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Allometry of the duration of flight feather molt in birds.

Rohwer S, Ricklefs RE, Rohwer VG, Copple MM - PLoS Biol. (2009)

Bottom Line: The ratio of length (mm) to rate (mm/day), which would be the time needed to replace all the primaries one by one, increases as the 0.14 power of mass (M(0.316)/M(0.171) = M(0.145)), illustrating why the time required to replace the primaries is so important to life history evolution in large birds.Smaller birds generally replace all their flight feathers annually, but larger birds that fly while renewing their primaries often extend the primary molt over two or more years.Finally, we propose two models that could account for the 1/6 power allometry between feather growth rate and body mass, both based on a length-to-surface relationship that transforms the linear, cylindrical growing region responsible for producing feather tissue into an essentially two-dimensional structure.

View Article: PubMed Central - PubMed

Affiliation: Burke Museum and Department of Biology, University of Washington, Seattle, United States of America. rohwer@u.washington.edu

ABSTRACT
We used allometric scaling to explain why the regular replacement of the primary flight feathers requires disproportionately more time for large birds. Primary growth rate scales to mass (M) as M(0.171), whereas the summed length of the primaries scales almost twice as fast (M(0.316)). The ratio of length (mm) to rate (mm/day), which would be the time needed to replace all the primaries one by one, increases as the 0.14 power of mass (M(0.316)/M(0.171) = M(0.145)), illustrating why the time required to replace the primaries is so important to life history evolution in large birds. Smaller birds generally replace all their flight feathers annually, but larger birds that fly while renewing their primaries often extend the primary molt over two or more years. Most flying birds exhibit one of three fundamentally different modes of primary replacement, and the size distributions of birds associated with these replacement modes suggest that birds that replace their primaries in a single wave of molt cannot approach the size of the largest flying birds without first transitioning to a more complex mode of primary replacement. Finally, we propose two models that could account for the 1/6 power allometry between feather growth rate and body mass, both based on a length-to-surface relationship that transforms the linear, cylindrical growing region responsible for producing feather tissue into an essentially two-dimensional structure. These allometric relationships offer a general explanation for flight feather replacement requiring disproportionately more time for large birds.

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Related in: MedlinePlus

Deviations from the growth rate regression in Figure 1, plotted separately for species that fly while molting and for species that replace their wing quills simultaneously.The latter grow their primaries no slower than birds that fly while molting, suggesting that follicular constraints on the rate of feather synthesis, rather than energetic costs, limit the rate at which flight feathers grow.
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pbio-1000132-g003: Deviations from the growth rate regression in Figure 1, plotted separately for species that fly while molting and for species that replace their wing quills simultaneously.The latter grow their primaries no slower than birds that fly while molting, suggesting that follicular constraints on the rate of feather synthesis, rather than energetic costs, limit the rate at which flight feathers grow.

Mentions: We found no evidence that primary growth rate during simultaneous molt is reduced by the energy and nutrient demands of growing all of the flight feathers at once. We divided the 43 species with feather growth rates (Table 1) into two groups, those that replace their primaries simultaneously (n = 15 species in two orders) and those that fly while molting (n = 28 species in eight orders). We used analysis of covariance (see Methods), with body mass as the covariate to compare feather growth rates between these groups. Remarkably, growth rate did not differ between species with simultaneous primary molt and those that fly while molting (F = 1.0; degrees of freedom = 1, 40; p = 0.32; Figure 3). Because primary growth rates are similar for birds that grow two or three versus ten primaries simultaneously, primary growth rate seems not to be limited by energy or nutrient demands; others have suggested that growth rate might be limited by follicular-level constraints on the rate at which feathers can be generated [1],[37], and we explore this below.


Allometry of the duration of flight feather molt in birds.

Rohwer S, Ricklefs RE, Rohwer VG, Copple MM - PLoS Biol. (2009)

Deviations from the growth rate regression in Figure 1, plotted separately for species that fly while molting and for species that replace their wing quills simultaneously.The latter grow their primaries no slower than birds that fly while molting, suggesting that follicular constraints on the rate of feather synthesis, rather than energetic costs, limit the rate at which flight feathers grow.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2690433&req=5

pbio-1000132-g003: Deviations from the growth rate regression in Figure 1, plotted separately for species that fly while molting and for species that replace their wing quills simultaneously.The latter grow their primaries no slower than birds that fly while molting, suggesting that follicular constraints on the rate of feather synthesis, rather than energetic costs, limit the rate at which flight feathers grow.
Mentions: We found no evidence that primary growth rate during simultaneous molt is reduced by the energy and nutrient demands of growing all of the flight feathers at once. We divided the 43 species with feather growth rates (Table 1) into two groups, those that replace their primaries simultaneously (n = 15 species in two orders) and those that fly while molting (n = 28 species in eight orders). We used analysis of covariance (see Methods), with body mass as the covariate to compare feather growth rates between these groups. Remarkably, growth rate did not differ between species with simultaneous primary molt and those that fly while molting (F = 1.0; degrees of freedom = 1, 40; p = 0.32; Figure 3). Because primary growth rates are similar for birds that grow two or three versus ten primaries simultaneously, primary growth rate seems not to be limited by energy or nutrient demands; others have suggested that growth rate might be limited by follicular-level constraints on the rate at which feathers can be generated [1],[37], and we explore this below.

Bottom Line: The ratio of length (mm) to rate (mm/day), which would be the time needed to replace all the primaries one by one, increases as the 0.14 power of mass (M(0.316)/M(0.171) = M(0.145)), illustrating why the time required to replace the primaries is so important to life history evolution in large birds.Smaller birds generally replace all their flight feathers annually, but larger birds that fly while renewing their primaries often extend the primary molt over two or more years.Finally, we propose two models that could account for the 1/6 power allometry between feather growth rate and body mass, both based on a length-to-surface relationship that transforms the linear, cylindrical growing region responsible for producing feather tissue into an essentially two-dimensional structure.

View Article: PubMed Central - PubMed

Affiliation: Burke Museum and Department of Biology, University of Washington, Seattle, United States of America. rohwer@u.washington.edu

ABSTRACT
We used allometric scaling to explain why the regular replacement of the primary flight feathers requires disproportionately more time for large birds. Primary growth rate scales to mass (M) as M(0.171), whereas the summed length of the primaries scales almost twice as fast (M(0.316)). The ratio of length (mm) to rate (mm/day), which would be the time needed to replace all the primaries one by one, increases as the 0.14 power of mass (M(0.316)/M(0.171) = M(0.145)), illustrating why the time required to replace the primaries is so important to life history evolution in large birds. Smaller birds generally replace all their flight feathers annually, but larger birds that fly while renewing their primaries often extend the primary molt over two or more years. Most flying birds exhibit one of three fundamentally different modes of primary replacement, and the size distributions of birds associated with these replacement modes suggest that birds that replace their primaries in a single wave of molt cannot approach the size of the largest flying birds without first transitioning to a more complex mode of primary replacement. Finally, we propose two models that could account for the 1/6 power allometry between feather growth rate and body mass, both based on a length-to-surface relationship that transforms the linear, cylindrical growing region responsible for producing feather tissue into an essentially two-dimensional structure. These allometric relationships offer a general explanation for flight feather replacement requiring disproportionately more time for large birds.

Show MeSH
Related in: MedlinePlus