Electonic Supplementary Material
Development of Lateralisation of the Avian Magnetic Compass
Dennis Gehring1, Wolfgang Wiltschko1, Onur Güntürkün2, Susanne Denzau1 and Roswitha Wiltschko1*
1 FB Biowissenschaften, J.W.Goethe-Universität Frankfurt, Siesmayerstr. 70,
D-60054 Frankfurt a.M., Germany
2 Abteilung Biopsychologie, Fakultät für Psychologie, Ruhr-Universität Bochum,
D-44780 Bochum, Germany
Part 1. Details on the Methods used
1.1 Photoperiodic treatment of the birds
The test birds of groups A1 and A2were caught in September 2010 during a period when the natural photoperiod decreased from about L:D 13:11 (13 h light, 11 h dark) to about L:D 12:12. The photoperiod in the bird room ran synchronous with the natural one during autumnuntil the beginning of December 2010, when it was reduced to L:D 8:16 h. It was prolonged in two steps to L:D 13:11 in the beginning of January 2011 to induce premature migratory restlessness for spring migration, and was kept constant at L:D 13:11 during the spring tests and afterwards until the day length outside had reached about 13 h at the end of March/beginning of April 2011. Then the birds of group A2were set free.
Group A1 and the robins of group Sp caught during return migration to the breeding ground in March/April 2011 were kept over the summer, first in a photoperiod simulating northward migration, that is, it was gradually prolonged from 13 h to 17 h light between 25.3. and 6.5.2011. From then onward, we stimulated the day lengths of 62° N. This meant a maximum day length of 19.5 h light that was kept constant for about 1 month and then again gradually decreasedto 17.5 h light from 12.7. to 30.7.2011. To simulate the effect of beginning southward migration, the photoperiod was further decreased from 8.8. to 26.8.2011 to L:D 14:10. On 28.8.2011, it was reduced in one step by 2 h 30 min to L:D 11.5:12:30.5to promote Zugunruhe (migratory restlessness) and synchronize to birds for testing. After the tests were finished the birds were kept in that photoperiod until, during the first days of October 2011, the natural photoperiod outside had reached 11.5 h light; then the birds of group A1 and group Sp were also released.
1.2. Data analysis and statistical treatment
The thermo-paper was removed from the cage divided into 24 sectorseach 15° wide, and the scratch marks leftby the birds in each sector were counted blind. From the distribution of the activity in the 24 sectors, we calculated a formal ‘vector’ of each test by vector addition, with the direction indicating the heading and the vector length representing the concentration of the activity. For further analysis, we used only the headings, as the concentration appears to reflect individual traits of the birds and their response to be kept on a small cage rather than their orientation. From three (or two) headings of each bird, the respective mean vector of that individual birdwith the headings b and the length rbwas determined(given in Part 2 of this Electronic Supplemental Material).
The mean headings b of test birds were comprised in the grand mean vector for each condition, with the direction N and the length rN(seeTable 1 in Main Text), which were tested by the Rayleigh test for significant directional preferences [S1]. The data of the various test conditions were compared with the respective binocular controls; for comparing two significant samples, we used the Watson Wheeler test[S1] indicating for differences in direction(it can only be applied if the vector length of both samples exceeds 0.65). When comparing the significant controls with non-significant samples, we tested for difference in variance by applying the Mann WhitneyU- test to the angular differences between the individual mean heading and the direction of the grand mean vector.
The vector length rbof the of the individual birds reflects the intra-individual variance. Here, the medians were determined and included in Table 1 in the Main Text.
S1. Batschelet, E. 1981. Circular Statistics in Biology. London: Academic press
Part 2. Orientation behaviour of the individual birds
The vectors (direction αb, length rb)of the individual birds are based on three recordings each, except for the tests in the field with the vertical component inverted (see Table S2), where they are based on only two recordings).
The birds of the two groups A1 and A2 had been caught September 2010 on their first migration to the winter quarters; the birds of group Sp had been caught in April 2011 on their return migration to the breeding grounds.
Table S1 Mean vectors of birds of group A1 in the geomagnetic field
Autumn 2010 / Spring 2011Binocular / Left eye only / Binocular / Left eye only
Bird / αb / rb / αb / rb / αb / rb / αb / rb
10-1 / 230° / 0.82 / 106° / 0.45 / 342° / 0.79 / 136° / 0.54
10-2 / 179° / 0.92 / 222° / 0.28 / 24° / 0.94 / 3° / 0.40
10-3 / 167° / 0.33 / 220° / 0.95 / 315° / 0.03 / 229° / 0.79
10-4 / 178° / 0.81 / 161° / 0.78 / 17° / 0.98 / 233° / 0.62
10-5 / 217° / 0.40 / 173° / 0.77 / 28° / 0.93 / 84° / 0.86
10-6 / 268° / 0.46 / 173° / 0.98 / 11° / 0.98 / 165° / 0.42
10-7 / 156° / 0.38 / 185° / 0.70 / 11° / 0.93 / 275° / 0.31
10-8 / 246° / 0.55 / 249° / 0.44 / 132° / 0.56 / 25° / 0.52
10-9 / 186° / 0.67 / 175° / 0.81 / 7° / 1.00 / 277° / 0.61
10-10 / 64° / 0.63 / 179° / 0.91 / 345° / 0.99 / 346° / 0.10
10-11 / 145° / 0.14 / 180° / 0.83 / 288° / 0.47 / 301° / 0.87
10-12 / 215° / 0.86 / 190° / 1.00 / 323° / 0.55 / 232° / 0.33
Table S2 Mean vectors of birds of group A2tested in spring 2011
Binocular / Left eye only / Monocularly left-eyed after 6 h pre-exposuregeomagnetic field / geomagnetic field / geomagnetic field / vertical comp. inverted
Bird / αb / rb / αb / rb / αb / rb / αb / rb
10-13 / 26° / 0.88 / 57° / 0.75 / 334° / 0.79 / 148° / 0.99
10-14 / 322° / 0.93 / 197° / 0.95 / 43° / 0.83 / 168° / 0.79
10-15 / 276° / 0.75 / 333° / 0.37 / 16° / 0.89 / 187° / 1.00
10-16 / 346° / 0.22 / 62° / 0.37 / 60° / 0.58 / 158° / 0.65
10-17 / 357° / 0.92 / 37° / 0.53 / 23° / 1.00 / 167° / 0.98
10-18 / 340° / 0.92 / 10° / 0.88 / 28° / 0.95 / 213° / 0.87
10-19 / 193° / 0.26 / 133° / 0.18 / 350° / 0.22 / 215° / 0.96
10-20 / 360° / 0.91 / 65° / 0.25 / 19° / 0.94 / 155° / 1.00
10-21 / 356° / 0.70 / 22° / 0.71 / 30° / 0.36 / 206° / 0.81
10-22 / 356° / 0.93 / 128° / 0.66 / 32° / 0.87 / 217° / 0.98
10-23 / 14° / 0.99 / 299° / 0.68 / 359° / 0.33 / 141° / 0.58
10-24 / 360° / 0.93 / 210° / 0.51 / 35° / 0.45 / 159° / 0.99
Table S3 Mean vectors of birds of group A1tested in autumn 2011 in the geomagnetic field
Bird / Binocular / Left eye only / Monoc. left-eyed after 6 h pre-exposureαb / rb / αb / rb / αb / rb
10-1 / 202° / 0.96 / 67° / 0.91 / 112° / 0.56
10-2 / 160° / 0.86 / 202° / 0.92 / 31° / 0.49
10-3 / 167° / 0.90 / 225° / 0.31 / 67° / 0.36
10-4 / 201° / 0.83 / 103° / 0.58 / 178° / 0.32
10-5 / 190° / 0.90 / 30° / 0.27 / 158° / 0.47
10-6 / 195° / 0.98 / 326° / 0.32 / 312° / 0.48
10-7 / 181° / 0.65 / 286° / 0.25 / 5° / 0.25
10-8 / 209° / 0.96 / 227° / 0.57 / 281° / 0.65
10-9 / 177° / 0.95 / 103° / 0.84 / 200° / 0.93
10-10 / 178° / 0.90 / 306° / 0.88 / 255° / 0.63
10-11 / 31° / 0.51 / 343° / 0.77 / 200° / 0.43
Table S4 Mean vectors of birds of group Sptested in autumn 2011 in the geomagnetic field
Bird / Binocular / Left eye only / Monoc. left-eyed after 6 h pre-exposureαb / rb / αb / rb / αb / rb
1-11 / 196° / 0.95 / 167° / 0.91 / 359° / 0.85
2-11 / 233° / 0.79 / 140° / 0.60 / 354° / 0.38
3-11 / 186° / 0.33 / 210° / 0.62 / 307° / 0.67
4-11 / 149° / 0.96 / 358° / 0.66 / 29° / 0.32
5-11 / 181° / 0.93 / 316° / 0.42 / 300° / 0.96
6-11 / 189° / 0.99 / 294° / 0.39 / 225° / 0.38
7-11 / 187° / 0.74 / 111° / 0.49 / 3° / 0.36
8-11 / 209° / 0.60 / 184° / 0.57 / 146° / 0.54
9-11 / 60° / 0.14 / 163° / 0.16 / 31° / 0.79
10-11 / 164° / 0.34 / 89° / 0.22 / 191° / 0.91
11-11 / 256° / 0.29 / 311° / 0.53 / 131° / 0.75