07 January 2016

The Gower Ringing Group at Oxwich: the story so far

The Gower Ringing Group began bird ringing at Oxwich National Nature Reserve in February 2013. Our initial aims included:

  • capture of reed bed warblers (to obtain data on site fidelity, timing of breeding, and to gain insight into whether the site appears to be of greater importance to these species during the breeding season or passage periods);
  • capture of large numbers of reed bunting, a species that previous ringing effort has established occurs at the site in good numbers, and which existing data suggests moves around numerous sites locally during the year;
  • capture of a good number of finches, particularly goldfinch, greenfinch and chaffinch - all typically undertake seasonal movements, and greenfinch abundance has been affected at the national level by disease (trichomonosis) in recent years; and,
  • capture of a range of migrant and wintering passerines species that are not likely to breed in the marsh, as the area is very challenging to survey due to its extent and inaccessibility, and also due to the fact that only a few birdwatchers regularly visit it
Since early 2013 we have processed over 10,000 birds on the marsh.  In 2015 we completed twice weekly ringing visits during passage periods and weekly sessions at other times, and processed 3,925 unique birds during the calendar year (this total includes birds recaptured [following initial ringing in a previous year] and controlled [ringed by someone else and recovered on the site] for the first time during the year but excludes multiple recaptures).

Common snipe (front) and jack snipe (Cedwyn Davies)

The data set emerging is both valuable and interesting.  It indicates, for example that while the site currently supports relatively small numbers of reed and sedge warblers, far larger numbers occur during autumn passage.  We have controlled reed bed warblers ringed in France and Spain, providing an indication of the areas these birds stage in on migration, and perhaps more unusually (in late November 2014) a Cetti's warbler ringed on Magor Marsh, Monmouthshire (which illustrates their ability to colonise new areas of habitat).

In 2015 we also managed to prove breeding in grasshopper warbler on the marsh, through the capture and recapture of birds at intervals during the breeding season, including a female with a brood patch, a male with a cloacal protrusion and recently fledged juveniles.

Reed bunting (Owain Gabb)
We have also ringed over 300 reed buntings, as well as recapturing a few additional venerable birds from when Barry Stewart ringed on the marsh (the oldest to date being a breeding male in excess of seven years of age).  Data are starting to come in relating to the movements of these reed buntings, which range relatively widely, and have been recaptured at the Nitten Field, Mewslade, and at Cefn Sidan, Carmarthenshire.  Numbers on the marsh vary over the year, with an apparent exodus in mid-winter, and large numbers in late winter / early spring and in autumn (peaking in September).

Brambling (Keith Vaughton)
We put out two feeders at Oxwich, both of which are stocked with sunflower hearts.  Since finches started using them regularly, in early 2014, we have ringed 805 greenfinch, 841 goldfinch, 456 chaffinch and 115 siskin around them.  There is still a very large greenfinch population in Gower (despite trichomonosis), as recoveries of these birds (mainly cat kills and birds that succumb to disease) are typically from surrounding villages such as Scurlage, Knelston and Reynoldston (all of which are within ~5 km).  Goldfinch disperse more widely, and some move to and from continental Europe.  We await a large movement, albeit a goldfinch retrapped on Lundy in spring 2015 was interesting and we are getting good data on timing of breeding.  Siskins bred on the marsh in both 2014 and 2015, possibly due to the food source provided by the feeders, which they visited throughout.  Two separate cohorts of young were apparent in 2015, the first appearing at the feeders in May and the second in July, indicating the siskin were double brooded.

The numbers of these 'common garden visitors' ringed at just two feeders indicates that there is considerable turnover of birds during the day and over weeks at feeding stations.  Just for good measure, since February 2013 we have also ringed 898 blue tits at the marsh, also capturing some six year old birds of Barry's.  To emphasise the point further, in 2015 we captured 23 different great spotted woodpeckers at the feeders. With these sorts of numbers of common birds, noting the stage of development of the brood patch and recording moult accurately helps build up important data that will assist the British Trust for Ornithology (who hold a database of information on the 1 million plus birds ringed in the UK annually) in understanding how birds are responding to changing climate and food availability.

Ironically, given all the 'typical' migrants we catch, perhaps the most interesting recovery of a bird to date has also been of a 'garden bird' species.  A dunnock ringed at Creeting St Mary, Suffolk in 2009 was controlled at Oxwich in 2014, a movement of 364 km west.

Firecrest (Keith Vaughton)
Finally, we capture a lot of passage migrants, particularly in the autumn, when there is always a chance of a local scarcity due to the large area of undisturbed and varied semi-natural habitat present.  Among the species captured over the last few years have been wood warbler (Spring 2014), yellow-browed warbler (autumn 2014), an eastern cline / 'tristis' chiffchaff (autumn 2014), two whinchat (early autumn 2015), seven firecrests (late autumn 2013-15 inc), a redstart (early autumn 2015), a brambling (late autumn 2014), three jack snipe, 16 tree pipit (a small proportion of birds seen around / heard over the marsh), and 26 garden warblers.  None of these species are particularly common on Gower, albeit all will be under recorded to some extent due tot he relatively limited number of birdwatchers active locally.

The work over the last few years has only been possible due to the effort of Gower RG members, particularly stalwarts such as Heather Coats, Charlie Sargent, Cedwyn Davies and Keith Vaughton, the support of Nick Edwards of Natural Resources Wales, and the grant funding provided by the Gower Society.

For further information, please visit our blog, which is regularly updated, and which includes a detailed summary of ringing in 2015.  Links are:

Further photos are below

Owain Gabb

Tree pipit (Owain Gabb)

Putative eastern cline / tristis chiffchaff (left) alongside a typical collybita (Charlie Sargent)

Wood warbler (Keith Vaughton)

Yellow-browed warbler (Charlie Sargent)

1 comment:

Barry Stewart said...

Fascinating reading Owain and the Dunnock control is quite remarkable! The totals provide a really good indication of how valuable some of our local sites are, for both resident and migrant species alike. Knowing how much effort it takes to generate the data you have been producing, I am most impressed by the commitment of the group and will enjoy reading the regular updates on the blog.