Consistent nest-site selection across habitats increases fitness in Asian Houbara | Une sélection du site de nidification consistante entre les habitats augmente la valeur adaptative chez Chlamydotis macqueenii

Nest-site choice profoundly influences reproductive success and the survival of incubating adult birds. Asian Houbara (Chlamydotis macqueenii) nest in subtly contrasting habitats where the main cause of nest failure is predation. We examined nest-site selection across 3 semiarid shrub habitats that differed in vegetation structure and hypothesized that increased concealment would reduce nest predation. We quantified vegetation structure at 210 nests and 194 random control sites at 2 scales, the “nest area” (50 m radius, considering mean “shrub height” and mean “shrub frequency”) and “nest scrape” (2 m radius, considering a “concealment index”). Variance ratio tests showed that variance in both shrub height and concealment index was lower at nests than at random sites, indicating nonrandom selection. Analysis of the probability of nest occurrence for nest area indicated consistent selection of intermediate shrub heights (shrub height + shrub height²) in the Astragalus, Salsola arbuscula, and S. rigida shrub assemblages (29.5–31.5 cm), although this was not supported statistically in S. rigida because the vegetation available was already similar to the optimal structure. Nest survival analysis, controlling for date, showed that shrub height (but not its quadratic term) in the nest area reduced nest predation rate. Females likely traded off nesting in even taller shrubs that may confer greater nest success against the ability to see approaching danger and thus to reduce the risk of being depredated themselves (head height during vigilance when incubating is ∼30 cm), given that we have no records of females being depredated on the nest. At the nest scrape, females strongly selected better-concealed locations, although the concealment index did not affect nest success. We suggest that concealing the scrape among shrubs may have other roles, such as thermoregulation.