|
Abstract from BTO
Research Report No. 432:
I.M.D. Maclean, N.H.K.
Burton & G.E. Austin (2006)
Declines in over-wintering diving ducks at Lough Neagh and Lough Beg:
comparisions of within site, regional, national and European trends.
ISBN 978-1-906204-06-8
EXECUTIVE SUMMARY
- The Lough Neagh and Lough Beg Special Protection Area (SPA) is the
most important site for diving ducks in Great Britain and Ireland.
In the late 1980s and early 1990s, the site hosted an estimated 40,000
Pochard, 30,000 Tufted Duck, 5,000 Scaup and 14,000 Goldeneye.
- Since the early 1990s, there have been substantial declines in the
numbers of three of these species. In the winter of 2003/04, the site
hosted an estimated 8,000 Pochard, 9,000 Tufted Duck, 2,600 Scaup
and 4,000 Goldeneye. Scaup numbers have since recovered and are now
present in higher numbers than at any time since the mid-1980s. The
declines occurred on all parts of the site and thus do not appear
to be related to a factor specific to one part of the Lough Neagh
and Lough Beg SPA.
- The declines in the number of Pochard, Tufted Duck and Goldeneye
on the site are an order of magnitude greater than declines occurring
at any other site in Great Britain or Ireland over the same period
and do not parallel trends in other regions of Great Britain and Ireland,
nor those of any other European region.
- There was a general downturn in the number of Scaup at a number
of other sites in Great Britain and Ireland over the same period,
for example the Tralee Bay complex in Kerry and the Solway Firth.
Even greater declines have occurred at the IJsselmeer in The Netherlands
and along the Baltic Coast of Germany, concurrent with the declines
at Lough Neagh and Lough Beg. This could be due to site related issues,
but may equally be indicative of a downturn in the breeding population
of this species.
- The causes of declines at the Lough Neagh and Lough Beg SPA are
not known with certainty, but the balance of evidence suggests that
site related issues are primarily responsible. Previous work has suggested
that high levels of nutrient input have caused hyper-trophic conditions,
with detrimental effects on the chironomid larvae that constitute
the major dietary component for all four of the diving duck species.
The results of this study lend some support to this theory, but further
work assessing how diving duck may have been impacted by any changes
in chironomid larvae that have occurred would need to be undertaken
before this could be established with certainty.
- It is possible that the ducks have been able to respond to these
changes by relocating to sites elsewhere in Great Britain or Ireland.
Pochard have increased at Lough Corrib, Tufted Duck at Rutland Water,
Scaup at Belfast Lough and Goldeneye at several inland sites in England.
However, the magnitude of increases at these sites is considerably
smaller than the decreases that have occurred at Lough Neagh and Lough
Beg and at the same time there have been decreases at other sites
in the UK.
- Pochard, Tufted Duck and Goldeneye have increased in the Baltic-Nordic
Region and in Central Europe. These increases are most probably due
to climate change. It is possible that the recent spate of milder
winters, which has rendered sites further east more favourable, has
facilitated relocation from Lough Neagh and Lough Beg. At this stage,
this suggestion cannot be confirmed, but it is perhaps more likely
that the increases in those regions are due to influxes from closer
by.
 Back
to Research Reports 345 onwards
|
