Sunday, 25 August 2013

Forest Monkeys reveal secrets

The Dutch name for Little Bittern is Woudaap, which in direct translation means Forest Monkey.  Last weeks work involved a great deal of nimble movement through reedbed ‘forests’, culminating in the Somerset Forest Monkeys revealing some of their secrets.

We started with a good deal of thrashing about in the reedbeds at Minsmere.  Thinking about climate change, the impact of too many Red Deer, and natural succession in an ageing reedbed.  How are we going to manage this site over the next 25 years?  Nothing beats getting into the habitat and experiencing it close-up to understand what needs to be done.

Then on to Snape, where new wetlands are being created.  A bit of electro-fishing to understand how the fish populations are developing, then a look at the area currently being created to add a few tweaks to the design; imagining yourself in a metre of water surrounded by reeds and thinking what features would attract a feeding Bittern or a Great White Egret.

Then down to Ham Wall, where after a summer of meticulous recording by a superb group of volunteers and local birders, we soon homed in on the Little Bittern nesting and feeding sites.  Water depths, edge profiles, reed characteristics were all recorded and some electro-fishing revealed the secrets of the Forest Monkeys favoured feeding areas.  Such details will be invaluable in creating similar habitat elsewhere.

One interesting fish caught in some numbers at Ham Wall was the Moderlieshen or Sunbleak Leucaspius delineatus, a non-native species that has a highly developed life history strategy. The majority of cyprinid fish species take 2-4 years to become sexually mature and spawn just once a year. The females scatter many thousands of eggs over aquatic macrophytes or gravel,and these are then left unguarded and vulnerable to predation.  Unusually for cyprinids, the Moderlieshen become sexually mature at one year old and are batch spawners, with females laying several batches of eggs, between April and July, which are guarded by the males until they hatch. They were first recorded in the Somerset Levels around 1990, their origin unknown but likely to have arrived via some fish stocking by anglers.

Photos above - Moderlieshen, Little Bittern nest.


Paul Tout said...

Interesting as usual. I often wonder how often these aliens positively contribute to the spread of formerly-rare species by bumping up the biomass available for food and wondered aloud with LGRE whether the spread of various crayfish was contributing to the spread of BN Grebe in the UK. Here in NE Italy the big invader is Red Swamp Crayfish (Procambarus clarkii)at massive densities. We also have Mosquitofish (Gambusia holbrookei ... sounds like it should have come from a specimen collected at Bowyers, eh?) which is a massively-prolific livebearer from N. America but Sunbleak was a new one on me.

On a separate note, talking about monitoring these reedbed nesting bitterns. Have you considered using a helicopter drone to locate nests or for census work? I saw one being used by Italians for training flights on an area of open grassland in Slovenia (too much bureaucracy needed in Italy) and was frankly amazed at how quiet it was and the superb quality of the (georeferenced) pictures obtained. I'm sure they've come a long way since this film was made:

Grumpy Ecologist said...

Thanks Paul.Yes, ironic that the Red Swamp Crayfish has become a major food source for ibis, bittern, herons etc whilst causing real harm to the aquatic envoronment.

We have tried using hextacopters with thermal imaging cameras to detect Bittern nests in the reeds. You can detect things in the reeds but is it a goose or a bittern? Also used for obtaining some superb aerial shots as you say.