Melanie Driscoll: We're braced for a heavy impact and the food-chain collapsing

It's really hit hard in the past couple of days. It seemed, initially, that it was little fingers of oil that would come in then get washed out again by the tide. Now it's coming in with thick waves. Heavy oil is washing up.

Behind it, more oil is spewing from the Gulf and that means there's a mass of oil that will continue to break up on to those shores and beaches.

We've been working there for 20-hour days. We're trying to work on this at a strategic level with a long-term conservation plan about how we maintain and protect habitats into the future as, hopefully, the leaking oil gets capped.

But we're bracing for a really heavy impact on the habitat and the birds. The area is incredibly rich. It's both rich in diversity but also in abundance. There are vast marshes and miles and miles of beaches and, at this time of the year, birds are just packed into those areas for breeding. The impact on the migrant birds will be very heavy, [especially on] the breeding terns and the breeding marsh birds. We're mobilising volunteers to help with individual birds, planning and documenting the effects of the spill.

While there's this large mass of oil that we can see on the surface, there are untold volumes of oil under the surface. We could see the food chain collapsing, which could cause as much damage to the birds as the oil. We could see the young born early being fed with tainted fish or abandoned because the parents die and don't come back.

What we're seeing now is very distressing. We've been working to save some of these habitats for years. I spoke to some of my co-workers – and we've been dealing with this for a month – and I have never heard them sound so depressed. They told me that they went to a restaurant on Grand Isle and the manager there started to cry. After all, it's her home.

Melanie Driscoll is the director of bird conservation for the National Audubon Society's Louisiana programme