Itinerant lifestyle and congregation of lesser kestrels in West Africa

Abstract

Migratory birds often spend a large proportion of their annual cycle in their non-breeding areas. While some species are sedentary after arriving in their non-breeding areas, others engage in itinerary or nomadic movements. Using GPS-tracking we aimed to investigate the little known non-breeding movements of the lesser kestrel Falco namumanni in sub-Saharan Africa. We segment non-breeding tracks (n = 78 tracks by 54 individuals) into staging events (131± 25 days), itinerant movements between staging sites (11 ± 10 days), and non-directed exploratory movements (6 ± 5 days). We then describe timing and directionality of itinerary movements by male and female kestrels, and explore shifts in habitat use throughout the non-breeding season. Regardless of sex, lesser kestrels spent on average 89% of the non-breeding season at 2-3 staging sites in West Africa. Upon arrival at the end of September, kestrels used disparate sites throughout the Sahel. By December, however, they congregated into two clearly delineated areas in Senegal and along the Malian-Mauritanian border. The birds stayed longer and showed greater daily activity in the latter areas, which were situated closer to wetlands compared to their first and intermediate ones. While 20 of 24 individuals tracked across multiple annual cycles showed consistent staging sites, a few switched between the Senegal and Mauritanian/Malian staging clusters. These results show that rather than tracking suitable climatic conditions southward, lesser kestrels survive the West African dry season by moving into wetland areas within the Sahelian climatic belt. Our findings match reports of lesser kestrel super-roosts in West Africa and stress the conservation value of wetlands along the Senegal River and the Inner Niger Delta in West Africa for the Spanish lesser kestrel population. These areas host 81% of lesser kestrels during 20% of their annual cycle.

Kestrels of the same colony do not overwinter together

“…In accordance with previous tracking studies on the Lesser Kestrel during the non breeding period, the repeatability of non-breeding areas was high in the individuals in our study (López-Ricaurte et al, 2022). Lesser kestrels tend to overwinter in the same region than in previous years, which is supported by our results on the year-to-year overlap of non-breeding areas, which ranged from 33 to 87% (49 ± 27 on average).…”

“…First, it may be due to the characteristic non-breeding movements of the lesser kestrel. While some species that overwinter in the Sahel are located in a single area which they use throughout the entire season, the lesser kestrels have an itinerant behavior, that is, they move along the longitudinal Sahelian strip and occupy several smaller areas (López-Ricaurte et al . 2022).…”

Itinerant lifestyle and congregation of lesser kestrels in West Africa

“…Data are available from the Dryad Digital Repository: https:// doi.org/10.5061/dryad.qjq2bvqnh (Lopez-Ricaurte et al 2023).…”

Recurrence, fidelity and proximity to previously visited sites throughout the annual cycle in a trans‐Saharan migrant, the common cuckoo

“…Migratory species exhibit a range of strategies during the non‐breeding season, from having short migration periods and one long sedentary winter stay, to itinerancy, having multiple winter stays, to a sequence of sedentary stays during the non‐breeding season. Most studies showing high fidelity have dealt with non‐itinerant wintering but also for example Montagu's harriers Circus pygargus and lesser kestrels Falco naumanni , two species that move during winter and show some degree of social gathering, have high site fidelity (Trierweiler et al 2013, Lopez‐Ricaurte et al 2023).…”