Archives for December 2017

Rothiemurchus – relocated!

One of the most interesting ospreys that we have satellite tagged in recent years is Rothiemurchus. After being tagged as a chick in a nest on the Rothiemurchus Estate near Aviemore in 2009 the young male headed south in early September and made a long overnight crossing of the Bay of Biscay. He drifted west in strong easterly winds and missed the north coast of Spain, before finally making landfall in Portugal after a flight of 1302 km in 33 hours. He then remained in Portugal for more than a month before continuing south and migrating to Djoudj National Park in northern Senegal. In January 2010 he made several exploratory flights into Guinea Bissau before settling in the backwaters of the River Gambia in Senegal. He obviously found excellent fishing on these marshes and spent the whole year there, with a little exploration into The Gambia. He remained in the same location until May 9th 2011, when he set off on his first migration back to Scotland. We followed this and seven subsequent migrations between Scotland and his wintering site in Senegal. During these journeys it was clear that he had learnt from his first arduous crossing of the Bay of Biscay and, in order to return to favoured stop-over locations in Galicia in northern Spain that he had used on his first northward migration, he made the most amazing dog-leg migration across the north coast of Spain, as shown in the animation below. It was also fascinating to see how widely he ranged in Scotland when he first returned in 2011 and then in subsequent summers.

We tracked Rothiemurchus for five years between 2009 and 2014. Orange lines = autumn migrations, white = spring.

Once back at his wintering site each year, Rothiemurchus settled into a very predictable pattern of behaviour, living in a very small area of less than 1 km². This enabled myself and colleagues from the Rutland Osprey Project to see him in January 2012 (watch video below) and Chris Wood to do the same in February 2013.

In November 2014 Rothiemurchus was back in Senegal but no signals were received from his transmitter after the night of 7/8 November. Having inspected the data closely, Roy felt sure that the transmitter had either failed or fallen off, but without seeing the bird could not be sure. The problem was that although Rothiemurchus was now five years old and had settled in Perthshire, he had yet to establish a nest site of his own; and so there was no specific place to look in spring 2015 when he should have returned to Scotland. A further two summers have since passed without a confirmed sighting, but on Wednesday this week Chris Wood and Joanna Dailey, along with Junkung Jadama and Fansu Bojang, decided to visit Rothiemurchus’s regular wintering site on the off chance that he might still be alive.

And guess what? They saw him! Here are two photos taken by Chris and Joanna in which you can just make out the transmitter on the bird’s back.

Rothiemurchus was perched on a dead tree in exactly the spot where he spent previous winters (photo by Chris Wood)

The transmitter is just visible in this photo – with a snapped aerial (photo by Joanna Dailey)

We are thrilled to know that Rothiemurchus is still alive, and that Chris and team have been able to prove that the lack of data was due to transmitter failure as Roy always suspected was the case. Sincere thanks to Chris, Joanna, Junkung and Fansu for making the effort to go and look – a superb piece of fieldwork. Here is an extract from an email from Joanna this evening:

“It was a real thrill to see what we hoped would be Rothiemurchus, and then to see the transmitter on my not very good photos. They will be special now.

He left his perch to escort an unringed Osprey away, although it wasn’t the determined removal you see in breeding Ospreys. He went high with the other one and they drifted away. We were still in the area for over 30 mins, but we didn’t see him return.

A villager was harvesting oysters fairly nearby, Rothiemurchus would have been aware of him. You can see the oyster shell piles on the Google Earth images I made, so villagers must be around the area quite a bit, in addition to fishermen in pirogues.”

As Joanna’s photo shows, the reason for the lack of data is now clear – the aerial on the transmitter has snapped off. Now we know this we will make a concerted effort to find Rothiemurchus once he has returned to Scotland in the spring, not only to discover where he is breeding (which he almost certainly will be by now) but also to attempt to re-catch him and remove the defunct transmitter. For now though it is just great to know that this osprey, whose migrations we have followed with such interest, is still alive.

The location of yesterday’s sighting was in exactly the same place as data from 2014.

Daily routines

Over the past two decades satellite tracking has provided a unique insight into the wintering behaviour of ospreys. Whereas juveniles usually wander over a large area after arriving in West Africa, adults head straight to a known wintering site. Many of the adult birds we have tracked have been remarkably sedentary in winter; often occupying a home range of 1-2 km². There are always exceptions to this rule, however, and it has been fascinating to follow the daily movements of Jules since he arrived at his winter home in the Casamance region of southern Senegal. Jules is living in a larger area than most adult ospreys, but mainly because his regular roost site is 16 km from his favoured daytime perching and fishing sites.

Jules has spent each night roosting in an area of dense mangroves, and has four favoured perches within an area of just 0.04 km².

Jules roosts in an area of dense mangroves each night.

In this part of the Casamance delta he is surrounded by potential foraging grounds, including a section of river that is almost 1 km wide, just 2 km to the south. However the satellite data indicates he does little or no fishing in this area, and instead flies 16 km WSW to spend each day on the coast. There he favours a 1.3 km stretch of sandy beach and hunts just offshore. The satellite data indicates he probably catches most of his fish around 200 m out to sea, but on occasion he flies further out, such as 1.1 km on 3rd December and 2.65 km on 19th November. Most of these fishing trips tend to be late morning or early afternoon, and he then eats his catch on the beach.

Jules spends most days perched on a sandy beach, and fishing just offshore.

The map below gives an indication of just how predictable his daily routine is. The red circle, centered on his roost sites, indicates an area with 50 % of GPS fixes while the orange area shows the location of 95 % of fixes. In other words, when he is not at his roost site he is nearly always at the coast. Interestingly he has flown east from his roost site on just two occasions in the past month.

Over the past month Jules has roosted in the mangroves each night and then flown 16 km WSW to spend the day on the coast. The red circle indicates an area with 50% of GPS fixes and orange shading 95% of GPS fixes (calculated using kernel method).

Jules’ winter home in Senegal is 30 km south of The Gambia and 20 km north of the Casamance River.

Don’t forget that Jules’ latest winter movements as well as his migration from Scotland are shown on our interactive map.