Working for birds in Africa

The Study and Ringing of Palaearctic Birds at Ngulia Lodge, Tsavo West National Park, Kenya, 1969–2012: an overview and update.

Mon, 08/10/2015 - 15:37 -- abc_admin
David Pearson, Graeme Backhurst and Colin Jackson, 2014. Scopus Special Supplement No. 4. East Africa Natural History Society, Nairobi, Kenya. 80 pp, colour photographs and maps. UK£8.50 (UK), UK£12.00 (rest of the world) from Graeme Backhurst, 2 Reed Cottages, Windmill Lane, Faversham, Kent ME13 7GT, UK. E-mail: graeme.backhurst@gmail.com
pp 118-119

It was way back in 1969 that it was first realised that large numbers of Palearctic passerines could be found at the lights of Ngulia Lodge, Tsavo West National Park, Kenya, during migration periods - primarily in November and December. The main concentrations were during low mist or rain at night under moonless conditions. This discovery led to the establishment of a ringing programme, which began in 1972 and continues until the present day, and this publication presents an overview of the main findings from the work.

Up to 2012 just short of half a million Palearctic birds had been ringed by the project, with three main species being involved: Marsh Warbler Acrocephalus palustris (42%), Thrush Nightingale Luscinia luscinia (21%) and Common Whitethroat Sylvia communis (20%). The remainder included several migrants little known west of the Kenyan highlands, but surprisingly few Afrotropical birds. The ringing team is renowned for its knowledge of different racial plumages and biometrics, and the records reveal that most species are from populations breeding in Eastern Europe or Western / Central Asia.

This report analyses their arrival patterns and provides details of the 222 recoveries recorded to date. These comprised 122 to or from Palearctic breeding areas, 81 to or from Middle Eastern passage sites, 18 from southern African wintering areas, and one from a probable Ethiopian stopover area. Of special interest is the fact that only 63 birds have been re-trapped at the lodge in a subsequent season.

One can only admire the enthusiasm of those involved in keeping this project going given the relatively low recovery rates, but the task has grown with assistance being provided by both African and international ringers. In fact the ringing site has been operated on well over 1,100 nights, with mist occurring on more than 60% of these and rain on 26%. 

Patterns of moult are summarised and details of mass are discussed. Some species are frequently 20–30% and sometimes 50% above lean weight, with the potential to complete long onward flights south of Ngulia. There is also discussion of the composition of catches over four decades, which show a recent increase in the percentage of Marsh Warblers and a decrease in Common Whitethroats. Others that are now less frequently caught are Isabelline Shrike Lanius isabellinus, Rufous Scrub Robin Erythropygia galactotes, Upcher’s Warbler Hippolais languida and Willow Warbler Phylloscopus trochilus.

The publication analyses the results from every angle - coverage, numbers ringed and recovered, origins and races of individual Palearctic species, diurnal changes in species pattern and seasonal timing of migration. Age proportions, patterns of wing moult, mass and fat loads are all summarised, together with apparent long-term trends.

The situation with the lights at Ngulia is, of course, completely artificial, and the authors consider the effects of such locations on migration strategy and stopover. They also consider the potential role of Ngulia in the future monitoring of Palearctic migrant bird populations.

The report contains many small photographs of the birds trapped and the location. A series of four maps indicates the recovery or ringing locations for the key species, although the idea of combining (in one case) up to six species on one map defeats the object. 

Those interested in the Ngulia work may wish to watch a lecture by David Pearson at the 2014 ABC Annual Meeting in which he summarised the achievements to date: http://youtu.be/3o5bN61VKLc

Keith Betton

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