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
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?
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.