Portsdown Hill

Site feature providing more detailed description, photos and other information for the butterfly observer

Photo 1 - View East Along Central Section Showing Chalkhill Blue Breeding Area

Highlights

Imposing chalk downland escarpment overlooking Portsmouth and the Solent

Central part of the escarpment designated SSSI for its variety of flora and fauna

Wildlife haven on the doorstep of a major city

Chalk downland butterflies include Chalkhill Blue and Small Blue

Green Hairstreak and Brown Argus also present

Fascinating military history including series of defensive forts built during the nineteenth century and second world war tunnels

Description

Portsdown Hill is a chalk downland escarpment stretching for several miles and overlooking Portsmouth, the Solent and the Isle of Wight. Its strategic position has resulted in the hill playing a significant role in Britain's military history over several centuries - a series of military forts (the Palmerston Forts) built during Napoleonic times being very obvious evidence of that. Despite its proximity to a large city, conservation management and scrub clearance efforts on Portsdown Hill in recent years have substantially improved the quality of its chalk downland, to the benefit of the wildlife, including butterflies. Even the flower rich ramparts of several of the military forts now provide good butterfly habitat.

The area of the hill (Photo 1) (map) located between the disused Paulsgrove and Wymering chalk quarries is probably the richest area for butterflies and is the main breeding site for Chalkhill Blue. Access to the area is though a gate (map) close to Lime Grove and just to the east of the largest of the disused quarries (Paulsgrove) which leads to a network of paths on the hillside. In May, spring species include Orange Tip, Brimstone, Red Admiral and Peacock.  Green Hairstreak can also be found in small numbers around the margins of bushy areas on the lower slopes. Late July/August is the best time for Chalkhills, but Common Blue, Marbled White, Meadow Brown and Gatekeeper should also be seen in this area. Other species to keep watch for include Brown Argus, Small Copper, Small Blue and Clouded Yellow.

Small Blue (especially the main spring brood) can usually be found amongst the scrub on the south side of the imposing chalk face of the Paulsgrove quarry. In particular, look in the area at the south west corner (Photo 2 below, map here) and also just to the east of the pond immediately below the quarry face. Incidentally newts live in this pond, their spawn and tadpoles being quite conspicuous in spring. Look out also Green Hairstreak amongst the gorse in the former location. Visits to this area can sometimes be accompanied by the raucous screeches of a pair of Peregrine Falcons which have been nesting high on the quarry face for several years.

 

Photo 2 - The Scrub Area To The South-West Of The Disused Quarry At Paulsgrove Has A Good Colony Of Small Blue

Since the hill provides such a good vantage point, it is not difficult to maintain ones bearings. You can gradually make your way east along the hill towards the other quarry at Wymering. The return can be made by retracing steps or introducing a variation using the network of paths.