The Journal understands two public works officers from Guernsey shot the feral birds last Thursday evening.
Bird lover Jeanne Mapp was at the airport when she heard the fatal shots being fired.
She said: "I could see the men shining lights in the trees and shooting the chickens.
"I am very upset about it. The States could have phoned me and told me what was going on. They know I have fed them for a long, long time. To go up there and find them like that is not very nice."
Mrs Mapp also visited the La Source site, which is close to the Bonne Terre water catchment, earlier in the day.
She said: "I went to the airport shortly after 1pm on Thursday to feed the chickens and saw two men there with guns. One of them came up to me and said that if I didn't leave he would call the police and get me arrested.
"I asked him whether he was shooting rats, or rats and chickens, and he didn't answer. He just said he would call the police if I didn't leave. I found his attitude really nasty."
Mrs Mapp believes the States could have re-housed the chickens.
"It wouldn't have been difficult to find a solution. The States has lots of land and could have re-housed the chickens had it really wanted to."
Mrs Mapp went on to describe the politicians who voted for the cull as "heartless".
"The States members who voted for this action are heartless. I certainly won't be voting for those involved and I don't think many other people will either. This isn't Alderney as I know it and I don't know what people who holiday here are going to think when they find out what has happened."
Chief executive David Jeremiah confirmed the destruction of rats and chickens in the Bonne Terre area had taken place.
The States originally gave the public two weeks to re-house the birds when it said they posed a "serious threat" to the island's water supply in April.
In May, States member Frank Dean said the chickens had pumped very worrying amounts of bacteria into the island's water supply.
He said test results proved the chickens were contaminating the water supply. However, the results have never been made available to the public.
Mr Dean, the member responsible for water, was not available for comment when approached by the Journal.
Mrs Mapp organised a sit-in to protest against the proposal to cull the chickens in May and encouraged more than 200 islanders and holidaymakers to sign a petition urging the States not to kill the birds.
Turn over for a detailed look at the events which led to the culling, from the GSC's first announcement in April to the eventual culling last week.
The Guernsey Bereavement Service has made three visits to Alderney over the past few months and would like to continue to help you. We are visiting the island again on
Tuesday, 23rd February 2024 and would invite anyone who feels they would like Bereavement Counselling to telephone the Bereavement Service Office on 257778 to make a time to meet one of our counsellors.
The Guernsey Bereavement Service has made three visits to Alderney over the past few months and would like to continue to help you. We are visiting the island again on
Tuesday, 23rd February 2024 and would invite anyone who feels they would like Bereavement Counselling to telephone the Bereavement Service Office on 257778 to make a time to meet one of our counsellors. 