Morphometrics of Houbara Bustards Chlamydotis spp: Sexual Size Dimorphism, Seasonal Changes and Differences between Species

Abstract

SummaryThis study presents for the first time morphometric data from large samples of free-living individuals of Chlamydotis bustards (448 MacQueen's Bustards, 288 African Houbaras, and 53 Canarian Houbaras). Linear measurements were largest in MacQueen's Bustards, intermediate in African Houbaras and smallest in Canarian Houbaras, with differences between the largest and smallest species ranging from 4.5% to 13.9%. Male MacQueen's Bustards were also the heaviest (4% and 15.5% heavier than, respectively, African and Canarian Houbara males) but, unexpectedly, there were no significant weight differences among females of the three bustards. Males of the three bustards were significantly larger than females in all linear measurements and weight. These between-species/subspecies differences are consistent with a slight trend to insular dwarfism that probably selects for smaller size in the Canarian subspecies. Males are larger and heavier than females in the three bustards, as expected in polygynous species, suggesting a moderate effect of sexual selection acting on male size. Finally, the slightly higher sexual size dimorphism values observed in wings and tarsi in MacQueen's bustards compared to both subspecies of African Houbaras are in line with the allometric constraint hypothesis.—Alonso, J.C., Dieuleveut, T., Palacín, C., Abril-Colón, I., Ucero, A. & Lucas, C. (2023). Morphometrics of Houbara Bustards Chlamydotis spp: sexual size dimorphism, seasonal changes and differences between species. Ardeola, 70: 235-247.

Anthropogenic mortality threatens the survival of Canarian houbara bustards

“…Higher mortality rates in males have also been reported for the great bustard, a species that also shows a female-biased sex ratio 37,38,96 . A higher male mortality is expected in polygynous species with male-biased sexual size dimorphism favoured by sexual selection 97,98 , and this could also be the case in houbara bustards, which have a mating system that fits the definition of dispersed lek, intense male sexual display, and a male-biased sexual size dimorphism [99][100][101] .…”

“…Sex was established in the field using distinctive plumage features 111 , 112 , and confirmed by genetic analysis using DNA extracted from 1–2 contour feathers plucked from each bird 113 . Only three birds (one female, two males) showed plumage and biometric characters that made us suspect they could be immatures, all other birds were identified as adults 101 .…”

“…The species is polygynous 107,108 and exhibits an exploded lek mating system 99,100 . It shows a moderate male-biased sexual size dimorphism 101 . The Canarian subspecies is a nocturnal and partial migrant 91 .…”