Abstract

We present optical methods at a wide range of wavelengths for remote classification of birds. The proposed methods include eye-safe fluorescence and depolarization lidar techniques, passive scattering spectroscopy, and infrared (IR) spectroscopy. In this paper we refine our previously presented method of remotely classifying birds with the help of laser-induced β-keratin fluorescence. Phenomena of excitation quenching are studied in the laboratory and are theoretically discussed in detail. It is shown how the ordered microstructures in bird feathers induce structural “colors” in the IR region with wavelengths of around 36μm. 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. 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.

© 2011 Optical Society of America

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    [CrossRef]

2010 (4)

H. Noh, S. F. Liew, V. Saranathan, S. G. J. Mochrie, R. O. Prum, E. R. Dufresne, and H. Cao, “How noniridescent colors are generated by quasi-ordered structures of bird feathers,” Adv. Mat. 22, 2871–288 (2010).
[CrossRef]

Z. G. Guan, P. Lundin, L. Mei, G. Somesfalean, and S. Svanberg, “Vertical lidar sounding of atomic mercury and nitric oxide in a major Chinese city,” Appl. Phys. B 101, 465–470 (2010).
[CrossRef]

M. Brydegaard, P. Lundin, Z. G. Guan, A. Runemark, S. Åkesson, and S. Svanberg, “Feasibility study: fluorescence lidar for remote bird classification,” Appl. Opt. 49, 4531–4544(2010).
[CrossRef] [PubMed]

Z. G. Guan, M. Brydegaard, P. Lundin, M. Wellenreuther, A. Runemark, E. I. Svensson, and S. Svanberg, “Insect monitoring with fluorescence lidar techniques: field experiments,” Appl. Opt. 49, 5133–5142 (2010).
[CrossRef] [PubMed]

2009 (2)

N. E. Seavy, J. H. Viers, and J. K. Wood, “Riparian bird response to vegetation structure: a multiscale analysis using lidar measurements of canopy height,” Ecol. Appl. 19, 1848–1857 (2009).
[CrossRef] [PubMed]

B. J. Stutchbury, S. A. Tarof, T. Done, E. Gow, P. M. Kramer, J. Tautin, J. W. Fox, and V. Afanasyev, “Tracking long-distance songbird migration by using geolocators,” Science 323, 896–896 (2009).
[CrossRef] [PubMed]

2008 (3)

P. Henningsson, G. Spedding, and A. Hedenstrom, “Vortex wake and flight kinematics of a swift in cruising flight in a wind tunnel,” J. Exp. Biol. 211, 717–730 (2008).
[CrossRef] [PubMed]

I. Newton, The Migration Ecology of Birds (Academic, 2008).

R. Clawges, K. Vierling, L. Vierling, and E. Rowell, “The use of airborne lidar to assess avian species diversity, density, and occurrence in a pine/aspen forest,” Remote Sens. Environ. 112, 2064–2073 (2008).
[CrossRef]

2007 (5)

S. Svanberg, “LIDAR,” in Springer Handbook of Lasers and Optics, F.Träger, ed. (Springer-Verlag, 2007), pp. 1031–1052.

U. Rascher, B. Gioli, and F. Miglietta, “FLEX—fluorescence explorer: a remote sensing approach to quantify spatio-temporal variations of photosynthetic efficiency from space,” Photosynth. Res. 91, 293–294 (2007).
[CrossRef]

S. Åkesson and A. Hedenström, “How migrants get there: migratory performance and orientation,” BioScience 57, 123–133 (2007).
[CrossRef]

T. Alerstam, J. Bäckman, G. A. Gudmundsson, A. Hedenström, S. S. Henningsson, H. Karlsson, M. Rosén, and R. Strandberg, “A polar system of intercontinental bird migration,” Proc. R. Soc. B 274, 2523–2530 (2007).
[CrossRef] [PubMed]

T. Alerstam, M. Rosén, J. Bäckman, P. G. Ericson, and O. Hellgren, “Flight speeds among bird species: allometric and phylogenetic effects,” PLos Biol. 5, 1656–1662 (2007).
[CrossRef]

2006 (3)

S. A. Gauthreaux and J. W. Livingston, “Monitoring bird migration with a fixed-beam radar and a thermal-imaging camera,” J. Field Ornithol. 77, 319–328 (2006).
[CrossRef]

G. E. Hill and K. J. McGraw, Bird Coloration, Mechanisms and Measurements, Vol.  1 (Harvard University Press, 2006).

R. O. Prum, “Anatomy, physics and evolution of structural colors,” in Bird Coloration, Mechanisms and Measurements, G.E.Hill and K.J.McGraw, eds., Vol.  1 (Harvard University Press, 2006), pp. 295–354.

2005 (6)

T.Fujii and T.Fukuchi, eds., Laser Remote Sensing (CRC Press, 2005).

R. B. Bradbury, R. A. Hill, D. C. Mason, S. A. Hinsley, J. D. Wilson, H. Balzter, G. Q. A. Anderson, M. J. Whittingham, I. J. Davenport, and P. E. Bellamy, “Modelling relationships between birds and vegetation structure using airborne lidar data: a review with case studies from agricultural and woodland environments,” Ibis 147, 443–452 (2005).
[CrossRef]

R. Grönlund, M. Sjöholm, P. Weibring, H. Edner, and S. Svanberg, “Elemental mercury emissions from chlor-alkali plants measured by lidar techniques,” Atmos. Environ. 39, 7474–7480 (2005).
[CrossRef]

A. Farnsworth and I. J. Lovette, “Evolution of nocturnal flight calls in migrating wood-warblers: apparent lack of morphological constraints,” J. Avian Biol. 36, 337–347 (2005).
[CrossRef]

N. Takeuchi, “Elastic lidar measurement of the troposphere,” in Laser Remote Sensing, T.Fujii and T.Fukuchi, eds. (CRC Press, 2005), pp. 63–122.
[CrossRef]

J. Meade, D. Biro, and T. Guilford, “Homing pigeons develop local route stereotypy,” Proc. R. Soc. B 272, 17–23 (2005).
[CrossRef] [PubMed]

2004 (2)

A. Farnsworth, S. A. Gauthreaux, Jr., and D. van Blaricom, “A comparison of nocturnal call counts of migrating birds and reflectivity measurements on Doppler radar,” J. Avian Biol. 35, 365–369 (2004).
[CrossRef]

S. Svanberg, Atomic and Molecular Spectroscopy—Basic Aspects and Practical Applications, 4th ed. (Springer-Verlag, 2004).

2003 (4)

R. O. Prum and R. H. Torres, “A Fourier tool for the analysis of coherent light scattering by bio-optical nanostructures,” Integr. Comp. Biol. 43, 591–602 (2003).
[CrossRef] [PubMed]

P. Weibring, H. Edner, and S. Svanberg, “Versatile mobile lidar system for environmental monitoring,” Appl. Opt. 42, 3583–3594 (2003).
[CrossRef] [PubMed]

M.A.Mycek and B.W.Pogue, eds., Handbook of Biomedical Fluorescence (CRC Press, 2003).

T. Alerstam, A. Hedenström, and S. Åkesson, “Long-distance migration: evolution and determinants,” Oikos 103, 247–260(2003).
[CrossRef]

2002 (1)

C. Giacovazzo, H. L. Monaco, G. Artioli, D. Viterbo, G. Ferraris, G. Gilli, G. Zanotti, and M. Catti, Fundamentals of Crystallography (Oxford University Press, 2002).
[PubMed]

2001 (4)

P. Weibring, T. Johansson, H. Edner, S. Svanberg, B. Sundnér, V. Raimondi, G. Cecchi, and L. Pantani, “Fluorescence lidar imaging of historical monuments,” Appl. Opt. 40, 6111–6120(2001).
[CrossRef]

S. Zehnder, S. Åkesson, F. Liechti, and B. Bruderer, “Nocturnal autumn bird migration at Falsterbo, south Sweden,” J. Avian Biol. 32, 239–248 (2001).
[CrossRef]

F. Liechti, “Calibrating the moon-watching method—changes and limits,” Avian Ecol. Beh. 7, 27–41 (2001).

J. Bäckman and T. Alerstam, “Confronting the winds: orientation and flight behaviour of roosting swifts, Apus apus,” Proc. R. Soc. B 268, 1081–1087 (2001).
[CrossRef] [PubMed]

2000 (1)

A. Ounis, Z. G. Cerovic, J. M. Briantais, and I. Moya, “DE-FLIDAR: a new remote sensing instrument for estimation of epidermal UV absorption in leaves and canopies,” in Proceedings of the European Association of Remote Sensing Laboratories (EARSeL)-SIGWorkshop LIDAR, Vol.  1 (EARSeL, 2000), pp. 196–204.

1999 (1)

M. Srinivasarau, “Nano-optics in the biological world,” Chem. Rev. 99, 1935–1961 (1999).
[CrossRef]

1998 (3)

N. S. Hart, J. C. Partridge, and I. C. Cuthill, “Visual pigments, cone oil droplets and cone photoreceptor distribution in the European starling (Sturnus vulgaris),” J. Exp. Biol. 201, 1433–1446 (1998).
[PubMed]

S. Hunt, A. T. Bennett, I. C. Cuthill, and R. Griffiths, “Blue tits are ultraviolet tits,” Proc. R. Soc. Lond. B 265, 451–455 (1998).
[CrossRef]

B. Bruderer and F. Liechti, “Intensität, Höhe und Richtung von Tag- und Nachtzug im Herbst über Südwestdeutschland,” Ornithol. Beob. 95, 113–128 (1998).

1996 (1)

F. Liechti, D. Peter, R. Lardelli, and B. Bruderer, “Herbstlicher Vogelzug im Alpenraum nach Mond-beobachtungen—Topographie un Wind beeinflussen den Zugverlauf,” Ornithol. Beob. 93, 131–152 (1996).

1995 (1)

F. Liechti, B. Bruderer, and H. Paproth, “Quantification of nocturnal bird migration by moonwatching: comparison with radar and infrared observations,” J. Field Ornithol. 66, 457–468 (1995).

1994 (1)

B. Bruderer and F. Liechti, “Quantification of bird migration—different means compared,” in Proceedings of the Bird Strike Committee, Europe, Vol.  22 (Bird Strike Committee Europe, 1994), pp. 243–254.

1993 (1)

S. Åkesson, “Coastal migration and wind drift compensation in nocturnal passerine migrants,” Ornis Scand. 24, 87–94(1993).
[CrossRef]

1990 (2)

Å. Lindström, “The role of predation risk in stopover habitat selection in migrating bramblings, Fringilla montifringilla,” Behav. Ecol. 1, 24–35 (1990).
[CrossRef]

T. Alerstam and Å. Lindström, “Optimal bird migration: the relative importance of time, energy and safety,” in Bird Migration: Physiology and Ecophysiology, E.Gewinner, ed. (Springer-Verlag, 1990), pp. 331–351.

1989 (1)

P. Kerlinger and F. R. Moore, Atmospheric Structure and Avian Migration (Plenum, 1989).

1987 (1)

C. M. R. Platt, J. C. Scott, and A. C. Dilley, “Remote sounding of high clouds. part VI: optical properties of mid-latitude and tropical cirrus,” J. Atmos. Sci. 44, 729–747 (1987).
[CrossRef]

1980 (1)

1976 (1)

T. Alerstam, “Nocturnal migration of thrushes (Turdus spp.) in southern Sweden,” Oikos 27, 457–475 (1976).
[CrossRef]

1973 (1)

1972 (2)

G. Benedetti-Michelangeli, F. Gongeduti, and G. Fiocco, “Measurement of aerosol motion and wind velocity in the lower troposphere by Doppler optical radar,” J. Atmos. Sci. 29, 906–910 (1972).
[CrossRef]

B. Bruderer and E. Weitnauer, “Radarbeobachtungen über Zug und Nachtflüge des Mauerseglers (Apus Apus),” Rev. Suisse Zool. 79, 1190–1200 (1972).
[PubMed]

1971 (2)

1969 (2)

J. L. F. Parslow, “The migration of passerine night migrants across the English Channel studied by radar,” Ibis 111, 48–79(1969).
[CrossRef]

S. A. Gauthreaux, Jr., “A portable ceilometer technique for studying low level nocturnal migration,” Bird Banding 40, 309–320 (1969).
[CrossRef]

1966 (1)

M. B. Casement, “Migration across the Mediterranean observed by radar,” Ibis 108, 461–491 (1966).
[CrossRef]

1962 (1)

D. W. H. Adams, “Radar observations of bird migration in Cyprus,” Ibis 104, 133–146 (1962).
[CrossRef]

1949 (1)

C.V. Raman, “The theory of the Christiansen experiment,” Proc. Indian Acad. Sci. A29, 381–390 (1949).

Adams, D. W. H.

D. W. H. Adams, “Radar observations of bird migration in Cyprus,” Ibis 104, 133–146 (1962).
[CrossRef]

Afanasyev, V.

B. J. Stutchbury, S. A. Tarof, T. Done, E. Gow, P. M. Kramer, J. Tautin, J. W. Fox, and V. Afanasyev, “Tracking long-distance songbird migration by using geolocators,” Science 323, 896–896 (2009).
[CrossRef] [PubMed]

Åkesson, S.

M. Brydegaard, P. Lundin, Z. G. Guan, A. Runemark, S. Åkesson, and S. Svanberg, “Feasibility study: fluorescence lidar for remote bird classification,” Appl. Opt. 49, 4531–4544(2010).
[CrossRef] [PubMed]

S. Åkesson and A. Hedenström, “How migrants get there: migratory performance and orientation,” BioScience 57, 123–133 (2007).
[CrossRef]

T. Alerstam, A. Hedenström, and S. Åkesson, “Long-distance migration: evolution and determinants,” Oikos 103, 247–260(2003).
[CrossRef]

S. Zehnder, S. Åkesson, F. Liechti, and B. Bruderer, “Nocturnal autumn bird migration at Falsterbo, south Sweden,” J. Avian Biol. 32, 239–248 (2001).
[CrossRef]

S. Åkesson, “Coastal migration and wind drift compensation in nocturnal passerine migrants,” Ornis Scand. 24, 87–94(1993).
[CrossRef]

Alerstam, T.

T. Alerstam, M. Rosén, J. Bäckman, P. G. Ericson, and O. Hellgren, “Flight speeds among bird species: allometric and phylogenetic effects,” PLos Biol. 5, 1656–1662 (2007).
[CrossRef]

T. Alerstam, J. Bäckman, G. A. Gudmundsson, A. Hedenström, S. S. Henningsson, H. Karlsson, M. Rosén, and R. Strandberg, “A polar system of intercontinental bird migration,” Proc. R. Soc. B 274, 2523–2530 (2007).
[CrossRef] [PubMed]

T. Alerstam, A. Hedenström, and S. Åkesson, “Long-distance migration: evolution and determinants,” Oikos 103, 247–260(2003).
[CrossRef]

J. Bäckman and T. Alerstam, “Confronting the winds: orientation and flight behaviour of roosting swifts, Apus apus,” Proc. R. Soc. B 268, 1081–1087 (2001).
[CrossRef] [PubMed]

T. Alerstam and Å. Lindström, “Optimal bird migration: the relative importance of time, energy and safety,” in Bird Migration: Physiology and Ecophysiology, E.Gewinner, ed. (Springer-Verlag, 1990), pp. 331–351.

T. Alerstam, “Nocturnal migration of thrushes (Turdus spp.) in southern Sweden,” Oikos 27, 457–475 (1976).
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S. Svanberg, “LIDAR,” in Springer Handbook of Lasers and Optics, F.Träger, ed. (Springer-Verlag, 2007), pp. 1031–1052.

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C. Giacovazzo, H. L. Monaco, G. Artioli, D. Viterbo, G. Ferraris, G. Gilli, G. Zanotti, and M. Catti, Fundamentals of Crystallography (Oxford University Press, 2002).
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Figures (12)

Fig. 1
Fig. 1

Photographic setup overview of the field site at Kullaberg and its location in Sweden. The site has the coordinates N 56 ° 18 , E 12 ° 26 . Shown are the locations of the lidar equipment, the center dome in which the IR cameras were installed, the east dome with the passive telescope, and a weather station. Also shown are two directions in which different lidar measurements were performed.

Fig. 2
Fig. 2

Schematic overview of the fluorescence and polarizing lidar system. The light from the laser is expanded and variably diverged before it is sent out vertically or in other inclinations. The returning light is focused onto the detector system with a 40 cm diameter telescope. Here it is separated into different spectral bands or two polarization directions, or it is sent through a fiber to an OMA.

Fig. 3
Fig. 3

a) Reflectance spectra for different birds at locations specified in the legend. All of the birds are specified elsewhere except for the budgerigar, the hummingbird, and the turaco with Latin names Melopsittacus undulates, Colibri thalassinus, and Tauraco erythrolophus, respectively. b) Fluorescence spectra ratios for the golden oriole. The fluorescence is given relative to unpigmented β-keratin. Excitation at 266, 308, and 355 nm .

Fig. 4
Fig. 4

Fluorescence spectra from six birds as remotely obtained by the optical multichannel system. a) The spectra are averaged over 250 shots and smoothed with a 20-channel floating average. Included in the figure is also the overall spectral transmittance in each channel. In these curves are included the transmittance through all optics after the telescope but not the quantum efficiency of the PMTs. What can be noticed is that the UV channel also has some transmittance in the yellow region. However, the lower quantum efficiency of the PMT in this region, in combination with the low emission from β-keratin here, makes the contribution from this region to the total signal small. b) The same spectra divided with the herring gull spectrum.

Fig. 5
Fig. 5

Isosurface 3D histogram plot for the fluorescence return from different birds. Depending on the fluorescence spectrum, different birds gather at different locations in the 3D space made from the three fluorescence channels normalized with the depolarized elastic channel.

Fig. 6
Fig. 6

Lidar signals in the depolarized elastic and the three fluorescence channels during a released bird event (for the geometry, see Fig. 1). The bird is a lesser whitethroat released at 23:34, 28 May.

Fig. 7
Fig. 7

Lidar returns in a copolarized (dotted curve, light gray) and a depolarized (solid curve, dark gray) channel for a) flying barn swallow, b) museum sample gray heron, and c) aluminum plate.

Fig. 8
Fig. 8

Histograms over the lidar return distributions in time and space for flying barn swallows recorded during a time span of 38 min . The direction in which the recordings are done is marked “Path North” in Fig. 1.

Fig. 9
Fig. 9

a) Spectral overview of structural MIR effects. The transmittance of three bird feathers at normal incidence shows significantly different spectral features in the wavelength region 3.5 5.5 μm . For demonstration purposes, the feather transmittance spectra have been normalized to the Christiansen peak at 5.9 μm wavelength and the transmittance dip at around 6.1 μm , due to β-keratin absorption. Gray areas denote atmospheric absorption with the primary responsible species indicated. Also shown is the normalized responsivity of three different semiconductor detector materials. Below, sections of the micrographs used for spatial frequency analysis, showing barbules attached to opposite side of the barbs of the same b) blackbird, c) sparrow-hawk, and d) pallid harrier feathers.

Fig. 10
Fig. 10

Correlation between the periodicity of the distal barbule separation and the wavelength of peak transmittance for different bird feathers. It must be stressed that there is a significant uncertainty regarding both the wavelength of peak transmittance as well as barbule periodicity. The keratin absorption bands near 3 and 6 μm , as well as the tail of the Christiansen peak, will affect the transmittance spectrum of keratin, resulting in a shift of the wavelength of maximum transmittance that would result from interference alone. Along the other axis, the measured interbarbule distances depend both on the location on the feather, and can be expected to further deviate for different feathers on the same individual bird.

Fig. 11
Fig. 11

Calculated ratio between long and short (wavelength) spectral bands (relative slope) for blackbird, sparrow-hawk, and pallid harrier feathers. Ideal bandpass filters were used for calculations, defined as having spectral transmittance equal to 1 for wavelengths λ in the interval I, and 0 otherwise, where I was chosen as 2.7 to 4.3 μm for the short-wavelength band, and 4.3 to 5.5 μm for the long-wavelength band, corresponding to the two atmospheric windows on either side of the CO 2 absorption band at around 4.3 μm .

Fig. 12
Fig. 12

a) Histogram of relative slopes in total intensity enables us to determine a threshold for rare events. Crosses mark the events detected in Fig. 12b). b) Change in total collected mean intensity when a barn swallow passes by at 12:49 on 26 May 2010. c) Spectral intensity change relative to the static sky spectrum during the same event as in b).

Tables (1)

Tables Icon

Table 1 Remotely Measured DPRs at 266 nm Reflectance for a Gray Heron (Ardea Cinerea), Sparrow-Hawk (Accipiter Nisus), Red Ibis (Eudocimus Ruber), Chattering Lory (Lorius Garrulus), Barn Owl (Tyto Alba Guttata), Herring Gull (Larus Argentatus), Pallid Harrier (Circus Macrourus), Styrofoam, and Aluminum

Equations (4)

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R keratin ( λ ) = A · exp ( exp ( λ λ 0 d ) ) + S ,
DPR = I I + I II ,
L b = L ( λ ) T ( λ ) S b ( λ ) d λ ,
B = L long L short L long + L short .

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