Effects of habitat and livestock on nest productivity of the Asian houbara Chlamydotis macqueenii in Bukhara Province, Uzbekistan

Abstract

To inform population support measures for the unsustainably hunted Asian houbara Chlamydotis macqueenii (IUCN Vulnerable), we examined potential habitat and landuse effects on nest productivity in the Kyzylkum Desert, Uzbekistan. We monitored 177 nests across different semiarid shrub assemblages (clay-sand and salinity gradients) and a range of livestock densities (0-80 km −2). Nest success (mean 51.4 %, 95 % CI 42.4-60.4 %) was similar across 4 years; predation caused 85 % of those failures for which the cause was known, and only three nests were trampled by livestock. Nesting begins within a few weeks of arrival when food appears scarce, but later nests were more likely to fail owing to the emergence of a key predator, suggesting that foraging conditions on wintering and passage sites may be important for nest productivity. Nest success was similar across three shrub assemblages and was unrelated to landscape rugosity, shrub frequency or livestock density but was greater with taller mean shrub height (range 13-67 cm) within 50 m. Clutch size (mean = 3.2 eggs) and per-egg hatchability in successful nests (87.5 %) did not differ with laying date, shrub assemblage or livestock density. We therefore found no evidence that livestock density reduced nest productivity across the range examined, while differing shrub assemblages appeared to offer similar habitat quality. Asian houbara appear well-adapted to a range of semi-desert habitats and tolerate moderate disturbance by pastoralism. No obvious in situ mitigation measures arise from these findings, leaving regulation and control as the key requirement to render hunting sustainable.

Consistent nest-site selection across habitats increases fitness in Asian Houbara

“…Although degraded areas were noted around water points and sheep camps, at the landscape scale even moderate (10-30 individuals km À2 ) to high (30-83 individuals km À2 ) sheep densities had little impact on shrub vegetation structure (Koshkin et al 2014), nor did they affect Asian Houbara clutch size, nest success, or egg hatchability (Koshkin et al 2016b). Therefore, when modeling nest-site selection and nest survival, we did not include measures of sheep density, focusing solely on vegetation structure.…”

“…The distribution of 5 shrub assemblages was previously classified and mapped, through extensive field survey (871 sampling locations; see Koshkin et al 2016aKoshkin et al , 2016b, as ''Salsola rigida, '' dominated by 2 saltwort species, S. rigida and S. gemmascens, on halophytic soils (2,180 km 2 ); ''Salsola arbuscula, '' characterized by high densities of this taller saltwort species, but also Artemisia diffusa and S. rigida, on gypseous and halophytic soils (3,904 km 2 ); ''Astragalus, '' categorized by the leguminous Astragalus villosissimus, with Convolvulus hamadae and Salsola spp., on semi-consolidated sands (3,778 km 2 ); ''Artemisia, '' largely dominated by A. diffusa, typical of gypseous or clay soils at slightly higher elevations (2,873 km 2 ); and ''Calligonum, '' comprising both Calligonum microcarpum and C. leucocladum and a high frequency of A. villosissimus and C. hamadae, characteristic of drifting and weakly consolidated sands (1,603 km 2 ).…”

“…A total of 210 nests were monitored under a standardized protocol (2012)(2013)(2014)(2015)(2016) with temperature loggers placed inside the nest scape (2013)(2014)(2015)(2016)) to determine when incubation ended (see Koshkin et al 2016b); additionally, 64 of these nests were also monitored with nest cameras. The exact date, and often time, of nest outcome was determined for 77% of the nests, using data from (in order of most accurate data) nest cameras (n ¼ 63), temperature loggers (n ¼ 30), nest visit on day of nest fate (n ¼ 53), or satellite tracking (n ¼ 16; showing the female permanently leaving the nest).…”

“…Searches were conducted during 5 breeding seasons (earliest laying date: March 7; latest laying date: May 7) from 2012 to 2016, in areas known to hold females, across a variety of substrates (consolidated sand, weakly consolidated sand and clay) within the 5 shrub assemblages, including areas with high and low sheep densities (Koshkin et al 2016b). However, in the hard clay substrates of the Artemisia shrub assemblage, our main nest-searching method, following tracks, was of limited use, and in Calligonum our nestsearching ability was reduced by higher densities of sheep and the presence of large shrubs and small dunes; therefore, these 2 shrub assemblages were excluded from analyses, owing to low sample size.…”

“…Female tracks were searched for by 2 observers from a vehicle driven at a precautionary low speed (5-10 km hr À1 ) in order to reduce the risk of flushing females directly off the nest at close range, which can have negative effects on nest survival (Koshkin et al 2016b). Searches were confined to the 2-3 hr after sunrise and before sunset, to reduce the risk of exposing eggs to high temperatures.…”