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Sexual Dimorphism and Population Differences in Structural Properties of Barn Swallow (Hirundo rustica) Wing and Tail Feathers.

Pap PL, Osváth G, Aparicio JM, Bărbos L, Matyjasiak P, Rubolini D, Saino N, Vágási CI, Vincze O, Møller AP - PLoS ONE (2015)

Bottom Line: Furthermore, we compared structural properties of Ta6 of barn swallows from six European populations.Ta6 elongation in males resulted in feathers with reduced resistance, as shown by the low barb density and reduced bending stiffness compared to females.Our results show that the material and structural properties of wing and tail feathers of barn swallows change as a result of aerodynamic forces and sexual selection, although the result of these changes can be contrasting.

View Article: PubMed Central - PubMed

Affiliation: Evolutionary Ecology Group, Hungarian Department of Biology and Ecology, Babeş-Bolyai University, Cluj Napoca, Romania; MTA-DE "Lendület" Behavioural Ecology Research Group, Department of Evolutionary Zoology and Human Biology, University of Debrecen, Debrecen, Hungary.

ABSTRACT
Sexual selection and aerodynamic forces affecting structural properties of the flight feathers of birds are poorly understood. Here, we compared the structural features of the innermost primary wing feather (P1) and the sexually dimorphic outermost (Ta6) and monomorphic second outermost (Ta5) tail feathers of barn swallows (Hirundo rustica) from a Romanian population to investigate how sexual selection and resistance to aerodynamic forces affect structural differences among these feathers. Furthermore, we compared structural properties of Ta6 of barn swallows from six European populations. Finally, we determined the relationship between feather growth bars width (GBW) and the structural properties of tail feathers. The structure of P1 indicates strong resistance against aerodynamic forces, while the narrow rachis, low vane density and low bending stiffness of tail feathers suggest reduced resistance against airflow. The highly elongated Ta6 is characterized by structural modifications such as large rachis width and increased barbule density in relation to the less elongated Ta5, which can be explained by increased length and/or high aerodynamic forces acting at the leading tail edge. However, these changes in Ta6 structure do not allow for full compensation of elongation, as reflected by the reduced bending stiffness of Ta6. Ta6 elongation in males resulted in feathers with reduced resistance, as shown by the low barb density and reduced bending stiffness compared to females. The inconsistency in sexual dimorphism and in change in quality traits of Ta6 among six European populations shows that multiple factors may contribute to shaping population differences. In general, the difference in quality traits between tail feathers cannot be explained by the GBW of feathers. Our results show that the material and structural properties of wing and tail feathers of barn swallows change as a result of aerodynamic forces and sexual selection, although the result of these changes can be contrasting.

No MeSH data available.


Related in: MedlinePlus

Variation in GBW of Ta6 in male (black) and female (white) barn swallows from six European populations (DK—Denmark, UA—Ukraine, RO—Romania, PL—Poland, IT—Italy, ES—Spain) (mean + SE).
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pone.0130844.g005: Variation in GBW of Ta6 in male (black) and female (white) barn swallows from six European populations (DK—Denmark, UA—Ukraine, RO—Romania, PL—Poland, IT—Italy, ES—Spain) (mean + SE).

Mentions: We tested if the difference between sexes and populations in feather quality traits of Ta6 could be explained by GBW. We included GBW as an explanatory variable in separate models, while controlling for the effect of sex and population. GBW of Ta6 was significantly larger in females than in males, while population had no effect on GBW (Table 4, Fig 5). Feather length, rachis width, barbule density and bending stiffness were unaffected by GBW (Table 4). However, GBW was significantly and negatively related to barb density: feathers that grew fast had low density of barbs in the vane (β (SE) = -1.15 (0.30), t = 3.77, P = 0.0002; Table 4).


Sexual Dimorphism and Population Differences in Structural Properties of Barn Swallow (Hirundo rustica) Wing and Tail Feathers.

Pap PL, Osváth G, Aparicio JM, Bărbos L, Matyjasiak P, Rubolini D, Saino N, Vágási CI, Vincze O, Møller AP - PLoS ONE (2015)

Variation in GBW of Ta6 in male (black) and female (white) barn swallows from six European populations (DK—Denmark, UA—Ukraine, RO—Romania, PL—Poland, IT—Italy, ES—Spain) (mean + SE).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4482263&req=5

pone.0130844.g005: Variation in GBW of Ta6 in male (black) and female (white) barn swallows from six European populations (DK—Denmark, UA—Ukraine, RO—Romania, PL—Poland, IT—Italy, ES—Spain) (mean + SE).
Mentions: We tested if the difference between sexes and populations in feather quality traits of Ta6 could be explained by GBW. We included GBW as an explanatory variable in separate models, while controlling for the effect of sex and population. GBW of Ta6 was significantly larger in females than in males, while population had no effect on GBW (Table 4, Fig 5). Feather length, rachis width, barbule density and bending stiffness were unaffected by GBW (Table 4). However, GBW was significantly and negatively related to barb density: feathers that grew fast had low density of barbs in the vane (β (SE) = -1.15 (0.30), t = 3.77, P = 0.0002; Table 4).

Bottom Line: Furthermore, we compared structural properties of Ta6 of barn swallows from six European populations.Ta6 elongation in males resulted in feathers with reduced resistance, as shown by the low barb density and reduced bending stiffness compared to females.Our results show that the material and structural properties of wing and tail feathers of barn swallows change as a result of aerodynamic forces and sexual selection, although the result of these changes can be contrasting.

View Article: PubMed Central - PubMed

Affiliation: Evolutionary Ecology Group, Hungarian Department of Biology and Ecology, Babeş-Bolyai University, Cluj Napoca, Romania; MTA-DE "Lendület" Behavioural Ecology Research Group, Department of Evolutionary Zoology and Human Biology, University of Debrecen, Debrecen, Hungary.

ABSTRACT
Sexual selection and aerodynamic forces affecting structural properties of the flight feathers of birds are poorly understood. Here, we compared the structural features of the innermost primary wing feather (P1) and the sexually dimorphic outermost (Ta6) and monomorphic second outermost (Ta5) tail feathers of barn swallows (Hirundo rustica) from a Romanian population to investigate how sexual selection and resistance to aerodynamic forces affect structural differences among these feathers. Furthermore, we compared structural properties of Ta6 of barn swallows from six European populations. Finally, we determined the relationship between feather growth bars width (GBW) and the structural properties of tail feathers. The structure of P1 indicates strong resistance against aerodynamic forces, while the narrow rachis, low vane density and low bending stiffness of tail feathers suggest reduced resistance against airflow. The highly elongated Ta6 is characterized by structural modifications such as large rachis width and increased barbule density in relation to the less elongated Ta5, which can be explained by increased length and/or high aerodynamic forces acting at the leading tail edge. However, these changes in Ta6 structure do not allow for full compensation of elongation, as reflected by the reduced bending stiffness of Ta6. Ta6 elongation in males resulted in feathers with reduced resistance, as shown by the low barb density and reduced bending stiffness compared to females. The inconsistency in sexual dimorphism and in change in quality traits of Ta6 among six European populations shows that multiple factors may contribute to shaping population differences. In general, the difference in quality traits between tail feathers cannot be explained by the GBW of feathers. Our results show that the material and structural properties of wing and tail feathers of barn swallows change as a result of aerodynamic forces and sexual selection, although the result of these changes can be contrasting.

No MeSH data available.


Related in: MedlinePlus