Diet composition of a declining steppe bird the Little Bustard (Tetrax tetrax) in relation to farming practices

Abstract

ABSTRACT. Foraging strategies and diet selection play an essential role in individual survival and reproductive success. The study of feeding ecology becomes crucial when it concerns endangered species such as the Little Bustard (Tetrax tetrax), whose populations are suffering strong declines as a consequence of agricultural intensification. Despite the fact that several populations are overwintering in areas affected by agricultural transformation, nothing is known about how feeding behavior responds to these changes. We studied for the first time the winter diet composition of the Little Bustard in Spain and compared it between areas with two different farming systems: dry and irrigated farmland. Diet was studied through the micro-histological analysis of 357 droppings collected in 16 locations across the wintering range of the Little Bustard in Spain. Up to 62 plant species were identified. Most consumed species were cultivated legumes (46.7%) and dicotyledon weeds (45.6%), while monocotyledons were scarcely consumed (7.7%). Diet composition differed significantly between dry and irrigated farmland areas. In irrigated areas, diet was mainly composed of legumes, in particular alfalfa (Medicago sativa). In contrast, in dry farmland areas diet was more diverse, composed mainly of weeds (Compositae, Papaveraceae, and Cruciferae) and also cultivated legumes, particularly vetch (Vicia sativa). These results suggest that legume crops could be an effective measure to improve habitat quality in areas with scarce food resources. However, in the case of irrigated areas, the strong reliance on alfalfa could make the Little Bustard more vulnerable to changes in land use. This study is the first step to understand the winter trophic requirements of the endangered Little Bustard, but further research is necessary to understand the food requirements of this species during the entire annual cycle.Régime alimentaire d'un oiseau de steppe en diminution, l'Outarde canepetière (Tetrax tetrax), en lien avec les pratiques agricoles RÉSUMÉ. Les stratégies d'alimentation et le choix du régime alimentaire jouent un rôle essentiel dans la survie et le succès reproducteur d'un individu. L'étude de l'écologie alimentaire revêt une importance cruciale lorsqu'il s'agit d'une espèce en voie de disparition telle que l'Outarde canepetière (Tetrax tetrax), dont les populations subissent des diminutions très marquées en raison de l'intensification des pratiques agricoles. Malgré le fait que plusieurs populations hivernent dans des endroits où se produisent des changements agricoles, on ne sait pas comment les oiseaux adaptent leur comportement alimentaire face à ces changements. Nous avons étudié pour la première fois la composition du régime alimentaire hivernal de l'Outarde canepetière en Espagne, et l'avons comparée dans deux systèmes agricoles : des terres cultivées sèches ou irriguées. Le régime alimentaire a été examiné au moyen de l'analyse micro-histologique de 357 fèces récoltées sur 16 sites répartis dans l'aire d'hivernage de l'outar...

Opposing population trajectories in two Bustard species: A long-term study in a protected area in Central Spain

“…Lane et al (1999) indicate that Great Bustards eat cereal leaves and seeds, which are a superabundant resource (their relatively larger intestinal caecum may allow them to more efficiently process fibre and cellulose). However, the few dietary studies available for Little Bustard (Jiguet 2002, Bravo et al 2017), the latter with data from several very different and distant wintering localities) show that there is no sign of cultivated graminae in faeces, neither green parts nor seeds. Furthermore, even in cereal farmland, Little Bustards show a marked preference for legumes (both cultivated and wild) and other wild plants, a landscape element clearly selected by lekking males and by breeding females (Martínez 1998, Faria et al 2012), which are much scarcer resources in current agrarian landscapes (Bravo et al 2017).…”

“…However, the few dietary studies available for Little Bustard (Jiguet 2002, Bravo et al 2017), the latter with data from several very different and distant wintering localities) show that there is no sign of cultivated graminae in faeces, neither green parts nor seeds. Furthermore, even in cereal farmland, Little Bustards show a marked preference for legumes (both cultivated and wild) and other wild plants, a landscape element clearly selected by lekking males and by breeding females (Martínez 1998, Faria et al 2012), which are much scarcer resources in current agrarian landscapes (Bravo et al 2017). In this sense, an adequate management of alfalfa fields promoted by EU agri-environmental aids has been key to recovering an almost extinct Little Bustard population in France for which this is a crucial breeding habitat (Bretagnolle et al 2011).…”

Inter-individual consistency in habitat selection patterns and spatial range constraints of female little bustards during the non-breeding season

“…Habitat models predicted a positive effect in the occurrence probability at heterogeneous sites, with positive effects of intermediate availabilities of irrigated alfalfa and corn stubbles, as well as sites dominated by irrigated cereal stubbles. The alfalfa crops are an attractive resource for little bustards during this period, since they provide abundant food [ 53 ] and shelter [ 71 , 72 ]. Additionally, recently harvested corn and cereal stubbles, holding a varied weed community, provide interesting food resources for little bustards complementary to alfalfa crops [ 53 ].…”

“…The alfalfa crops are an attractive resource for little bustards during this period, since they provide abundant food [ 53 ] and shelter [ 71 , 72 ]. Additionally, recently harvested corn and cereal stubbles, holding a varied weed community, provide interesting food resources for little bustards complementary to alfalfa crops [ 53 ].…”

“…We compiled landscape composition data on five dominant crop cover type variables to represent habitat variability in the study area as well as human influence predictors and terrain slope (Table 1 ). These variables are likely to affect the species ranging patterns during the non-breeding period due to their different vegetation structure and management that affect provision of food availability, food accessibility and shelter [ 42 – 44 , 53 ].…”