Offspring sex ratio is unrelated to parental quality and time of breeding in a multiple-breeding shorebird

  • Pinjia Que
  • Tamás Székely
  • Pengcheng Wang
  • Qi Lu
  • Weipan Lei
  • Yang Liu
  • Zhengwang Zhang
Original Article


Sex ratio is a fundamental concept in evolutional biology, and theory predicts that parents should invest in sons and daughters according to the fitness returns they expect from them. The fitness returns may depend on the timing of breeding and on parental conditions leading to sex ratios that depend on breeding date and/or parental quality. Here, we investigate the offspring sex ratio in a small shorebird, the Kentish Plover Charadrius alexandrinus, in a large breeding population in Eastern China, and test whether the parents adjust their offspring’s sex in response to hatch date, brood age and their own body condition. Using 1264 chicks from 676 broods that were molecularly sexed, we show that hatchling sex ratio was not significantly different from unity. Hatchling sex ratios were not related to hatch date or to the body condition of parents. In addition, we sexed 138 eggs that were confiscated from illegal egg collectors and found that the mortality of female and male embryos was not significantly different. The latter result is important by suggesting that neither primary sex ratio (i.e., at conception) nor secondary sex ratio (i.e., at hatching) is biased. Taken together, the even offspring sex ratio in Chinese Kentish Plovers is consistent with recent analyses of six plover populations that found even sex ratios at hatching. Future works should investigate whether the even sex ratio persists into adulthood, or it may shift toward more males (or females) due to sex-biased mortalities of juveniles and/or adults.


Brood age Parental investment Parental size Sex-biased mortality Trivers-Willard hypothesis 


Das Geschlechterverhältnis des Nachwuchses einer Küstenlimikole ist unabhängig von den Eigenschaften der Eltern und dem Brutzeitbeginn

Das Geschlechterverhältnis ist ein fundamentales Konzept der Evolutionsbiologie, und die Theorie sagt voraus, dass Eltern in Söhne und Töchter proportional zu dem von ihnen erwarteten Fitnessertrag investieren sollten. Der Fitnessertrag hängt möglicherweise vom Brutzeitbeginn und der elterlichen Qualität ab, was dazu führen kann, dass das Geschlechterverhältnis selbst vom Beginn der Brutzeit und den Eigenschaften der Eltern abhängt. Hier untersuchen wir das Geschlechterverhältnis des Nachwuchses einer kleinen Küstenvogelart, dem Seeregenpfeifer Charadrius alexandrinus, in einer großen Brutpopulation in Ostchina und testen, ob die Eltern das Geschlechterverhältnis ihres Nachwuchses dem Schlüpfzeitpunkt, Brutalter und den eigenen körperlichen Bedingungen anpassen. Mittels 1264 Küken aus 676 Bruten, die alle molekular geschlechtsbestimmt waren, zeigen wir, dass das Geschlechterverhältnis nicht signifikant von gleichförmig abwich. Das Geschlechterverhältnis beim Schlupf war weder vom Schlüpfzeitpunkt noch von der Körperkondition der Eltern abhängig. Zusätzlich bestimmten wird das Geschlecht von 138 Eiern, die von illegalen Eisammlern beschlagnahmt wurden, und fanden, dass die Sterblichkeit von weiblichen und männlichen Embryos nicht signifikant verschieden war. Dies zeigt, dass weder das primäre Geschlechterverhältnis (bei der Zeugung) noch das sekundäre Geschlechterverhältnis (beim Schlupf) unausgeglichen sind. Das ausgeglichene Geschlechterverhältnis in den chinesischen Seeregenpfeifern stimmt mit jüngsten Ergebnissen von sechs Regenpfeiferpopulationen überein, die auch ausgeglichene Geschlechterverhältnisse beim Schlupf fanden. Zukünftige Arbeiten sollten untersuchen, ob das ausgeglichene Geschlechterverhältnis bis in das Erwachsenenalter fortbesteht, oder ob es sich zu mehr Männchen (oder Weibchen) verschiebt aufgrund von geschlechtsabhängigen Sterberaten von Jung- und/oder Altvögeln.



This study was supported by the National Natural Science Foundation of China (nos. 31600297 and 31572288). We especially thank Zhiwei Tian and Jianli Song, who provided much help in the fieldwork. We are grateful to Yajing Chang, Bingrun Zhu, Jin Liu, Jia Zheng, Boshi Liang, Siyuan Huang, Karen Kim, Siyao Zhong, Zhuoxue Chen, Guang Yang, Pei Luo, Christopher Dudley, Carrie Wendt, Rebecca Gouge, Robert Weber, Kai Chen, Xiaoyan Long, Nan Zhang, and Xuecong Zhang for field assistance. We also thank Xunqiang Mo and Jianmin Wang for intercepting the illegal egg collectors and bringing the confiscated eggs to us. We thank Dr. Benjamin Werner for translating the abstract to German. Tamás Székely was a fellow of the Advanced Institute of Berlin at the time of writing the manuscript, and his work was funded by a Royal Society Wolfson Merit Award (WM170050), and by the Hungarian scientific funding agency, NKFIH (ÉLVONAL KKP-126949, K-116310). All experiments described in this study comply with current Chinese laws.

Supplementary material

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Supplementary material 1 (DOCX 392 kb)


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© Deutsche Ornithologen-Gesellschaft e.V. 2019

Authors and Affiliations

  1. 1.Ministry of Education Key Laboratory for Biodiversity Sciences and Ecological Engineering, College of Life SciencesBeijing Normal UniversityBeijingChina
  2. 2.Milner Centre for Evolution, Department of Biology and BiochemistryUniversity of BathBathUK
  3. 3.State Key Laboratory of Biocontrol, Department of Ecology, School of Life SciencesSun Yat-sen UniversityGuangzhouChina

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