Report from Liz Corry

Captive choughs at Durrell

On the 7^th Gianna was taken from quarantine to the vets to be x-rayed under anaesthetic and then moved to the shut-off cage in the Display Aviary to join the two breeding pairs. She weighed 294g on leaving quarantine which is an average weight for our adult females.

When she first went into the new aviary, Gianna was greeted by Tristan and Issy who sat on top of the cage and took a great interest in her. However, this interest was short lived and they did not really bother with her after that. Gianna was let out of the cage after a week so she could acclimatise to the new surroundings and the birds got to know each other. For the first fifteen minutes she quietly walked up and down the shelving at the back weighing up her options. The pairs were perched high preening each other and paid no attention. However, as soon as she vocalised, Tristan and Issy flew straight down and Tristan started fighting with Gianna. The contact only lasted a few seconds until Gianna flew up and circled the aviary a couple of times. Whenever she flew near Arthur and Gwinny they would display to her and sometimes chase her but it was only half-hearted. Once the hierarchy was explained, Gianna was left alone. She spends a lot of the time on the ground or on the rocks at the back left corner of the aviary.

With Gianna now in the display aviary and getting attention from the keepers, the other choughs perch lower and come down to the ground when the keepers are present, making the exhibit a lot more interesting for the public.

After a few days of being mixed, Gianna was seen to be holding up her left leg quite a bit. Often birds do this to thermo-regulate but they usually swap between legs. The fact that she was using the same leg became a concern and the problem became more pronounced so on the 27^th she was caught up to be seen by the vet. She can grip with her left foot but doesn’t want to put any weight on it. The left leg felt slightly warmer than the right which could suggest an infection. She was put on a five day course of antibiotic but showed no improvement. The course has been extended to see if that makes any difference before opting for more invasive measures. Gianna remains in the Display Aviary but is temporarily separated from the other birds.

It is interesting to note that Gianna has a higher pitch call than the other choughs. This could be a consequence of something she picked up whilst being isolated in captivity when young. Maybe it’s the Italian in her!

Trial of new ID rings for released choughs

When the choughs are finally released into Jersey and free to roam, we need to be able to follow them around and differentiate between individuals. There is always the possibility too that they may fly off the Island and head elsewhere. If they do, then people away from Jersey need to be able to identify that they are ‘Jersey’ choughs. For this reason we have been investigating the best possible ID ringing programme that will not conflict with UK or France ringing schemes.

We plan to attach a standard issue metal ring to one leg of the bird which will have the Jersey Museum address stamped on it. The address will only be visible if the bird is in the hand, e.g. caught in a mist-net, found injured/dead, or the observer is extremely lucky with their binoculars. A colour plastic ring will be also be used to identify individuals. All birds within the Durrell collection are fitted with plastic and metal rings so they are quite used to wearing them.

After discussions with Tony Cross, who is responsible for ringing Cornish and Welsh choughs, we have decided to try a new type of ring with the choughs. Darvic style incoloy (nickel-chromium alloy) rings are hard wearing rings used for coastal birds. They can be made the same diameter as standard chough rings, but are much longer allowing for a number to be engraved along the length. Paul Veron in Guernsey kindly supplied us with some perfect rings originally made for black-headed gulls.

On the 8^th we caught up one of the juveniles not being released (B6977) and attached the new ring. She is now identified by “2A01” on her left leg and white on her right. After twenty days she was caught up again to check the fitting and make sure there was no rubbing or injury to the leg. The ring is free to rotate and so far no rubbing can be seen and she doesn’t show any particular interest in the tag which is also a good sign. She has put on 25g in weight since the tag was attached. This could simply be due to eating more as the temperature has dropped.

Radio-transmitter trials

This month, video cameras were placed in the two aviaries housing the juveniles during feeding time. One aviary houses the birds with dummy radio transmitters and the other aviary has the candidates for release, i.e. with no dummy transmitters. The aim of this was to see if there were any behavioural differences between the two groups. The weather restricted the number of days this could be done since the cameras are outside and not waterproof. However, we were able to get footage of the birds which is still being reviewed. At present there seems to be no significant difference between the groups. All birds forage and fly with no restrictions.

B6975 and B6976 were caught up on the 28^th to check on the condition of the dummy radio transmitters and the birds themselves. The birds appear fine with minimal disturbance to the tail feathers. There was no further damage to the glued areas although it does look like one of the threads is looser than when first attached. An order has now been placed for the real transmitters to be built with delivery expected in January.

An interesting note is that the three birds under various trials in one aviary (SF2) are spending less time hiding in the nest-box when keepers are present. The other group (in SF3), chosen for release because they were more confident, still hide every time.

Progress of the release aviary

Planning permission for building a release aviary at Sorel was granted on the 13^th. After preliminary meetings with the National Trust for Jersey and Aaron Le Couteur, the shepherd, groundwork began on the aviary.

The field where the aviary is being built will also be used to graze sheep in the spring. For this reason there needs to be a sheep-proof fence erected not just around the field but also the aviary itself. Hopefully, this will also act as a deterrent for the public getting too close to the birds. During the time we have been present at the site there have been dog walkers every day either next to or in the same field and often with their dogs off the leads. Whilst we do not want to discourage dog walkers in the area we do need to ensure that the birds in the aviary do not suffer any stress related to this. There will be publicity including messaging boards around the site to inform people of the project and ask for their support.

Trevor Smith from Durrell’s Maintenance Department is leading the build onsite with assistance from staff and volunteers. The first post went in in the ground on Friday 23^rd and so far, despite battling the elements, Trevor has made great progress. Aaron Le Couteur has kindly loaned the team the use of his lockable trailer for equipment and water tank for the duration of the build. The weather will be the deciding factor on when the building can be completed, but we hope to finish by Christmas.