Scribner, Stephen

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  The Evolution and Selection Pressures of Facial Stripes in Birds  Stephen Scribner, Dr. Brent Burt  Stephen F. Austin State UniversityIntroduction: The use of facial characteristics in birds has been well documented in previous studies. Bill color has been found to reduce glare in birds residing in open habitats (Williams & Burtt, 2010), a study on the Common Yellowthroat showed that the melanin based ornament they feature was used for both female attraction and male-male competition (Thusius et al., 2001), and that the loss or gain of facial stripes have been shown to be related to the environment the bird lives in (Ortolani 1999). This study focuses on using pairwise comparison (Maddison 2000) to determine the selection pressure of various species within the families Falconidae, Paridae, Tyrannidae, and Parulidae. The pressures tested for were glare reduction, sexual selection, and individual recognition through use of a melanin-based facial stripe.Methods: The Handbook of the Birds of the World was used to determine facial stripe Once facial stripe was determined, habitat preference, dimorphism, and diet were recorded into a Mesquite data matrix The Maddison Test was run on each family to detect character associations Those tests showing low tail probabilities were considered significantFigure 1. Falconidae pairwise comparison of glare reduction Closed HabitatNo Facial StripeFacial StripeResults: The Probability results of the four families are represented in Table 1. With the lowest numbers representing the most significant selection pressure. Those highlighted in purple represent the most supported use of the facial stripe in the family.  Refer to Figure 1. for the mirror tree used to test glare reduction in the Falconidae family. The “X” represents no species found to use stripe for that selection pressure. Discussion: The facial stripe in birds is found to support the needs of individual species through various selection pressures; be it glare reduction, sexual selection, or social recognition.Conclusion: In conclusion, this study suggest that many aerial predators such as falcons or flycatchers use a facial stripe for glare reduction; in particular, a melanin-based stripe that goes just through the eye. In other cases, such as warblers, the stripe is used for sexual selection. A few species have even been noted as using the stripe for individual recognition. More research is suggested to confirm the idea of a facial stripe being used for recognition. Open HabitatAvian FamilySelection PressureGlare ReductionSexual SelectionSocial RecognitionFalconidae 4.88x10-4 X XParidae 6.25x10-2 6.25x10-2 3.13x10-2Tyrannidae 4.80x10-7 3.13x10-2 2.50x10-1Parulidae 1.95x10-3 7.45x10-9 XOpen Habitat http://www.fhwa.dot.gov/Closed Habitat http://www.illinoiscleanenergy.org/ Table 1. Significance values of avian families for different selection pressuresFalco biarmicus featuring a facial stripeFalco nuamanni lacking a melanin facial stripeMale (Bottom) Vermivora chrysoptera displaying the facial stripe for the use of sexual selectionPoecile davidi using the facial strip for glare reductionAnairetes alpinus using a melanin facial stripe to reduce glareReferences:  Bowie, R. C. K. (2013). Handbook of the Birds of the World Gill, F.B., B. Slikas, F.H. Sheldon. 2005.  Phylogeny of titmice (Paridae): II. Species relationships based on sequences of the mitochondrial cytochrome-b gene. Auk, 122:121-143. Lovette, I.J., J.L. Pérez-Emán, and J.P. Sullivan. 2010. A Comprehensive multilocus phylogeny for the wood-warblers and a revised classification of the Parulidae (Aves). Molecular Phylogenetics      and Evolution 57:753-70. Maddison, W. P. (2000). Testing character correlation using pairwise comparisons on a phylogeny. Biol, 195-204 Ohlson J, J. Fjeldså, and P. Ericson. 2008. Tyrant flycatchers coming out in the open: phylogeny and ecological radiation of Tyrannidae (Aves, Passeriformes). Zoologica Scripta. 37:315-335. Ortolani, A. (1998, October 19). Spots, stripes, tail tips and dark eyes: Predicting the function of carnivore colour patterns using the comparative method. Biological Journal of the Linnean Society, 67, 433-476. Thusius, K. J., Peterson, K. A., Dunn, P. O., & Whittingham, L. A. (2001, February 8). Male mask size is correlated with mating success in the common yellowthroat. Animal Behavior, 433-446. Williams, S. M., & Burtt, Jr., E. H. (2010, September). How birds' bills help them see. Birding. Wink, M. and H. Sauer-Gürth. 2004. Phylogenetic relationships in diurnal raptors based on nucleotide sequences of mitochondrial and nuclear marker genes. Pp. 483-498, In: Chancelor RD, Meyburg B-U (eds) Raptors worldwide. WWGBP, Berlin. Falco biarmicus featuring a facial stripe for glare reduction

The Evolution and Selection Pressures of Facial Stripes in Birds

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The Evolution and Selection Pressures of Facial Stripes in Birds

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