The results are in, 99% of all birds have fledged and after a changeable summer, the 2011 Havergate island breeding bird story is ready to be told.
The final counts of the large gulls where 460 herring gulls and 1030 lesser blacked backed gulls, a grand total of 1490 large gulls, how does this compare to last year? In 2010 552 herring gulls nested on the island and 1169 lesser black backed gulls. Lesser black backed gulls continue to decline on the island and after a couple of years of growth the herring gulls have fallen away, this is the first overall fall in the gull population since 2009 but lesser's have not dipped below a 1000 for the first time since 2007.
Productivity results of the gulls was also interesting (this is the measure of how many young where produced per nest). Overall across the island herring gulls performed marginally better producing 0.57 young per nest compared with 0.50 young per nest for lesser black backs. Last year both species where down at 0.35.
Visitors to the island will be familiar with the gull colony along the shingle bank, this area proved the most successful of all the gull colonies, producing a staggering 1.61 (herring gulls) and 1.58 (lesser black backs) young per nest. The Doveys lagoon powerhouse produced a respectable 0.85 (herring gulls) and 0.86 (lesser black backs) young per nest. Less successful was the salt-marsh colonies which produced on average for both species 0.41 young per nest.
How did the other key species on Havergate fare? Well, it was a mixed summer. The common terns produced only 4 young from 34 nests. A productivity of 0.11. In many ways its hard to know how to feel about this, it is very disappointing that we didn’t get close to last years figures of 11 from 29. However, the four this year where produced in a normal time frame, by this I mean unlike least year which where produced exclusively by re-lays, these where laid in late may and fledged in early July, we can therefore rightfully think of this as a Havergate island colony. However, the relative paucity of young produced suggests that we will have to cross our fingers again to see if they return next year.
Common gulls produced four from 19 nests, one less than last year and a productivity of 0.21. A slightly disappointing return, and one down from last year from one more nest. There would seem to be other factors at play here, other than just predation, possibly a food issue may be depressing production. The gorse should offer a natural protection against predation but often young do not seem to make it, at least two chicks possibly more died of starvation this year, allied with one having a leg injury making it a difficult year for the common gulls.
However, if we compare both common terns and gulls productivity from this year with the desert years of 2005 to 2009 where no young where produced at all, it has still been a good year.
Only 3 avocets pairs bred this year (producing no young) and 2011 may well mark the final year this species nests on Havergate, better news was had from oystercatchers which produced 1 young, the first in a very long time. Ending on a positve note, the Barn owls produced two young, making it a grand total of 6 young produced in 3 years.
What is the reason for the avocets decline in recent years at Havergate Island when it used to have a healthy population and at one time was the only place in the UK that had a breeding colony?
Ian.
It's complicated. Avocets are increasing in the UK, and generally do very well at newer colonies, while more established colonies tend to attract more predators.
On Havergate we have a problem with rats - these are being eradicated as part of our EU-LIFE funded work with the National Trust.
Also, the recent large increase in breeding gulls has had a serious negative impact on avocets, terns and other breeding birds. This increase is partly the result of disturbance and habitat loss elsewhere, something which the EU-LIFe project is trying to address on Orfordness.
To complicate things further, both herring and lesser black-backed gulls are birds of conservation concern, while recent increases mean that avocets are currently not listed as under threat.
I hope this helps.