 in Busse’s cage in 2001-2007.
The following conclusions were drawn: (1) Busse’s flat cage design and its standard procedures yield results fully compatible with those obtained using Emlen’s funnel and the associated procedures; this means full compatibility in terms of the directionality of tested birds in the diurnal and nocturnal tests; (2) the procedures compared have distinct differences in terms of constraints on the methods:
– Emlen’s cage is extremely stressful for the bird and should be avoided as much as possible in practice due to animal welfare concerns;
– Emlen’s standard procedure of testing the bird for 60 minutes is completely useless, as this is inefficient in terms of quality of results and causes more stress to the bird than is necessary;
– Busse’s 10-minute standard makes it possible to collect a vast amount of data (12 birds per hour and person) in real field work, even performed in wilderness areas;
(3) At the stage of evaluation of raw data it is essential to use evaluation tools which take into account the fact that raw data items show a high percentage of multimodal distributions, and therefore tools assuming unimodal distribution are unsuitable.
Adamska K., Filar M. 2005. Directional preferences of the Chiffchaff (Phylloscopus collybita) and the Robin (Erithacus rubecula) on autumn migration in the Beskid Niski Mountains (S Poland). Ring 27, 2: 159-176.
Batschelet E. 1981. Circular statistics in biology. Acad. Press, London
Bianco G., Ilieva M., Veilbäck C., Öfjäll K., Gadomska A. Hendeby G., Felsberg M., Gustafsson F., Akesson S. 2016. Emlen funnel experiments revisited: methods update for studying compass orientation in songbirds. Ecology and Evolution 6, 19: 6930-6942.
Busse P. 1995. New technique of a field study of directional preferences of night migrants. Ring 17, 1-2: 97-116.
Busse P. 2006. Bird migration models as a theoretical basis for field cage tests. Journ. Of Ornithology 147,5, Suppl. 1: 119.
Busse P., Trociñska A. 1999. Evaluation of orientation experiment data using circular statistics – doubts and pitfals in assumptions. Ring 21, 2: 107-130.
Emlen S.T., Emlen J.T. 1966. A technique of recording migratory orientation of captive birds. Auk 83: 361-367.
Formella M., Busse P. 2002. Directional preferences of the Reed Warbler (acrocephalus scirpaceus) and the Sedge Warbler (A. schoenobaenus) on autumn migration at Lake Drużno (N Poland). Ring 24, 2: 15-29.
Holmquist B., Sandberg R. 1991. The broken axis approach - a new way to analyse bi-directional circular data. Experientia 47: 845-851.
Kramer G. 1949. Über Richnungstendenzen bei der nächtlichem Zugungruhe gekäftiger Vögel. In: Ornithologie als Biologische Wissenschaft. Heidelberg.
Muheim R., Henshaw I., Sjöberg S., Deutschlander M. E. 2014. BirdOriTrack: a new video-tracking program for orientation research with migratory birds. J. Field Ornithol. 85, 1: 91-105. DOI: 10.1111/jofo.12053
Newton I. 2008. The Migration Ecology of Birds. Academic Press, Amsterdam… ISBN: 978-0-12-517367-4
Nowakowski J. K., Malecka A. 1999. Test of Busse’s method of studying directional preferences of migrating small Passeriformes. Acta orn. 34: 37-44.
Ożarowska A., Ilieva M., Zehtindjiev P., Akesson S., Muś K. 2013. A new approach to evaluate multimodal orientation behaviour of migratory passerine birds recorded in circular orientation cages. Journal of Experimental Biology 216: 4038-4046. DOI: 10.11242/jeb088757
Sauer E. G. 1957. Die Sternorientierungnhlih zeihender Grasmucken (Sylvia atricapilla, borin und curruca) Zeit. Tierpsychol. 14: 29-70.
Ściborska M., Busse P. 2004. Intraseasonal changes in directional preferences of Robins (Erithacus rubecula) caught on autumn migration at Bukowo-Kopañ ringing station (N Poland). Ring 26, 1: 41-58.
Stępniewska K., El-Hallah A., Busse P. 2011. Migration dynamics and directional preferences of paasserine migrants in Azraq (E Jordan) in spring 2008. Ring 33, 1-2: 3-23. DOI: 10.2478/v10050-011-0001-9
Zehtindjiev P., Ilieva M., Ożarowska A., Busse P. 2003. Directional behaviour of the Sedge Warbler (Acrocephalus schoenobaenus) studied in two types of orientation cages during autumn migration – a case study. Ring 25, 1-2: 53-63.