An unexpected benefit of being on a long school break was being able to join Phil Round and Andy Pierce for four days netting and ringing birds on Ko Man Nai during 17 – 22 March 2014. This really was field biology as opposed to birding and for me it was a huge learning opportunity.
Ko Man Nai is a small island situated a short boat ride off the coast of Rayong province in Thailand’s south-eastern seaboard. It is the first landfall for migratory birds whose north bound trajectory during “spring” takes them across the Gulf of Thailand from Malaysia and Sumatra, Indonesia. (“Spring” in Thailand and South-east Asia is in fact the beginning of hottest part of the year.) From a bird watching perspective I and many other birders have been salivating at the list of new and rare birds found on the island during “spring”migration over the last two years. Mid-April is generally considered to be the peak migration period so this visit was scheduled in mid-March to enable study of early migration.
The island comes under the management of the Department of Marine and Coastal Resources so it has not been developed for tourism, and more pertinently the island hasn’t been degraded by it. Its raison d’être today is it provides a home to an extensive captive turtle breeding and release programme.It’s a very peaceful,relaxing sort of place – a joy to land at the pier and proceed onwards without having to wade through a throng of touts intent on redistribution.
For four days we caught birds in fixed mist nets, extracting and moving them to a processing station where we ringed them by fixing a small, lightweight band to their tarsus, and then measuring and recording their biometrics before releasing them back into the forest and in most cases their onward, northbound migration. So what is this all about?
In the first instance catching the birds is a far more reliable method of establishing the true diversity of species in a given area. That is, more reliable than sight records. This is, if you like, an interface between conservation and ecology. Secondly there are species which are very difficult to separate from each other in the field, for example, those in the phylloscopus or acrocephalus genera. Thirdly it is possible to create a dataset: birds were sexed and aged and a range of other biometric data was recorded: weight and measurements of bill, wing and feathers, etc. This data, inter alia, informs conservation and ecological considerations. Fourthly every bird is fitted with a band with a unique numeric identifier and geolocation details. A sort of ‘message in a bottle’ : “I want to know if you find this bird”. This is where it gets particularly interesting as this enables the possibility of “retraps” to be identified. This, inter alia, provides comparative data. Every now and then a banded bird is trapped in another part of the region or, vice versa, a bird is “retrapped” that has been banded or flagged elsewhere. This provides information about bird movements and migration.
The British Trust for Ornithology (‘BTO’) website offers a very succinct summary of ringing:
“Ringing aims to understand what is happening to birds in the places they live and how this affects population increases and decreases, this knowledge is vital for conservation. It also gives information on the movements individual birds make and how long many live for.”
I guess I am becoming a reasonably competent ringer: I am reasonably confident handling small to medium sized birds. The most difficult part of the whole process for me is extracting the birds from the mist nets. Sometimes a fair amount of unfankling ( Scots for undoing!) is required. Birds trapped in nets can understandably get very agitated and so this is an area I gladly leave to the experts. I should add that everything I do is supervised.
It is important to stress that at every stage of the process the bird’s welfare is paramount. Furthermore the nets are constantly checked to both minimise the amount of time birds are in the nets and to minimise predation from other birds like raptors. I doubt whether any of the 83 birds we trapped were in captivity for longer than 40 minutes during our session.
From a birding perspective the highlights of the trapped birds were: a Malayan Night-heron, a Ruddy Kingfisher, Siberian Thrush (3), a White’s Thrush and a number of Eye-browed Thrush, Sakhalin and Pale-legged Leaf Warblers, Eastern Crowned Warbler, a Pallas’s Grasshopper Warbler, a Hodgson’s Hawk Cuckoo, a Himalayan Cuckoo, Asian Drongo Cuckoo, Crow-billed Drongo, an Asian Paradise Flycatcher, a Zappy’s Flycatcher, a Blue and White Flycatcher and a Hainan Flycatcher. These are all migrants.
Of course there were great birds at large which included a Red-billed Starling (third Thai record thanks to Andy Pierce), Daurian Starling, Grey-headed Lapwing, a number of Dollarbirds, Swinhoe’s Minivet, Blue Rockthrush, Grey Wagtail and Forest Wagtail.
I added fourteen (!) lifers to my list so very productive in this respect.
From a scientific perspective the main finding was that Sakhalin Leaf-warbler appears to be the default species passing through the island on migration. I’ll spare the details here but I think the data will enable some scientific papers to be written in due course.
Finally grateful thanks to Phil Round and Andy Pierce for allowing me to tag along.