Exploring the Relationship between Skeletal Mass and Total Body Mass in Birds

Martin-Silverstone, Elizabeth; Vincze, Orsolya; McCann, Ria; Jonsson, Carl H. W.; Palmer, Colin; Kaiser, Gary W.; Dyke, Gareth J.

doi:10.1371/journal.pone.0141794

Cited by 30 publications

(10 citation statements)

References 46 publications

(84 reference statements)

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“…where M is body mass (kg) and b is wingspan (m) (though see 47 and 48 for discussions on the use of this mass estimation method). Wing area is difficult to calculate for pterosaurs because wing membrane fossils are rare, difficult to interpret precisely 49 , and generalisations made about some pterosaurs may not apply to all taxa.…”

Section: Glide Analysismentioning

confidence: 99%

Powered flight in hatchling pterosaurs: evidence from wing form and bone strength

Naish

Witton

Martin-Silverstone

2021

Sci Rep

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Competing views exist on the behaviour and lifestyle of pterosaurs during the earliest phases of life. A ‘flap-early’ model proposes that hatchlings were capable of independent life and flapping flight, a ‘fly-late’ model posits that juveniles were not flight capable until 50% of adult size, and a ‘glide-early’ model requires that young juveniles were flight-capable but only able to glide. We test these models by quantifying the flight abilities of very young juvenile pterosaurs via analysis of wing bone strength, wing loading, wingspan and wing aspect ratios, primarily using data from embryonic and hatchling specimens of Pterodaustro guinazui and Sinopterus dongi. We argue that a young Sinopterus specimen has been mischaracterised as a distinct taxon. The humeri of pterosaur juveniles are similar in bending strength to those of adults and able to withstand launch and flight; wing size and wing aspect ratios of young juveniles are also in keeping with powered flight. We therefore reject the ‘fly-late’ and ‘glide-early’ models. We further show that young juveniles were excellent gliders, albeit not reliant on specialist gliding. The wing forms of very young juveniles differ significantly from larger individuals, meaning that variation in speed, manoeuvrability, take-off angle and so on was present across a species as it matured. Juveniles appear to have been adapted for flight in cluttered environments, in contrast to larger, older individuals. We propose on the basis of these conclusions that pterosaur species occupied distinct niches across ontogeny.

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Section: Glide Analysismentioning

confidence: 99%

Powered flight in hatchling pterosaurs: evidence from wing form and bone strength

Naish

Witton

Martin-Silverstone

2021

Sci Rep

Self Cite

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“…Additionally, high calcium carbonate content in eggs that are larger than predicted for a species' body size would probably represent a substantial investment. Body mass is tightly positively correlated with skeletal mass in birds [ 98 ] and will likewise affect the potential quantity of circulating blood calcium that can be maintained during egg production, thereby increasing the rate at which calcium must be obtained during the period of shell formation [ 34 , 82 , 99 ]. This is relevant to our understanding of the costs of egg production and how they affect investment strategies across avian families.…”

Section: Discussionmentioning

confidence: 99%

How much calcium to shell out? Eggshell calcium carbonate content is greater in birds with thinner shells, larger clutches and longer lifespans

McClelland

Cassey

Maurer

et al. 2021

J. R. Soc. Interface.

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The avian eggshell is a bio-ceramic structure that protects the embryo. It is composed almost entirely of calcium carbonate and a small amount of organic material. An optimal amount of calcium carbonate in the eggshell is essential for the embryo's development, yet how the ratio of calcium carbonate to organic matter varies between species has not been investigated. Calcium is a limiting resource for most birds, so its investment in their eggs should be optimized for a bird's life history. We measured the relative calcium carbonate content of eggshells in 222 bird species and tested hypotheses for how this trait has evolved with the life-history strategies of these species and other traits of their respective egg physiologies. We found that (i) eggshell calcium carbonate content was positively correlated with species having thinner eggshells and smaller than expected eggs relative to incubating parental mass, (ii) species with small mean clutch sizes had lower calcium carbonate content in their eggshells, and (iii) for species with larger clutch sizes, eggshell calcium carbonate content was negatively correlated with their mean lifespan. The pattern of lower eggshell calcium carbonate in longer lived, larger clutched birds suggests that calcium provision to the eggshell has long-term costs for the individual.

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“…Neck length was normalized by neck length/(body mass 0.33 ). Diets were assigned to birds based on data from multiple volumes of Handbook of the Birds of the World [33][34][35][36][37][38][39][40][41][42][43], and locomotor mode was collated from the literature [44][45][46].…”

Section: (B) Explanatory Variablesmentioning

confidence: 99%

Evolutionary versatility of the avian neck

Marek

Falkingham²,

Benson

et al. 2021

Proc. R. Soc. B.

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Bird necks display unparalleled levels of morphological diversity compared to other vertebrates, yet it is unclear what factors have structured this variation. Using three-dimensional geometric morphometrics and multivariate statistics, we show that the avian cervical column is a hierarchical morpho-functional appendage, with varying magnitudes of ecologically driven osteological variation at different scales of organization. Contrary to expectations given the widely varying ecological functions of necks in different species, we find that regional modularity of the avian neck is highly conserved, with an overall structural blueprint that is significantly altered only by the most mechanically demanding ecological functions. Nevertheless, the morphologies of vertebrae within subregions of the neck show more prominent signals of adaptation to ecological pressures. We also find that both neck length allometry and the nature of neck elongation in birds are different from other vertebrates. In contrast with mammals, neck length scales isometrically with head mass and, contrary to previous work, we show that neck elongation in birds is achieved predominantly by increasing vertebral lengths rather than counts. Birds therefore possess a cervical spine that may be unique in its versatility among extant vertebrates, one that, since the origin of flight, has adapted to function as a surrogate forelimb in varied ecological niches.

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Exploring the Relationship between Skeletal Mass and Total Body Mass in Birds

Cited by 30 publications

References 46 publications

Powered flight in hatchling pterosaurs: evidence from wing form and bone strength

Powered flight in hatchling pterosaurs: evidence from wing form and bone strength

How much calcium to shell out? Eggshell calcium carbonate content is greater in birds with thinner shells, larger clutches and longer lifespans

Evolutionary versatility of the avian neck

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