Gone with the wind – fidelity to migratory paths and patterns of wind compensation during migration in adult ospreys

Submitted by Michi on 13 January 2023.

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A new paper by Bernd Meyburg and Daniel Holte shows that adult ospreys demonstrate high fidelity to migratory paths in autumn and spring, as well as to the timing of migration in autumn; and sidewinds are predominantly compensated, especially when sidewinds are strong. Furthermore, during autumn migration, the proportion of compensation increases in most regions with decreasing distances to the next goal; however, during spring migration, drift behaviour was detected more often at smaller distances to the next goal than at higher distances in the regions Mediterranean and Central Europe. In general, ospreys compensate for unfavourable sidewinds and utilise supporting tailwinds on their journeys to the wintering sites in Africa and back to Central Europe.

Bernd Meyburg also remembers an interesting anecdote from fieldwork when a female osprey showed what they thought was unexpected memory and, in particular, insight into the capture method:

"As decoys for trapping adult ospreys with the Dho Gaza method (you can read more about the capture technique in this book), adult white-tailed eagles have proved most effective, so they have been used for this in the vast majority of cases. One year, we wanted to capture a male whose female we had already trapped and fitted with a transmitter two years before. The pair was breeding in open country on high voltage pylons. We feared that the female would fly right back into the net. However, when we placed the white-tailed eagle on the perch a short distance from the nest, there were no attacks from the female. Rather, it watched the proceedings from about 100 m away without moving, while the male attacked immediately and soon became entangled in the net. To keep the disturbance as short as possible, we quickly moved away with the male to ring and fit the transmitter, but left the white-tailed eagle and the net. Contrary to expectations, the female remained sitting quietly. When we released the male again and removed the net, the female immediately attacked the white-tailed eagle, which was still standing on its block. It was immediately clear to us that the female remembered the situation two years earlier and the net as the real danger and resisted the drive to attack the white-tailed eagle as long as the net had not been removed. This was very surprising for us, as most ospreys react very violently to white-tailed eagles, even before the observers have moved further away. The female seemed to have understood the trapping method. "
 

Osprey attacking a white-tailed eagle placed in front of the net.

 

Abstract

Birds that repeatedly visit distinct places along their migratory routes in consecutive years must be able to navigate to these places and respond appropriately to unfavourable wind conditions. This study analysed the migratory routes, repeatedly-visited areas and responses to sidewinds of 15 GPS-tracked adult ospreys Pandion haliaetus from northeast Germany migrating to their wintering sites in Africa and back. We determined stopovers and intermediate goal areas and performed repeatability estimations on timing and migratory paths in four regions. The orientation behaviour of the ospreys was analysed with regard to perpendicular wind components at each GPS point during autumn and spring migrations. Generalised linear mixed models were used to test the dependence of orientation behaviour on region and the distance to the next goal. The findings showed that ospreys demonstrate high fidelity to migratory paths in autumn and spring, as well as to the timing of migration in autumn; and sidewinds are predominantly compensated, especially when sidewinds are strong. Furthermore, during autumn migration, the proportion of compensation increases in most regions with decreasing distances to the next goal; however, during spring migration, drift behaviour was detected more often at smaller distances to the next goal than at higher distances in the regions Mediterranean and central Europe. In general, ospreys compensate for unfavourable sidewinds and utilise supporting tailwinds on their journeys to the wintering sites in Africa and back to central Europe.

Read the paper here.

Osprey coming out of the water with a big fish.

Photos: Frank Burchett

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