Traversing the Sahara

Having negotiated two long sea crossings, including a 28 hour flight across the Mediterranean from the south of France to Algeria, the next challenge for the young honey buzzard on her first migration south from Scotland, was to cross the Sahara. This is one of the hazardous elements of the journey and previous satellite tracking studies have shown that many young raptors perish as they attempt to cross the vast and unforgiving terrain.

The satellite tag, which has enabled us to follow her journey south in such precise detail, logs the bird’s location as regularly as once every minute, and then transmits the data at pre-determined intervals when within range of a mobile phone mast. This meant that as she headed across the Sahara – where mobile phone coverage is patchy at best – it was likely we would have to wait some time before receiving an update on her progress. That long-awaited update finally arrived over the weekend, and we were delighted to see that she had reached the River Niger in Mali, having flown 2678 km across the Sahara in 11 days.

In our last update we reported that the young bird had reached the northern edge of the Sahara on 29th September. She set-out across the desert the next morning and flew 205 km south-east to the Atlas Saharien Mountains, where she roosted at an altitude of 1675 metres.

The next morning, 1st October, she resumed her journey south 1.5 hours after sunrise, at 07:30 GMT. Unlike the previous day she maintained a south-westerly heading all day, reaching a maximum altitude of 1766 metres (above ground level) as she flew across the desert during the afternoon. She eventually settled to roost on the ground at 17:30, having flown exactly 300 km during ten hours of non-stop-flight.

Whilst her course had been directly south-west on 1st October, it was very different the next day. She resumed her journey at 07:45, initially on the same south-westerly heading as the previous day. However at 09:40 she turned and flew 24 km north-west in 2.5 hours, before turning 180 degrees at 12:07 and then flying back in the opposite direction. There is no way of knowing what caused this sudden change of course, but perhaps she encountered other migrating honey buzzards, and joined them? Whatever the case, she maintained the south-easterly heading for the rest of the day before stopping to roost at 17:00. She had flown 183 km during the day, but thanks to two changes of direction, had actually only travelled 92 km south-east from her position overnight.

On the morning of 3rd October, she left her roost site on the desert floor at 08:30 and flew 124 km south-west. At 14:00 she was circling over the remote village of Zaouiet Debagh and at that point changed course to the south-east, flying a further 56 km before stopping to roost at 17:00.

The honey buzzard made a later start the next day, remaining at the roost site until 09:35. When she did resume her journey it was on the same south-easterly heading as the previous evening. By 16:00 she had travelled 174km, and at that point she turned to an easterly course, and continued onwards for another 71km. She eventually settled to roost at 17:30, having flown 245 km during the course of the day, reaching a maximum altitude of 1952 metres during the afternoon.

Unlike the previous two days, the young honey buzzard maintained the same SSE heading throughout the day on 5th October, leaving her roost site at 08:45 and flying 269 km in just under nine hours. That night she roosted on a rocky hillside above what appeared to be an ephemeral river bed.

The next morning she landed beside the river bed for approximately 15 minutes, suggesting it may have contained some water. She then resumed her migration at 08:45.

Conditions must have been favourable for migration because she made excellent progress during the course of the day, flying 404 km on a south-westerly heading. The thermal updrafts were obviously very strong because during the afternoon she was circling up to more than 3000 metres on occasion. In fact as she passed over a mountainous region, she reached a maximum altitude of 3133 metres above ground level.

She left her roost site at 07:30 on 7th October and again flew strongly south-west, crossing the border into Mali at 12:02, and flying at an average speed of 54 km/h. She maintained the same heading all day, flying at altitudes of over 2000 metres, and eventually settled to roost on the desert floor just before 17:30 having flown 503 km in 11 hours of non-stop migration.

After two very good days of migration, conditions evidently became more difficult on 8th October. She left her roost site at 08:30 and initially flew 54 km south-west. However, she then changed course by 90 degrees, switching to a south-easterly heading at 11:30. She subsequently travelled a further 70 km before stopping much earlier than usual at 15:20. She had flown 124 km at an average speed of 18 km/h, but due to the change of direction, had actually only covered 87 km south from her overnight roost.

It appears from the Google Earth imagery that she may have roosted in a vegetated area – suggesting it may have been possible to find food.

The suspicion that she may have been able to feed around the roost site was given further credence by the fact that she left much later than usual the next morning, not setting off until 10:10. When she did resume her journey the honey buzzard flew WSW for 169 km before turning to a southerly heading at 16:22. She continued flying until 17:30, covering a further 49km, and thus a total of 169 km during the course of the day.

On the morning of 10th October she left her roost at 09:50, initially flying due south, and then turning to the south-west at 11:00. At 14:35 she was approaching the north shore of the vast River Niger and then, twenty minutes later, was perched on the ground nearby. She remained in the local area for the rest of the day.

After 11 days and 2678 km, she had successfully crossed the Sahara. Her daily distances on each day of the Saharan crossing are shown in the table below.

Yesterday the young honey buzzard flew across the River Niger just after 09:30 and then perched close to the south bank of the river for the next half an hour.

Having successfully crossed the desert, it will be fascinating to see where the young honey buzzard goes next. It is now a month since she left her nest site in Moray and she has made excellent progress so far. Will she continues south towards Burkina Faso and Ghana, or south-west towards Guinea? We’ll have another update soon.