Collaboration: Dr. Reuven Yosef from the Ben-Gurion University in Negev, Israël, Dr. Piotr Tryjanowski and Anna Kubicka from the Institute of Zoology, Poznan University of Life Sciences in Poznań, Poland.
Reuven Yosef discovered my project and collection BCP (Black Code Project). He saw this collection as a starting point, to combine this with data of the condition of the same individual Great Grey Shrikes (Lanius excubitor).
Reuven Yosef and I evaluated 324 skins of Great Grey Shrike at the Naturalis Biodiversity Center at Leiden, The Netherlands, in August 2014. Due to varying states of preservation and other considerations the final analyses was done on 63 (19.4%) tails. The black markings of the BCP are used in order to evaluate the symmetry of the two sides of each shrike. Anna Kubicka used a Tps dig 2 program to measure these patterns with landmarks. In addition, ptilochronology was applied by Reuven Yosef to understand if symmetry was affected by nutritional condition. Ptilochronology (Grubb 1989) is based on the evaluation of the width of feather growth bars during each 24-h period at the time of moult and depends on the amount of energy and nutrients invested by an individual into the regeneration process, which at the same time depends on the nutritional condition and quality of an individual (Grubb 1989, 2006). The growing and fault bars are best seen under very good lightning conditions.
According to the Israeli researcher, something can be learned from the tail feather patterns about the fitness of the birds and even about sexual selection for Great Grey Shrikes. This all has to do with the degree of symmetry and asymmetry of the patterns, combined with data about the speed at which the feathers grow.
Asymmetry in the wild is a controversial, and to date, unresolved subject. Fluctuating asymmetry (FA) is described as the developmental instability (intra-individual variation) while, directional asymmetry (DA) expresses the asymmetry of the population mean.
Prof. Reuven Yosef used the ptilochronological method by pricking with a needle on the growing bars (T1)
Fault and growing bars on the tailfeathers
Image by Anna Kubicka using Tps dig 2 program.