Saturday, 31 October 2015

Bird of the week - Little egret

The little egret (Egretta garzetta) is a small heron with white feathers, black legs and yellow feet.

It has a very different fishing technique from a grey heron as it runs about in the shallows in search of small fish.

This photo shows the size of a little egret relative to a black-headed gull.  The gull was intruding on the egret's personal space and was chased away.

Not so long ago this was a rare British bird.  It first arrived from France around 25 years ago and has been breeding here since 1996.  Its numbers have increased every year as it has spread north apart from a setback after the very cold winter of 2010/2011.  The data below are from the BTO Wetland Bird Survey (WeBS).

Little egrets are mainly found in the south and east of the country.  This map shows their breeding distribution in the latest Bird Atlas.

This map shows their winter distribution.

Judging from these data, I expect the little egret will soon be a regular breeding bird up here in the North East.  You can listen to the BBC Radio 4 Tweet of the Day on the little egret here.

Wednesday, 28 October 2015

Cup lichen

I have started a major restoration of my greenhouse.  It is 25 years old and made of western red cedar but is in poor repair in some parts and is in danger of falling down.  It has become home to several sorts of moss and lichen, including this cup lichen, which I think is a Cladonia species.

I can just about remember from A-level biology almost 50 years ago that a lichen is a symbiosis between a fungus and a green alga.  I read on the website British Lichens that there are around 1800 species in the UK - slightly more than the number of species of vascular plants.

The goblet-like structures are podetia which are growing out of the main body of the lichen - the thallus.  The podetia support the spore-producing apothecia involved in sexual reproduction.  The spores contain only the fungus part of the organism and when they germinate they have to relichenise by acquiring the right green alga.  While taking the pictures above I remembered photos of a similar lichen I saw on top of Mam Tor in Derbyshire in spring, showing its red spore-producing apothecia.

By the time I have finished the greenhouse it will look like new and the lichens and mosses will have to find somewhere else to live.

Monday, 26 October 2015

More intruders

It seems that I have only to leave a window or door open for a few minutes before someone comes in to look round. And nothing escapes without having its photograph taken.

This young goldfinch seemed quite attached to me and didn't seem to realise it could fly away.

By contrast, this great tit has a very sharp beak and knows how to use it.

Saturday, 24 October 2015

Bird of the week - Black-headed gull

The black-headed gull (Chroicocephalus ridibundus) is a handsome bird in summer and then lives up to its name. Chroicephalus is Greek for coloured head and ridibundus is sort of Latin for laughs a lot.  In fact the birds look a bit glum in these photos taken on the Farne Islands in June.

In winter it is a bit less distinguished, especially when plodding round in the mud.  It still doesn't look happy.

Black-headed gulls are common all year round up here in the North and breed in Gosforth Park.  It looks from the Bird Atlas as though they are less common in the west and south, particularly as breeding birds.

Read more about black-headed gulls here.  Listen to the BBC Radio 4 Tweet of the Day on black-headed gull here.

Thursday, 22 October 2015

Leaping salmon at Hexham weir

It is just over a year since I first saw the salmon jumping up Hexham weir on the River Tyne.  There has been very little rain in recent weeks so the river level has been very low and the fish have struggled to get upstream.  A release of water from Kielder Water over the past few days has raised the river a little so the fish are having a go, although it still isn't easy for them.

It is fun when two or three jump together.  It seems that they all have a go together and then things quieten down for a few minutes before they have another go.

The different colours of the fish are amazing.  Last year I posted this link to the Atlantic Salmon Trust showing the significance of the colours but it is worth doing so again.  I think some of the silver fish are probably sea trout but Phil will put me right.

Construction of a fish pass alongside the weir is nearing completion.  It will make life easier for the fish but may diminish the spectacle so if you are nearby be sure to see it while you can.   

Wednesday, 21 October 2015

Knopper gall

Many of the acorns on my English oak trees look very strange this year - having been deformed by gall formation, as shown in this photo taken a month ago.

These are knopper galls, caused by the knopper gall wasp (Andricus quercuscalicis).  It is a small solitary wasp which arrived in Devon from the Channel Islands more than 50 years ago and has gradually spread north.  I have noticed the gall in recent years but this year it looks as though almost every acorn is affected.

Andricus quercuscalicis has a very strange life cycle.  The first generation develops in spring in small conical galls on the male catkins of the Turkey oak (Quercus cerris) and a second parthenogenetic (all female) generation in the acorns of English oak (Quercus robur).  As I have several mature examples of both trees in my garden it is perhaps only to be expected that the knopper gall wasp would thrive here.

The gall develops in the summer after the wasp lays an egg in the developing acorn.  The gall mainly or completely replaces the normal acorn.  

I cut this gall in half last month to show the larva inside.

In the past week or two the galls have turned woody and brown and are beginning to fall off the trees.

I cut this one in half to show the eaten out core of the gall and the cocoon.

This one shows the grub inside the cocoon.

The female wasp emerges from the gall in the spring to start the cycle all over again by laying both male and female eggs in the Turkey oak.  You can watch a short video from David Attenborough's programme Life in the Undergrowth on knopper gall wasps here.

Monday, 19 October 2015

Another alien invader

It is a beautiful animal but it shouldn't be here.  This is the American mink (Neovison vison), an invasive non-native species. The UK population originated from escapes and deliberate releases from fur farms by pea-brained so-called "animal rights activists".  The number of mink may be declining as the otter population increases but mink are widespread in this country and are responsible for the destruction of much of our native fauna and the extinction of water voles in large parts of the countryside.

Although the original farmed animals were of all sorts of colours most have reverted to the wild type dark brown like this one.