Willow flowers (or Vegetable Goslings)

Willows (Salix genus) are one of the earliest flowering tree species in the UK and are a fantastic nectar source for early pollinators such as bumblebees and butterflies. These trees are dioecious which means that there are separate male and female trees which can be distinguished by their flowers. Another more commonly known example of a dioecious tree would be the holly – only the female trees bear the red berries. One of the traditional names for willow flowers was ‘vegetable goslings’ which seems a perfect description to me!

Male willow flowers
Male willow flowers – the bright yellow pollen is on the end of the stamens and this brushes onto the pollinators when the come to drink from the nectar.

The flowers are quite unusual when compared with a simple flower such as a buttercup which follows the classic textbook diagram. Willow flowers are catkins – these are spikes of numerous tiny flowers rather than each catkin representing a single flower. Each of the yellow-tipped spikes in the male flower is one of the stamens and there are generally two or more of these to each individual flower within the catkin – the number varies with species. The same is true, although less easily illustrated, for the female flowers which have two or more stigmas per flower.

Female willow flowers
Female willow flowers – these are much less showy and do not have the yellow pollen of the male flowers. They also provide nectar to attract pollinators with the hope that the previous flower visited will be a male willow of the same species and thus the pollen will be transferred and the female flower fertilised.

The male and female flowers appear at the same time in order that the pollen from the male flowers is able to fertilise the female flowers. The flowers are quite different from one another in appearance and, side by side, it would be easy to assume that a male and a female willow tree were two different species.

Development of male willow flowers
Development of male willow flowers. On the left you can see the red outer scale to the bud which breaks and the catkin emerges from beneath. The first flowers on the catkin begin to open – the red tipped stamens can be seen. The yellow pollen then begins to be produced and finally the bumblebee comes to drink from the nectar and incidentally collect the pollen whilst doing so. This is an early bumblebee (Bombus pratorum) and the willow species is Salix x laestadiana which is a hybrid of goat willow and downy willow.

The willow flowers are an excellent source of nectar for early pollinating species, such as queen bumblebees which have emerged from hibernation and are establishing nests, or the early Nymphalidae butterflies which hibernate through the winter.

Small tortoiseshell butterfly on female willow flower
Small tortoiseshell (Aglaise urticae) butterfly on female willow flower. Note the presence of the nectar source in the centre of the catkin whilst the yellow-tipped stigma is higher. The stigma is where the pollen must reach in order to fertilise the female flower and this design encourages successful pollination which is an incidental rather than intentional act on the part of the pollinator which is only interested in a free feed!
Unidentified solitary wasp on female willow flower
Unidentified solitary wasp on female willow flower – any ID tips would be most welcome! This demonstrates the effectiveness of the design of the female flower – see how the wasp must bend low into the flower to reach the nectar source, so bringing its body (which will hopefully be dusted with pollen from a male flower) into contact with the female stigma.

Bats hang in the belfry… right?

We were carrying out a building inspection earlier this week, looking into nooks and crannies to see if we could find bats, or evidence of their presence. To reach these features safely, a cherry-picker was hired to lift us into place. The operator was very friendly and interested in what we were doing. When I asked him to take me up to a crevice above a window, he said;

‘You’ll never get a bat in there’

‘You will…’

‘No way… how small are they? I thought they hung up in the rafters?’

The ‘hanging bat’ stereotype is very widespread but really not true of many of bat species in this country. The two horseshoe species will always be found hanging upside-down in the classic pose and some other species will also hang upside down, including the brown long-eared and some of the myotis species. However a number of UK species, including the common pipistrelle – the species you are most likely to see flying in gardens – prefer to roost in crevices where they wedge themselves in quite tightly. Other species falling into the ‘crevice dwelling’ category include the other two pipistrelle species – soprano and Nathusius – the Daubenton’s bat, the larger noctule, serotine and Leisler’s bats, and the rarer woodland dwelling barbastelle bat.

The common pipistrelle bat is often found roosting in crevice-type features in houses, such as beneath lifted hanging tiles or roof tiles, in gaps around windows, in gaps in brickwork or underneath lifted flashing. The gaps they can squeeze into are really very small – 2cm is quite enough for them to get inside.

Last week I was lucky enough to spend a few days climbing trees and inspecting potential roosting features up in Cumbria where we found a common pipistrelle bat roosting in a hollow in a tree limb over a stream. The video quality isn’t fantastic because it is filmed using an endoscope – this invaluable piece of kit is a camera and light mounted on a long flexible ‘snake’ attached to a hand-held screen which you can feed carefully into potential roosting features and look for the bats in places you could never otherwise inspect. Although the quality isn’t great, I think this clip gives a nice insight into the kind of places these bats will choose to roost.

For many more video clips of bats roosting in trees, I would recommend you to check out the Bat Tree Habitat Key page on Facebook.

Ash dieback disease – do you know what to look for?

I noticed that the buds of the hawthorn at the back of my garden are starting to break – always an early starter but a good omen of spring just around the corner. With the return of the leaves to the trees, now is a good time to familiarise yourself with the symptoms of ash dieback ready for the spring as it could well be that 2013 is the year that this disease is really going to take hold in the UK. With so many trees in so many locations across the country, the best chance for monitoring the spread is for people who walk, work and live in the countryside to be vigilant. There are a number of locations in East Anglia where the disease is confirmed which makes the risk of cases around Grantham a real possibility.

Ash is a widespread species in the UK – as an ecological surveyor I have been to many sites in the east midlands and beyond and it is very rare that any broad leaf woodland doesn’t have a component of ash – it is the third most common UK tree species.

Ash is the first species I learnt to ID in the winter as it really is so distinctive, the buds are jet black and triangular in shape. The bark is smooth and ash (!) gray in colour. The leaves are pinnate – that is the leaflets come off a central stem in pairs.

Ash whips within grassland - note the black buds!
Ash whips within grassland – note the black buds!

You come across large impressive old trees within hedgerows and older woodlands, they also have a strong presence within secondary woodlands where they can be the dominant tree – there are some good examples of this type of woodland just down the road in Oakham. You can also come across them invading fields in the first wave of succession from grassland to woodland, here they grow as single stems, “whips”, a very appropriate name if one snaps back and cracks you across the leg! It is therefore quite diverse tree – they can be a constituent of a climax community, they grow quickly enough to gain dominance within a woodland after only 50 years or so, but they can also be the first woody species to stake its claim on a woodland-to-be.

Ash trees are prevalent in and around Grantham, older specimens can be found in Belton House and around the town close to the river, whilst newer specimens form part of the planting at the Woodland Trust’s Londonthorpe Woods.

Chalara fraxinea (the second part of the latin relating to the ash genus – Fraxinus) is the fungus which causes ash dieback. It is thought to have come from nursery stock brought across from the Netherlands, a location which instantly brings to mind the Dutch elm disease which decimated the English elm in the middle of the last century. It spreads by spores which are tiny airborne particles which means that it is easily spread by the wind within a certain radius, up to around 10 miles. Over longer distances, it is thought that the movement of diseased material such as nursery trees is likely to be the main cause which is why import and movement was banned in the UK at the end of October in 2012.

The disease can be detected even now, in the winter and spring, but becomes more obvious when the trees come out of dormancy and the leaves are in evidence. The Forestry Commission has a very thorough guide on how to recognise which I would urge everybody to read so that you know the symptoms. There are other diseases, pathogens, fungi and environmental impacts which can cause an ash tree to be in poor condition – this guide should help you to spot the distinctive signs of this particular disease.

Ash trees within a hedgerow

The Dutch Elm epidemic in the 1970’s did not kill every elm tree and a small number still stand around the country – only a tiny fraction. It is assumed that these trees have immunity to the disease and, on this basis, The Conservation Foundation has begun a project of collecting cuttings from these trees, propagating them and distributing them to schools and other locations all around the country. This was begun in 2009 so it is too soon yet to know whether this is to be a success but, because the cutting method ensures that the derived seedlings are clones of the original tree, there is every reason to think it will be and hopefully, one day, English elm will be a common sight in our countryside once more.

Based on the existence of some similarly disease resistant trees in Denmark, there is a NERC funded project currently under way to sequence the ash genome and try to identify the genetic basis for immunity. This would put us in a position where the lost ash trees (and it is almost inevitable that at least a proportion will be lost) can be replaced with disease resistant trees. The strong hope is that these resistant trees will be identified in the UK so that any replacement planting programme will not require stock from abroad but will remain of British origin.

What can you do to help?

  1. Familiarise yourself with the symptoms of ash dieback here or watch the Forestry Commission produced video so that you know what to look for when out and about;
  2. Report any findings, or suspicions of chalara to the Forestry Commission using their Tree Alert form here – they will want to know the exact location of the tree, the symptoms noted and any other information which will help them to find it. Photographs are also very useful and there is a chance to upload these;
  3. Install the Tree Alert app on your phone to issue reports when you’re out and about – link here for android or iOS
The brown hairstreak is a butterfly which uses ash trees as 'master trees' where the males and females gather to mate before the females descend down lower to lay their eggs on the larval foodplant, blackthorn. They are one of the species which might be impacted if chalara has a serious detrimental impact on the UK ash population.
The brown hairstreak is a butterfly which uses ash trees as ‘master trees’ where the males and females gather to mate before the females descend down lower to lay their eggs on the larval foodplant, blackthorn. They are one of the species which might be impacted if chalara has a serious detrimental impact on the UK ash population.

What do you need to climb-and-inspect trees for bats?

I have put this post together as a brief guide for anybody wanting to know more about what is required to climb and inspect trees for bats. When I was looking into the requirements, I couldn’t find anything which simply set out the steps so I hope this will be useful!

Climber in an oak treeTrees can be difficult to assess for bat roosts. Sometimes you can spot a feature – a woodpecker hole, split or fissure for example – which you can identify with reasonable confidence as a bat roost, perhaps by signs such as scratch marks, fur rubbing or droppings. But, in my experience, these types of features are the exception. You are much more likely to spot, what Henry Andrews would call, PRF’s or Potential Roost Features – see his website here for perhaps the best resource I’ve come across dealing with the use of tree roosts by bats.

You might want to be have more confidence in your assessment for a range of reasons; perhaps as a local bat group simply gathering data on local roosts, perhaps as part of research into bat distribution or movement, perhaps to protect the bats for example if the tree is dangerous and must be removed.

There are two approaches that can then be taken. Firstly, you could carry out a dusk/dawn emergence survey to watch for bats leaving or returning to a roost. This is quite labour intensive and has a number of limitations, such as the difficulty in being confident that a bat appeared from a particular location and the transient use of many roosts providing little confidence in a negative result. A second option is to inspect the feature closer up, using an endoscope perhaps to look within and see whether there are any bats residing within and whether the feature is actually as suitable as it may appear from the ground.

In order to carry out this “climb and inspect”, you will need two things:

Firstly, a licence to disturb bats with a handling endorsement. This is because bats are legally protected under both domestic and European legislation and it is an offence to intentionally or recklessly disturb them in their place of rest. See the BCT website for more info. This licence requires a large amount of specialist knowledge and experience of bats and their roosts. If you are interested in gaining the experience and, ultimately the licence, getting in touch with your local bat group is the best place to start. If you are already working in a professional capacity, I can highly recommend the Bat Licence Training Course run by Richard Crompton and Sandie Sowler.

Secondly, you need the competence and equipment to safely ascend to the feature. The basic qualification for this is the City and Guilds CS38 – Tree Climbing and Aerial Rescue Operations course. This not only teaches you the basics of climbing but also how to rescue somebody from a tree – if an accident does occur, it is critical that you know how to safely bring somebody down to the ground where they can be treated. This is usually a week long course which takes you through the principals, the theory, the legislation and the best practise for tree climbing before teaching you the practical techniques of climbing. At the end of the week, there is usually a separate assessment taking several hours where your competence will be assessed. As well as the climbing technique and principal, there is a requirement to identify a range of common tree species so this is something to brush up on beforehand. Another hint – you will probably not need to spike up trees for climb-and-inspect work, this is damaging to the trees and is only to be done if you are an arborist who is going to take the tree in question down (or in an emergence rescue situation).

Once you are qualified to climb, there are a few more things you will need before you can start:

1) The climbing equipment. The basic kit consists of a harness with leg-loops, rope, prussock cords, caribinas and a secondary support strop. These must all conform to the minimum legal requirements.
2) The safety equipment – this includes a helmet with a chin-strap, a knife with a retractable blade, a first aid kit and sturdy (steel toe) boots. High visibility jackets are also useful, especially for a groundsman. See point 3…
3) A groundsman! If something happens in the tree, you must have somebody with you who is qualified to climb and perform an aerial rescue. This might be required is for example there is a problem with your equipment meaning you can’t descend upon it, or if you were to hit your head and become unconscious. You should only ever climb if you have this second qualified climber on the ground the entire time that you are in the tree.
4) The kit to inspect the feature – an endoscope is either an eyepiece or, commonly now, a screen attached to a fibre-optic snake which allows you to see around corners and in deep, dark cavities of trees where bats might be hiding. This has the potential to cause disturbance to bats which is why the relevent licence and experience are critical. Other pieces of kit which might be useful include binoculars, a torch and a mirror!

If you were climbing for your own pleasure on your own land, this may be all that you require. However, if this is being undertaken in any kind of professional capacity, you would also need the appropriate insurance in terms both of personal safety and public liability.

For more information on the assessment and CS38 qualification, you can see the assessment criteria provided by NPTC here.

I work for a local Ecological Consultancy based in Grantham and we do offer professional climb and inspect services in the East Midlands area and beyond – if you would like more info then drop me a message and I will get in touch with you!

Potential Roost Feature (PRF) worthy of closer inspection!
Potential Roost Feature (PRF) worthy of closer inspection!