Pear Wood Nature Reserve

Stanmore Country Park

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Pear Wood Nature Reserve


Rosemary Etheridge & Claire Abbott


Southern wood ants


smooth newt

grass snakes

Rosemary Etheridge gave an introduction to Pear Wood and spoke about the ants.  Claire Abbott then spoke about the amphibians and reptiles in Pear Wood.  This was followed by a brief presentation on Stanmore Country Park by the Warden, John Hollingdale.


Pear Wood is ancient woodland in the manor of Little Stanmore.  Its name does not relate to the fruit but derives from Sir William Parys, who owned the wood in the 13th century.  The name appears in various forms – Parys, Pares, Pare, Pear – in historical records.  In 1314, it was acquired by the canons of the Augustine priory of St Bartholomew the Great in Smithfield and this is the origin of the name of Canons Park.  After the dissolution of the monasteries, the priory lands, including Pear Wood passed into private ownership, prominent among whom was James Brydges, first Duke of Chandos.


Covering 36.1 acres (14.6 hectares) to the south of Wood Lane, Pear Wood is separated from the A5 by Brackley Hill Field to the east.  To the west is Wood Farm, where a development proposal for 10 houses right up against the wood has recently been permitted despite strong opposition from the Harrow Nature Conservation Forum.  To the south, the Scout Field and Guide Field separate the wood from Stanmore Country Park.  The fish pond (Pear Lake) is leased to the Royal British Legion.  In the middle of the wood is the ancient monument of Grimsdyke, which may be pre-Roman or early Saxon.  It has a big gap in it where material was removed by the Duke of Chandos to create an open vista to Canons Park.  There are also semi-detached cottages, which were abandoned in the late 20th century.



Pear Wood is mixed woodland with 40 different species of trees and shrubs.  The main species are beech, English oak, birch and sweet chestnut.  Other species include hazel coppice, wild cherry and wild service, the last two of which are ancient woodland indicators.  A most important feature of the wood is the amount of standing and fallen dead wood, which is covered in mosses, lichens and fungi with birds and bats in holes and beetles and other invertebrates.  A beetle survey is being carried out by Edward Milner and among those found is the lesser stag beetle, a fairly common species.



Hazel coppice

Lesser stag beetle

Southern wood ants


Southern wood ants


Southern wood ants (formica rafa) are the largest ants in the UK at up to 1cm long.  They are fierce predators and can bite and squirt formic acid up to 1m.  They keep on adding queens to the nest.  This is the last remaining site in Middlesex, though they occur widely in southern England.  They are believed to have been introduced by the Duke of Chandos as food for pheasants.  There is a nest on the pavement by the hospital entrance on Wood Lane and other large nests in the grounds of the hospital.


The favourable conditions arise from the Stanmore pebble gravel providing free drainage and warmer soil conditions and the large dead and dying trees, which are a good habitat for ants’ nests.  The nest comprises lots of twigs, pine needles and other debris.  The ants love honeydew from aphids and also feed on insects, including some as large as grasshoppers.



Nest on pavement by hospital entrance

 Farming aphids

Spring sunbathing















Wood ants are a near-threatened species in the Red Data Book.  In 1975, Philip Attewell found 20 nests but by 2004 there was only one left.  This is largely due to the tenants of Wood Farm using it as a landfill, destroying the nests in the extension of Pear Wood onto Wood Farm.  Colonies in the hospital grounds were also threatened by development plans. 




A successful new nest


A decision was therefore taken to re-introduce the ants into Pear Wood.  Advice from a document on translocation of wood ants produced by the German Office for the Protection of Ants was followed.  It is essential that some queens are obtained.  These are usually deep down underground laying eggs except in the spring when they come to the surface to sunbathe.  A suitable site for a nest must be located – warm, preferably south-facing in a clearing with trees around for foraging and some dead wood.  The ants were then collected in a sack, tipped on a suitable site and fed with mealworms and bread and honey every day for 3 weeks.  Success can only be judged after a year or so. 


Translocation has been going on at Pear Wood for about 7 years and there have been 6 successful new nests so far.  This year flying ants were found.


Pear Lake was established for the Duke of Chandos towards the end of the 18th century.  It has at least 4 species of freshwater fish, including large pike and carp.


Pear Lake



Toads are found only in the breeding season and are very abundant.  They outnumber frogs and newts because they taste horrible to fish, even the tadpoles.  Toad tadpoles are easily distinguished from the brownish/greenish tadpoles with pointed tails of frogs by being black with a round tail.  While frogs spawn in clumps, toads spawn in strings, which are attached to something.  Mating balls, with a group of toads up to football size can be seen and frogs also form mating balls.  The tadpoles hatch I about 2 weeks and the toadlets leave the water en masse in June/July.


Common toad


Toad tadpoles


Generally, toads have been declining for a number of years but not in Pear Wood.  The main reason is the danger crossing roads and loss of habitat but the effect of the former has been reduced by toad crossings being patrolled by volunteers.


English Heritage wanted the bracken on Grimsdyke controlled and a number of options were examined.  Cutting is labour-intensive, strimming is noisy and trampling, while effective in controlling bracken threatened toads sheltering in the bracken.  As a result, control is restricted to cutting and strimming for the time being.


Common frog

Common frog

Frog tadpoles


Smooth newt

Grass snake


Common frogs (Rana rana) are present but in much smaller numbers than toads.


Smooth newts


Smooth newts are also present but they are tasty for fish, who like the eggs, efts and adults.  The males have a crest in the breeding season but it is much smaller than that of Great Crested newts (some of which are in Gilbert’s Lake at the Grimsdyke Hotel).  They used to be much more common in Stanmore.


Grass snake


There is an enormous population of grass snakes all over Pear Wood, though they are more likely near water.  Some large ones are up to 5 feet long; hatchlings are earthworm-size.  Refugia of roofing felt, corrugated iron etc have been installed and hibernacula have been added – like a compost heap with roofing felt covering it. 


Small hibernaculum

Large hibernaculum

Hibernaculum entrance


The snakes emerge from hibernation in March, mate in Aril and eggs are laid in June.  Larger females lay up to 40 eggs and smaller ones about 16.  Warmer weather leads to more female eggs.  The snakes shed their skin every 6-10 weeks, which takes about 10 days.


Generally, grass snakes have declined in recent decades, with the population estimated at 365,000 15 years ago and now 180,000, mainly due to loss of habitat linked to the decline in amphibians, which make up most of their diet.  The large population of grass snakes in Pear Wood is due to the abundance of toads.


It is more than probable that adders are also present.


Stanmore Country Park


John Hollingdale


Stanmore Country Park was part of the Warren House estate in the 18th century.  It was purchased by Sir Robert Smirke (designer of the British Museum).  John Fitzgerald took it over in 1922 and changed from grazing Jersey cows to Kerry Blacks.  In the 1930s, he sold lands to the south for housing and the remaining 110-acre area was acquired as regional open space by Hendon urban district council in 1937.  In the 1940s, it was declared as green belt and transferred to the Greater London Council.  In 1976, it was transferred to the London Borough of Harrow.  The field names are not ancient names but were given by the first surveyor of the country park. 


Stanmore Country Park 1945

(Google Earth image)

Stanmore Country Park 2012

(Google Earth image}


In 1945, the land was grazed and had hedges only with no trees.  Gradually, oaks have taken over, probably planted largely by jays and most of the oaks are straight-stemmed because of competition, though there are occasional examples in the open.  Other trees include wild service and cockspur thorn (a variety of hawthorn).  Muntjacs are common.  Ringlet butterflies were not there 10-15 years ago but now several have moved into the London area.  Other butterflies shown included purple hairstreak and small copper.




Bracket fungus

Oak tree in the open


Management is generally through regular working parties, with assistance from a range of organisations, including, for example, geocachers, who plant around Tupperware boxes with map references as part of a treasure hunt.