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

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 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, which is gaining ground on the hill, Small Copper, Small Blue and Clouded Yellow. A more reliable location for Small Blue (especially the main spring brood) is amongst the scrub at the foot of the imposing chalk face of the Paulsgrove quarry (Photo 2), just to the east of the pond (map). Wall Brown also used to breed at the disused quarries, but after a tenuous few years, it is feared that this species is now lost from Portsdown. 

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.