A 2023 Butterfly Survey of part of the RSPB Reserve at North Warren
The Route North Warren was one of the early RSPB reserves and is a remnant of the Suffolk Sandlings heathland. The route covered heathland, two separate areas of woodland and two boardwalks, the first adjacent to the large reedbed known as The Fen and the second leading into the second wood. The small RSPB sign along the road from Aldeburgh to Leiston is easily overlooked, being about a mile from the Aldeburgh roundabout. ‘Pinehurst’ is to the left and the short stretch of lane, leading to a small carpark, is on the right, between ‘Danelagh’ and ‘Snape Cottage’. From here the route passes under Buddleia, best viewed from the far side, under a belt of Silver Birches and onto heathland. The path continues to a dragonfly sculpture on the left but during the flowering of heather, mainly Ling and some Bell Heather, a short diversion was made to the right, as no flowering heather clumps were actually on the main path. From the dragonfly statue the path ahead soon becomes a boardwalk skirting The Fen, crossing the river Hundred, passing an elevated Viewpoint and progressing upward through a narrow path. At the top is a produce stall and a notice warning that sheep are ‘gazing’ (sic). Here the route is to the right, past ‘Pantiles’, then a green seat, followed by two installations by Karen Chard illustrating many of the reserve’s species. ‘The Pine Cottage’ is to the right, then a Buddleia bush just outside the garden gate and nearby a footpath sign leading into the first woodland. This is mainly
of English Oak, Holly and some impressive mature Silver Birches. A right turn at the end of the woodland takes the route through Church Farm, now appearing to be divided into four separate dwellings. A long field to the left can be viewed from the footpath then what can be a muddy section leads to a second boardwalk and bridge, with several steps missing. The second woodland consists mainly of tall English Oaks, many garlanded by Honeysuckle. At the end a short path through bracken joins the old railway walk permissive path at Crossing Cottage, with a nearby seat giving a commanding view over North Marsh. The total distance is less than two miles.
Eleven visits were made from 28 April to 23 September 2023. Frequency was increased during the months of most butterfly activity, with two in June, three in July and two in August. Notes were also made of other wildlife, and these are covered next.
Mammals
Rabbits and Grey Squirrels were frequent. Three sightings of Chinese Water Deer occurred. The first was disturbed from the boardwalk adjacent to The Fen and dashed off quickly into the reedbed. This was on 19 May and the second was on 15 June, at the far edge of the field opposite Church farm and quickly moving into the cover of nearby woodland. The third on 29 June was partially visible as it moved through the reedbed close to the elevated Viewpoint. Muntjac were heard often, with two sightings. The first was at the far side of the field opposite Church Farm and initially it moved quickly away along the field margin when a Fox suddenly appeared. Probably realising that the Fox wasn’t a threat it moved back towards its original position causing the Fox to move back into cover. This was on 19 May and on 29 June I encountered a Muntjac in a wide sunlit glade of the first wood. I immediately stood absolutely still, knowing I had woodland cover behind me. Obviously, it couldn’t pick up my scent as it moved slowly towards me, ending up about sixteen yards away before it ran off. Two observations were made of signs that could have been of Fallow or Red Deer. On 27 July slots larger than for Muntjac were seen emerging from the field opposite Church Farm and crossing over the footpath. In the first wood there was damage to thin saplings, known as fraying and part of both Fallow bucks and Red Deer stags when marking territory during the rutting season.
Reptiles
Surprisingly, no snakes were seen but lizards were observed on six visits, one at the end of the walk and the rest on sunlit areas of the boardwalk close to the elevated Viewpoint. The maximum number was fifteen on 27 July, varying in size from juveniles to adults, one showing signs of a new tail.
Dragonflies
The first sighting was of Azure Damselflies just past the elevated Viewpoint on 15 June. Common Darters, both male and female, were abundant on all visits from 15 June onwards. Just one Ruddy Darter was recorded on 4 September. Black-tailed Skimmers were seen on the first boardwalk on two dates, 20 and 27 July. A Migrant Hawker was observed at rest along the first lane on 23 September and Willow Emerald Damselflies were first seen on 17 August and then on subsequent visits, with a maximum of five at the start of the second wood on 23 September.
Birds
On most of the visits my binoculars were close range Papilio Pentax, ideal for close study of insects, but requiring considerable focus adjustment for distant birds. Consequently, some sightings were not identified. Those recognised either by call or sight included: Swallow, Swift, Water Rail, Cetti’s Warbler, Moorhen, Heron, Blue Tit, Great Tit, Pied Wagtail, Wren, Robin, Blackbird, Goldfinch, Linnet, Skylark, Stonechat, Chiffchaff, Chaffinch, Jackdaw, Carrion Crow, Jay, Magpie, Green Woodpecker, Great Spotted Woodpecker, Woodpigeon, Nightingale which was singing close to the car park on 19 May. The Hobby was seen singly and in a pair from the elevated Viewpoint and the seat at the end of the route. Records of both single and pairs also applied to Common Buzzards and Marsh Harriers, again from both the elevated Viewpoint and seat overlooking Noth Marsh. The two rarest records were of a Bittern booming from The Fen on 28 April and one seen flying low over the North Marsh reedbed on 19 May. The other rarity was a good, prolonged view of a Hen Harrier flying above the second woodland towards the North Marsh reedbed on 10 August.
Butterfly Nectar Sources
These are listed in seasonal order: Dandelion, Red Dead-nettle, Gorse, Stinging Nettle, Goat Willow, Bluebell, Holly, Hawthorn and Rowan blossom, Hawkweed, Bramble, Sow-thistle, Marsh thistle, Ragged Robin, Yellow Flag Iris, Ragwort, Bird’s-foot trefoil, Hemp-nettle, Yarrow, Buddleia, Himalayan Balsam, Purple Loosestrife, Ling and Bell heather, Hemp Agrimony and Ivy umbels.
The three Buddleias, the first by the car park, the second in ‘Pantiles’ garden, and the third at the start of the first wood, attracted 129 butterflies on six visits between 20 July and 23 September. This total was 22.7% of all the butterflies seen. Species using Buddleia were Brimstone, Large White, Small White, Red Admiral, Small Tortoiseshell, Peacock, Comma, Silver-washed Fritillary, Grayling, Gatekeeper and Meadow brown, representing approximately 55% of the species recorded. Two migratory moths, Silver -Y and Hummingbird Hawk moth were also observed nectaring on Buddleia. Ragwort and Bramble flowers were the other two most visited nectar sources with all but one Small Copper seen on Ragwort. Himalayan Balsam was visited by Peacock, Small
White and many bee species, especially on the 23 September. This alien invasive species was the dominant plant around the elevated viewpoint and has spread beyond the Hundred river into the adjacent reedbed.
Larval Food Plants
The first wood had an abundance of Holly with Ivy plentiful along the route. These are the two larval food plants needed by the Holly Blue. Beds of Stinging Nettles were also abundant, with the largest concentration near the Hundred river footbridge. This plant is used for ovipositing by Red Admiral, Small Tortoiseshell, Comma and Peacock. Two Commas were seen near Hops, growing along the first boardwalk and the original larval food plant for this species. Various grass species used for ovipositing by many summer flying butterflies were mainly in the heathland and areas between the woodlands. Gorse was abundant along the heathland path, being the larval food plant for the Green Hairstreak. Three small sections of Elm were located close to ‘Pantiles’ but no White-letter Hairstreaks were seen. Purple hairstreaks also use a specific tree as their larval food plant, the English Oak. Given its frequency, the sightings around just one tree were disappointing. However, no visits were made early or late in the day, when they are usually most active. Ragwort, abundant along the heathland path, is used for ovipositing by the Cinnabar moth. None were seen but a few plants contained their conspicuous caterpillars. Sorrel, one of the Small Copper’s larval food plants, was abundant on the heathland and Honeysuckle was seen on many parts of the route, especially in the second wood. This is used for ovipositing by the White Admiral.
Butterfly Species Recorded
The route was not walked as a transect as every butterfly seen and identified was included, irrespective of distance. A total of 542 butterflies represented 22 different species:
Small Skipper: just one on 20 July, nectaring on Ragwort.
Essex Skipper: as for Small Skipper.
Brimstone: two recorded on 10 August, on the first and third Buddleias, with the distance between suggesting two separate individuals.
Large White: 25 recorded, over seven visits with a maximum of ten on 10 August. It was seen on all the Buddleias.
Small White: 19 recorded, which was a surprisingly small number. This compared with a total of 207 between Shingle Street TM 3642 and East Lane Bawdsey, TM3540 on 30 August, suggesting an influx from the continent. Small White was seen nectaring on two of the Buddleias and Himalayan Balsam.
Green-veined White: just three recorded on two visits.
Orange Tip: only seen on 19 May, with a total of three. One of its main larval food plants, Hedge Mustard, was rare along the route.
Green Hairstreak: three were seen on Gorse during the 19 May visit.
Purple Hairstreak: Four were seen on two visits, 13 and 20 July. Both sightings were around the same sunlit tree in the middle of the first wood.
Small Copper: A total of 12 spanned four visits, almost all on or close to Ragwort.
Brown Argus: a tattered specimen was seen along the heathland path on 4 September.
Holly Blue: 18 were seen, spread over six visits. Most were seen between ‘Pantiles’ and the first wood.
Red Admiral: this species was included in the main BBC television news on 15 September, with Butterfly Conservation’s national Great Butterfly Count reporting an increase in Red Admiral sightings of 338%. This was reflected in the 115 seen with the highest day’s total being 37 on 10 August. It was seen nectaring on all three Buddleias, Bramble flowers, Hawthorn blossom and Hemp Agrimony.
Small Tortoiseshell: two sightings were of one individual, the first at the end of the route on 15 June and the second on the ‘Pantiles’ Buddleia on 23 September.
Peacock: 31 were recorded on six visits, with a maximum of nine on both 27 July and 10 August. It was feeding on all three Buddleias, Marsh Thistle and Himalayan Balsam.
Comma: 16 were seen on seven visits, feeding on Bramble flowers and all three Buddleias.
Silver-washed Fritillary: two were seen on 10 August, with the two Buddleias concerned far enough from each other to count as two different sightings.
Speckled Wood: just six sightings on four visits, surprisingly low given plenty of dappled shade, its preferred habitat.
Grayling: 26 were recorded with a maximum of 15 on 10 August. Most were seen along the heathland path plus it was recorded on all three Buddleias and ling.
Gatekeeper: A total of 262 spanned the last seven visits, with a maximum of 118 on 17 August. It was seen nectaring on ling and all three Buddleias. Most sightings were along the heathland path.
Meadow Brown: the total of just 16 was very low for a species usually common in summer. A late Meadow Brown was nectaring on the first Buddleia on 23 September.
Small Heath: just one seen on 23 September.
Summary
Butterflies expected, but not seen, were Large Skipper, Common Blue, Painted Lady, White Admiral and Ringlet. On reflection the short detour into heathland mentioned in the route details should have been made on every trip, not just when heather was flowering. This might have improved numbers of several species, especially Green Hairstreak, Small Copper, Grayling, Meadow Brown, Small Heath and Skippers. The complete lack of the Ringlet, which prefers damper habitats plentiful along the route, was puzzling but my own records from eight sites during its normal flight period produced Ringlets in just one location, at Wolves Wood TM 0543 and 0544. Perhaps this was not just a site-specific problem. Honeysuckle was plentiful along the route, with large clumps in the last wood seemingly ideal for ovipositing. This species was included in my book ‘The Wildlife Garden at Aldeburgh’, based on occasional records from the nearby ten-acre garden at Prior’s Oak. However, even though I spent more time in the second wood during the White Admiral’s normal flight period, none were seen.
Finally, all records from this study will be sent to the relevant County Recorder. Richard Stewart
‘Valezina’ 112, Westerfield Road Ipswich, IP4 2 XW