On the Exploitation of Mid-infrared Iridescence of Plumage for Remote Classification of Nocturnal Migrating Birds

Abstract

A challenging task in ornithology lies in identifying high-altitude nocturnal migrating bird species and genders. While the current approaches including radar, lunar obscuration, and single-band thermal imaging provide means of detection, a more detailed spectral or polarimetric analysis of light has the potential for retrieval of additional information whereby the species and sex could be determined. In this paper, we explore remote classification opportunities provided by iridescent features within feathers in the mid-infrared region. Our approach first involves characterizing the microstructural features of the feather by using rotation and straining, and a scheme for their remote detection is proposed by correlating these microstructural changes to spectral and polarimetric effects. Furthermore, we simulate the spectral signature of the entire bird by using a model that demonstrates how classification would be achieved. Finally, we apply infrared hyperspectral polarization imaging, showing that the net iridescent effect persists for the bird as a whole.

SUPER RESOLUTION LASER RADAR WITH BLINKING ATMOSPHERIC PARTICLES ---- APPLICATION TO INTERACTING FLYING INSECTS (Invited Paper)

“…We have earlier shown how detailed wing beat waveforms in several spectral bands can yield remote microscopic information in bird feathers [5]. Equivalently, remote nanoscopy may be conducted of insect wing membranes using multi-band lidars, which, so far, have been developed for conventional aerosol particle characterization [17,18].…”

“…While research in the area of radar entomology has been conducted over several decades and numerous interesting applications have been described [4], laser radar (light detection and ranging; lidar) systems in the optical regime have the potential of achieving a far better sensitivity and address and classify even the tiniest insects, simply because most insects are much smaller than the wavelengths of microwaves used in radars but larger than the wavelengths of light. Further, optical off-the-shelf components allow spectral-and polarimetric target classification, providing molecular as well as microstructure information [5,6]. Along these lines our group has previously demonstrated lidar remote detection of insects labeled with fluorescent powders, e.g., for assessing dispersal rates on a landscape scale [7,8].…”

Classification of peacock feather reflectance using principal component analysis similarity factors from multispectral imaging data

“…Classification of spatial reflectance patterns using PCA-based similarity factors can be applied to similar animal species when the effects of disorder and spatial averaging over repeated nanostructures contribute to smooth angular color variations [1,9,11]. However, there are iridescent birds and other animal species that have tetrachromatic vision, from the UV to the visible region, and show polarization effects and reflection maxima in the UV [1, 14-17, 19, 20, 43] and in the IR spectra [15,22,25]. This issue remains open and requires multispectral or hyperspectral polarization imaging methods in those spectral ranges [22,25].…”

“…Harvey et al have investigated the dependence between scattered light and orientation of feather barbs of the Purple Glossy Starling (Lamprotornis purpureus) and the African Emerald Cuckoo (Chrysococcyx cupreus) using a imaging scatterometer based on a spherical gantry configuration and an RGB camera [23,24]. Brydegaard et al have investigated the existence of iridescent effects in the mid-IR region of many avian species for remote classification at long distances [25]. They have concluded that these IR iridescent features have a structural origin at the micrometer level.…”

“…They have concluded that these IR iridescent features have a structural origin at the micrometer level. These authors have performed hyperspectral reflectance polarization imaging [26][27][28] of the Mallard (Anas platyrhynchos) demonstrating that IR iridescence persists in the entire bird [25].…”