Male post‐breeding movements and stopover habitat selection of an endangered short‐distance migrant, the Little Bustard Tetrax tetrax

Abstract

Migratory decisions, such as the selection of stopover sites, are critical for the success of post‐breeding migratory movements and subsequent survival. Recent advances in bio‐logging have revealed the stopover strategies of many long‐distance migrants, but far less attention has been given to short‐distance migrants. We investigated the stopover ecology of an endangered grassland bird, the Little Bustard Tetrax tetrax, a short‐distance migrant in Iberia. Using high‐resolution spatial GPS/GSM data, 27 male Little Bustards breeding in southern Portugal were tracked between 2009 and 2011. We studied post‐breeding movements using Dynamic Brownian Bridge models to identify the main stopover sites, and generalized linear mixed models to examine habitat selection in stopovers. During their post‐breeding movements, males were essentially nocturnal migrants, making frequent stopovers while maintaining a relatively fast pace to reach more productive agricultural post‐breeding areas. Stopovers occurred in most post‐breeding movements (83%) regardless of the total distance covered (average 64.3 km), and most stopovers (84%) lasted less than 24 h. Birds used mostly agricultural non‐irrigated and irrigated croplands as stopover sites and avoided other land uses and rugged terrain. There was a negative relationship between stopovers and the proximity to roads, but not to power lines. The high frequency of stopovers during post‐breeding movements, despite the short distances travelled, together with the nocturnal migratory behaviour of bustards, may impose additional risks to a bird mainly threatened by collision with power lines in non‐breeding areas. We also conclude that even for short‐distance migrants, habitat connectivity between breeding and post‐breeding areas is likely to be a key conservation concern.

Effectiveness of the European Natura 2000 network at protecting Western Europe's agro-steppes

“…These results suggest that agro-steppe areas are becoming increasingly isolated and restricted to protected areas, progressively becoming clusters of "steppe habitat islands", potentially decreasing the connectivity between conservation priority sites. Maintaining connectivity is important for population viability and to facilitate dispersal (Guixé & Arroyo, 2011;Hanski, 2011;Alonso et al, 2019), which is particularly important under climate change (Hanski, 2011;Branbilla et al, 2015;Gillingham et al, 2015).…”

Power line routing and configuration as major drivers of collision risk in two bustard species

“…Temporal patterns in collisions may be explained by differences in flocking behaviour, activity and flight patterns. In the case of the little bustard, the peak of mortality during the post-breeding season is probably related to (1) the migratory movements that some individuals perform from the breeding grounds to areas with higher food resources (Silva et al, 2007; García de la Morena et al, 2015) and the use of stop-over sites in areas with poor habitat conditions during such periods (Alonso et al, 2019), (2) the increased distance travelled daily searching for food (Silva et al, 2014), (3) the higher frequency of flights at heights with an increased collision risk (Silva et al, 2014), and (4) the species’ gregarious behaviour during this season. The collision pattern of the little bustard also varied across space: there was (1) a high number of collisions outside Special Protected Areas during summer (July–September), when birds leave their breeding grounds (Silva et al, 2007), (2) a peak of mortality during the autumn (October–December) within Special Protected Areas, probably associated with the return to the breeding grounds after the onset of rains (García de la Morena et al, 2015), and (3) a third mortality peak during the beginning of the breeding season inside Special Protected Areas, which coincides with the onset of the mating period (March–May) when males settle in breeding sites and females move between lekking areas.…”

“…Both are short distance migrants, performing seasonal movements of up to 260 km (great bustard)/300 km (little bustard). The majority of birds (65% in the great bustard, 89–96% in the little bustard) move from their breeding grounds to areas with higher food availability during late spring and summer (Rocha, 2006; García de la Morena et al, 2015; Palacín et al, 2017; Alonso et al, 2019). Collisions are more frequent during the post-breeding and wintering seasons (Silva et al, 2014; Palacín et al, 2017), when bustards make most migratory movements.…”

Changes in grassland management and linear infrastructures associated to the decline of an endangered bird population

“…In fact, multiple threats, such as loss of post-breeding and wintering areas, high anthropogenic mortality and global warming 40 , 67 , 68 , may be acting synergistically. Little bustards are short-distance migrants 69 , 70 that move towards more productive agriculture areas in northern, coastal or higher-altitude locations in Iberia during the dry summer season, in search of green vegetation 69 , 71 . Hence, the patterns we are witnessing at breeding areas may also be a consequence of the still unknown drivers occurring elsewhere.…”