Dogs are the four legged foes of natural wildlife and not their friends, according to the first study to quantify the effects on local birds of taking them for a walk.

Experiments show that dog-walking causes more than 40 per cent reduction in bird abundance and more than 35 per cent reduction in bird diversity in woodlands, even if the pets are kept on a lead.

"These results support the ban on access for dog-walking to sensitive natural areas," said Dr Peter Banks, who did the study at the University of New South Wales with Jessica Bryant. "I can't see why it wouldn't be relevant to the UK and other places," he told The Daily Telegraph.

Dog-walking is among the world's most popular outdoor activities, with clear benefits to both human and canine health.

But conservation managers often ban dogs from natural areas, fearing they will deter local wildlife, resulting in outcry at the restricted access to public land.

Earlier work showed that that human walkers (without dogs) make birds more vigilant or likely to fly off, and that off-lead dog walking can disturb some species of breeding shorebird.

But dog-walking lobbyists argued there was a lack of hard evidence that dog walking was harmful. Arguments are passionate on both sides and have remained unresolved without proof of the ecological impacts of dog-walking.

Dogs evolved from wolves as the "top predators" in many ecosystems - able to hunt without facing any threat - and today's study shows that wildlife still perceives domestic dogs as a threat. "These results argue against access by dog walkers to sensitive conservation areas," said Dr Banks, who reports the findings in the journal Biology Letters.

In the new study the team controlled dog walking at 90 sites in woodland on the urban fringe of Sydney and monitored the responses of many kinds of birds, one of the key wildlife groups at risk from disturbance, when presented with walkers with dogs, walkers without dogs and a control (no walkers or dogs).

The sites included those where dog walking was permitted and frequent, where birds may have become used to dogs, and national park sites, where dog walking was prohibited. They also used a range of dog sizes and breeds and a range of different walkers, and dogs were kept on leads.

Observers monitored all native birds seen or heard within 50 metres of a 250-metre trail. Monitoring commenced 20 seconds after the walker/dog-walker had set off and continued for 10 minutes.

"Dog walking caused a 41 per cent reduction in the numbers of bird individuals detected and a 35 per cent reduction in species richness compared with untreated controls," they concluded. "Humans walking alone also induced some disturbance but typically less than half that induced by dogs."

Ground dwelling birds such as painted button-quails, the fairy wrens and finches appeared most affected; 50 per cent of the species recorded in control sites were absent from dog-walked sites, he told the Daily Telegraph.

This was of concern because it could lead to a "cascade" of behavioural changes that could further threaten these species, Dr Banks said.

Even for birds which did not flee the site, there were 76 per cent fewer individuals within 10 yards of the trail when dog walking occurred compared with control sites, suggesting that birds were seeking refuge.

"These results reveal that even dogs restrained on leads can disturb birds," they conclude, confirming the need for them not to be walked in sensitive bushland and conservation areas. "The effect occurs even in areas where dog-walking is common and where they are prohibited, indicating that birds don't become accustomed to continued disturbance by dogs," said Dr Banks.

The revelation has immediate implications for popular recreations such as bird-watching and eco-tourism, where visitor satisfaction has a strong relationship to the number of species seen.

"The issue is here that dog walking will displace birds meaning bird watchers and ecotourists will not see as many birds, detracting from their experience...of course ecotourism without dogs still has its own impacts on wildlife," Dr Banks told the Telegraph.

Dog-walking was also likely to affect the accuracy of wildlife surveys that are used to map bird distributions around the world.