Monday, 15 July 2013

Unbelievable weather

We have just been through the warmest couple of weeks in recent years. This has brought out an incredible number of insects and has affected our wildlife in some very interesting ways.

The year was very late in getting started, with a long-term and very cold east wind that delayed spring by 4-6 weeks. As an example, queen bumblebees were seen hunting for nesting spots some 4 weeks later than usual. But by the middle of June I was seeing new queens and males, which is weeks earlier than usual. Bumblebee nests go through a fixed cycle. First, the queen can be seen gathering pollen which will be eaten by the larvae from her initial batch of eggs. These workers then emerge and can be seen foraging for pollen to take back for subsequent batches. The next stage is when the nest is mature, and new queens and males are created. These then emerge and start up new nests. Many nests this year have gone through those stages much more quickly than usual, and after a delayed start the nests are now actually ahead of the normal schedule. In the last two weeks I have seen fewer new queens and males, so it is clear that new nests have already been established. It seems as if the bumblebees were able to predict that we were going to experience a hot summer: so much so that they accelerated the production of males and new queens in order to produce two generations, rather than a single one. I checked my findings with the national database, and this phenomenon has been recorded throughout the country: it's not just local to me.

I accidentally discovered a new (to me) orchid site last week. Donegal International Airport is situated on a strip of land that extends out into the atlantic on our North West coast, and I had an opportunity to explore the sand dunes while waiting for a delayed flight. Coastal grassland behind dunes is often a good hunting ground for orchids and I quickly found Northern Marsh Orchid:

Northern Marsh Orchid
Pyramidal Orchid:

Pyramidal Orchid
And Fragrant Orchid:

Fragrant Orchid

These orchid species were present in their hundreds, with orchids as far as the eye could see, but what intrigued me particularly was the fact that the Northern Marsh Orchids were very 'pure': they all appeared to have no influence from other spotted orchids. This is in direct contrast to the specimens in my home location, where the Northern Marsh Orchids can have toothed lips or paler flowers. This led me to deduce that the more frequent Heath Spotted Orchid and Common Spotted Orchids were not in the close vicinity. Then I found the following specimen, which is clearly Northern Marsh Orchid in origin, but has three very well-developed lobes in the lower lip:

Hybrid Orchid
My first conclusion was that this was a hybrid between Northern Marsh and one of the other two orchids from the immediate vicinity, with Pyramidal being the most likely in terms of shape. Intergeneric hybrids are known (which tells me that the definition of genera in these orchids is wrong!), but the hybrid between Northern Marsh and Pyramidal orchids has not been documented (and I don't even know if it's possible).

Much discussion ensued (and is still ongoing), and one possible candidate that was suggested was Southern Marsh Orchid, which has strong similarities to the specimen shown. I checked the distribution map for Southern Marsh, and it is clearly a south-eastern species, and hasn't (yet!) been recorded from Ireland:

Distribution of Southern Marsh Orchid
I hunted around a bit more, and discovered that there is another orchid that I have never seen - Western Marsh Orchid. This has 3 lobes, red-purple flowers and has the correct (mainly western) distribution:

Distribution of Western Marsh Orchid
Western Marsh Orchid is known to hybridise with Northern Marsh Orchid, and the literature says that the hybrid has been discovered in Anglesey and Scotland, and 'probably exists in Ireland'. Once the various authorities have delivered their verdict, I'll update this page.

Late note: The specimen has now been identified as Dactylorhiza hebridensis, otherwise known as Dactylorhiza fuchsii subsp. hebridensis, the Hebridean Spotted Orchid.

As an aside, here's the distribution of another orchid that I have never knowingly seen:

Distribution of Narrow-leaved Marsh Orchid - Dactylorhiza traunsteineri
Compare that with the other distributions shown above, and it will be seen that this has no clear rationale behind the distribution: it goes from north to south and east to west. I cannot see anything that would govern distribution other than a bias towards coastal habitat. It seems to have a specific requirement which is scarcely found, but can be found anywhere. When I see a distribution map that looks like that I just know something is wrong. Maybe someone can enlighten me.

Coastal grassland is also home to some of the day-flying moths, with the Burnet family being very prominent. This is the 6-Spot Burnet from the same location:

6-spot Burnet Moth
The larvae and pupal cases from these can be found in vast numbers on the grasses near the coast. (The flower is Lady's Bedstraw, another coastal plant in this area)

4 comments:

The Weaver of Grass said...

We have plenty of Lady's Bedstraw Stuart but I have never seen a Burnet moth - beautiful wings.

stuart dunlop said...

Weaver: Burnet moths are usually associated with coastal grassland hereabouts, but I don't know where it can be found near you. Perhaps Gill has some information.

Caroline Gill said...

We saw many Burnets mating at Carlton Marshes near Lowestoft a week ago. The Skipper butterflies liked to share the same plants! I haven't posted the photos yet ... but I will.

Gill said...

We havw burnet moths on dryish flower-rich meadows/grassland.

We also have the narrow-leaved marsh orchid D. traunsteinioides as I believe it is now called - beautiful plant with noticeably narrow (say half an inch max width), usually heavily spotted leaves and elegant tall spikes of usually purple flowers, though I have seen a pure white one.

Dunno about the western marsh orchid (if that is D. majalis I've been reading that its status is up iin the air - well what Dacylorchid isn't?).