Abstract from BTO Research Report No 337:

Newson, S.E., Noble, D.G. & Marchant, J.H.

Analysis of population trends for waterways birds: a comparison of Waterways Bird Survey indices.
ISBN: 1-904870-62-7

Executive summary

1 The Waterways Bird Survey (WBS), a territory-mapping census carried out by BTO volunteers, was introduced in 1974 to monitor populations of breeding waterbirds along linear waterways in the UK. Estimates of breeding territories are used to calculate estimates of population change, which in turn contribute to various conservation initiatives. The GAMs method used in this study allowed objective assessment of trends and of their confidence intervals and turning points during the period 1975-99.

2 Of eighteen species monitored since 1974 by the WBS, five species (Common Sandpiper, Yellow Wagtail, Grey Wagtail, Pied Wagtail and Reed Bunting) experienced a significant decline over the period 1975 to 1999. Kingfishers declined significantly during the first half of this period but recovered between 1987 and 1999. Three species (Mute Swan, Mallard and Oystercatcher) increased significantly over the period 1975 to 1999.

3 Analysis of the pattern of turning points in the population trajectories revealed similarities among species that reflect their ecological characteristics, in particular wintering area and preferred habitat. Turning points in the population trends were similar for Sedge Warbler, Sand Martin and Whitethroat (although Whitethroats have increased at a much higher rate). The similarity between Dipper and Grey Wagtail suggests a relationship to environmental conditions on fast-flowing riverine habitat.

4 Events during the winter appeared to influence trends for some species. For Mute Swan, Moorhen, Kingfisher, and Grey and Pied Wagtails, annual changes in abundance were related to mean winter temperature. The only relationship between previous spring temperature and abundance the following year was for the Reed Warbler, which may be related to higher productivity in the first year as a result of the milder climate.

5 Trends for two trans-Saharan migrants, Sedge Warbler and Reed Warbler, were linked to May-October rainfall in the Sahel region of West Africa in the season just prior to their arrival in winter quarters.

Back to Research Reports 289 - 344