Dotards of Ditchling

The Eurasian dotterel is a bird which doesn’t seem so far removed from its close relatives upon first glance, yet a sortie into its ecology soon proves this to be untrue. Its appearance, particularly in the winter months, resembles a golden plover, although the dotterel is classified in the same genus as the ringed plovers. However, unlike the ringed plovers – and practically every other European plover – dotterel are very rarely found near water. Dotterel will breed in the summer months at the very top of mountains and plateaux, which in the UK means upland Scotland and a select few sites in northern England. So how did I manage to photograph the bird below at Ditchling Beacon, in south coast Sussex?

Eurasian dotterel, Ditchling Beacon, photographed with my phone through my telescope.

Apart from its unusual habitat choices, another interesting aspect of this species’ behaviour is its migration habits. In spring, and occasionally in autumn, this species will migrate in parties known as ‘trips’, which can number about 20-30 individuals nowadays. In both seasons another peculiar feature of their migration is that they regularly stop over at traditional sites, which many decades ago would draw hunters from far and wide. These traditional sites seem to be clustered further north but there are a handful in southern counties, with Ditchling Beacon occasionally hosting the bird. The ‘trips’ won’t always stay true to their traditional sites, with the first group of dotterel to be recorded in Surrey for 128 years appearing near Banstead in 2012.

On passage, the group of 3 dotterel I was fortunate enough to see last week had swapped the mountaintops of the Scottish Highlands for the stubble fields of Ditchling Beacon, with the English Channel just visible in the distance to the right of the image.

The word ‘dotterel’ was used in the 1400s for someone simple-minded or a dotard as well as for the bird, and it is unsure which word stemmed from which. The dotterel is so-called due to the ease with which one can approach them, making them easy targets for hunters in addition to their predictable movements. As you can see from the photo above, I was not willing to approach the Ditchling birds too closely in case they were disturbed. Birds on migration have enough trials to overcome without the added pressures of humans and dogs disturbing birds when they could be feeding and putting on weight for the next leg of their journey.

An identification composite from Crossley.

Third in the list of unusual details of dotterel ecology is their plumage. The three Ditchling birds were all either juveniles or winter-plumaged, so more dull than one would expect to see them on their breeding grounds. However, as the ID composite above shows, dotterel are very attractive birds in the summer months. As you might anticipate, the two birds in the foreground are adults in breeding plumage, although the sex of each might surprise you. The duller bird on the left is the male, while the more strikingly-plumaged individual on the right is the female.

The dotterel is one of the very few bird species in which the roles of either sex could be considered reversed, with the male incubating the eggs and taking care of the chicks, and therefore requiring more camouflaged feathering. The females on the other hand are polyandrous, producing several clutches with different males each season. This is rare in birds, with only a tiny fraction of species exhibiting this behaviour, mostly shorebirds such as phalaropes and jacanas. Polygyny, the male equivalent, is much more frequent, occurring in 8% of bird species, such as birds-of-paradise and grouse, in comparison to the 0.4% of bird species which are polyandrous. Polygynandry is the rarest mating system, where both the males and females are promiscuous. There may be several reasons why these behaviours are practised, but in polyandrous species the clutch success rate is often lower. As a result, it is more beneficial for the female to have her progeny guarded by multiple males in the hope that at least one of them is a competent father.

As you can see, the dotterel is a fascinating bird, much more so than one would have assumed from my photo above. I hope that trips of dotterel will long be stopping off at their regular haunts for many migration cycles to come, and I hope that soon I’ll have the chance to see their unusual breeding behaviour first hand.

Apples on sticks

Yesterday the south-east group of the British Bryological Society visited the town of Wadhurst in the far east of Sussex, near Tunbridge Wells. A variety of habitats including streams, woodland, grassland and ditches led to an array of moss and liverwort species being recorded. All were new for the area as this was a place no bryologist had dared to tread before.

Highlights included my favourite liverwort, the large and fragrant Conocephalum conicum (Great Scented Liverwort), as well as non-bryophytes such as two new plant species for me – Orpine and Soft Shield Fern – and a new carabid in the form of Carabus monilis with its bronze lustre. However, apparently the best find of the day was one of mine. This was the apple-moss, Bartramia pomiformis.

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Bartramia pomiformis

This moss immediately struck me, growing on a sandy bank on the edge of a narrow lane. The patch was almost perfectly circular, a richer green than the surrounding winter vegetation. And it was easy to see how it got its name, from the rounded apple-like capsules.

These capsules, that many mosses have in some form or another, form the final stage in the life cycle of a moss. The capsules contain the spores. Like a fruit, the capsules darken with maturity, starting off green such as these but soon becoming dry and brown with age, at which point the spores will be released.

These spores, upon germination, will then grow into a protonema, which will develop into a sheet of felt-like rhizoids, from which the gametophore will arise. The gametophore will be the stage of a moss that many people will be familiar with. It is the typical plant-like form, with stems and leaves, resembling a flowering plant although without vascular structure. This means that mosses lack the transport systems that vascular plants use to transport water, nutrients and minerals to their cells through tubes such as the xylem and the phloem.

Mosses can be dioicous or monoicous. Dioicous mosses have the male and female reproductive organs on different individual gametophores, while monoicous mosses have both sex organs on the same plant. In both cases, the sperm from the male sex organ will be transported to the female sex organ by a drop of water, which is one reason why there is a higher density of moss species in wetter climates such as the Atlantic rainforests of western Scotland and Ireland.

Once fertilisation takes place, a sporophyte begins to emerge from the venter, where the embryo develops. Over a period of many months, a seta (stalk) will grow, on top of which a capsule will be produced. Eventually this will release spores, and the cycle will repeat itself.

When diving into the life cycles of many taxonomic groups, I am often amazed by the complexity behind what appear to be fairly simple organisms at a cursory glance.

Myrmecomorphy in action!

Sunday the 15th October was the date of the Amateur Entomologists’ Society field meeting at Rye Harbour Sussex Wildlife Trust reserve. It’s not often that I do a focused invertebrate hunt at this time of year, so I was looking forward to seeing what we found.

The field meeting was unexpectedly good on the arachnid side of things. I had no idea that the reserve was so rich in numbers and species of spider. We spent most of our time in a compartment of saltmarsh and shingle, where the shingle was really shallow. The layer of shingle was about two stones thick, and the soil beneath it was compact. This meant that the spiders could not escape deeper into the shingle as they would at most shingle sites.

One of the highlights of the field meeting spider-wise was the fantastic Myrmarachne formicaria. As the scientific name suggests, this species of spider is an ant-mimic (the prefix ‘myrm’ means ‘ant’ and a formicarium is an ant farm). The mimicry of ants in the animal kingdom is known as ‘myrmecomorphy’ and is quite common across a number of invertebrate orders. Invertebrates that are known to be ant mimics include young grasshoppers, true bugs (Hemiptera), flies, beetles and of course spiders.

But why do so many invertebrates mimic ants? Ants are known among the predators of invertebrates to be aggressive or distasteful, so they are avoided. And the predators will also avoid any insects that look like them, but lack any means of defence such as the young grasshoppers. This is known as Batesian mimicry, as it was first described by H W Bates. Some ant mimics have even gone as far as to mimic the ants chemically as well, by emitting ant-like pheromones, which is referred to as Wasmannian mimicry.

However, Myrmarachne formicaria may mimic ants for a different reason. It is thought that some spiders mimic ants not only for protection against predators but also so that they can hunt the ants themselves. Ants will overlook the spiders as one of their own colony, giving the spider the perfect opportunity for a meal. This type of mimicry is aggressive mimicry. As you can see from the photo below, the spider has a long abdomen, which helps it to resemble an ant.

Myrmarachne formicaria male by Evan Jones

Myrmarachne formicaria, photo by Evan Jones, one of the field meeting attendees.

Myrmarachne formicaria really was a fantastic sight, and I hadn’t personally seen anything like it before. It was fascinating to learn how and why so many different invertebrates mimic ants. The sheer number of ant mimics must indicate that ants are one of the most successful of all invertebrates.

There’s a fungus on the Town Hall Clock!

If you’ve read my latest post you would know that I am a regular participant of #wildflowerhour. During last week’s Wildflower Hour there were predictably more photos due to the increase in flowering plants as spring progresses. Among these flowering plants was the easy-to-overlook Moschatel (Adoxa moschatellina), which I had never recorded before.

So last week I set out with a picture of Moschatel in my mind so that if I did come across the species I would recognise it. Yesterday I visited Pulborough Brooks RSPB reserve in West Sussex and I did both of those things: I came across a couple of large patches and I recognised it!

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The flower head. You can see that it is cube-shaped, which is what lead to the alternative vernacular name of ‘Town Hall Clock’.

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The whole plant

As you can see from the above photographs, Moschatel is not a hard plant to miss. Its flower heads are only slightly lighter than the leaves and therefore not easy to spot when they are lined up against the foliage of a woodland floor. To be honest, I was quite pleased with myself for managing to spot this indistinctive plant!

However once I had a closer look, there was more to see. One particular patch was very heavily infected with what appeared to be the fungus Puccinia albescens, which covered the leaves, stem and flowers of several plants. This species is a rust fungus, which is a type of fungus that usually parasitises wildflowers and other small plants. There is an incredible diversity of host plants within the 7000 species of rust fungi as most plants are only infected by a single species.

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The close-up photograph above shows the pustules of the rust fungus, which is just one part of the complex life-cycle of rust fungi. These pustules erupt at this time of year and produce uredospores which are carried on the wind to new plants of the same species to infect.

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Telia

Also present alongside these pustules are what I believe to be the telia of the same species. These telia – the dark, round spots – are produced in the autumn in most species and would have overwintered. The telia produce teliospores, which are another method the fungus uses to spread as they disperse to find more plants of the same species to infect, just as the uredospores do.

The life-cycle of rust fungi is very complex and here I have explained it only briefly – different species of rust fungi can have different life-cycles and some infect two completely unrelated species during their life-cycle. These multi-host fungi are known as heteroecious fungi and one host plant is infected by the uredospores and the other is infected by teliospores. As Puccinia albescens is not heteroecious (and is autoecious), its life-cycle can be completed on just a single host species – Moschatel – and the single host species is infected by both the uredospores and the teliospores. Some good websites to visit for more information on the life-cycle of rust fungi are:

http://www.biologydiscussion.com/fungi/life-cycle-and-the-spore-stage-of-rust-fungi-fungi/64083

http://website.nbm-mnb.ca/mycologywebpages/NaturalHistoryOfFungi/Pucciniales.html – this one includes a lot of information, however it also contains a lot of scientific jargon and complicated vocabulary.

It’s Popping Hot

Some people find plants boring. However, they are very clever. How can a plant be clever? Through evolution, plants have developed many fascinating ways to survive and thrive.

The key to a plant’s success is largely in the seed dispersal technique. Without a way to disperse seeds, plants would not be able to colonise new suitable habitat and spread. Therefore plants have learnt to be ingenious in their methods of ensuring the future of generations to come.

Yesterday afternoon I was walking through my local farm when I heard a few pops coming from the vegetation beside the path. At first I thought they were the calls of a grasshopper or a cricket, but definitely not a species I had heard before. I stopped and waited to see if I could hear anymore. I did, and this time I thought they sounded like click beetles, but why would so many be clicking at the same time? I was puzzled by this strange sound until, accompanied by a pop, I saw a quick movement out of the corner of my eye. I looked closer to where the movement had come from but I couldn’t see anything that I thought could have made the sound, just a patch of vetch. Then I realised that the sound was coming from the vetch itself!

Vetches are plants related to peas, they have pods like peas although usually much smaller. The pods begin green, the same colour as the leaves, and then as they mature they turn darker until they are brown. Plants in the pea family often have pods that pop, which is advantageous to the plant as it is a great method of seed dispersal. This method ensures the seed is enough distance away from the parent plant to prevent overcrowding.

Before I witnessed the popping of the seed pods yesterday I had no idea how it actually worked. How did the pods pop? I have done a bit of research and what I found out was fascinating. On hot days like yesterday the seed pods dry out, aided by the dark colour of the mature pods in some species which absorb heat. During the drying process forces build up inside the pod until it reaches a point when the pod explodes. In most pods there are two lines of weakness running along the pod, and it is here where the tensions which are set up in the wall of the pod cause the pod to explode. Similar to when a pulled spring is let back, the two halves of the pod curl back at lightning speed which flicks the seeds out of the pod!

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These two pods are still green and have not dried enough to pop.

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Two seed pods which are ready to pop! They have dried in the hot weather and turned brown.

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Two freshly-popped seed pods, showing the two halves of the pod

 

Some interesting Blackbird behaviour

There has been some drama happening with our Blackbirds this year. Before exactly a month ago, we had a regular pair of Blackbirds that inhabited our garden and regularly visited the space under our feeders. We could tell this pair from the other Blackbirds as both were ringed earlier in the year. They had built a nest in the middle of March, which had 3 eggs in by the time I left on holiday to South Africa. When I returned the eggs should have been at the nestling stage, but the nest was empty.

On the 1st of May I noticed 4 male Blackbirds chasing each other around the garden pursued by a female. They disappeared out of view until a few hours later I spotted a male singing in the tallest Oak that I can see from my bedroom window, which leans over into our garden from our neighbour’s. It wasn’t ringed.

A few days later something I wasn’t expecting appeared below our feeders. A juvenile Blackbird. There was still no sign of the original pair, so this one must have been brought in by the currently dominant pair. But why only one? I think that as this is still quite early in the year, the parents might not have been able to find enough food for all 3 or 4 of their chicks, especially considering the strange weather we have been having. I will keep watching the Blackbirds to see if the ringed pair re-appear.

From what I have researched about Blackbird territories, I think that my garden must be quite a good habitat for them. The RSPB say that they are solitary birds, but “Small feeding and roosting aggregation sometimes form at good sites”. We have around six Blackbirds in our garden throughout the year and more in the winter when migrants from the mainland come in. There currently seem to be 3 pairs and therefore 3 territories in our garden, one in the front garden, one in the front half of our back garden and one at the back of our back garden. The size of these territories seems quite small for Blackbirds, so there must be good concentration of food. Inevitably, there have been squabbles from time to time.

I will continue to watch these Blackbirds. Who knows what interesting behaviour I could see next or will I locate the ringed pair?

 

 

 

 

Cell Rap!

My name is James

And I love all cells

There’re animal and plant cells

‘N’ I think they’re swell!

 

Both types have a nucleus

That stores the DNA

It also helps to make protein

And control its ev’ry way.

 

Chloroplasts are clever

And only plant cells have ‘em

They help in photosynthesis

And the plant’ll die without ‘em!

 

Starch grains are very useful

And unique to only plants

The membrane decides what’s in and out

And helps both animals ‘n’ plants

 

Cytoplasm is jelly-like

And the site of all reactions

Now let’s move on to more cell parts

My favourite plan of action!

 

All plant cells have a wall

To help keep the cell’s structure

It also seems to save the cell

From a devastating fracture

 

The vacuole is vital

‘Cos it helps to keep its shape

It also has a special sap

And resembles a tiny grape!