Calcium carbinate content data_species means.csv from How much calcium to shell out? Eggshell calcium carbonate content is greater in birds with thinner shells, larger clutches and longer lifespans

The avian eggshell is a bio-ceramic structure that protects the embryo. It is composed almost entirely of calcium carbonate and a small organic component. 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 these specie's life-history strategies 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.

鸟蛋壳是一种保护胚胎的生物陶瓷（bio-ceramic）结构，其组成几乎完全为碳酸钙，仅含少量有机组分。蛋壳中适量的碳酸钙对于胚胎发育不可或缺，但不同鸟类物种间蛋壳碳酸钙与有机质的比例差异及其演化规律尚未得到研究。钙对多数鸟类而言属于限制性营养资源，因此鸟类为卵投入的钙量应当适配其生活史策略进行优化。本研究测定了222个鸟类物种的蛋壳相对碳酸钙含量，并针对该性状如何随物种的生活史策略及各自卵生理的其他特征演化的相关假说进行了检验。研究结果表明：（1）蛋壳碳酸钙含量与物种的蛋壳更薄、且相对于孵卵亲本体重而言尺寸小于预期的卵呈正相关；（2）平均窝卵数较小的物种，其蛋壳碳酸钙含量更低；（3）对于窝卵数较大的物种，蛋壳碳酸钙含量与其平均寿命呈负相关。寿命更长、窝卵数更大的鸟类蛋壳碳酸钙含量更低这一规律表明，为蛋壳提供钙会对个体产生长期的生理成本。