Ashley Sendell – Price

Common cuckoo fitted with a platform transmitter terminal (PTT). Image source: Natural History Museum of Denmark/M. Willemoes

Humans have long been aware of the seasonal comings and goings of bird populations. But for centuries much of what was known about where birds went was based on speculation, and thus often lead to conclusions that today seem comical or far-fetched. For example, in The History of Animals, Aristotle states:

the redbreast [robin] and the so-called redstart change into one another: the former is a winter bird, the latter a summer one’1

A miraculous transmutation that offered, at the time, a plausible explanation as to why robins and redstarts were not observed in Greece at the same time.

Today, it seems obvious to us that such miraculous transmutations do not exist. Instead, we know that redstarts migrate to sub-Saharan Africa at a time when robins, having left northern breeding grounds, come to winter in Greece.  Hence, providing an explanation of why the two species are not observed simultaneously in Aristotle’s homeland. However how do we know where birds go? Well, the answer is ‘wearable’ bird technology.

The origins of ‘bird tech’ are humble, starting with the small, individually numbered aluminum rings fitted to European starlings in 1899 by Danish school teacher Hans Mortensen. Following Mortensen’s the first ringing scheme was subsequently established in Germany in 1903, followed by various other national schemes across Europe in the beginning of the 20th Century.

Since the hatching of the British Trust for Ornithology’s ringing scheme in 1909, more than 32 million2 wild birds have been fitted with identification rings in the UK. Of these, over 600,000 have been re-observed and reported back to the BTO2, providing valuable insight into the movement of individual birds both locally and further afield. For example, one of the earliest insights into ‘our’ cuckoos’ wintering grounds is an account from 1928, in which a cuckoo ringed in Eton, Berkshire, was reported as killed in Nanga-Eboko, West Africa3. Had this cuckoo not been individually identifiable due to its ‘wearable tech’ we would have never known of its demise 4,700 miles away.

The old technology – a recovery slip from the only UK ringed cuckoo to be found and reported in Africa in 1930. Image: British Trust for Ornithology.

The process of catching, ringing and waiting for a small proportion of birds to be re-observed is a slow one, and doesn’t tell us much about the routes birds take between sighting locations and the various stopover sights they may utilise during their journeys to/from wintering grounds. However, the development of satellite tracking technology has offered a new dimension to avian ‘wearable tech’. Through the fitting of tiny transmitters to birds, often carried in custom built harnesses, ornithologists are now able to track individual birds continuously, thereby filling in some of the gaps in the data. For example, the fitting of Platform Transmitter Terminals (PTTs) to 11 male common cuckoos in 2011 has allowed two main migration routes between the UK and their wintering grounds in central Africa (as well as various stop over sites) to be identified in real time4.

However, at present the use of PTTs is limited to birds over 100 grams due to the weight/size of power-hungry GPS technology. But with that said, as the next generation of GPS tags are developed, becoming increasingly smaller and lighter, more species than ever are able to upgrade their tech!

  1. Aristotle. The history of animals. Translated from Greek by D. W. Thompson. Cambridge, MA: Massachusetts Institute of Technology.
  2. BTO. 2005. A bird in the hand: Ringing birds for conservation. 
  3. BTO. 2014. Cuckoo tracking: Tracking technology. [Online]. Available at: [Accessed 30 October 2015].
  4. BTO. 2014. Cuckoo tracking: What have we learnt so far? [Online]. Available at: [Accessed: 28 October 2015].

17077807_10155003256629194_1461324927_n “I am a PhD student in the Department of Zoology where I conduct genomics based research exploring various aspects of diversification in the silvereye bird. My interests are broadly centred around understanding how organisms adapt to environmental change, with a particular interest in the evolutionary changes that occur during the early stages of adaptation.”