Abstract

Colorful traits can vary in response to neural control, hormone levels, reproductive state, or abiotic factors. In birds, colorful plumage traits are generally considered static ornaments that only vary irreversibly due to abrasion, bacterial degradation, or wear. However, in this work it is shown that iridescent feather color varies rapidly and reversibly in response to changes in ambient humidity. Based on optical models and sorption experiments, these changes appear to be caused by a swelling of the outer keratin cortex following water absorption. To our knowledge, this is the first study describing dynamic color changes in any keratinous biophotonic nanostructure.

© 2010 OSA

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. B. Sillén-Tullberg, “Higher survival of an aposematic than of a cryptic form of a distasteful bug,” Oecologia 67(3), 411–415 (1985).
    [CrossRef]
  2. T. Slagsvold, S. Dale, and A. Kruszewicz, “Predation favours cryptic coloration in breeding male pied flycatchers,” Anim. Behav. 50(4), 1109–1121 (1995).
    [CrossRef]
  3. M. Stevens and S. Merilaita, “Animal camouflage: current issues and new perspectives,” Philos. Trans. R. Soc. Lond. B Biol. Sci. 364(1516), 423–427 (2009).
    [CrossRef]
  4. M. Andersson, Sexual Selection (Princeton University Press, Princeton, NJ, 1994).
  5. K. McGraw, “Mechanics of carotenoid-based coloration,” in Bird Coloration Volume I: Mechanisms and Measurements, K. McGraw, and G. Hill, eds. (Harvard University Press, Cambridge, MS, 2006), pp. 177–242.
  6. P. Vukusic and J. R. Sambles, “Photonic structures in biology,” Nature 424(6950), 852–855 (2003).
    [CrossRef] [PubMed]
  7. R. O. Prum, “Anatomy, physics, and evolution of structural colors,” in Bird Coloration Volume I: Mechanisms and Measurements, G. E. Hill, and K. J. McGraw, eds. (Harvard University Press, Cambridge, MS, 2006), pp. 295–353.
  8. S. Kinoshita, Structural Colors in the Realm of Nature (World Scientific Publishing Co., Singapore, 2008).
  9. R. T. Hanlon, and J. B. Messenger, Cephalopod Behaviour (Cambridge University Press, Cambridge, UK, 1988).
  10. L. M. Mäthger, M. F. Land, U. E. Siebeck, and N. J. Marshall, “Rapid colour changes in multilayer reflecting stripes in the paradise whiptail, Pentapodus paradiseus,” J. Exp. Biol. 206(20), 3607–3613 (2003).
    [CrossRef] [PubMed]
  11. S. M. Doucet and D. J. Mennill, “Dynamic sexual dichromatism in an explosively breeding Neotropical toad,” Biol. Lett. 6(1), 63–66 (2010).
    [CrossRef]
  12. R. Potyrailo, H. Ghiradella, A. Vertiatchikh, K. Dovidenko, J. Cournoyer, and E. Olson, “Morpho butterfly wing scales demonstrate highly selective vapour response,” Nat. Photonics 1(2), 123–128 (2007).
    [CrossRef]
  13. F. Liu, B. Q. Dong, X. H. Liu, Y. M. Zheng, and J. Zi, “Structural color change in longhorn beetles Tmesisternus isabellae,” Opt. Express 17(18), 16183–16191 (2009).
    [CrossRef] [PubMed]
  14. M. Rassart, P. Simonis, A. Bay, O. Deparis, and J. P. Vigneron, “Scale coloration change following water absorption in the beetle Hoplia coerulea (Coleoptera),” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 80(3), 031910 (2009).
    [CrossRef] [PubMed]
  15. M. D. Shawkey, S. R. Pillai, G. E. Hill, L. M. Siefferman, and S. R. Roberts, “Bacteria as an agent for change in structural plumage color: correlational and experimental evidence,” Am. Nat. 169(s1Suppl 1), S112–S121 (2007).
    [CrossRef] [PubMed]
  16. E. H. Burtt, “Tips on Wings and Other Things,” in The Behavioral Significance of Color, E. H. Burtt, ed. (Garland Publishing, Inc., New York, NY, 1986), pp. 75–110.
  17. J. Örnborg, S. Andersson, S. Griffith, and B. C. Sheldon, “Seasonal changes in a ultraviolet structural colour signal in blue tits, Parus caeruleus,” Biol. J. Linn. Soc. Lond. 76(2), 237–245 (2002).
    [CrossRef]
  18. S. Andersson, and M. Prager, “Quantifying Colors,” in Bird Coloration: Mechanisms & Measurements, G. Hill, and K. McGraw, eds. (Harvard University Press, Cambridge, MS, 2006), pp. 41–89.
  19. I. Watt, “Sorption of water vapor by keratin,” Pol. Rev. 18(2), 169–245 (1980).
  20. M. D. Shawkey, A. M. Estes, L. M. Siefferman, and G. E. Hill, “Nanostructure predicts intraspecific variation in ultraviolet-blue plumage colour,” Proc. Biol. Sci. 270(1523), 1455–1460 (2003).
    [CrossRef] [PubMed]
  21. M. D. Abramoff, P. J. Magelhae, and S. J. Ram, “Image processing with ImageJ,” Biophotonics International 11, 36–42 (2004).
  22. I. Agnarsson, A. Dhinojwala, V. Sahni, and T. A. Blackledge, “Spider silk as a novel high performance biomimetic muscle driven by humidity,” J. Exp. Biol. 212(13), 1990–1994 (2009).
    [CrossRef] [PubMed]
  23. G. E. Hill, “House Finch,” in The Birds of North America Online, A. Poole, ed. (Cornell Lab of Ornithology, Ithaca, NY, 1993).
  24. P. A. Gowaty, and J. H. Plissner, “Eastern Bluebird,” in The Birds of North America Online, A. Poole, ed. (Cornell Lab of Ornithology, Ithaca, NY, 1998).
  25. R. Montgomerie, “Analyzing Colors,” in Bird Coloration Volume I: Mechanisms and Measurements, G. E. Hill, and K. J. McGraw, eds. (Harvard University Press, Cambridge, MS, 2006), pp. 90–147.
  26. G. Jellison., “Data analysis for spectroscopic ellipsometry,” Thin Solid Films 234(1-2), 416–422 (1993).
    [CrossRef]
  27. R. Maia, J. V. O. Caetano, S. N. Báo, and R. H. Macedo, “Iridescent structural colour production in male blue-black grassquit feather barbules: the role of keratin and melanin,” J. R. Soc. Interface 6(Suppl 2), S203–S211 (2009).
    [PubMed]
  28. D. J. Brink and N. van der Berg, “Structural colours from the feathers of the bird Bostrychia hagedash,” J. Phys. D Appl. Phys. 37(5), 813–818 (2004).
    [CrossRef]
  29. M. F. Land, “The physics and biology of animal reflectors,” Prog. Biophys. Mol. Biol. 24, 75–106 (1972).
    [CrossRef] [PubMed]
  30. R Development Core Team, “R: A Language and Environment for Statistical Computing,” (Vienna, Austria, 2009).
  31. H. Durrer, “Schillerfarben der vogelfeder als evolutionsproblem,” Denkschriften der Schweizerischen Naturforschenden Gesellschaft 91, 1–127 (1977).
  32. D. Vanhecke, L. Studer, and D. Studer, “Cryoultramicrotomy,” in Electron Microscopy: Methods and Protocols, J. M. Walker, ed. (Humana Press, Totowa, New Jersey, 2007).
  33. D. Osorio and A. D. Ham, “Spectral reflectance and directional properties of structural coloration in bird plumage,” J. Exp. Biol. 205(Pt 14), 2017–2027 (2002).
    [PubMed]
  34. J. Morrison and J. Hanlan, “Swelling of fibrous proteins,” Nature 179(4558), 528–529 (1957).
    [CrossRef]
  35. D. Beaglehole and H. K. Christenson, “Vapor adsorption on mica and silicon: entropy effects, layering, and surface forces,” J. Phys. Chem. 96(8), 3395–3403 (1992).
    [CrossRef]
  36. B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
    [CrossRef] [PubMed]
  37. K. Manoli, D. Goustouridis, S. Chatzandroulis, I. Raptis, E. Valamontes, and M. Sanopoulou, “Vapor sorption in thin supported polymer films studied by white light interferometry,” Polymer (Guildf.) 47(17), 6117–6122 (2006).
    [CrossRef]
  38. G. Harsányi, “Polymer films in sensor applications: a review of present uses and future possibilities,” Sens. Rev. 20(2), 98–105 (2000).
    [CrossRef]
  39. M. Björkqvist, J. Salonen, J. Paski, and E. Laine, “Characterization of thermally carbonized porous silicon humidity sensor,” Sens. Actuators A Phys. 112(2-3), 244–247 (2004).
    [CrossRef]
  40. A. Taylor, R. H. C. Bonser, and J. Farrent, “The influence of hydration on the tensile and compressive properties of avian keratinous tissues,” J. Mater. Sci. 39(3), 939–942 (2004).
    [CrossRef]
  41. M. Greenfield and R. Rodriguez, “Genotype–environment interaction and the reliability of mating signals,” Anim. Behav. 68(6), 1461–1468 (2004).
    [CrossRef]
  42. P. Bitton, R. Dawson, and C. Ochs, “Plumage characteristics, reproductive investment and assortative mating in tree swallows Tachycineta bicolor,” Behav. Ecol. Sociobiol. 62(10), 1543–1550 (2008).
    [CrossRef]

2010 (1)

S. M. Doucet and D. J. Mennill, “Dynamic sexual dichromatism in an explosively breeding Neotropical toad,” Biol. Lett. 6(1), 63–66 (2010).
[CrossRef]

2009 (5)

I. Agnarsson, A. Dhinojwala, V. Sahni, and T. A. Blackledge, “Spider silk as a novel high performance biomimetic muscle driven by humidity,” J. Exp. Biol. 212(13), 1990–1994 (2009).
[CrossRef] [PubMed]

R. Maia, J. V. O. Caetano, S. N. Báo, and R. H. Macedo, “Iridescent structural colour production in male blue-black grassquit feather barbules: the role of keratin and melanin,” J. R. Soc. Interface 6(Suppl 2), S203–S211 (2009).
[PubMed]

M. Stevens and S. Merilaita, “Animal camouflage: current issues and new perspectives,” Philos. Trans. R. Soc. Lond. B Biol. Sci. 364(1516), 423–427 (2009).
[CrossRef]

F. Liu, B. Q. Dong, X. H. Liu, Y. M. Zheng, and J. Zi, “Structural color change in longhorn beetles Tmesisternus isabellae,” Opt. Express 17(18), 16183–16191 (2009).
[CrossRef] [PubMed]

M. Rassart, P. Simonis, A. Bay, O. Deparis, and J. P. Vigneron, “Scale coloration change following water absorption in the beetle Hoplia coerulea (Coleoptera),” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 80(3), 031910 (2009).
[CrossRef] [PubMed]

2008 (1)

P. Bitton, R. Dawson, and C. Ochs, “Plumage characteristics, reproductive investment and assortative mating in tree swallows Tachycineta bicolor,” Behav. Ecol. Sociobiol. 62(10), 1543–1550 (2008).
[CrossRef]

2007 (2)

M. D. Shawkey, S. R. Pillai, G. E. Hill, L. M. Siefferman, and S. R. Roberts, “Bacteria as an agent for change in structural plumage color: correlational and experimental evidence,” Am. Nat. 169(s1Suppl 1), S112–S121 (2007).
[CrossRef] [PubMed]

R. Potyrailo, H. Ghiradella, A. Vertiatchikh, K. Dovidenko, J. Cournoyer, and E. Olson, “Morpho butterfly wing scales demonstrate highly selective vapour response,” Nat. Photonics 1(2), 123–128 (2007).
[CrossRef]

2006 (1)

K. Manoli, D. Goustouridis, S. Chatzandroulis, I. Raptis, E. Valamontes, and M. Sanopoulou, “Vapor sorption in thin supported polymer films studied by white light interferometry,” Polymer (Guildf.) 47(17), 6117–6122 (2006).
[CrossRef]

2004 (5)

M. Björkqvist, J. Salonen, J. Paski, and E. Laine, “Characterization of thermally carbonized porous silicon humidity sensor,” Sens. Actuators A Phys. 112(2-3), 244–247 (2004).
[CrossRef]

A. Taylor, R. H. C. Bonser, and J. Farrent, “The influence of hydration on the tensile and compressive properties of avian keratinous tissues,” J. Mater. Sci. 39(3), 939–942 (2004).
[CrossRef]

M. Greenfield and R. Rodriguez, “Genotype–environment interaction and the reliability of mating signals,” Anim. Behav. 68(6), 1461–1468 (2004).
[CrossRef]

M. D. Abramoff, P. J. Magelhae, and S. J. Ram, “Image processing with ImageJ,” Biophotonics International 11, 36–42 (2004).

D. J. Brink and N. van der Berg, “Structural colours from the feathers of the bird Bostrychia hagedash,” J. Phys. D Appl. Phys. 37(5), 813–818 (2004).
[CrossRef]

2003 (3)

M. D. Shawkey, A. M. Estes, L. M. Siefferman, and G. E. Hill, “Nanostructure predicts intraspecific variation in ultraviolet-blue plumage colour,” Proc. Biol. Sci. 270(1523), 1455–1460 (2003).
[CrossRef] [PubMed]

P. Vukusic and J. R. Sambles, “Photonic structures in biology,” Nature 424(6950), 852–855 (2003).
[CrossRef] [PubMed]

L. M. Mäthger, M. F. Land, U. E. Siebeck, and N. J. Marshall, “Rapid colour changes in multilayer reflecting stripes in the paradise whiptail, Pentapodus paradiseus,” J. Exp. Biol. 206(20), 3607–3613 (2003).
[CrossRef] [PubMed]

2002 (3)

J. Örnborg, S. Andersson, S. Griffith, and B. C. Sheldon, “Seasonal changes in a ultraviolet structural colour signal in blue tits, Parus caeruleus,” Biol. J. Linn. Soc. Lond. 76(2), 237–245 (2002).
[CrossRef]

D. Osorio and A. D. Ham, “Spectral reflectance and directional properties of structural coloration in bird plumage,” J. Exp. Biol. 205(Pt 14), 2017–2027 (2002).
[PubMed]

B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
[CrossRef] [PubMed]

2000 (1)

G. Harsányi, “Polymer films in sensor applications: a review of present uses and future possibilities,” Sens. Rev. 20(2), 98–105 (2000).
[CrossRef]

1995 (1)

T. Slagsvold, S. Dale, and A. Kruszewicz, “Predation favours cryptic coloration in breeding male pied flycatchers,” Anim. Behav. 50(4), 1109–1121 (1995).
[CrossRef]

1993 (1)

G. Jellison., “Data analysis for spectroscopic ellipsometry,” Thin Solid Films 234(1-2), 416–422 (1993).
[CrossRef]

1992 (1)

D. Beaglehole and H. K. Christenson, “Vapor adsorption on mica and silicon: entropy effects, layering, and surface forces,” J. Phys. Chem. 96(8), 3395–3403 (1992).
[CrossRef]

1985 (1)

B. Sillén-Tullberg, “Higher survival of an aposematic than of a cryptic form of a distasteful bug,” Oecologia 67(3), 411–415 (1985).
[CrossRef]

1980 (1)

I. Watt, “Sorption of water vapor by keratin,” Pol. Rev. 18(2), 169–245 (1980).

1977 (1)

H. Durrer, “Schillerfarben der vogelfeder als evolutionsproblem,” Denkschriften der Schweizerischen Naturforschenden Gesellschaft 91, 1–127 (1977).

1972 (1)

M. F. Land, “The physics and biology of animal reflectors,” Prog. Biophys. Mol. Biol. 24, 75–106 (1972).
[CrossRef] [PubMed]

1957 (1)

J. Morrison and J. Hanlan, “Swelling of fibrous proteins,” Nature 179(4558), 528–529 (1957).
[CrossRef]

Abramoff, M. D.

M. D. Abramoff, P. J. Magelhae, and S. J. Ram, “Image processing with ImageJ,” Biophotonics International 11, 36–42 (2004).

Agnarsson, I.

I. Agnarsson, A. Dhinojwala, V. Sahni, and T. A. Blackledge, “Spider silk as a novel high performance biomimetic muscle driven by humidity,” J. Exp. Biol. 212(13), 1990–1994 (2009).
[CrossRef] [PubMed]

Andersson, S.

J. Örnborg, S. Andersson, S. Griffith, and B. C. Sheldon, “Seasonal changes in a ultraviolet structural colour signal in blue tits, Parus caeruleus,” Biol. J. Linn. Soc. Lond. 76(2), 237–245 (2002).
[CrossRef]

Bäckström, J.

B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
[CrossRef] [PubMed]

Báo, S. N.

R. Maia, J. V. O. Caetano, S. N. Báo, and R. H. Macedo, “Iridescent structural colour production in male blue-black grassquit feather barbules: the role of keratin and melanin,” J. R. Soc. Interface 6(Suppl 2), S203–S211 (2009).
[PubMed]

Bay, A.

M. Rassart, P. Simonis, A. Bay, O. Deparis, and J. P. Vigneron, “Scale coloration change following water absorption in the beetle Hoplia coerulea (Coleoptera),” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 80(3), 031910 (2009).
[CrossRef] [PubMed]

Beaglehole, D.

D. Beaglehole and H. K. Christenson, “Vapor adsorption on mica and silicon: entropy effects, layering, and surface forces,” J. Phys. Chem. 96(8), 3395–3403 (1992).
[CrossRef]

Bitton, P.

P. Bitton, R. Dawson, and C. Ochs, “Plumage characteristics, reproductive investment and assortative mating in tree swallows Tachycineta bicolor,” Behav. Ecol. Sociobiol. 62(10), 1543–1550 (2008).
[CrossRef]

Björkqvist, M.

M. Björkqvist, J. Salonen, J. Paski, and E. Laine, “Characterization of thermally carbonized porous silicon humidity sensor,” Sens. Actuators A Phys. 112(2-3), 244–247 (2004).
[CrossRef]

Blackledge, T. A.

I. Agnarsson, A. Dhinojwala, V. Sahni, and T. A. Blackledge, “Spider silk as a novel high performance biomimetic muscle driven by humidity,” J. Exp. Biol. 212(13), 1990–1994 (2009).
[CrossRef] [PubMed]

Bonser, R. H. C.

A. Taylor, R. H. C. Bonser, and J. Farrent, “The influence of hydration on the tensile and compressive properties of avian keratinous tissues,” J. Mater. Sci. 39(3), 939–942 (2004).
[CrossRef]

Brink, D. J.

D. J. Brink and N. van der Berg, “Structural colours from the feathers of the bird Bostrychia hagedash,” J. Phys. D Appl. Phys. 37(5), 813–818 (2004).
[CrossRef]

Caetano, J. V. O.

R. Maia, J. V. O. Caetano, S. N. Báo, and R. H. Macedo, “Iridescent structural colour production in male blue-black grassquit feather barbules: the role of keratin and melanin,” J. R. Soc. Interface 6(Suppl 2), S203–S211 (2009).
[PubMed]

Chan, D.

B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
[CrossRef] [PubMed]

Chatzandroulis, S.

K. Manoli, D. Goustouridis, S. Chatzandroulis, I. Raptis, E. Valamontes, and M. Sanopoulou, “Vapor sorption in thin supported polymer films studied by white light interferometry,” Polymer (Guildf.) 47(17), 6117–6122 (2006).
[CrossRef]

Christenson, H. K.

D. Beaglehole and H. K. Christenson, “Vapor adsorption on mica and silicon: entropy effects, layering, and surface forces,” J. Phys. Chem. 96(8), 3395–3403 (1992).
[CrossRef]

Cournoyer, J.

R. Potyrailo, H. Ghiradella, A. Vertiatchikh, K. Dovidenko, J. Cournoyer, and E. Olson, “Morpho butterfly wing scales demonstrate highly selective vapour response,” Nat. Photonics 1(2), 123–128 (2007).
[CrossRef]

Dale, S.

T. Slagsvold, S. Dale, and A. Kruszewicz, “Predation favours cryptic coloration in breeding male pied flycatchers,” Anim. Behav. 50(4), 1109–1121 (1995).
[CrossRef]

Dawson, R.

P. Bitton, R. Dawson, and C. Ochs, “Plumage characteristics, reproductive investment and assortative mating in tree swallows Tachycineta bicolor,” Behav. Ecol. Sociobiol. 62(10), 1543–1550 (2008).
[CrossRef]

Deparis, O.

M. Rassart, P. Simonis, A. Bay, O. Deparis, and J. P. Vigneron, “Scale coloration change following water absorption in the beetle Hoplia coerulea (Coleoptera),” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 80(3), 031910 (2009).
[CrossRef] [PubMed]

Dhinojwala, A.

I. Agnarsson, A. Dhinojwala, V. Sahni, and T. A. Blackledge, “Spider silk as a novel high performance biomimetic muscle driven by humidity,” J. Exp. Biol. 212(13), 1990–1994 (2009).
[CrossRef] [PubMed]

Dong, B. Q.

Doucet, S. M.

S. M. Doucet and D. J. Mennill, “Dynamic sexual dichromatism in an explosively breeding Neotropical toad,” Biol. Lett. 6(1), 63–66 (2010).
[CrossRef]

Dovidenko, K.

R. Potyrailo, H. Ghiradella, A. Vertiatchikh, K. Dovidenko, J. Cournoyer, and E. Olson, “Morpho butterfly wing scales demonstrate highly selective vapour response,” Nat. Photonics 1(2), 123–128 (2007).
[CrossRef]

Durrer, H.

H. Durrer, “Schillerfarben der vogelfeder als evolutionsproblem,” Denkschriften der Schweizerischen Naturforschenden Gesellschaft 91, 1–127 (1977).

Estes, A. M.

M. D. Shawkey, A. M. Estes, L. M. Siefferman, and G. E. Hill, “Nanostructure predicts intraspecific variation in ultraviolet-blue plumage colour,” Proc. Biol. Sci. 270(1523), 1455–1460 (2003).
[CrossRef] [PubMed]

Farrent, J.

A. Taylor, R. H. C. Bonser, and J. Farrent, “The influence of hydration on the tensile and compressive properties of avian keratinous tissues,” J. Mater. Sci. 39(3), 939–942 (2004).
[CrossRef]

Ghiradella, H.

R. Potyrailo, H. Ghiradella, A. Vertiatchikh, K. Dovidenko, J. Cournoyer, and E. Olson, “Morpho butterfly wing scales demonstrate highly selective vapour response,” Nat. Photonics 1(2), 123–128 (2007).
[CrossRef]

Goustouridis, D.

K. Manoli, D. Goustouridis, S. Chatzandroulis, I. Raptis, E. Valamontes, and M. Sanopoulou, “Vapor sorption in thin supported polymer films studied by white light interferometry,” Polymer (Guildf.) 47(17), 6117–6122 (2006).
[CrossRef]

Greenfield, M.

M. Greenfield and R. Rodriguez, “Genotype–environment interaction and the reliability of mating signals,” Anim. Behav. 68(6), 1461–1468 (2004).
[CrossRef]

Griffith, S.

J. Örnborg, S. Andersson, S. Griffith, and B. C. Sheldon, “Seasonal changes in a ultraviolet structural colour signal in blue tits, Parus caeruleus,” Biol. J. Linn. Soc. Lond. 76(2), 237–245 (2002).
[CrossRef]

Ham, A. D.

D. Osorio and A. D. Ham, “Spectral reflectance and directional properties of structural coloration in bird plumage,” J. Exp. Biol. 205(Pt 14), 2017–2027 (2002).
[PubMed]

Hanlan, J.

J. Morrison and J. Hanlan, “Swelling of fibrous proteins,” Nature 179(4558), 528–529 (1957).
[CrossRef]

Harsányi, G.

G. Harsányi, “Polymer films in sensor applications: a review of present uses and future possibilities,” Sens. Rev. 20(2), 98–105 (2000).
[CrossRef]

Hill, G. E.

M. D. Shawkey, S. R. Pillai, G. E. Hill, L. M. Siefferman, and S. R. Roberts, “Bacteria as an agent for change in structural plumage color: correlational and experimental evidence,” Am. Nat. 169(s1Suppl 1), S112–S121 (2007).
[CrossRef] [PubMed]

M. D. Shawkey, A. M. Estes, L. M. Siefferman, and G. E. Hill, “Nanostructure predicts intraspecific variation in ultraviolet-blue plumage colour,” Proc. Biol. Sci. 270(1523), 1455–1460 (2003).
[CrossRef] [PubMed]

Jellison, G.

G. Jellison., “Data analysis for spectroscopic ellipsometry,” Thin Solid Films 234(1-2), 416–422 (1993).
[CrossRef]

Kruszewicz, A.

T. Slagsvold, S. Dale, and A. Kruszewicz, “Predation favours cryptic coloration in breeding male pied flycatchers,” Anim. Behav. 50(4), 1109–1121 (1995).
[CrossRef]

Laine, E.

M. Björkqvist, J. Salonen, J. Paski, and E. Laine, “Characterization of thermally carbonized porous silicon humidity sensor,” Sens. Actuators A Phys. 112(2-3), 244–247 (2004).
[CrossRef]

Land, M. F.

L. M. Mäthger, M. F. Land, U. E. Siebeck, and N. J. Marshall, “Rapid colour changes in multilayer reflecting stripes in the paradise whiptail, Pentapodus paradiseus,” J. Exp. Biol. 206(20), 3607–3613 (2003).
[CrossRef] [PubMed]

M. F. Land, “The physics and biology of animal reflectors,” Prog. Biophys. Mol. Biol. 24, 75–106 (1972).
[CrossRef] [PubMed]

Liu, F.

Liu, X. H.

Macedo, R. H.

R. Maia, J. V. O. Caetano, S. N. Báo, and R. H. Macedo, “Iridescent structural colour production in male blue-black grassquit feather barbules: the role of keratin and melanin,” J. R. Soc. Interface 6(Suppl 2), S203–S211 (2009).
[PubMed]

Magelhae, P. J.

M. D. Abramoff, P. J. Magelhae, and S. J. Ram, “Image processing with ImageJ,” Biophotonics International 11, 36–42 (2004).

Maia, R.

R. Maia, J. V. O. Caetano, S. N. Báo, and R. H. Macedo, “Iridescent structural colour production in male blue-black grassquit feather barbules: the role of keratin and melanin,” J. R. Soc. Interface 6(Suppl 2), S203–S211 (2009).
[PubMed]

Manoli, K.

K. Manoli, D. Goustouridis, S. Chatzandroulis, I. Raptis, E. Valamontes, and M. Sanopoulou, “Vapor sorption in thin supported polymer films studied by white light interferometry,” Polymer (Guildf.) 47(17), 6117–6122 (2006).
[CrossRef]

Marshall, N. J.

L. M. Mäthger, M. F. Land, U. E. Siebeck, and N. J. Marshall, “Rapid colour changes in multilayer reflecting stripes in the paradise whiptail, Pentapodus paradiseus,” J. Exp. Biol. 206(20), 3607–3613 (2003).
[CrossRef] [PubMed]

Mäthger, L. M.

L. M. Mäthger, M. F. Land, U. E. Siebeck, and N. J. Marshall, “Rapid colour changes in multilayer reflecting stripes in the paradise whiptail, Pentapodus paradiseus,” J. Exp. Biol. 206(20), 3607–3613 (2003).
[CrossRef] [PubMed]

Mennill, D. J.

S. M. Doucet and D. J. Mennill, “Dynamic sexual dichromatism in an explosively breeding Neotropical toad,” Biol. Lett. 6(1), 63–66 (2010).
[CrossRef]

Merilaita, S.

M. Stevens and S. Merilaita, “Animal camouflage: current issues and new perspectives,” Philos. Trans. R. Soc. Lond. B Biol. Sci. 364(1516), 423–427 (2009).
[CrossRef]

Morrison, J.

J. Morrison and J. Hanlan, “Swelling of fibrous proteins,” Nature 179(4558), 528–529 (1957).
[CrossRef]

Ochs, C.

P. Bitton, R. Dawson, and C. Ochs, “Plumage characteristics, reproductive investment and assortative mating in tree swallows Tachycineta bicolor,” Behav. Ecol. Sociobiol. 62(10), 1543–1550 (2008).
[CrossRef]

Olson, E.

R. Potyrailo, H. Ghiradella, A. Vertiatchikh, K. Dovidenko, J. Cournoyer, and E. Olson, “Morpho butterfly wing scales demonstrate highly selective vapour response,” Nat. Photonics 1(2), 123–128 (2007).
[CrossRef]

Örnborg, J.

J. Örnborg, S. Andersson, S. Griffith, and B. C. Sheldon, “Seasonal changes in a ultraviolet structural colour signal in blue tits, Parus caeruleus,” Biol. J. Linn. Soc. Lond. 76(2), 237–245 (2002).
[CrossRef]

Osorio, D.

D. Osorio and A. D. Ham, “Spectral reflectance and directional properties of structural coloration in bird plumage,” J. Exp. Biol. 205(Pt 14), 2017–2027 (2002).
[PubMed]

Paski, J.

M. Björkqvist, J. Salonen, J. Paski, and E. Laine, “Characterization of thermally carbonized porous silicon humidity sensor,” Sens. Actuators A Phys. 112(2-3), 244–247 (2004).
[CrossRef]

Pillai, S. R.

M. D. Shawkey, S. R. Pillai, G. E. Hill, L. M. Siefferman, and S. R. Roberts, “Bacteria as an agent for change in structural plumage color: correlational and experimental evidence,” Am. Nat. 169(s1Suppl 1), S112–S121 (2007).
[CrossRef] [PubMed]

Potyrailo, R.

R. Potyrailo, H. Ghiradella, A. Vertiatchikh, K. Dovidenko, J. Cournoyer, and E. Olson, “Morpho butterfly wing scales demonstrate highly selective vapour response,” Nat. Photonics 1(2), 123–128 (2007).
[CrossRef]

Ram, S. J.

M. D. Abramoff, P. J. Magelhae, and S. J. Ram, “Image processing with ImageJ,” Biophotonics International 11, 36–42 (2004).

Raptis, I.

K. Manoli, D. Goustouridis, S. Chatzandroulis, I. Raptis, E. Valamontes, and M. Sanopoulou, “Vapor sorption in thin supported polymer films studied by white light interferometry,” Polymer (Guildf.) 47(17), 6117–6122 (2006).
[CrossRef]

Rassart, M.

M. Rassart, P. Simonis, A. Bay, O. Deparis, and J. P. Vigneron, “Scale coloration change following water absorption in the beetle Hoplia coerulea (Coleoptera),” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 80(3), 031910 (2009).
[CrossRef] [PubMed]

Roberts, S. R.

M. D. Shawkey, S. R. Pillai, G. E. Hill, L. M. Siefferman, and S. R. Roberts, “Bacteria as an agent for change in structural plumage color: correlational and experimental evidence,” Am. Nat. 169(s1Suppl 1), S112–S121 (2007).
[CrossRef] [PubMed]

Rodriguez, R.

M. Greenfield and R. Rodriguez, “Genotype–environment interaction and the reliability of mating signals,” Anim. Behav. 68(6), 1461–1468 (2004).
[CrossRef]

Rübhausen, M.

B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
[CrossRef] [PubMed]

Sahni, V.

I. Agnarsson, A. Dhinojwala, V. Sahni, and T. A. Blackledge, “Spider silk as a novel high performance biomimetic muscle driven by humidity,” J. Exp. Biol. 212(13), 1990–1994 (2009).
[CrossRef] [PubMed]

Salonen, J.

M. Björkqvist, J. Salonen, J. Paski, and E. Laine, “Characterization of thermally carbonized porous silicon humidity sensor,” Sens. Actuators A Phys. 112(2-3), 244–247 (2004).
[CrossRef]

Sambles, J. R.

P. Vukusic and J. R. Sambles, “Photonic structures in biology,” Nature 424(6950), 852–855 (2003).
[CrossRef] [PubMed]

Sanopoulou, M.

K. Manoli, D. Goustouridis, S. Chatzandroulis, I. Raptis, E. Valamontes, and M. Sanopoulou, “Vapor sorption in thin supported polymer films studied by white light interferometry,” Polymer (Guildf.) 47(17), 6117–6122 (2006).
[CrossRef]

Schulz, B.

B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
[CrossRef] [PubMed]

Shawkey, M. D.

M. D. Shawkey, S. R. Pillai, G. E. Hill, L. M. Siefferman, and S. R. Roberts, “Bacteria as an agent for change in structural plumage color: correlational and experimental evidence,” Am. Nat. 169(s1Suppl 1), S112–S121 (2007).
[CrossRef] [PubMed]

M. D. Shawkey, A. M. Estes, L. M. Siefferman, and G. E. Hill, “Nanostructure predicts intraspecific variation in ultraviolet-blue plumage colour,” Proc. Biol. Sci. 270(1523), 1455–1460 (2003).
[CrossRef] [PubMed]

Sheldon, B. C.

J. Örnborg, S. Andersson, S. Griffith, and B. C. Sheldon, “Seasonal changes in a ultraviolet structural colour signal in blue tits, Parus caeruleus,” Biol. J. Linn. Soc. Lond. 76(2), 237–245 (2002).
[CrossRef]

Siebeck, U. E.

L. M. Mäthger, M. F. Land, U. E. Siebeck, and N. J. Marshall, “Rapid colour changes in multilayer reflecting stripes in the paradise whiptail, Pentapodus paradiseus,” J. Exp. Biol. 206(20), 3607–3613 (2003).
[CrossRef] [PubMed]

Siefferman, L. M.

M. D. Shawkey, S. R. Pillai, G. E. Hill, L. M. Siefferman, and S. R. Roberts, “Bacteria as an agent for change in structural plumage color: correlational and experimental evidence,” Am. Nat. 169(s1Suppl 1), S112–S121 (2007).
[CrossRef] [PubMed]

M. D. Shawkey, A. M. Estes, L. M. Siefferman, and G. E. Hill, “Nanostructure predicts intraspecific variation in ultraviolet-blue plumage colour,” Proc. Biol. Sci. 270(1523), 1455–1460 (2003).
[CrossRef] [PubMed]

Sillén-Tullberg, B.

B. Sillén-Tullberg, “Higher survival of an aposematic than of a cryptic form of a distasteful bug,” Oecologia 67(3), 411–415 (1985).
[CrossRef]

Simonis, P.

M. Rassart, P. Simonis, A. Bay, O. Deparis, and J. P. Vigneron, “Scale coloration change following water absorption in the beetle Hoplia coerulea (Coleoptera),” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 80(3), 031910 (2009).
[CrossRef] [PubMed]

Slagsvold, T.

T. Slagsvold, S. Dale, and A. Kruszewicz, “Predation favours cryptic coloration in breeding male pied flycatchers,” Anim. Behav. 50(4), 1109–1121 (1995).
[CrossRef]

Stevens, M.

M. Stevens and S. Merilaita, “Animal camouflage: current issues and new perspectives,” Philos. Trans. R. Soc. Lond. B Biol. Sci. 364(1516), 423–427 (2009).
[CrossRef]

Taylor, A.

A. Taylor, R. H. C. Bonser, and J. Farrent, “The influence of hydration on the tensile and compressive properties of avian keratinous tissues,” J. Mater. Sci. 39(3), 939–942 (2004).
[CrossRef]

Valamontes, E.

K. Manoli, D. Goustouridis, S. Chatzandroulis, I. Raptis, E. Valamontes, and M. Sanopoulou, “Vapor sorption in thin supported polymer films studied by white light interferometry,” Polymer (Guildf.) 47(17), 6117–6122 (2006).
[CrossRef]

van der Berg, N.

D. J. Brink and N. van der Berg, “Structural colours from the feathers of the bird Bostrychia hagedash,” J. Phys. D Appl. Phys. 37(5), 813–818 (2004).
[CrossRef]

Vertiatchikh, A.

R. Potyrailo, H. Ghiradella, A. Vertiatchikh, K. Dovidenko, J. Cournoyer, and E. Olson, “Morpho butterfly wing scales demonstrate highly selective vapour response,” Nat. Photonics 1(2), 123–128 (2007).
[CrossRef]

Vigneron, J. P.

M. Rassart, P. Simonis, A. Bay, O. Deparis, and J. P. Vigneron, “Scale coloration change following water absorption in the beetle Hoplia coerulea (Coleoptera),” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 80(3), 031910 (2009).
[CrossRef] [PubMed]

Vukusic, P.

P. Vukusic and J. R. Sambles, “Photonic structures in biology,” Nature 424(6950), 852–855 (2003).
[CrossRef] [PubMed]

Watt, I.

I. Watt, “Sorption of water vapor by keratin,” Pol. Rev. 18(2), 169–245 (1980).

Wepf, R.

B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
[CrossRef] [PubMed]

Wessel, S.

B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
[CrossRef] [PubMed]

Williams, S.

B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
[CrossRef] [PubMed]

Wittern, K. P.

B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
[CrossRef] [PubMed]

Zheng, Y. M.

Zi, J.

Am. Nat. (1)

M. D. Shawkey, S. R. Pillai, G. E. Hill, L. M. Siefferman, and S. R. Roberts, “Bacteria as an agent for change in structural plumage color: correlational and experimental evidence,” Am. Nat. 169(s1Suppl 1), S112–S121 (2007).
[CrossRef] [PubMed]

Anim. Behav. (2)

T. Slagsvold, S. Dale, and A. Kruszewicz, “Predation favours cryptic coloration in breeding male pied flycatchers,” Anim. Behav. 50(4), 1109–1121 (1995).
[CrossRef]

M. Greenfield and R. Rodriguez, “Genotype–environment interaction and the reliability of mating signals,” Anim. Behav. 68(6), 1461–1468 (2004).
[CrossRef]

Behav. Ecol. Sociobiol. (1)

P. Bitton, R. Dawson, and C. Ochs, “Plumage characteristics, reproductive investment and assortative mating in tree swallows Tachycineta bicolor,” Behav. Ecol. Sociobiol. 62(10), 1543–1550 (2008).
[CrossRef]

Biol. J. Linn. Soc. Lond. (1)

J. Örnborg, S. Andersson, S. Griffith, and B. C. Sheldon, “Seasonal changes in a ultraviolet structural colour signal in blue tits, Parus caeruleus,” Biol. J. Linn. Soc. Lond. 76(2), 237–245 (2002).
[CrossRef]

Biol. Lett. (1)

S. M. Doucet and D. J. Mennill, “Dynamic sexual dichromatism in an explosively breeding Neotropical toad,” Biol. Lett. 6(1), 63–66 (2010).
[CrossRef]

Biophotonics International (1)

M. D. Abramoff, P. J. Magelhae, and S. J. Ram, “Image processing with ImageJ,” Biophotonics International 11, 36–42 (2004).

Denkschriften der Schweizerischen Naturforschenden Gesellschaft (1)

H. Durrer, “Schillerfarben der vogelfeder als evolutionsproblem,” Denkschriften der Schweizerischen Naturforschenden Gesellschaft 91, 1–127 (1977).

J. Exp. Biol. (3)

D. Osorio and A. D. Ham, “Spectral reflectance and directional properties of structural coloration in bird plumage,” J. Exp. Biol. 205(Pt 14), 2017–2027 (2002).
[PubMed]

I. Agnarsson, A. Dhinojwala, V. Sahni, and T. A. Blackledge, “Spider silk as a novel high performance biomimetic muscle driven by humidity,” J. Exp. Biol. 212(13), 1990–1994 (2009).
[CrossRef] [PubMed]

L. M. Mäthger, M. F. Land, U. E. Siebeck, and N. J. Marshall, “Rapid colour changes in multilayer reflecting stripes in the paradise whiptail, Pentapodus paradiseus,” J. Exp. Biol. 206(20), 3607–3613 (2003).
[CrossRef] [PubMed]

J. Mater. Sci. (1)

A. Taylor, R. H. C. Bonser, and J. Farrent, “The influence of hydration on the tensile and compressive properties of avian keratinous tissues,” J. Mater. Sci. 39(3), 939–942 (2004).
[CrossRef]

J. Phys. Chem. (1)

D. Beaglehole and H. K. Christenson, “Vapor adsorption on mica and silicon: entropy effects, layering, and surface forces,” J. Phys. Chem. 96(8), 3395–3403 (1992).
[CrossRef]

J. Phys. D Appl. Phys. (1)

D. J. Brink and N. van der Berg, “Structural colours from the feathers of the bird Bostrychia hagedash,” J. Phys. D Appl. Phys. 37(5), 813–818 (2004).
[CrossRef]

J. R. Soc. Interface (1)

R. Maia, J. V. O. Caetano, S. N. Báo, and R. H. Macedo, “Iridescent structural colour production in male blue-black grassquit feather barbules: the role of keratin and melanin,” J. R. Soc. Interface 6(Suppl 2), S203–S211 (2009).
[PubMed]

Nat. Photonics (1)

R. Potyrailo, H. Ghiradella, A. Vertiatchikh, K. Dovidenko, J. Cournoyer, and E. Olson, “Morpho butterfly wing scales demonstrate highly selective vapour response,” Nat. Photonics 1(2), 123–128 (2007).
[CrossRef]

Nature (2)

P. Vukusic and J. R. Sambles, “Photonic structures in biology,” Nature 424(6950), 852–855 (2003).
[CrossRef] [PubMed]

J. Morrison and J. Hanlan, “Swelling of fibrous proteins,” Nature 179(4558), 528–529 (1957).
[CrossRef]

Oecologia (1)

B. Sillén-Tullberg, “Higher survival of an aposematic than of a cryptic form of a distasteful bug,” Oecologia 67(3), 411–415 (1985).
[CrossRef]

Opt. Express (1)

Philos. Trans. R. Soc. Lond. B Biol. Sci. (1)

M. Stevens and S. Merilaita, “Animal camouflage: current issues and new perspectives,” Philos. Trans. R. Soc. Lond. B Biol. Sci. 364(1516), 423–427 (2009).
[CrossRef]

Phys. Rev. E Stat. Nonlin. Soft Matter Phys. (2)

M. Rassart, P. Simonis, A. Bay, O. Deparis, and J. P. Vigneron, “Scale coloration change following water absorption in the beetle Hoplia coerulea (Coleoptera),” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 80(3), 031910 (2009).
[CrossRef] [PubMed]

B. Schulz, D. Chan, J. Bäckström, M. Rübhausen, K. P. Wittern, S. Wessel, R. Wepf, and S. Williams, “Hydration dynamics of human fingernails: an ellipsometric study,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 65(6), 061913 (2002).
[CrossRef] [PubMed]

Pol. Rev. (1)

I. Watt, “Sorption of water vapor by keratin,” Pol. Rev. 18(2), 169–245 (1980).

Polymer (Guildf.) (1)

K. Manoli, D. Goustouridis, S. Chatzandroulis, I. Raptis, E. Valamontes, and M. Sanopoulou, “Vapor sorption in thin supported polymer films studied by white light interferometry,” Polymer (Guildf.) 47(17), 6117–6122 (2006).
[CrossRef]

Proc. Biol. Sci. (1)

M. D. Shawkey, A. M. Estes, L. M. Siefferman, and G. E. Hill, “Nanostructure predicts intraspecific variation in ultraviolet-blue plumage colour,” Proc. Biol. Sci. 270(1523), 1455–1460 (2003).
[CrossRef] [PubMed]

Prog. Biophys. Mol. Biol. (1)

M. F. Land, “The physics and biology of animal reflectors,” Prog. Biophys. Mol. Biol. 24, 75–106 (1972).
[CrossRef] [PubMed]

Sens. Actuators A Phys. (1)

M. Björkqvist, J. Salonen, J. Paski, and E. Laine, “Characterization of thermally carbonized porous silicon humidity sensor,” Sens. Actuators A Phys. 112(2-3), 244–247 (2004).
[CrossRef]

Sens. Rev. (1)

G. Harsányi, “Polymer films in sensor applications: a review of present uses and future possibilities,” Sens. Rev. 20(2), 98–105 (2000).
[CrossRef]

Thin Solid Films (1)

G. Jellison., “Data analysis for spectroscopic ellipsometry,” Thin Solid Films 234(1-2), 416–422 (1993).
[CrossRef]

Other (12)

R Development Core Team, “R: A Language and Environment for Statistical Computing,” (Vienna, Austria, 2009).

D. Vanhecke, L. Studer, and D. Studer, “Cryoultramicrotomy,” in Electron Microscopy: Methods and Protocols, J. M. Walker, ed. (Humana Press, Totowa, New Jersey, 2007).

S. Andersson, and M. Prager, “Quantifying Colors,” in Bird Coloration: Mechanisms & Measurements, G. Hill, and K. McGraw, eds. (Harvard University Press, Cambridge, MS, 2006), pp. 41–89.

G. E. Hill, “House Finch,” in The Birds of North America Online, A. Poole, ed. (Cornell Lab of Ornithology, Ithaca, NY, 1993).

P. A. Gowaty, and J. H. Plissner, “Eastern Bluebird,” in The Birds of North America Online, A. Poole, ed. (Cornell Lab of Ornithology, Ithaca, NY, 1998).

R. Montgomerie, “Analyzing Colors,” in Bird Coloration Volume I: Mechanisms and Measurements, G. E. Hill, and K. J. McGraw, eds. (Harvard University Press, Cambridge, MS, 2006), pp. 90–147.

E. H. Burtt, “Tips on Wings and Other Things,” in The Behavioral Significance of Color, E. H. Burtt, ed. (Garland Publishing, Inc., New York, NY, 1986), pp. 75–110.

M. Andersson, Sexual Selection (Princeton University Press, Princeton, NJ, 1994).

K. McGraw, “Mechanics of carotenoid-based coloration,” in Bird Coloration Volume I: Mechanisms and Measurements, K. McGraw, and G. Hill, eds. (Harvard University Press, Cambridge, MS, 2006), pp. 177–242.

R. O. Prum, “Anatomy, physics, and evolution of structural colors,” in Bird Coloration Volume I: Mechanisms and Measurements, G. E. Hill, and K. J. McGraw, eds. (Harvard University Press, Cambridge, MS, 2006), pp. 295–353.

S. Kinoshita, Structural Colors in the Realm of Nature (World Scientific Publishing Co., Singapore, 2008).

R. T. Hanlon, and J. B. Messenger, Cephalopod Behaviour (Cambridge University Press, Cambridge, UK, 1988).

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (4)

Fig. 1
Fig. 1

TEM cross-section of an iridescent T. bicolor feather barbule used to predict reflectance (b). Iridescent tree swallow feather (a) and magnified barbules (inset) showing plane of cross-section (white line perpendicular to barbules). Representative barbule cross-section (b) shows melanosomes (black) and keratin cortex (grey region surrounding melanosomes). Scale bar = 500 nm. Letters correspond to dorsal (d) and ventral (v) surfaces. Measured (solid line) and predicted (dashed line) reflectance based on thin-film optical model (c).

Fig. 2
Fig. 2

Reversible color change in tree swallow feathers. Reflectance of feathers at 0% RH (solid line) and after an abrupt increase to 80% RH (dashed line) [a]. Representative response of λmax to abrupt increases (vertical dashed line, t = 2 sec) and decreases (vertical dashed line, t = 304 sec) in humidity (b). Points connected with grey line to aid in trend visualization. Inset shows plot of hue vs. time1/2 and linear regression (solid line) for times under 70 sec.

Fig. 3
Fig. 3

Potential mechanisms for the observed color change. Observed mean reflectance change of tree swallow feathers (n = 9) before (black line) and after (red line) humidity change from 20 to 80% RH (insets are images of a single feather taken at 0% and 100% RH). Model predictions before (black line) and after humidity increases (red line) for keratin swelling (b), surface adsorption (c), and increases (solid line) or decreases (dashed line) in the refractive index of keratin (d). Insets are schematic drawings of barbule cross-sections showing melanosomes (black), keratin cortex (grey), and water molecules (blue circles). Drawings not to scale, allowing for easier visualization of mechanisms.

Fig. 4
Fig. 4

Variation in color response of different color-producing mechanisms. Filled circles show mean hue change before and after humidity changes and error bars show ± 2 SE. Hue was calculated as λmax in bluebirds and swallows and as wavelength of maximum positive slope in house finches (see Materials & methods for details). Overall effect of species on hue change was significant (ANOVA, F2,24 = 49.21, P<0.0001), and all pair-wise comparisons were significant (Tukey tests, P<0.05).

Metrics