|The LIDAR bus at the field site during the Kullaberg campaign May 2010. |
Photo: Mikkel Brygdegaard.
In a recent paper by P. Lundin et al. (2011; doi:10.1364/AO.50.003396) published in the July issue of Applied Optics a team of scientists from two of the Linnaeus environments at Lund University, Lund Laser Centre and CAnMove, report on new optical methods at a wide range of wavelengths used for remote bird classification. The team applied a variety of methods including eye-safe fluorescence and depolarization lidar techniques, passive scattering spectroscopy, and infrared (IR) spectroscopy in the field campaign at Kullaberg spring 2010. In this paper the team has refined the previously presented method of remotely classifying birds by using laser-induced beta-keratin fluorescence. Phenomena of excitation quenching were studied in the laboratory and were theoretically discussed in detail in the paper. It is shown how the ordered microstructures in bird feathers induce structural "colours" in the IR region with wavelengths of around 3-6 mu m. We show that transmittance in this region depends on the angle of incidence of the transmitted light in a species-specific way and that the transmittance exhibits a close correlation to the spatial periodicity in the arrangement of the feather barbules. Furthermore, we present a method by which the microstructure of feathers can be monitored in a remote fashion by utilization of thermal radiation and the wing beating of the bird.
The application of these remote techniques in bird migration studies is novel and shows a high potential to finally resolve the question what bird species are flying above in a pitch dark night sky. I find it exciting to see how CAnMove in this innovative way can contribute to development and application of new technology and how the field of animal movement research may benefit from these findings.