Authors: Natalie dos Remedios, Tamás Székely, Clemens Küpper, Patricia L. M. Lee, András Kosztolányi
Source: IBIS, 157(3), 590–600, July 2015
Brief summary of the paper: Why are males sometimes bigger than females? Or vice versa? Theories and studies on sexual size dimorphism (SSD) abound, but few have considered when the individual sexes begin to diverge in morphology.
Here we found that Kentish Plover and Snowy Plover (closely related species with adult SSD) populations at four locations varied in the timing of SSD emergence.
Snowy Plover chicks in Mexico had divergent SSD at hatching, whereas for Cape Verdean Kentish Plover chicks, there were no sex differences in body size before fledging. However, for Kentish Plovers in Turkey and United Arab Emirates, males and females hatched at equal size but subsequently diverged in growth rates.
We conclude that SSD may indeed emerge at different stages of development in different populations. In cases of moderate SSD, larger juveniles survive better, so the timing of SSD emergence may have implications for the relative survival of the sexes.
Survival differences may impact on operational sex ratios and consequentially, the evolution of mating systems and parental care.
Full article available HERE (PDF).