Oystercatcher – 2021-22 WeBS

Haematopus ostralegus – PIODEN Y MOR – Breeding resident and passage migrant

Updates to the Wetland Bird Survey counts for this season.

Data for June and July are collected by Jane Hodges during the annual surveillance of summer shelduck populations on the Cleddau Estuary complex. There are no counts in August. The September to March data is collected from sites across Pembrokeshire (including the Teifi Estuary) for the BTO Wetland Bird Survey.

Annie Haycock (BBS & WeBS local organiser)

HODGES J E. (2010-2020) Daugleddau Estuary and Milford Haven Waterway: annual surveillance of summer shelduck populations. Reports to the Milford Haven Waterway Environmental Surveillance Group.

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Oystercatcher -Ringing

Haematopus ostralegus – PIODEN Y MOR – Breeding resident and passage migrant

In recent years, a number of waders have been ringed in Pembrokeshire, mainly around the Gann Estuary. Many have been resighted locally (in Pembrokeshire), but those oystercatchers that have been seen further afield are shown below. The number shown against each pin is the number on the ring.

Please report all sightings, including those in Pembrokeshire, so that we get a better picture of where the birds wintering here go to, how long they stay here, etc.

The furthest recorded Oystercatcher (number 55) was ringed 7th March 2018, it had not been resighted until it turned up on the 2nd April 2020 in Brynjudalsvogur, Hvalfjörður, Iceland (please use your own pronunciation!)


Pembs Ringing Group
From the Pembrokeshire Bird Blog 04/05/2020


2021

Icelandic ringed individual (yellow-orange-white) at Amroth on 15 Feb, had been ringed as an adult near Selfoss, Iceland in May 2017, later that year, in August, it was seen in Pontevedra, Galicia, Spain. The following year it was back near Selfoss and in 2019. In February 2020 it was again seen in Pontevedra, then back in Selfoss.
Another Icelandic bird (niger over green left leg; pale grey UY right leg), that had been ringed in SW Iceland as a pullus on 2/6/2020, was at the Gann on 30 April and at Kilpaison, Angle Bay in May. It had previously been seen near Black Mixen (Carew/Cresswell) on 12 Dec 2020.

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Oystercatcher – 2003-07 breeding

Haematopus ostralegus – PIODEN Y MOR – Breeding resident and passage migrant

Comparison with previous atlas:

1984-882003-07
Breeding confirmed5025
Breeding probable1425
Breeding possible2326
No of tetrads occupied87 (of 478)76 (of 490)
Percentage of tetrads18.2%15.5%

In Pembrokeshire oystercatchers are largely restricted to the coast, breeding on rocky shores, sea-cliffs and tops of small islets and larger offshore islands. On the mainland they have a fairly regular, if thinly spread, linear distribution along the coast. However, on the larger islands, Skomer and Skokholm for example, they can form loose colonies at a higher concentration.

Oystercatchers are long-lived birds and it is possible that some of the same birds observed in the 1980s were still breeding in the recent survey period.

Comparing the total number of tetrads in which they were found suggests a small and probably insignificant decline in breeding population distribution between 1984-88 and 2003-07, down by about 13%.  Although there was a large decline in the number of tetrads where confirmed breeding was reported, this was more or less balanced by the number of tetrads that registered probable and possible breeding evidence.

Scrutiny of the tetrad distribution map suggests that, although there are fewer tetrads with confirmed breeding, overall there was generally very little change in their distribution on the mainland coast and offshore islands north of Milford Haven. A close look at the map suggests that their distribution has thinned out a little along parts of the south coast.

In 1984-88, it was estimated that there were about 300 pairs of breeding Oystercatchers. At least 50% of these were on the offshore islands, where more regular monitoring is conducted. In 2003-07, the island populations again recorded in the region of 140-160 pairs. This suggests that the Pembrokeshire population is probably reasonably stable, at least in optimal habitat locations.

Monitoring of a small Oystercatcher population along the Castlemartin peninsula, between 2003 and 2007, has provided evidence of 7 – 8 regularly nesting pairs along a 20 km length of limestone coast, covering seven coastal tetrads. Nesting density was quite low and nests were patchily distributed, ranging from one – three per tetrad, but they were absent from some tetrads. Three of these pairs regularly breed at Stackpole each year in one tetrad, in some years with limited success. They are monitored annually and this number has not changed much over the last 20 years.

In 2006, it was reported that in one fairly remote nest, on the shore of Carew River, 8 eggs had been laid which was almost certainly a result of egg dumping involving two females.

Based on 76 tetrads where Oystercatchers were found along the mainland coast of Pembrokeshire, an average of two pairs per occupied tetrad would seem to be a reasonable assumption. This would suggest at least 150 pairs which, when combined with the most recent Islands totals, is similar to the 300 pairs in Pembrokeshire as a whole, estimated in the mid 1980s.

If the decline in distribution and confirmed breeding status along parts of the south coast is real and not due to observer bias, then perhaps parts of the coast are sub-optimal for this species. However, it is also worth considering other possible reasons why they could have thinned out, or their breeding success may have been affected here.

Oystercatchers breeding on the rocky coast are dependent for food on good populations of molluscs and other marine prey in the inter-tidal zone. Perhaps their apparent thinning out, and lack of confirmed breeding, along parts of the south coast is a legacy of the Sea Empress oil spill that affected this coastline in winter/spring 1996.

Surveys have shown that the coastal habitats have recovered well since, but perhaps the density and range of age structures of molluscs, limpets, whelks, mussels, and other marine prey have not yet fully recovered in some locations. Perhaps there are still insufficient food resources to fully support them throughout the breeding season?

Another possible issue that needs consideration is the increase being made of the coastal inter-tidal zone by people undertaking “coasteering”. This activity (involving combinations of rock-clambering and swimming along a linear course at the base of the cliffs, usually by groups of people) has become extremely popular along parts of the south coast and along other sections of the Pembrokeshire coastline during the last 20 years.

Whilst the routes used may not cause too much lasting damage to marine food sources in an already harsh, wave-lashed environment; breeding birds on the lower ledges and cliff-crevices may now be more frequently disturbed in areas used for recreation than was the case in the past.

The Pembrokeshire Outdoor Charter Group, involving Activity Centres and conservation bodies, are attempting to improve knowledge of the range and sensitivities of species and habitats on the coast. Hopefully this will ensure that the small number of breeding and roosting birds specialising in the harsh rocky inter-tidal zone will be afforded sympathetic protection. There is still a need to identify the areas used by wildlife and for more detailed monitoring.

Bob Haycock (BTO rep & Chairman of the Pembs Bird Group)

Records extracted from the Pembrokeshire Bird Reports which may contain more detail than shown here

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Oystercatcher – 1994

Haematopus ostralegus – PIODEN Y MOR – Breeding resident and passage migrant

1984-88
Breeding confirmed50
Breeding probable14
Breeding possible23
No of tetrads occupied87 (of 478)
Percentage of tetrads18.2%

Mathew (1894) mentions breeding at only three coastal sites, the “Bishop Rock”, Skomer and “on an island at the entrance to Milford Haven”. If this was a true reflection of the Oystercatcher’s breeding status at that time, it had increased considerably by 1949 when Lockley et al. estimated that 120 pairs bred around the mainland coast and noted that it bred on all the islands. They reported that 36 pairs nested at Skomer in 1946 and over 50 pairs on Skokholm in 1947 and 1948. The range remains the same today (see map) and a total of about 300 pairs breed in Pembrokeshire, with about 150 pairs on the islands of Skokholm and Skomer, where recent breeding success has been low due to an increase in predation by gulls.

Ringing has shown that some young birds move out of Pembrokeshire after the breeding season, to winter on the western European seaboard as far south as Spain. Older birds tend to winter nearer home, on the Cleddau Estuary and as far as the Burry Inlet in West Glamorgan. Winter numbers are augmented by immigrants, as an Oystercatcher marked with a wing-tag has illustrated. This bird bred near Aberdeen in 1986 and had moved to the Gann by September of that year, having been seen on route at Belfast Lough in August. It wintered at the Gann and continued to commute between Scotland and Wales until at least 1989.

Numbers build up in Pembrokeshire during July and August, when flocks are seen passing south off Strumble Head and as demonstrated by counts from the Cleddau Estuary (see Table 6), where peak numbers are reached between September and November.  Numbers decrease slowly thereafter with a more rapid departure of most of the winter birds during March and April.

Smaller winter concentrations are found on the Teifi (50-80 birds) and Nevern (30-60) estuaries and at Fishguard Harbour (40-50) when Oystercatchers also use the outer coast: a survey in the winter of 1985 found 928 birds were present, thus the midwinter population for the whole county runs to about 1400 birds.

Oystercatchers are heard passing over the county at night during arrival and departure periods but the only diurnal inland record is of a single bird at Llysyfran reservoir on 13 March 1983.

Donovan J.W. & Rees G.H, 1994, Birds of Pembrokeshire

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Oystercatcher – 1980s winter

Haematopus ostralegus – PIODEN Y MOR – Breeding resident and passage migrant

The BTO winter atlas showed that Oystercatchers were present in all coastal and estuarine 10km squares during the winters of 1981-82, 1982-82 and 1983-84.

The darker the colour, the higher the relative total count for each 10km square.  The darkest blue represents 45-225 birds.

Graham Rees. Pembrokeshire County Bird Recorder 1981-2007

Data collected by volunteers for the BTO. Lack, P. 1986 Atlas of wintering birds in Britain and Ireland. T & A.D. Poyser.

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British Oystercatcher – 1949

Haematopus ostralegus occidentalis

Mathew mentions breeding only on the Bishop’s Rock and Skomer, also on “a small island at the entrance to Milford Haven”.

Now apparently much increased, especially Skokholm (over 50 pairs 1947 and 1948).  Breeding round all coasts and on all islands, including South Bishop and Grassholm.

R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society

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Oystercatcher – 1894

OYSTER-CATCHER, Hamatopus ostralegus – Resident.

The Oyster-catcher occurs in small numbers at various places on the coast, and nests on the Bishop’s Rock, also on Skomer, where we found pairs of old birds and their newly-hatched young on the last day of May, 1886. In their handsome plumage of vividly-contrasted black and white the old birds, as they flew anxiously low overhead against the blue sky, were beautiful objects.

Mr. Tracy states that, on several occasions, he took the eggs of the Oyster-catcher on a small island at the entrance of Milford Haven, and Sir Hugh Owen has shot the bird on the sands at Goodwick. The plaintive whistle of the Oyster-catcher, or Sea Pie (to give it its commoner name), is one of the characteristic bird-notes of the pebbly beaches around our coasts. We have not often met with the bird on a sandy shore.

Mathew M.A. 1894, Birds of Pembrokeshire and its Islands

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