Guest blog by Dr John Mallord, Senior Conservation Scientist, RSPB Centre for Conservation Science
Titan is the first UK-breeding Turtle dove to be tracked on his complete migratory journey to and from Africa, he is also the first Turtle dove in the world who has been tracked over two consecutive years, giving us a unique opportunity to compare and contrast his behaviour over two successive migratory cycles
No news from Titan since April 2016
Unfortunately, we have not received a transmission from Titan’s satellite tag since 22nd April, when he was still on his wintering grounds in Mali. This could be because the tag’s battery has failed. The tag’s performance had been worrying us throughout the winter, with very low battery voltages; after all, it was nearly two years old, the tag’s predicted lifespan An alternative explanation for not hearing from Titan is that he may have perished prior to beginning his northward migration back to the UK. We may never know for sure; however, colleagues have been out to look for him on his breeding grounds in Suffolk this summer, and have seen a number of turtle doves, there was no sign of Titan.
Photo of Titan, the satellite tagged Turtle dove just about to be released.
Titan appears to be a creature of habit always leaving UK on the same day
Titan appears to be partially a creature of habit. he appears to have left his breeding grounds in Suffolk around the same time (ca. 19 September) in both years (2014 and 2015). The timing of his arrival in Spain a few days later, and at his first stopover locations south of the Sahara at the end of the first week of October were also very similar. However, his timings of arrival in his first and second wintering sites differed between years.
Titan is site faithful to his breeding and wintering grounds
Many species of birds are faithful to their breeding territories, and Titan was no different, occupying the same breeding grounds – an area of heathland, ca.1 km from the garden in which he was caught, - in both 2014 and 2015. But even this information, whether Turtle doves were site faithful, was uncertain before the advent of tracking technology.
Site faithfulness to particular African wintering grounds has also increasingly been shown for long-distance migrants, but it was unknown whether this was the case for Turtle doves. Now Titan has shown that it is the case! When he first arrived in Mali in October 2015, he was less than 4 km from where he had been at the same time the previous year. This is not really that surprising as it makes sense for birds to return to places where they successfully survived the year before.
Titan changed stop-over locations in response to environmental conditions
However, at other times, Titan showed more flexibility in the places he chose to frequent. Although he passed through Spain on both occasions, his autumn stopover sites were separated by ca.100 km.
Interestingly, his choices of stopover site just south of the Sahara in successive years were separated by an even greater distance, 300+ km; in October 2015, Titan didn’t enter Senegal at all, remaining north of that country’s main, and namesake, river in southern Mauretania.
The different choices that Titan made may have been due to the variation in environmental conditions that he encountered when he arrived in the Sahel. Our colleagues in Senegal have told us that the rainy season in 2015 (lasting from around June to September each year) was a particularly wet one, which could well have resulted in there being more plentiful food and water further north than in 2014 (which, incidentally, was a particularly dry year!). Similar factors may have played a role in Titan’s decision to not travel not quite as far to his second wintering area.
Photo of Turtle dove roost site along the Senegal River, October 2015.
Unfavorable weather conditions in the Sahara made Titan arrive late in the UK
Getting back to the breeding grounds early enough to successfully find a mate is a strong driving force behind migrant birds’ rapid return to Europe from Africa each spring. So it was with some concern that we had to wait until 22nd June for Titan to finally make his return to Suffolk. By this time, there had already been Turtle doves on territory for up to two months, so it is not surprising that, with all this competition, it is unlikely that he attracted a female and successfully bred. It wasn’t for lack of trying, as he sat every morning, purring from his favourite songpost, one of the taller pine trees within his territory. On one occasion, our Film Unit captured him on camera, perched on an overhead wire displaying to a female; sadly, she didn’t seem that impressed.
The interesting thing is that the probable cause of Titan’s not finding a mate in Suffolk was unfavourable weather conditions in the Sahara two months earlier. So-called carry-over effects, whereby the impacts of conditions at one stage of the migratory cycle literally carry over to affect an organism at a later stage, have become a popular research topic in recent years.
For Titan it may have been down to sandstorms on the edge of the desert. Having travelled north 500 km, crossing the border into Mauretania, on the southern edge of the Sahara, he appears to have been forced back on himself, returning 300 km back to Mali.
It was the work of Dutch researchers tracking Honey Buzzards, who found that their birds were taking circuitous routes in the Sahara, which first suggested that sandstorms may be a problem. The peak of this phenomenon is in late April / early May, exactly when Titan had started his journey north, so although we will never be 100% sure, it certainly is plausible that this is what held him up for so long.
Photo of Titan on his favourite songpost where he used to spend each morning purring in order to try to attract a mate
Titan targets wooded river channels for water and roosting
Although satellite tags do not have the same accuracy as those based on GPS, zooming in to Titan’s locations gives us a good idea of the kind of habitats he used throughout his journey. Perhaps not surprisingly, three characteristics were repeated time and again: a safe place to roost, a source of water and plenty of foraging habitat.
In Africa, this has usually meant targeting river channels, where the added moisture in the soil allows greater tree growth, water is readily available, not only to drink, but often to provide irrigation to surrounding fields, thus also providing ample food.
An insight into what Titan may have been up to was afforded us when a team of researchers from RSPB travelled to Senegal to work with staff from a local organisation, Nature Communauté Dévelopment (NCD), to study what Turtle doves get up to when they are on their wintering grounds.
Using a combination of radio and GPS tags, the team were able to follow birds on their daily routine. Highlighting the importance of water, birds’ first task in the morning after leaving the roost was to find water, often entailing a 6 km flight to the nearest source. From here, birds would home in on certain food – either cultivated, such as fields of sorghum and peanuts, or natural scrubby grasslands. This fits nicely with the data we received from Titan, his locations centred on wooded river channels, with daily movements of 2 km or more into surrounding fields.
Photo of Turtle doves in arable fallow with grass.
Titan’s legacy allows us to satellite tag more birds
In addition to all of the things we have learnt from following Titan’s journey, his final legacy has been to enable us to carry on this important work. Along with rigorous testing of the safety of the tagging method on captive Turtle doves at Pensthorpe Natural Park in Norfolk, successfully following Titan over 21 months helped in being granted permission to tag more birds in 2016.
After spending nearly two months baiting sites with seed to attract birds, using a combination of walk-in traps and whoosh nets, from 2nd to 22nd June our team successfully caught and tagged more birds. We look forward to finding out what the journeys of these new birds can add to what Titan taught us in the months ahead........
Photo of Turtle doves coming down to our baited cage just prior to catching and tagging our first bird of the summer
Find out more
Follow Titan’s migration journey by taking a look at his story map
To follow our new satellite tagged Turtle doves visit www.rspb.org.uk/turtledovetracking