An update on the conservation status of the Little Bustard Tetrax tetrax: global and local population estimates, trends, and threats

Abstract

Summary The Little Bustard Tetrax tetrax is an iconic species and an indicator of healthy grassland and farmland ecosystems. It formerly ranged almost continuously from north-western Africa and Iberia to central Asia, encompassing France, Italy, southern Russia, and the Middle East, occupying natural grass steppes, pastured grasslands, and extensive cereal farmland. Today, two main distribution sub-ranges persist: a western one comprising the Iberian Peninsula, France, and Sardinia, and an eastern one encompassing mainly southern Russia and Kazakhstan but reaching north-western China and isolated spots in Turkey. We describe the changes that occurred across the species’ range and were documented during the last and current centuries and revise the status and trends of Little Bustard populations throughout that range. We provide the first global estimate of the world population, as well as those of the two sub-ranges, discussing the main threats and global conservation implications of these estimates. Historically abundant in Europe and northern Africa, the Little Bustard has strongly declined over the second half of the 20th century, becoming extinct in at least 15 countries. Such spectacular regression is mainly associated with land-use change and agricultural intensification. Other threats are legal hunting, poaching, and collision with powerlines. In the last two decades, the species has severely declined (c.6% yearly rate) in its traditional population stronghold, the Iberian Peninsula. Conversely, there is evidence of recent population growth in some areas of the Eastern range, but increases are unquantified and require further study. Many populations are probably small and scattered, with no reliable information on size and trends. Nevertheless, the Eastern range may now be considered the species’ stronghold with more than half the world’s population. The diverging dynamics and ecological differences between the two sub-ranges require a global conservation strategy that treats each as a different conservation unit to assure the species’ recovery.

Biased adult sex ratios in Western Europe populations of Little BustardTetrax tetraxas a potential warning signal of unbalanced mortalities

“…Overall, therefore, the percentages of females described in this study are considerably low, and our results thus raise serious concerns about the viability of Little Bustard populations in Western Europe. Indeed, all study populations have moderately or strongly decreased in the last 10 years (García de la Morena et al 2018, Bretagnolle et al 2018, Morales and Bretagnolle 2021), except for South France (see Devoucoux et al 2018). The West France migratory population has in fact undergone one of the steepest declines documented for any bird species in Europe, with 94% loss of displaying males in 30 years (Inchausti and Bretagnolle 2005).…”

“…The species’ range has greatly reduced over the last century, becoming extinct in at least 10 European countries (Morales and Bretagnolle 2022). Western European populations are nowadays restricted to France, Spain, Portugal, and Sardinia (Morales and Bretagnolle 2021). At present, the Little Bustard is considered “Near-Threatened” worldwide and “Vulnerable” in Europe (BirdLife International 2018), but it is red-listed as “Endangered” in France (IUCN France et al 2016) and Spain (López-Jiménez et al 2021), and as “Vulnerable” in Portugal (Cabral et al .…”

Functional habitat suitability and urban encroachment explain temporal and spatial variations in abundance of a declining farmland bird, the Little Bustard Tetrax tetrax

“…The Little Bustard is a charismatic species of European agroecosystems, and its most important Western European breeding populations are in Spain (García de la Morena et al 2018). The species suffered strong population declines throughout its range during the last century (Morales and Bretagnolle 2021) and has disappeared from many European countries (Schulz 1985). It is classified as "Near Threatened" worldwide and "Vulnerable" in Europe (BirdLife International 2015).…”

“…We explored the associations between habitat suitability inferred from resource-based models and abundance of a farmland bird of conservation concern, the Little Bustard (Tetrax tetrax). This species has suffered strong declines throughout its breeding range in western Europe (Morales and Bretagnolle 2021), which are associated with changes in agricultural land uses and practices that are thought to reduce availability of suitable nesting areas or food supply (e.g., Wolff et al 2001, Martínez and Tapia 2002, although the specific processes behind the declines or the relative contribution of different processes are still not clear in all areas. Additionally, this species is known to be sensitive to human disturbance (Casas et al 2009, Tarjuelo et al 2015, Estrada et al 2016, and increasing pressure from infrastructures in farmland is considered a threat to the species (Silva et al 2021).…”

Alarming decline of the Great Bustard Otis tarda world population over the last two decades

“…It is therefore most important to monitor their status and keep it up-to-date (e.g. Morales and Bretagnolle 2021 for the Little Bustard).…”