Shelduck - 2013 - Cleddau Estuary WeBS counts

Shelduck in Pembrokeshire winter mainly on the Cleddau Estuary, with a few being recorded on the Teifi and Nevern Estuaries, and one or two occasionally on fresh-water sites. 

In the 1980s birds would typically start arriving in November, with about a thousand present by January.  These stayed until March, when numbers fell rapidly as birds moved back to their breeding grounds or moulting grounds.  During the 1990s numbers built up steadily from October to a peak in January, then fell steadily. The peak counts were slightly lower than in the 1980s, and this was generally thought to be due to milder winters allowing birds to return earlier to more northerly areas.  The GB national index remained reasonably steady during this time, suggesting that the population overall was not declining.

In the late 1990s the GB index fell slightly, but has now levelled out again.  However, the numbers on the Cleddau have continued to decline and were below the level of national importance during the early 2000s. Numbers on the Burry Inlet also fell at this time. Outside of Wales, Poole Harbour, for example, has experienced a decline of about 60% in recent years (Musgrove, 2007).  Not surprisingly the threshold has now been lowered, but the Cleddau system still only barely qualifies on a five-year average peak count.

The change in timing of birds arriving and departing the Cleddau may be linked to the recent run of mild winters, and to an increase in protected areas on the continental mainland. 

Adult birds move from their wintering grounds to the breeding grounds and from there to moulting grounds in mid-late summer (Wernham, 2002).  Young birds may move more slowly towards the moulting grounds.  The locations used for moult may be changing, for example, most birds went to the Helgoland Bight in the German Waddensee, but in recent years the numbers of birds on British moulting grounds such as the Wash, Bridgewater Bay and the Dee/Mersey estuary have been increasing.  The change in distances travelled may influence the timing of birds arriving back in their wintering grounds. There has been one ringing recovery showing movement of a bird between Pembrokeshire and the Waddensee, but are they still going there?  These changes in moulting grounds may be linked to increasing numbers of shelduck breeding in Ireland. 

There is no indication of any changes in food supply or other environmental factors on the estuary system that would explain observed trends.

Annie Haycock

Pembrokeshire WeBS coordinator

Sheld-Duck - 1949

Tadorna tadorna

Mathew mentions that "a pair or two nest on sandhills below Milford Haven" and says it has been seen on Goodwick Sands, and once captured at Orielton.  Breeds annually on sandy banks, Mullock Bridge, Angle, and on the upper reaches of the Cleddau; also a few pairs at Newport and Teifi estuary.

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

Shelduck - 2003-07

In Pembrokeshire, Shelducks are strongly associated with estuaries, in particular the Milford Haven Waterway and Daugleddau Estuary, and its associated embayments and tributaries. In the 1984-88 survey, breeding Shelducks were also recorded on the Teifi Estuary, and on Caldey Island.

A comparison between the 1984-88 and 2003-07 breeding surveys reveals changes in the distribution of breeding Shelducks in the county, as shown on the tetrad maps.

Some of the more significant changes include the disappearance of Shelducks as a breeding species from the southern side of the outer Milford Haven Waterway, e.g. in Angle Bay/Kilpaison, and from coastal sites such as in the Freshwater West area.  There have also been gains, with Shelducks breeding on Skomer and Skokholm Islands and on the Nevern Estuary. Breeding Shelducks were also present on the Teifi Estuary. The number of tetrads in which Shelducks were recorded as confirmed or probable breeding had also increased by 2003-07, from 31 to 36, with possible breeding recorded in a further 14 tetrads.

One or two of the records of possible breeding  on the exposed open coast need to be treated with caution.  Pairs and small groups of Shelducks are a common occurrence on the open coast in May and June, either resting on the surface of the sea, or on the cliffs above (J. E. Hodges, pers. obs.). 

Some of these birds may well be non-breeders en-route to moult grounds.  Moult migration in Shelducks is well-defined.  First and second year birds leave for the moult grounds from May onwards, to be followed by non-breeding adults or failed breeders later in June and early Jul.  By mid-July all non-breeding Shelducks, together with adults that are not minding ducklings, have left the Milford Haven Waterway and Daugleddau Estuary for the moult grounds (Hodges, 1992-2008).

Following the 1984-88 survey, the breeding population of Shelducks in the county was estimated to be around 50 pairs.  In the period 2003-07, the numbers and sizes of broods of ducklings seen in the Milford Haven Waterway & Daugleddau Estuary varied each year, from 10 to 22 broods.  In addition, several territorial males and pairs without broods (but which may have attempted to breed) were recorded in each of the five seasons. Taking into account the breeding pairs on the islands; in the Newport area and on the Teifi Estuary, together with pairs scattered around the county, 60 – 70 breeding pairs might be a reasonable population estimate. 

Caution should, however be exercised, since Shelducks are known to “dump-nest”, whereby females lay their eggs in another female’s nest, leaving the owner of the nest to incubate the eggs and lead the newly hatched ducklings to water along with their own ducklings.  “Dump-nesting” is sometimes indicated by large broods, e.g. of nine ducklings or more, and almost certainly occurs amongst the Shelduck population in Pembrokeshire.

Jane Hodges

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 23

Orange = breeding probable = 13

Yellow = breeding possible = 14

Total tetrads in which registered = 50 (10.2%)

Shelduck - 1994

Breeding resident and winter visitor.

Mathew (1894) noted breeding on the Cleddau Estuary and that it had been seen at Goodwick and Orielton, suggesting Shelducks were not common at that time. It now breeds in most parts of the Cleddau Estuary, with a few also on the Teifi, but no longer on the Nevem, a site included by Lockley et al. (1949). Shelducks bred on Caldey Island during the Breeding Birds Survey of 1984-1988 and on Skomer in 1969 and 1973 and they are occasionally seen flying inland during the breeding season. The average breeding population is estimated to be 50 pairs. Productivity is variable judging by duckling counts from the Cleddau Estuary, which averaged 137 young per annum from 1953 to 1955 but only 67 from 1983 to 1987. A census in 1991 revealed 79 ducklings (Hodges 1992).

Most of the adults leave the county to complete their moult migration during July. It is not known whether any of our birds moult in Bridgewater Bay, but there is a January ringing recovery from Pembrokeshire of an adult ringed in Germany in August, suggesting that some use the Heligoland Bight in the German Waddenzee.

Wintering birds begin to arrive in Pembrokeshire during November and build up to a peak in January and February. The average of the peak counts for the Cleddau Estuary from 1983 to 1986 was 1,340 birds, but 2,174 were counted there during the cold weather of January 1987. Shelducks are only occasionally seen away from the Cleddau, pausing briefly in coastal localities such as the Nevem Estuary, Fishguard Harbour and the offshore islands, and around 100 winter on the Teifi Estuary.

Fieldwork 1984-88 (based on 478 tetrads)

Red = breeding confirmed = 21

Orange = breeding probable = 10

Yellow = breeding possible = 13

Total tetrads in which registered = 44 (9.2%)

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

Shelduck - 1970s breeding

Red = breeding confirmed

Orange = breeding probable

Yellow = breeding possible

Shelduck - 1980s winter

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

The colour for each 10km square represents over 81 birds seen in a day.

Graham Rees 

Common Sheldrake - 1894

Species account from M Mathew, 1894, "The Birds of Pembrokeshire and its islands"

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