From early on in our work, it became clear that technology would be a critical tool in unravelling the mystery of where Sociable Lapwings went during the year. Platform Transmitter Terminals (PTTs) are powered by an internal battery that is charged by a solar panel and sits comfortably on the back of the birds using a soft, light, and strong harness made of Teflon. While the tag is being fitted, a dark hood is usually placed over the bird’s head to keep it calm, and the process is completed in a matter of just a few minutes. Tagged birds are typically incubating adults caught on the nest and they resume incubation and normal behavioural patterns immediately, the tags not having a measurable effect. The PTT transmits a signal periodically, and as a recording satellite passes over, it records the frequency and wavelength of the transmission and estimates the position of the tag to within just a few kilometres.
Having coordinates for tagged birds not only enables their routes to be mapped as they migrate, but also helps researchers on the ground to pinpoint where individuals are and search for congregations by locating a tagged bird. Since 2007, 29 birds have been tagged, and this work has led to some stunning discoveries and several surprises.
Generally, most of the tagged birds have taken the western flyway, highlighting both the routes taken and the important areas where birds stop to refuel and rest (staging areas).
One of the most informative periods was the 2015 autumn migration, when nine tags were transmitting (eight fitted that summer). From monitoring previous journeys, the Tallymerjan area on the Uzbekistan/Turkmenistan border was known to be an important staging site, with all tagged birds on the eastern flyway having stopped there to refuel before the difficult journey across the high mountains of the Hindu Kush. Using the two birds heading in that direction to guide research teams on the ground in both countries, simultaneous counts in 2015 yielded an astounding maximum of 4,225 birds in Turkmenistan and 3,675 across the border, meaning an estimated one third of the global population use this site and the flyway. A follow up survey in October 2016 confirmed that these large numbers were not an anomaly, and shed further light on the way birds are using three relatively separate locations in the area, with evidence of at least one other important site close to the border (but inaccessible for surveying).
Given the unexpected importance of the flyway and Tallymerjan, this begged the question – where do the birds go once they cross the mountains?
Read more soon…