It's been a busy few weeks on Havergate with the survey season and monitoring season in full swing.
Typically this brings mixed results and this year is no different but most excitingly was the discovery or more accurately the rediscovery of a very rare spider on the island.
Arctosa fulvolineata or to give it its common name. Yellow striped bear spider.
Arctosa fulvolineata male Courtesy of Peter Harvey
Not a huge amount is known about this spider but it lives in tidal debris hunting for insects and other prey amongst bits of seaweed washed up. In an island context it was first recorded in 1997 probably in the last real systematic survey of the islands rare arachnids. It then was not recorded until 2013. I suspect it as always been present just a combination of never having been looked for and no observers.
The real interest for this spider is in its national context. Nationally there have been less than 60 records since systematic counting begun. Its habitat shingle and saltmarsh are increasingly under threat by development and erosion. So much so that it is a RDB3 species in the UK (nationally rare) and UKBAP priority species. We are therefore very pleased to see that it is hanging on in at Havergate. Living in the tidal scraps and on what is left of the bare shingle.
Most people have probably noticed but it's been rather cold! Even this week whilst the rest of the country basks in 20 degree+ temperatures out on the coast it's been closer to 14 to 14 degrees.
The cold spring and late start to summer has meant that around the UK water temperature has been around 3 degrees lower than average. These cold temperatures haven't been great for the island and its birds but a closer look reveals that the real victims have been insects and fish living in the lagoons. Those trusty keys to the web of life.
Take a look at the photo below:
You can see fish (three spined sticklebacks mostly), gobies; a type of fish that spends its life in the lagoons, brown shrimps known as paleomentes varians and possibly the most abundant animal in the lagoons and borderline uncountable numbers of lagoons slaters (small dark insects that look a bit like woodlice).
Now take a look at this photo:
There are still some numbers of lagoon slaters but the abundance of fish and paleomentes varians has been gone.
The top photo was taken in spring 2012 and the latter in spring 2013.
There's obviously a huge amount of variables to take into account however, reserve management hasn't changed and this is more or less the only thing we can control. We manage the northern lagoons by opening up the sluices in the spring too bring lots of inverts and fish into the lagoons this then multiples within Havergate and come July provides an abundance of food for birds using the island.
What has been assumed is that due to the cold weather and corresponding colder sea temperatures the inverts and fish haven't arrived, at least not in the same numbers. Sadly, this potentially could have a knock on effect well into late summer with less food being available too migrating waders; spoonbills come late July, August and September. Hopefully temperatureswill rise and allow a spawning of what is in the lagoon but all this serves to remind us just how precariously balanced nature is.
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