On Monday 26^th March 2018, a fine spring-like day, I took a group of students visiting Cambridge for the Student Conference on Conservation Science for a walk to Paradise local nature reserve. I chatted about the management of the area while we walked and enjoyed the world around us. We started at the Mill Pond, where I pointed out Hart’s-tongue Fern Asplenium scolopendrium growing on the damp stonework of the weir and then walked along the river towards Robinson Crusoe Island.

There we found the Purple Toothwort Lathraea clandestine, (right) a parasitic plant introduced from Europe about 1888. It was first recorded in the wild in 1908, here on Coe Fen in Cambridge.

There was also Colt’s-foot Tussilago farfara in flower, while by the banks of one of the streams crossing Coe Fen were yellow patches of both Lesser Celandine Ficaria verna and Garden Daffodil. We also noticed a bird in a nest box high in one of the trees and through binoculars, identified it as a Kestrel Falco tinnunculus.

Crossing Fen Causeway, we noted another parasitic plant, Mistletoe Viscum album. Then, as we walked south, we got good views of a Little Egret Egretta garzetta in the stream running parallel to the main river. By Sheep’s Green Bridge, there were two Swans Cygnus olor and several Mallards Anas platyrhynchos.

In Paradise, we found Butterbur Petasites hybridus (left) growing where it had been recorded over 400 years ago by the notable Cambridge botanist, John Ray. As we left Paradise, we noticed a strip of Few-flowered Leek Allium paradoxum spreading along the edge of the Lammas Land car park. This non-native garlic crops up quite a lot around Cambridge and seems to be somewhat invasive.

Walking back towards Fen Causeway, one of the group saw a small blunt-nosed mammal in the ditch which, from his description, could have been a Water Vole Arvicola terrestris. I didn’t see it, so cannot confirm the identification, but they have been seen in that area. We then headed back towards the Mill Pond, distracted on the way by several Long-tailed Tits Aegithalos caudatus and a Goldfinch Carduelis carduelis in some scrub near Laundress Green. Altogether, in about 2 ½ hours and a few kilometres we recorded 18 species of bird. The others were Blackbird, Black-headed Gull, Blue Tit, Canada Geese, Carrion Crow, Grey Heron, Magpie, Moorhen, Pheasant, Robin, Woodpigeon and a Wren.

Monica Frisch, 27^th March 2018

In the late 1980s I remember driving through Normandy and being impressed by the amount of Mistletoe (Viscum album) growing at the tops of roadside Poplars; there was nothing like it just across the Channel in England. The only Mistletoe I knew of then grew on back garden apple trees in Huntingdon Road and Coldham’s Lane – I suspect these Mistletoes had been deliberately established by gardeners. The clump in Coldham’s Lane was half the size of the small apple tree on which in grew.

A paper in Volume 51 of Nature in Cambridgeshire (Cadbury and Oswald, 2009) describes the explosive increase of Mistletoe in Cambridge. Most of their records come from west Cambridge – the University parklands, gardens and sports fields; I am sure the increase was just the same in the residential north and east of the City but less obvious. The authors speculate that two decades of milder winters enabled Mistletoe to establish itself so successfully.

Every time I travel along Madingley Road I am impressed by the number and size of Mistletoe clumps; lower down in the apple trees and hawthorn there is just as much Mistletoe. An apple tree in a Huntingdon Road garden is so infected with Mistletoe that the host has died. In Chesterton and Arbury it is well established in garden apple trees and boundary trees to recreation grounds.

A principal vector of Mistletoe is the Mistle Thrush (Turdus viscivorus). It’s an early nester and establishes territories from mid-winter, singing from the tops of trees. Its song is like a Blackbirds but less varied, loud and mournful! It feeds on winter berries and vigorously defends shrubs and bushes with berries within its territory, including Mistletoe, from other thrushes. I don’t know if the generic name for thrush means what it sounds like but Mistle Thrush droppings are very “viscivorous”! Mistletoe seeds are excreted by the thrushes with their sticky seed coating intact and stick to branches and stems. The seeds do not need any pre-germination treatment by passing through the thrushes’ gut. Mistle Thrushes probably account for most of the Mistletoe established in the tops of trees.

There is another bird which may be a more efficient Mistletoe vector. Blackcaps (Sylvia atricapilla) are “scrub” warblers nesting in low thickets and feeding in the woodland mid-storey. They are mostly summer visitors. Between 1981 and 2011 the number of Blackcaps overwintering in England, Scotland and Wales has increased by 57% (Balmer et al., 2013). Most of these overwintering birds are from central Europe and have migrated NW to the UK rather than SW to Iberia. (See Blackcaps blog). Milder winters and the easy availability of food from garden bird feeders are thought to be the reasons for this change in migration behaviour. Blackcaps do not excrete Mistletoe seeds but wipe them off their bills directly onto a tree branch with the seeds sticky seed coat, viscin, attaching the seed to the host plant. Blackcaps are therefore probably the reason for the explosive increase in Mistletoe in garden trees and shrubs.

Viscin was (and probably still is) used to make bird lime – the sticky paste that illegal trappers spread on stems and branches in southern Europe to catch migrating songbirds. The cruel irony is that their major target species is the Blackcap.

Bob Jarman

January 2017

Please let us know where you see Mistletoe growing in Cambridge. See our Mistletoe survey for more information.

As Christmas Day was quite mild and sunny, though rather windy, I went for a walk around my local patch. Although I live in suburban southern Cambridge, I am fortunate to have Cherry Hinton Brook near me. The Brook rises from springs at Giant’s Grave, near the crossroads at Cherry Hinton High Street, Cherry Hinton Road, Queen Edith’s Way and Fulbourn Road and runs roughly north-west, through the grounds of Cherry Hinton Hall to eventually reach the River Cam on Stourbridge Common about 4km from its source.

Near my house I found some of the usual street weeds still in flower: Chickweed, Shepherd’s Purse, Petty Spurge and Annual Mercury, while there were Daisies in some of the lawns. There was not much in flower along the Brook until I got to near St Bede’s Gardens where one or two of the Sweet Violets were already out. Also already in flower in the grounds of Cherry Hinton Hall was Butcher’s Broom which has inconspicuous greenish flowers which eventually produce bright red berries.

But instead of flowers there was birdlife. I got several good views of a Kingfisher, as it flew upstream, stopping from time to time to perch on an overhanging branch. Then I spotted a large white bird on the path: not a seagull but an elegant Little Egret. It flew off but did not disappear from sight for long and soon I noticed that there were two. Little Egrets have been expanding north-west from Europe for the last few decades and have been seen near Cherry Hinton Brook in winter since 2014. In the hedge there was a Robin and various Tits: one sounded as if it was saying “CwistmasTwee; CwistmasTwee”. I also saw a Moorhen or two on the Brook, Blackbirds, Wood Pigeons and Seagulls swirling over the lake in the grounds of Cherry Hinton Hall.

Not a bad tally for a short walk. I was only out for about an hour and mostly within one 1km square (TL4757) though Cherry Hinton Hall is a different one (TL4856) and I briefly passed through a third one.