Langstone Harbour by Chris Cockburn

The remit to Chris Cockburn, as with every other contributor, was please send in an article, but make it short or it will not be read by the public, a page of A4 will suffice. My heart sank when I received a CD disc of 7 pages. Out with the edit scissors and the highlighter pen. How do I break this to him? Having read the article, not a word has been changed.

Not only masterful, but this gives insight into the work of an RSPB warden, and this cannot be read elsewhere. Chris is ‘Species Protection Warden’ for Langstone Harbour, and ‘Health and Safety Coordinator SE Region RSPB'.

It’s such a glamorous job, out birdwatching all day long, chatting to the public, just having a good time. We know that Chris works 7 days a week, reality dictates that most of the time is given to paperwork, Health and Safety, assembling data, and so forth. Like all wardens, it is not a job; it’s a way of life.

Although the Wildlife Trusts figures strongly in this locality, strangely, Langstone is not only an isolated solitary RSPB Reserve in Hampshire, but the nearest other establishments are Pulborough Brooks (the most visited RSPB Reserve in Britain) and a slightly less known reserve several time zones distant at ‘ Pilsey Island and Adur Estuary’ Shoreham?! Chris is also the warden here!

All birdwatchers know Chris, an excellent lecturer, will always stop for a chat, and if you look out towards the islands in the summer, and see a tiny boat being hurled about in the surf, there protecting his breeding birds from disturbance from unknowing boaters, will be Chris.

Thanks to him and others, we have by far the highest number of the stunning Mediterranean Gulls in Britain. Langstone Harbour is Internationally Important for Brent Geese and Dunlins and the assemblage of over wintering waders; Nationally Important for Little Egrets, Red-breasted Mergansers, Grey Plovers, Black-tailed Godwits, Whimbrels and Curlews

The Langstone Harbour RSPB Nature Reserve Chris Cockburn

The RSPB owns approximately one third of Langstone Harbour, extending northwards from Sword Sands to the shore at Broadmarsh.

Much of the reserve is composed of invertebrate-rich intertidal mudflats and sandflats that are the feeding grounds for many wildfowl and waders during low tide periods. The alga Enteromorpha and the plant Zostera provide food for wildfowl, including dark-bellied brent geese and wigeon.

Mudflats and moribund Spartina beds north of Sword Sands and (right) Zostera beds at low tide

The small shellfish Hydrobia is particularly abundant and is often the prey taken by dunlins, the most numerous wader in the harbour.

Hydrobia feeding on silt and (right) Hydrobia shells

Most of the harbour birds do not breed here; their breeding quarters are typically in the far north of Europe and Asia, often within the Arctic Circle. There are two broad groups of such birds using the harbour, ‘passage’ and ‘over-wintering’.

Passage birds, such as whimbrel, use the harbour in spring and autumn as a stopover on their annual migrations between the far north and places far south of the UK. During their stay here, they moult into or out of their breeding plumage, a process that requires a great deal of energy that they can only derive from their food.

Over-wintering birds, such as the dark-bellied brent geese, go no further south on their migration from their breeding grounds and spend the winter months here because there is a reliable and abundant source of food. Many of the wintering waders, such as black-tailed godwits, also perform their autumn and spring moults here.

Food is not the only criterion that makes a site attractive to these birds; more importantly, they need safe, undisturbed places to roost during the high tide periods when no food is available.

In Langstone Harbour at high tide, only 5% of the reserve remains visible as five small islands. The islands are predominantly saltmarsh, typically with shingle ridges and beaches on their southern and western edges, and are important for the variety of nationally scarce plants that grow there and for the abundant invertebrate life. There is also an area of scrub with oak trees on North Binness Island

Saltmarsh on South Binness with Sea Lavender in bloom and (right) Lax Sea Lavender Limonium humile

Little Robin Geranium purpureum Long Island and (right) Trees and scrub on North Binness Island

Since 1979, when the RSPB acquired the site, the implementation of a restricted access policy, with the willing cooperation of harbour users, has resulted in much reduced levels of disturbance on the islands and hence ideal roosting sites for wildfowl and waders. Baker’s Island is presently the most favoured roost site, particularly for oystercatchers, bar-tailed godwits and curlews.

Prior to 1979, there were anecdotal records of seabirds attempting to breed on the islands, but disturbance inevitably led to breeding failure. Many seabirds had successfully nested in Chichester Harbour since at least 1964, but tidal flooding was often a problem. The RSPB’s restricted access policy led to an immediate colonisation of the reserve’s islands by breeding seabirds; in 1979, five pairs of black-headed gulls, two pairs of common terns and twenty-seven pairs of little terns bred on Round Nap Island. The gulls generally nest on the higher parts of the shingle ridges that are vegetated with Sea Beet Beta vulgaris subsp. maritima or on the upper saltmarsh areas. The following pictures show the effect on Sea Beet of a large colony of gulls:

Before breeding South Binness and After breeding South Binness

Recently hatched black-headed gull chick and eggs in nest

Common terns generally nest on the bare or sparsely vegetated shingle at the top of the beach, sometimes dangerously close to the strandline.

Common tern nest on South Binness

(Photo courtesy of Jason Crook)

Tidal flooding is probably the biggest factor in the low productivity rate for little terns because they often nest in areas where the annual plant Sea-blite Suaeda maritima grows. When the little terns first start nesting in May, the shoots of Sea-blite are only just appearing through the bare shingle. This plant grows in the mean-springs high water level area and is therefore flooded by high spring tides. Despite clearly noticeable strand lines above the Sea-blite zone, little terns persist in nesting in this risky area.

Little tern nesting area South Binness

Prior to 1996, an average of one hundred pairs of little terns, forty-two pairs of black-headed gulls and twenty-six pairs of common terns bred on the reserve, mostly on South Binness Island. The little tern colony was often the second largest in the country during this period. Tidal flooding and predation by foxes and crows often caused poor breeding success for the little terns, but they have managed to produce a yearly average of thirty young between 1979 and 2005, with a productivity rate of 0.35 young per pair.

In 1996, there was a sudden surge in the numbers of black-headed gulls, probably birds that had previously bred in Chichester Harbour. The increased numbers of breeding gulls, with the associated increase in competition for nesting places, caused severe problems for the little terns, which were forced onto less suitable breeding sites. During the 1997-2005 period, the average number of little terns nesting on the reserve fell to 54 pairs, with a 23% drop in productivity, while the total number of black-headed gull pairs rose to 4743 in 2005.

(See chart below)

Under pressure for nesting places, many little terns moved to the artificial island in the Saline Lagoon at the West Hayling LNR where they initially enjoyed very high productivity. Inevitably, black-headed gulls and common terns also started nesting there and, in 2005, suspected predation of eggs by rats led to a complete breeding failure for all of the seabirds on the island.

The large black-headed gull colony has some merits, however; crows and kestrels are kept at bay, foxes target the large concentrations of black-headed gull eggs and chicks and other seabirds are attracted to the site.

Sandwich terns, which had bred in only four years during the 1979 to 1995 period, are now regular colonists with 271 pairs present in 2005. Sandwich terns breed on bare shingle in densely packed groups and characteristically create guano deposits, immediately noticeable as a large, pungent white-coloured area on the shingle ridge. Like most seabirds, Sandwich terns regularly wash in the sea and then shake off the excess water as they fly off. Their 180-degree head movement is captured in the following photo of a juvenile bird:

Juvenile Sandwich tern after bathing

Perhaps the most attractive seabird that has colonised the reserve is the Mediterranean gull, pictured below:

Adult Mediterranean gull in full breeding plumage

One or two pairs of these handsome birds were recorded breeding in Chichester Harbour for most years between 1985 and 1995. When the black-headed gulls largely deserted Chichester Harbour in 1996, it was unsurprising that breeding started on the RSPB reserve. By 2005, the colony had grown to one hundred and ten pairs, probably half the total UK breeding population.

Mediterranean gulls are known to prey on terrestrial invertebrates, almost exclusively; during their breeding season and in the UK this behaviour results in them needing to forage far from their breeding colony. In contrast to black-headed gulls, Mediterranean chicks rarely move far from their nest sites and, even after fledging, are often seen at the nest in the few days before they head off from the harbour. Their ‘parenting’ behaviour is also noticeable; until a youngster finally fledges, there will always be at least one parent ‘guarding’ it.

Mediterranean gull – parent on duty, watching youngsters

Mediterranean gulls seem to act as the perfect ‘decoy’ for Sandwich terns; the Sandwich tern breeding groups are always close to the territories of Mediterranean gulls, which start nesting earlier. It is presumed, by the reserve warden, that the black hood is probably the key!

Other birds regularly breed on the reserve, as the following table shows:

Bird	Nesting habitat	Average(Pairs) 1979-2005	Comments
Oystercatcher	Bare shingle(Occasionally saltmarsh)	34	Low productivity, often due to crow predation
Ringed plover	Bare shingle	24	Declining numbers in recent years, possibly due to habitat erosion caused by wind-generated wave action
Redshank	Saltmarsh	35
Skylark	Saltmarsh	15
Blackbird	Scrub	1
Meadow pipit	Saltmarsh	20
Reed bunting	Saltmarsh	4	Declining numbers in recent years

Contact details:

Chris Cockburn
Warden Langstone Harbour RSPB Reserve
Unit B3 WREN Centre
Westbourne Road
Emsworth
Hampshire
PO10 7SU
Phone 01243 378784: Mobile 07764 290629
Fax 01243 378785
E-mail chris.cockburn@rspb.org.uk
www.rspb.org.uk

The RSPB is the UK charity working to secure a healthy environment for birds and wildlife, helping to create a better world for us all

Registered Charity No. 207076

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