An Egyptian escapee and a resurgent bird of prey are just two of the winged species thriving in Sussex.

But a comprehensive new survey of the county’s bird population has also revealed that many species are on the “brink of extinction”.

The results of the Sussex Ornithological Society’s (SOS) new study will be revealed in the Birds of Sussex book, published on January 25.

Author Adrian Thomas said that native species are leaving the county for cooler climes and species favouring a Mediterranean climate are making new homes here.

The red kite, resurgent from its 1970s level of just one breeding female in the UK, can now be seen across the South Downs.

After escaping into the wild in Norfolk in 2000 the non-native Egyptian goose now flourishes in Sussex, with Petworth Park a hotspot.

Milder winters have helped the little egret hunt for small fish, unhindered by frozen waters.

The population of buzzards has increased the most in the county, while barn owl populations have increased from about five pairs to 200.

The snipe is struggling because of diminishing wetlands from being abundant around Pevensey Levels 30 years ago to just five breeding pairs in the county today.

While the wood warbler heads further north out of Sussex because of climate change, the Cetti’s warbler steps in as Sussex becomes this Mediterranean bird’s northern extreme.

The Eastern European migratory starlings that usually form the stunning murmurations that spiral along the Sussex coast are currently in decline because of advances in farming techniques on the continent.

But experts are unsure why the willow tit and hawfinches are dying out in Sussex.

All these findings have been uncovered by the observations of more than 1,000 volunteers who have charted the fortunes of almost 400 species of bird through almost 8,000 hours of observation over a four-year period.

Mr Thomas, of the Royal Society for the Protection of Birds, said: “We still can be proud of our bird population but the warning bells are sounding, there are a lot of species out there struggling.”

The book costs £35 plus postage and packaging. Non-members of SOS can take advantage of a special membership and book offer.