Updates from our Cuckoos

One week after apparently settling in Burkina Faso, Clement had been on the move again and popped up in Togo! On Friday 19 August we received a series of positions for him just inside the extreme north of Togo, close to the border with Benin. By yesterday evening (Sunday 21 August), however, he had continued his journey to the east and was in western Nigeria, having travelled 500km (312 miles) ESE since Friday and 1025km (640 miles) almost due east since Wednesday.

Clement is now our most southerly Cuckoo, having reached 9.5 degrees N. His rapid easterly movement over the past two weeks mean that the four Cuckoos that have crossed the Sahara are now separated by about 1,500km, compared to the 3,500km soon after they had crossed the desert. It is fascinating that they have taken quite different routes to end up in very similar positions!
 

Clement has continued making his way east. On Friday morning (12 August) he had reached southern Burkina Faso and was 30km ESE of Bobo-Dioulasso. He was still at the same location at midday on Wednesday (17 August). This is the first British Cuckoo to be recorded in Burkina Faso and he is in an area of scattered bushes near the village of Houet (see the picture here taken only 200m from our last fix!).

Since 2009, BTO has been working on migrant birds in Burkina Faso and Ghana as part of its Out of Africa project with RSPB and the two BirdLife International partners, the Ghana Wildlife Society and Naturama. BTO research has shown that migrants wintering in the humid zones of West Africa are in rapid decline. Our field project, spanning habitats from the arid Sahel in Burkina Faso to the humid rainforests in Ghana, is looking to understand the wintering and stop-over ecology of migrants and how changes in land use and climate are impacting their populations.

The migrant team works closely with partners in Burkina Faso and Ghana. More information and news from the project can be found at www.migrantbirdsinafrica.blogspot.com.
 

Locations received yesterday early morning (10 August) revealed that Clement had left his residency in Senegal and was heading ESE over the south-western corner of Mali! He was still actively migrating when transmissions began at 0200hrs and appeared to have been migrating throughout the night. He had stopped by 0600hrs when had travelled 450km ESE from Foret Diambour. Although just inside the north-eastern tip of Guinea, Clement is only 200km (122 miles) form Bamako, the capital of Mali.

Clement appears to be skirting the closed forested zone to the south, and the area he is in is still just inside the semi-arid zone. It is, however, criss-crossed with watercourses which drain water from the high rainfall zone to the south and south-west. Many of these flow into the headwaters of the River Niger, which flows north-eastwards through Mali and into the southern Sahara Desert before turning east then back south in a huge arc into Nigeria. This massive flow of water from the humid south-western corner of West Africa forms a verdant strip in the otherwise barren desert, and is vital both for the humans who farm the Inner Niger Delta and other seasonally-flooded parts of Mali, and the millions of migrating birds who either winter there or use it on passage. For an account of the area and its importance to migratory birds, check out ‘Living on the Edge – Wetlands and birds in a changing Sahel’ by Leo Swarts, Rob Bijlsma, Jan van der Kamp and Eddy Wymenga.
 

Yesterday evening (8 August) Clement was still in the Foret de Diambour, Senegal. Today’s weather should suit him, it is 25° C, dry and overcast.

Clement has continued his slow but steady movement SE. He has moved another 100km (61 miles) in this direction and is now 76km east of the eastern tip of Gambia. Although he is still moving obliquely, relative to the rainfall gradients, he is now in a heavily wooded area called Foret Diambour. The weather today is a pleasant 29 degrees there with broken high cloud. Annual rainfall increases very rapidly to the south and southwest of here, and the comparatively lush forests of Niokolo-Koba National Park adjoin the Foret to the south. Conditions for Clement in this area should be very good at this time of year.

Clement has settled in an area for the past few days and with the good light conditions, the solar-powered tag is performing well. We have had a number of fixes but these are not of sufficient accuracy to be sure whether he is moving about the area or not.

We really don't know exactly how important the Sahel is for migrating Cuckoos. This is the area just below the Sahara desert that has a three month period of rainfall starting in June/July. By September the area is green but, in our spring when migrants start to return, it is dry and arid and conditions are tough.

We the Cuckoos to winter further south in the humid zone of central Africa and they could spend from only a few days to maybe 2-3 months in the Sahel. With the rains having just started, this area is going to be lush and green if rainfall is good, so they may well stick around for some time. Satellite tagging is really giving some new and very valuable insights into Cuckoos' behaviour.

New positions received today (22 July), show that Clement has moved 93km (56 miles) SE along the Ferlo river system since Wednesday (20 July). Having gone so far west initially, it will be interesting to see how much he compensates with an easterly movement.

Clement continued his south-westerly flight into Mauritania on Friday afternoon (15 July), advancing his position by 340km (210 miles) during the course of the day. This provides evidence that at least some Cuckoos migrate across the Sahara by day and night - previously we had thought they would rest in any shade that could be found by day to avoid dehydration. Perhaps by flying at altitude Clement was able to avoid the searing desert heat?

On Sunday evening (17 July) new locations placed him in northern Senegal, on the Ferlo River 140km (88 miles) ESE from St Louis – he had safely crossed the desert! Although towards the southern edge of the arid Sahel region, the area will be green by now having received the first rains of the wet season. Over the coming month, the Ferlo will swell under heavy rainfall – the outline of seasonal pools at Clement’s current location can clearly be seen on the google earth map. He has arrived at just the right time to take advantage of the pulse of productivity the rains will bring.

Clement has moved 3,100km (1,940 miles) SSW from his stopover in Valencia to his current position in Senegal in a maximum of seven days. From the Algerian coast, he took a constant south-westerly heading all the way to Senegal. This is the first information we have demonstrating a south-westerly migration into Africa for a UK Cuckoo – we were expecting them to migrate east of south given the information we had from ringing recoveries.