Worcestershire butterfly transects

John Tilt

The Butterfly Transect is our way of measuring butterfly populations either on a site basis or within an area. The Transect involves walking a predetermined route within the site over a period of 26 weeks each year. The route can be divided into sections dependant on habitat types (up to 15 different sections can be used). When the route is walked the recorder counts all the butterflies seen within a 5m or 10m distance, taking care not to count a butterfly twice. The Species - Number and Section are recorded. The weather on each visit is also recorded.

At the end of the walk the counts are entered into free software - Transect Walker 2.5 and at the end of the season the data are packaged and sent to the UK Butterfly Recording Scheme via the Transect Coordinator. The data are analysed and an annual report is compiled showing species trends.

The data from Worcestershire Transects have been extracted and analysed.

Worcestershire has 21 transects. These tend to be on nature reserves and on areas where some of the rarer butterflies are found. So these results do not reflect what is happening in the wider countryside. There is a separate recording scheme for doing this.

In 2010, 32000 butterflies were recorded 63 people and over 1000 man-hours were involved.

The Analysis.

First, the transect results are adjusted for missed weeks (holidays or bad weather etc). Where transects are walked on consecutive years trends can be calculated by pairing the counts from consecutive years.

Table 1 shows the trends for Worcestershire over the last 5 years for the commoner butterflies. Starting at 2006 showing +/-% for 2007 to 2010.

The figures show that in 2007, 26 of the 33 commoner species were declining compared with 2006. Nationally 2007 was the second lowest year in the 31 years since the scheme was started. This was put down largely to weather conditions - cold wet spring etc.

2008 and 2009 showed a considerable recovery of most species and 2010 consolidated that recovery.

Looking at individual species.

Brown Argus shows a considerable increase, particularly in 2010. The species is double brooded and has a fairly small first brood, when the second brood emerges the adults scatter widely into all sorts of habitats a number of sites only have a second brood.

Exactly the same pattern is shown for Common Blue with very high numbers in 2010, particularly for the second brood.

The migration explosion of Painted Lady is clearly shown in 2009

Small Tortoiseshells are showing a recovery after a few poor years due to the well documented parasite Sturmia bella.

Table 2 shows the butterfly numbers on 12 of Worcestershire sites which have been walked consistently over the last 5 years. After adjusting for missed weeks this enables us to calculate and index for the commoner butterflies. 2006 is shown as an index of 100 and the succeeding year calculated in relation to this.

Showing clearly the decline in 2007 (index of 82) in recovering to 121 in 2010.

This shows again significant increases for Brown Argus and common Blue.

The steadily improving species are highlighted in blue and species not doing so well are highlighted in red.

By far our commonest butterfly on our 12 sites was Meadow Brown but in 2010 only Ringlet showed to be more common.

Regional Action Span Species

Grizzled Skipper – Still present on Honebourne Railway line, Throckmorton Landfill site, Hipton Hill, Wyre Forest.

Dingy Skipper – Two Sites on the west side of the Malverns – Pennyhill Bank.

Pearl-bordered Fritillary – Doing quite well in Wyre and will be introduced to Grafton Wood this spring.

Small Pearl-bordered – Improved counts in Wyre

White Admiral – Showing a decline on the 12 sites and also a nationally.

Silver-washed Fritillary – Showing improvements in Worcestershire (Best year ever in Grafton Wood)

Dark Green Fritillary – Only very small numbers on west side of Malvern Hill.

High Brown Fritillary – Now lost to Worcestershire none seen on Malvern in 2010.

Wood White – Lost now in Worcestershire but small numbers found in Wyre and doing well over the border in Hereford but nationally a significant decline.

White Letter Hairstreak – Small colonies are being found around the county, for example in Trench Wood and at Brotheridge Green reserve.

Brown Hairstreak – Numbers stable – a good egg-count in 2010.

Grayling – Small colony is stable around North Hill Malvern

If any of the above species are recorded in Worcestershire please send the records to myself at john.tilt2@btopenworld.com.

Paired Counts 2006 -2010

.	% increase/Decrease
Species	2007	2008	2009	2010
Brimstone	-2	-37	94	13
Brown Argus	-88	138	49	516
Brown Hairstreak	-83	60	108	7
Comma	-45	-9	249	-21
Common Blue	-87	114	111	463
Dark Green Fritillary	-74	296	-36	-94
Essex Skipper	-31	261	51	-37
Gatekeeper	-42	85	9	-12
Green Hairstreak	2	122	-9	-65
Green-veined White	81	16	190	-20
Holly Blue	117	-5	-58	154
Large Skipper	7	-28	124	71
Large White	-2	17	250	-56
Marbled White	-30	-31	44	-29
Meadow Brown	-2	62	-14	-37
Orange-tip	26	-36	184	20
Painted Lady	-90	-93	90248	-97
Peacock	169	-62	78	38
Pearl-bordered Fritillary	765	-94	200	33
Purple Hairstreak	-81	117	27	112
Red Admiral	-6	-48	90	-29
Ringlet	-25	32	87	25
Silver-washed Fritillary	-4	21	70	50
Small Copper	-61	16	26	69
Small Heath	-42	-31	2	161
Small Pearl-bordered Fritillary	-24	-85	250	1129
Small Skipper	-80	45	290	-16
Small Tortoiseshell	-30	-31	127	120
Small White	-25	18	207	-19
Small/Essex Skipper	-12	27	29	-48
Speckled Wood	-27	69	84	-18
White Admiral	-50	3	19	69
White-letter Hairstreak	-100		0	850

Increases	7	19	28	18
Decreases	26	13	4	15

Table 1. Paired counts 2006-2010.

In Worcestershire we have 12 sites which have been walked for the last five years, this gives us a good indication of population changes over that period. Table 2 shows this. An index has been calculated using 100 for 2006 then the relative index for subsequent years for each species.

The 12 Sites are: Blackminster, Castlemorton Common, Chaddesely Woods Chase End Malvern, Grafton Wood, Knapp and Papermill, Monkwood, St Wulstans Reserve (Malvern), West Malvern, Windmill Hill, Wyre Forest East, Wyre Forest West.

The species highlighted in red show declines and those in blue increases. It must be appreciated that this is a very small sample. However in is clear to see that there has been a recovery after the seriously poor year of 2007.

Good news that the Small Tortoiseshell is recovering after the well documented parasite problems. In general table 2 shows a fairly optimistic situation. A lot the sites in this sample have had some management work for butterflies e.g. The Malverns, Grafton Wood, Monkwood and Knapp and Papermill.

Worcestershire Wildlife Trust has now recognised the importance of monitoring the effects of their management and has set up Transect on 12 of their reserves. The data are fed back to the reserve management to help plan habitat work.

The results of nationwide transects can be viewed on the UK butterfly monitoring site http://www.ukbms.org/ where data from all transects can be viewed together with the annual report.

Anyone interested in helping with a transect should contact John Tilt at john.tilt2@btopenworld.com.

Table 2

Sum of Value						Index 2006=100
	2006	2007	2008	2009	2010	2006	2007	2008	2009	2010
Brimstone	465	443	278	412	491	100	95	60	89	106
Brown Argus	40	5	11	14	78	100	12	28	34	194
Brown Hairstreak	10	2	3	5	6	100	17	27	56	59
Clouded Yellow	20					100	0	0	0	0
Comma	372	193	170	422	348	100	52	46	113	94
Common Blue	533	71	145	276	1309	100	13	27	52	246
Dark Green Fritillary	26	7	18	14		100	26	70	53	0
Dingy Skipper	1	7			3	100	700	0	0	300
Essex Skipper	13	9	33	36	29	100	69	250	277	221
Gatekeeper	2089	1153	1836	1778	1636	100	55	88	85	78
Grayling	1				1	100	0	0	0	100
Green Hairstreak	10	10	13	20	7	100	102	129	205	72
Green-veined White	559	887	990	2565	1918	100	159	177	459	343
Holly Blue	35	58	48	24	33	100	167	138	69	94
Large Skipper	190	202	136	228	436	100	106	72	120	229
Large White	452	417	477	1228	425	100	92	106	272	94
Marbled White	716	472	305	299	247	100	66	43	42	35
Meadow Brown	3908	3567	5505	3967	2537	100	91	141	102	65
Orange-tip	209	251	159	420	491	100	120	76	201	235
Painted Lady	138	14	1	705	19	100	10	1	511	14
Peacock	463	1237	466	583	941	100	267	101	126	203
Pearl-bordered Fritillary	31	268	17	51	68	100	865	55	164	218
Purple Hairstreak	27	5	11	12	19	100	19	41	45	70
Red Admiral	165	146	78	82	59	100	88	47	50	36
Ringlet	2333	1647	2133	2961	4180	100	71	91	127	179
Silver-washed Fritillary	201	193	234	381	530	100	96	116	189	264
	2006	2007	2008	2009	2010	2006	2007	2008	2009	2010
Small Copper	225	86	86	94	187	100	38	38	42	83
Small Heath	84	49	18	30	89	100	58	22	36	106
Small Pearl-bordered Fritillary	17	13	2	7	86	100	76	12	41	506
Small Skipper	237	48	68	214	225	100	20	29	90	95
Small Tortoiseshell	64	44	29	51	134	100	68	45	79	208
Small White	597	440	502	829	926	100	74	84	139	155
Small/Essex Skipper	316	278	315	433	199	100	88	100	137	63
Speckled Wood	1010	620	1025	1521	1299	100	61	101	151	129
White Admiral	207	104	107	109	166	100	50	52	52	80
White-letter Hairstreak	3		2	1	17	100	0	67	33	567
Wood White	16	4	5		1	100	23	34	0	6
Grand Total	15783	12948	15227	19770	19140	100	82	96	125	121

Worcestershire butterfly transects

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