So far...

by Mike McGrady, Bernd Meyburg, Faisal Al Lamki and Andrew Spalton

In January we fitted transmitters to 13 Steppe eagles wintering in southern Oman, and feeding at the rubbish dump at Raysut, near Salalah.  So far the movements of those birds have fallen into three broad groups. 

First, some birds move in a rather limited area south of the escarpment, making regular use of the Rayut rubbish dump, and roosting mostly in forested areas on the escarpment, or nearby.  The map below is an example of this type of movement pattern.

A Steppe eagle's movements during January 2019. This bird has moved in a fairly limited area, feeding during the day at the rubbish dump at Raysut, and roosting at night at various locations on the escarpmet.

Other birds have wandered more widely, including visits to Yemen, but have stayed mostly within about a 100 km radius around Salalah.  Birds in this group also mostly made continued use of the rubbish dump at Raysut, but some seem to have settled farther north. The map below is an example of this type of movement pattern.

A Steppe eagle's movement during January 2019.  This bird moved immediately away from Salalah and flew into Yemen, then returned, and has recently settled near a chicken farm north of Thumrayt,Oman

A third group of birds have flown deeper into Yemen, and have not (yet) returned. See map below.

A Steppe eagle's movement during January 2019.  This bird spent about 10 days around Salalah before moving into east-central Yemen.  The gap in the track is due to a lack of GSM coverage.  When the bird moves into an area of better coverage for an extended period that gap will be filled with logged data.

At first glance, one might be surprised by the differences in movements.  Why do some birds wander so widely or apparently leave southern Oman when there is a reliable source of plentiful food at the rubbish dump at Raysut?  However, in the case of the Steppe eagles, one needs to remember that these birds are migratory, and their journeys back to breeding areas can start in January (ref. migration counts at Eilat).  Also, because the Steppe eagles wintering in southern Oman are surviving as scavengers, and not active hunters, their movements at that time might mimic more those of obligate scavengers (i.e. vultures) rather than active hunters (e.g. Steppe eagles in summer).  So, what we have been seeing over these few short weeks of tracking may be "surprising" simply because these birds are scavenging, and some may be initiating migration.  The fact that we have only been tracking these birds for a few short weeks contributes to the "surprising" nature of the movements, mostly because we know so little about them. 

It is an essential part of the scientific enterprise to admit ignorance, even to exult in ignorance as a challenge to future conquests. - Richard Dawkins