The itinerant movements of lesser kestrels in West Africa
Submitted by Michi on 23 November 2023.
The lesser kestrel is highly dependent on large invertebrates such as the centipede shown here, whilst over-wintering in West Africa. (Photo Thomas Galewski)
This blogpost is based on the article by Lopez-Ricaurte et al. about the non-breeding movements of lesser kestrels in sub-Saharan Africa.
The whereabouts of many long-distance migrants when they are away from their breeding areas has remained a real challenge that has only recently been addressed through the development of lighter and more affordable tracking technology. Whilst many migrants return to the same non-breeding grounds each year, other species show high mobility, becoming nomadic as they seek the best ecological conditions.
In their study, Lopez-Ricaurte et al characterised the itinerant movements of lesser kestrels Falco naumanni, after they left the Mediterranean region and head to West Africa. The team caught adult lesser kestrels across 28 breeding sites in Spain, as part of their ongoing studies, and equipped 111 males, and 105 females with one of two models of solar GPS-UHF biologgers. From these birds, the team managed to retrieve data on the non-breeding movements of 25 males and 29 females from 20 of the breeding sites.
The tracked individuals were caught at studied breeding sites in Spain such as this nest box tower in Doñana (Photo: Lina Lopez-Ricaurte)
On average lesser kestrels spent about 40% of their annual cycle in the non-breeding areas in West Africa, spread over a broad front from the Northeast Senegalese border to the easternmost part of the Mauritania-Mali border. Only three of the 79 tracked birds took up residency at a single site during their stay in Africa. All the other birds followed an itinerant strategy, with no differences found in the movements of males and females. Typically, the tracked birds settled for around a month on first arrival just to the south of the Sahara Desert, before then moving through two or three other staging sites during their stay in Africa. The movements of individuals were in bursts, with the birds being resident within the staging sites for about 90% of their time in Africa and transiting between them for only about 10 days.
Lesser kestrels in the study were fitted with GPS-UHF biologgers such as the one illustrated here. (Photo: Javier Bustamante)
The itinerant movements of individuals in West Africa typically covered about 490 km and individuals moved either eastward or westward, with the final staging posts before the return to Europe centred on wetlands towards the eastern or western edges of the non-breeding range of the lesser kestrel.
Through their study, Lopez-Ricaurte and co-authors have uncovered important previously unknown details of the movements made by a relatively large number of individual lesser kestrels during their time in Africa. The work emphasises the importance of a relatively small part of West Africa for the lesser kestrel. In particular, the last staging sites identified are the focus of significant aggregations of lesser kestrels as they refuel ready for the migration back to the European breeding grounds. These final staging posts in relatively small areas make the European population of lesser kestrels highly vulnerable to environmental change in these regions.
Text by Simon Griffith