Common Blues Emerge

A stroll around the Brickworks this morning in warm, sunny, calm conditions. The Common Blue butterflies are now emerging in abundance.

Singing birds of note:

12+ Whitethroats
2 Willow Warblers
7+ Chiffchaff
6+ Blackcaps
3 Song Thrushes

Butterflies of note:

45+ Common Blue
3 Dingy Skipper
2 Speckled Wood
1 Orange-tip (male)
2 Green-veined White
6 Large White
5 Small White
1 Small Tortoiseshell
I couldn’t find any Brown Argus but didn't spend too long looking/waiting in their favoured area.

Brown Argus Foodplant & Emergence

A quick update on the Brown Argus (Aricia agestis) colony at the Brickworks. It’s located on the rough ground east of Baker’s Wood (the area surrounding the grid reference TL00790260).

Brown Argus (Aricia agestis), Bovingdon Brickworks, 21/05/2015

We've identified the presence of Cut-leaved Crane's-bill (Geranium dissectum) growing in shallow, nutrient poor soil on the top of the concrete slabs which now act as a pathway. This is the likely larval foodplant and is exactly the area the Brown Arguses were favouring last August. Being dependant on a low-growing, annual plant (rather than its typical perennial, Common Rock-rose (Heliantbemum chamaecistus), which grows on chalk and limestone soils) puts the colony in rather a precarious position. This is very well explained in the short article by Roger Kemp, HERE.

Brown Argus colony location

Cut-leaved Crane's-bill (Geranium dissectum), Bovingdon Brickworks, 13/05/2015

Cut-leaved Crane's-bill (Geranium dissectum), Bovingdon Brickworks, 13/05/2015

Having spotted the first fresh adult on 10/05/2015, I was very pleased to find 7+ Brown Argus enjoying the warm, sunny conditions this morning in the same area.

Brown Argus (Aricia agestis), Bovingdon Brickworks, 20/05/2015

Other butterflies and moths of note: Orange tip (2m, 1f), Large White (m & f), Small White, Green-veined White, Small Tortoiseshell (3), Peacock (2), Dingy Skipper (3), Common Blue (2m), Burnet Companion moth (1), Silver-ground Carpet moth (2).

In other news... 

...another Box Moor Trust volunteer and experienced butterfly surveyor, counted at least 18 Dingy Skippers on site on 13/05/2015, along with the first record of a Green Hairstreak. Very encouraging indeed!

The Brown Argus are Back!

Brown Argus (Aricia agestis), Bovingdon Brickworks, 10 May 2015

The Brown Argus (Aricia agestis) are back at the Brickworks! Well, one is...and hopefully more will soon emerge. After coming across the colony of 14 at the very end of August last year, it’s encouraging to find that a fresh adult, first generation, is on site. I’ve yet to locate the larval food plants but my flora knowledge is very limited so hopefully someone more clued up will have success. The area in which the adults are seen flying is the rough ground surrounding grid reference TL00800262. The food plants to look out for are:

Common Rock-rose (Helianthemum nummularium), which is used almost exclusively on calcareous grasslands. In other habitats it uses annual foodplants, mainly Dove's-foot Crane's-bill (Geranium molle) and Common Stork'-bill (Erodium cicutarium). There are also recent reports of egg-laying on Cut-leaved Crane's-bill (G. dissectum), Meadow Crane's-bill (G. pratense), and Hedgerow Crane's-bill (G. pyrenaicum).

The Brown Argus butterfly doesn’t seem to be rare across Herts and Middlesex, according to last year’s transect survey results. It was recorded at 26 of the 62 surveyed sites. And, in terms of abundance, it was on a par with the Small Copper. However, its habit of occurring only in small, compact colonies, travelling no more than a couple of hundred metres, at most, from where it emerged, means that the species can be rare at a local level. Ultimately, a total of only 30-35 Brown Argus butterflies were seen at the 9 nearest monitored sites to the Bovingdon Brickworks last year (excluding Aldbury Nowers, a Brown Argus stronghold), so, it is very good news to see it again:

Location Tring Park, Tring Miswell Lane, Tring Lakeside Nature Reserve, Finchley Heartwood Forrest, St Albans Stocker’s Lake, Rickmansworth Sherrards Park Wood, Welwyn Garden City       Roughdown Common, Hemel Hempstead Shrubhill Common, Hemel Hempstead Harpenden Common, Harpenden

Quantity      15 (18)    0    0    9 (9)    0    0    1 (3)    5 (5)    0

(The numbers in brackets represent the total including estimates for weeks missed during the survey)

Dingy Skippers Emerge

Should your heart’s desire be a Dingy Skipper (Erynnis tages), you’ll be hard-pressed to find one in Hertfordshire, unless you visit one or two key sites. Although distributed throughout Britain and Ireland, colonies are often small and localised, and numbers generally have declined rapidly in recent years. In Hertfordshire, it’s as rare as the Green Hairstreaks (Callophrys rubi), according to the results of the 2014 transect survey. There are small populations at Aldbury Nowers (6 recorded in 2013; 12 recorded in 2014); Shrubhill Common (4 recorded in 2014) and Tring Park (1 recorded in 2014).

Last year, I noted 3 possibly 4 Dingy Skippers at Bovingdon Brickworks, which is pretty good going given the other county records. Adults emerge the first week of May so I optimistically visited the Brickworks at the end of last week. No luck. But, today, I was really chuffed to find 2, although keeping track of them and getting even one photograph proved tricky. Best effort below - hopefully there will be other opportunities in the coming weeks.

Dingy Skipper (Erynnis tages), Bovingdon Brickworks, 4 May 2015

There’s no sign yet of last year’s Brown Argus (Aricia agestis) colony. The only other butterflies I saw today were 3 Small White (Pieris rapae), 5 Peacock (Aglais io) and 1 Small Tortoiseshell (Aglais urticae). Not great going for warm conditions (15°C) with sunny spells.

I should also mentioned the Common Whitethroats are back on territory, singing away.