October, 2010

Havergate Island

Havergate Island
Welcome to the Havergate community group. Havergate is a magical place, Suffolk’s only island! The reserve is nestled within the Alde & Ore estuary and is well known for its year round bird spectacle.

Havergate Island

  • Ola! Wish you where here

    It feels now that winter has truly arrived, the temperatures are plunging and the nights are drawing in and the clocks are about to go back. A chilling sentence for anyone who lives in the British Isles.

    It was therefore nice to get an update on the movements of the ringed gull chicks on Havergate this year. Those who have read previous blogs will know that in July the landgard ringing group came out to ring the young nestling Herring gulls, Lesser Black backed gulls, Great Black backed gulls and Common gulls in early and mid July.  The final totals are in, 245 Lesser Black backed gulls where ringed including 5 adults, 81 Herring gulls, including 4 adults, 2 greater black backed gulls all juveniles and finally 3 Common gulls, again all juvenile.

    Giving a grand total of 335, more than three times what was ringed last year.  Largely due to the team making two visits as opposed to the normal one.  

    Due to virtual collapse of the colony on Orfordness, dropping from a peak of 25,000 in the late 80’s to less than 500 pairs this year. Havergate is now a nationally significant gull colony, especially noteworthy for its high population of Lesser Black backed gulls. It is therefore important to be able to ring large totals on Havergate to continue advancing the knowledge for the reasons in the decline of Herring gull numbers and to advance the studies in the ecology of Lesser Black backed gulls.

    So, now comes the exciting time when the results start coming in. It is still early in the season but this year’s juvenile lesser black backed gulls have been seen in Portugal (18), Spain (10) and France (1). Whilst unusually a Herring gull has been seen in Belgium.  

    Picture courtesy of Michael Davies

    Lesser Black backed gulls movements have gone through a rather significant change in the last 50 years or so, revealed by observations and ringing data. Previously the entire species was migratory,  in winter it would be relatively unusual to see a “British” Lesser Black backed gull  as most would migrate to Spain or even as far as Morocco. However, now the species can be best described as a partial migrant. The juveniles still head south, wintering in Southern Europe, whilst adults see out the winter on estuaries and rubbish dumps in England.  This is quite a radical shift in ecology and the reasons behind it are not fully understood.

    Herring gulls are not migratory and can be found all year round. However, despite being considered relatively common they are now a red listed species, due to a 53% decline in their breeding population since 1969.  Like the Lesser Black backed gull recent changes are not fully understood but it is believed disturbance, predation, disease and changes in availability of food from waste tips have had an impact. It could even be that the numbers are returning to a more “natural” level. However, these declines are masked by an incredible 570% increase in Herring gulls nesting in urban areas. The RSPB is now involved in determining the reasons for the decline and what can be done to aid previously healthy populations of Herring gulls.

    So, if you see a colour ringed gull remember to report it in and think about all the migratory species when its snowing and freezing outside.

  • Invasion from the North

    Of late the blog seems to have been dominated by articles on “issues”. As a change I thought it would be nice to update people about what has been going on, on the island.

    Every day seems to bring a good species to the island and the island is jumping with birds. Most lagoons are full of wintering ducks, on the recent Webs count 1104 Teal and over 1300 Wigeon where counted. These are not far away from our winter peaks. Interestingly, and I’m not sure if this has been repeated elsewhere but the moult process seems to have been a long drawn out process, there are still a lot of scruffy looking ducks on the lagoons.

    Pintail numbers are relatively low (29), however since I believe there are still is a decent sized flock at Minsmere that would seem to account for this. The first Brent geese have returned to the estuary, never more than a transitory visitor in the Alde – Ore estuary, the truly big numbers are found on the Stour estuary, the small skeins that fly over the island and occasionally land on the reserve are more than welcome.

    In the past week, the island has played host to its 15th ever Bonxie (Great Skua), the first Kingfisher since 2003, the first Rough Legged Buzzard since 1994, the first Stonechat since 2008, the first Blackcap since 2005 and the first Redwings, Fieldfares and Goldcrests of the year. Two Spoonbills and a Spotted Redshank flew over on Thursday and three Marsh Harriers. A Hen Harrier and Two Short eared Owls have been around all week.

    In recent years both Hen Harrier and Short eared Owls have reflected national trends on Havergate by becoming increasingly scarce. That both these species have been around for the past week raises hope that both may chose to winter on the island, as was always the case up to the late 1990’s.

    The story of the discovery of the Rough Legged Buzzard is worthy of repeating. It owes quite a lot to chance. Initially, I was not intending upon visiting the island on Sunday, planning instead on taking that day off but due to the calm winds decided to take my chance and head out to the island to complete the saline monitoring. As I was walking down to Doveys lagoon, I noticed a disturbance in the crows and the Starling on the Saltmarsh, pondering that it had been a while since I had seen the Peregrine. As I got closer the crows where mobbing a specific spot. I decided to go and inspect closer, suspecting that I would flush one of the shorties. I must have got to within 5metres of the bird, when it exploded out from under my feet, immediately recognising it as an extremely pale Buzzard, the give away was the white upper tail feathers, found on Rough legged Buzzards but not on common Buzzards.  

    The Rough legged Buzzard is a rare bird of prey in this country. The ones we get are almost certainly from northern Scandinavia and between 10 and 150 winter in the country, seeing out the winter in the relatively mild conditions of the UK. It is much like our Common Buzzard but paler and with a different feather arrangement and a subtly different flight style. Given the numbers that have arrived in the country in the last few days, the potential for an invasion year is high. This is caused by a good breeding season and immediately followed by a collapse in the Buzzards food, in this case Lemmings. Therefore many juveniles and adults are forced to take flight to find more food.

  • Marine Life

    Lately the island has been visited by a Great Skua (Bonxie) these fearsome birds from the north have reminded me of a cause important to me and important to the nation’s biodiversity, that of the marine environment.

    Whilst Bonxies have largely been spared the ravages of Sandeel shortages and unpredictable weather during the summer months other seabirds have not been so lucky.

    Species that have suffered in the last few years include the kittiwake, which has seen numbers fall by 40 per cent since 2000. The Arctic skua population has dropped by 57 per cent and even the herring gull a species familiar to all those that have visited Havergate island has dropped by one third. Many people won’t believe this but there are now more Puffins in the world then Herring gulls.

    Whilst the exact causes of the seabird collapse seem uncertain and the effects far from uniform with Northern Scotland and the Shetlands particularly badly affected. One thing that seems to be agreed is that the plankton systems that underpin the entire marine ecosystem are in a state of flux. This seems to be caused by rising sea temperatures which are causing the plankton to bloom early or even move into cooler parts of the sea; this in turn seems to be having an effect on Sandeels which are either moving from traditional spawning sites or spawning in vastly reduced numbers. So, that when the top predator in this case birds come to feed and raise their young this proves to be a onerous task, leading to increased nest and young failure.

    This situation can be exacerbated by commercial overfishing, which can drive down stocks of replacement food sources e.g. Sprats or whitetails. However, the trouble in the marine environment is not just limited to food sources for seabirds many of our household fishes have been badly reduced in recent years; fishes such as cod are no longer the superabundant fish that they were in previous years.

    The troubles that effect the marine environment are not just limited to Great Britain; a recent study suggests that if overfishing continues at the same rate then global fish stocks will be all but depleted by 2050 and fishing has been identified as the most immediate agent of change on the global marine environment.  I often think that if the scale of fishing was repeated on land then we would rightly be horrified.

    The RSPB is campaigning for greater protection of our marine environment both at a national and European level. Raising awareness of the perils of overfishing and the risk posed by climate change on our sea life. We are also campaigning for the government to establish a coherent network of marine protected areas in the UK by 2012, called Marine protected areas. In these areas usage of the sea and its associated features will put the needs of wildlife first and all other activity will be regulated.

    If you wish to get further involved or seek more information please visit our safeguard our seas website.