This article is the second instalment to the one I wrote in the May 2005 newsletter. West Kirby shore high tide roost is monitored on a daily basis between mid-September and mid-March by the Dee Estuary Voluntary Wardens (DEVW) when the tide height is over 8.8 metres, in effect about 50% of the days available. West Kirby is an important roost for nine species of waders, in particular Knot and Dunlin (see map for location of West Kirby relative to the rest of the Dee Estuary).
So if we just include the four species which definitely show the cyclic pattern we come up with the following graph. A remarkably smooth and pronounced sine wave like pattern with only one winter (1999/00) in nineteen slightly out of line. It is important here to stress that the data represent average counts, rather than peak counts which are more often used to illustrate trends.
It is not surprising that Oystercatchers, Redshank and Curlew do not show this cyclic pattern as, apart from anything else, their main roosts lie elsewhere on the estuary and West Kirby just gets a small and irregular proportion. An exception to this are Oystercatchers in autumn when quite large numbers can be present at West Kirby - and it is intriguing that they are the only one of these three species that appears to show a pattern, albeit different from the main sine wave like graph.
It would be interesting to look at data from other roosting sites both on the Dee and elsewhere to see whether they too show a cyclic pattern. Unfortunately there is not a great deal of data available, but I do have Wetland Bird Survey (WeBS) counts for Hoylake, a major roosting site for Dunlin, Knot, Bar-tailed Godwit and Grey Plover, just a short distance from West Kirby. The graph below shows the average November to February count from Hoylake, for the years 1993/94 to 2002/03.
Here we have what appears to be another sine wave pattern but different to that at West Kirby. Some caution is in order here as the data available is for a shorter time period than that for West Kirby, and WeBS counts are only carried out once a month, far less frequently than DEVW counts at West Kirby. But despite the limited amount of data there does appear to be a sine wave with a six year cycle, in contrast with West Kirby which has an eight year cycle.
Before we go on, and for those that don't know the area, let me explain what the differences are between West Kirby and Hoylake and why that may possibly lead to different patterns. First of all take a look at the map of the estuary (the link below this map may be a bit clearer). The two roost sites are little more than a mile apart and by and large they attract the same species, both are major roosts for Knot and Dunlin but also attract the other six species mentioned in this article. One difference is that the sand bank at Hoylake is slightly higher than West Kirby and therefore remains dry at higher tides, but both get covered during high spring tides. But the major difference between the roosts is where the birds come from, i.e. where they are feeding at low tide. There is a major feeding area off north Wirral at Mockbeggar Wharf/Leasowe Shore (in the area covered by the word Wallasey in the 'Streetmap' map). Most of the birds feeding here usually roost either at Hoylake or across the River Mersey at the Alt Estuary. Another major feeding area is Dawpool Bank off Thurstaston and most of the birds using this area usually roost at West Kirby. The two feeding areas are therefore quite different, one being well within the Dee Estuary and sheltered from the Irish Sea, and the other on the north Wirral coast exposed to the winds of the Irish Sea and close to the mouth of the River Mersey with its strong tidal currents. In reality there is quite a lot of interchange between the West Kirby and Hoylake roosts, and some birds will fly from one to another during a single high tide, but the general trend would seem to be as I have described above.
As far as I'm aware there hasn't been any scientific study, or even statistical analysis, of wader population dynamics at single roosts such as we see at West Kirby. I'm also not aware of any study which shows a clear sine wave like pattern at any other roost. Below are a few of my own ideas as to the possible causes of this pattern:-
* based on an average winter count (Nov to Feb). Peak counts, on the other hand, showed a slight drop in numbers over the same period.
Many thanks to:
Wetland Bird Survey Data in this article should not be used in any way without permission of the WeBS Office. To access official WeBS data please contact the WeBS Office - BTO, The Nunnery, Thetford, Norfolk IP 24 2 PU, http://www.bto.org.
June Bird News
A Black Stork flying high over
Barry Barnacal's house in
was certainly a good garden tick! A first for Cheshire and Wirral. This
species has been increasing its breeding range in France although still
rare throughout North West Europe.
Inner Marsh Farm has been full of waders throughout June, making for a spectacular sight. The usual over-summering Black-tailed Godwits have been present, about 600 or so, although they seem to have hung around more than most years instead of undertaking their normal tour of the wetlands of Cheshire! More unexpected was the presence of over 1,000 Knot, the first time any have over-summered at this reserve. Immature Knot are quite a common sight through June on the Ribble Estuary and the Wash but they are very unusual on the Dee, although 10,000 were seen from Hilbre Island during June 2001. Two Avocet called in briefly early in the month and one Green-winged Teal towards the end was unexpected at this time of year.
The usual terns, Gannets and
Common Scoters have been seen out in Liverpool Bay although the latter two
species only in small numbers. An Osprey was seen a few times early in the
month, too late to be a breeding bird perhaps this was an unpaired bird
looking for a potential nesting site for next year. It seems neither of
our tern colonies are going to have a record breaking year, something we
have got used to over the past couple of years! At
Shotton there are 547
pairs of Common Terns, down from last year's 656.
Gronant has about 60
pairs of Little Tern breeding, down from 89 pairs in 2004.
What to expect in July
One of the months I most look forward to. Waders will be back in the estuary in good numbers with plenty of Redshank, Curlew and Oystercatchers at Heswall - most of these will have bred in this country. In addition passage waders start coming through with Whimbrel, Spotted Redshank, Greenshank, Common Sandpiper and Green Sandpiper. It was July when we had a Marsh Sandpiper at Inner Marsh Farm two years ago. Dunlin and Sanderling can also be seen on the beaches and sand banks of the mouth of the estuary.
Tern numbers really begin to build up from mid-month onwards following the breeding season, and the most noticeable will be Sandwich Terns with their loud raucous cries. Hilbre Island at low tide is an excellent spot to see these birds, and Hoylake, West Kirby and Gronant at high tide is also good. Large post breeding flocks of gulls build up at the same locations.
Little Egret numbers will increase rapidly with may be 30 or so coming to roost at Burton. July can also be good for a visiting Spoonbill or two. Marsh Harriers pass through on their way back south, and look out also for the odd Osprey or Red Kite dispersing after the breeding season.
Many thanks go to David Haigh, Clive Ashton, Charles Farnell, Graham Thompson, Laura Bimson, John Campbell, Mark Warren, Shaun Williams, Steve Williams, Chris Butterworth, Jane Turner, Allan Conlin, Mike Hart, Tanny Robinson, Dave Wilde, Mark O'Sullivan, Steve Renshaw, Jean Morgan, Richard Hurst, Eric Sherry, the Dee Estuary Voluntary Wardens and the Hilbre Bird Observatory for their sightings during June. All sightings are gratefully received.
Highest Spring Tides,
23rd July, 13:37hrs 9.4m. Times BST.
24th July, 14:24hrs 9.4m.
Forthcoming Events (organised by the
Wirral Ranger Service,
Flintshire Countryside Service and/or the RSPB):
Saturday 2nd July 2005, 11:00am - 3:00pm. Open Day at the
Connah's Quay Reserve.
Saturday 23rd July 8:00pm, Birds, Bats, Moths and BBQ .
Sunday 7th August, 10:30am, Banks Road Birdwatch at
Note: Many of these forthcoming events are extracted from the 'Birdwatchers Diary 2005', which covers both the Dee and Mersey regions. Hard copies available from the visitor centre at Thurstaston, Wirral Country Park 0151 648 4371.
All material in this newsletter, and indeed the whole web site, has been written by myself, Richard Smith, unless specified.
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