In order to ensure there is viable population of the threatened species, conservationists have set up a number of captive breeding centres.
The Indian network, underpinned by the UK government's Darwin Initiative, is being led by Bombay Natural History Society (BNHS), with support from overseas organisations, including the RSPB and ZSL.
Oriental white-backed vulture chicks (Image: Nick Lindsay/ZSL)
Captive breeding may be the only hope for a number of species
One of the centres recently enjoyed its first success when two oriental white-backed vulture chicks were born.
"They look as if they are doing well," Dr Cunningham told BBC News.
"It is quite heart-warming to have a bit of light at the end of the tunnel, but it is going to be a long, long haul over the next 15-20 years before we get anywhere near to being able to release any birds.
"These birds are difficult to catch in the wild now because there are so few of them, so it is easier to find where they are nesting and get them as youngsters.
"But they are not sexually mature until they are about five years of age, and successful breeding normally takes two or three seasons."
The ZSL researcher is also concerned that the problems facing vultures in India could occur elsewhere in the world.
"We are particularly worried about Africa because diclofenac has recently started to be marketed as a veterinary drug.
"There are vultures there that are very closely related to the Indian vultures, so we know that they are susceptible.
Dr Cunningham added that the drug was also being used in South America, but the vulture species there were evolutionarily distinct from old world vultures and not affected.
"I don't think we should take our eye off the ball as far as getting this drug out of the ecosystem is concerned."
First chicks
In order to ensure there is viable population of the threatened species, conservationists have set up a number of captive breeding centres.
The Indian network, underpinned by the UK government's Darwin Initiative, is being led by Bombay Natural History Society (BNHS), with support from overseas organisations, including the RSPB and ZSL.
Oriental white-backed vulture chicks (Image: Nick Lindsay/ZSL)
Captive breeding may be the only hope for a number of species
One of the centres recently enjoyed its first success when two oriental white-backed vulture chicks were born.
"They look as if they are doing well," Dr Cunningham told BBC News.
"It is quite heart-warming to have a bit of light at the end of the tunnel, but it is going to be a long, long haul over the next 15-20 years before we get anywhere near to being able to release any birds.
"These birds are difficult to catch in the wild now because there are so few of them, so it is easier to find where they are nesting and get them as youngsters.
"But they are not sexually mature until they are about five years of age, and successful breeding normally takes two or three seasons."
The ZSL researcher is also concerned that the problems facing vultures in India could occur elsewhere in the world.
"We are particularly worried about Africa because diclofenac has recently started to be marketed as a veterinary drug.
"There are vultures there that are very closely related to the Indian vultures, so we know that they are susceptible.
Dr Cunningham added that the drug was also being used in South America, but the vulture species there were evolutionarily distinct from old world vultures and not affected.
"I don't think we should take our eye off the ball as far as getting this drug out of the ecosystem is concerned."
