If choughs in Jersey have been as dead as the dodo for the past 100 years, how do you go about returning them? This was the first question we had to ask ourselves. There were two options: translocation or reintroduction.
A translocation is where an animal is moved from one area and released into another. A nice example of this is the work Durrell and keepers from Jersey Zoo have done to save orange-tailed skinks on off-shore islands in Mauritius. To do this with choughs would mean taking birds from the wild where they are already under threat. If it was to fail it would mean no choughs in Jersey and fewer choughs left in the wild.
A reintroduction is when you move animal on purpose into part of its native range from which it has disappeared. You can do this by captive breeding animals until you have enough individuals to release in the wild to start a new population. This is what we did with the choughs.
In partnership with Paradise Park, Cornwall we started a captive breeding programme for choughs at Jersey Zoo. Paradise Park have been keeping choughs since 1973 so we did not need to take any birds from the wild.
The aim of the captive breeding program is to produce choughs that we can release into Jersey soon after fledging. Releasing young birds rather than adults is much better as young birds are more able to adapt to their new environment. Tomorrow we will talk more about how we breed choughs. Lets pretend for now that we now have chicks to release. What next?
A successful reintroduction requires lots of support for the animals before and after release. The young choughs are kept in an aviary at the release site for a few weeks before they are due to be released.
For our choughs this meant leaving the zoo and heading up to the cliff tops of Sorel on the north coast of Jersey. Spending time in the release aviary allows them to get used to the outside environment, and practice flying in a large secure area.
We also train the choughs to come to food dishes on cue. They quickly learn to associate the sound of a sports whistle with food. When they hear the whistle they know we have left food in specific 'target areas'.
This is important as it is how we provide them with supplemental food once they have been released. We know that the Jersey habitat is not perfect yet, so it doesn't have all the insects the choughs need. We also know that insect numbers are low in winter time because the weather is too cold. So we provide a special diet each day in addition to the food they can find in the wild.
Watch this video of the released choughs returning to the aviary for supplemental food.
We give them coloured leg rings so we can identify individuals. One leg ring tells us which year they hatched. For example, all chicks hatched in 2014 wear a blue ring.
They are also fitted with radio-transmitters that allow us to track the bird's movements. We learn where they like to feed, where they roost at night, and how far they will travel in a day in search of food. The transmitter it fitted to the tail so it will fall off when they moult their feathers in summer.
When they return to the aviary for supplemental food we can also observe the choughs and look for signs of ill health like sneezing or injuries. If there are any problems we can trap the bird in the aviary and get the vet to take a look. Just the same as we would back at the zoo.
We will not do this for the rest of their life. At some point they need to learn to cope in the wild. However, in these first few years it is important to look after as many as you can until the population is strong enough.
How many choughs have been released into Jersey?
We have released 40 choughs over the past four years. Eleven have disappeared or died in that time.
A chough's natural predator is the peregrine falcon. Raven are known to steal chough chicks and eggs from the nest. We cannot control these types of threats. It is part of nature and the reason why you need to release a large number of birds.
The good news is that the released choughs have started breeding in the wild. Below is a photo of one of the wild-hatched chicks (pink over orange leg rings) who followed his parents back to the release aviary for supplemental food.
We will talk more about the chicks tomorrow.
- How do the choughs know when to arrive for their supplemental food?
- Name one way in which staff monitor the choughs after they have been released?
- How many of the released choughs are still flying free today?