Great results for 2019 with the Durrell Chough Project

By Liz Corry - Senior keeper and Chough Field Manager at Durrell Wildlife Conservation Trust

Red-billed choughs have been resident in the quarry since the reintroduction project began in 2013. Using it first as a roost site then in 2015, as a breeding site which resulted in the first wild-hatched chough chick in almost 100 years for Jersey.

Support from Ronez Quarry has been crucial to the success of the reintroduction and growth in the population. The ability to closely monitor nests and ring chicks has allowed Durrell to keep track of individuals, monitor the health of the population, and determine fledging success rates. This data feeds into the overall conservation management plan for the species in Jersey. It has also provided evidence-based support to other overseas reintroduction projects that now use the Jersey choughs as a model species.

In 2019, the team witnessed a record number of breeding attempts. All bar two of the fifteen breeding pairs nested in Ronez quarry. Some pairs were on their fifth season nesting in the quarry whilst others were attempting for the first time. This naturally leads to varying degrees of success; 11 nests were located in different operational buildings, 7 of those succeeded in hatching chicks. The successful nests are due to fledge any day now. Thanks to two sites visits (May and June) and communication with quarry staff, we were able to account for a total of nineteen healthy chicks. If all of these successfully fledge, the Jersey population will have increased by almost 50% in one year.
 

            

Figure 1: Numbers of wild hatched and fledged chough chicks since breeding began (all in Ronez Quarry) and the numbers of those who survived more than six months post-fledge in Jersey.
 

One reason for an increase in numbers of chicks is down to certain pairs using the nest boxes fitted by Ronez. There are four nest boxes in place in the lower quarry; two inside buildings, one external, and one on a rock face. The two boxes inside buildings were fitted to encourage the birds off working machinery for the benefit of Ronez and for the safety of the birds. In 2017 and 2018, one pair residing in the asphalt plant built there nest directly on hot pipes. This resulted in their clutch of four eggs overheating each year and failing. This year they have been encouraged into the box and managed to hatch three chicks. All three have been fitted with leg rings by a licensed ringer and will be monitored closely by Durrell staff.

 

      

Figure 2: Licensed bird ringer Dave Buxton accessing the asphalt plant nest box in 2018 (left) and ringing a chick from the surge pile nest in 2018 (right). Photo: Liz Corry
 

In 2019, Ronez and Durrell submitted a joint proposal to the Insurance Corporation Conservation Awards. We were very proud to be awarded the main prize of Best Conservation Project in Jersey and received £1500. This money has helped purchase monitoring equipment for Durrell including paying for DNA sexing tests on all of the chicks hatched in 2018. Choughs are not sexually dimorphic which means staff rely on DNA tests alone. The remaining money went towards equipment for school children who visit the quarry on educational outings. Inspiring a new generation of conservationists and quarry engineers and most importantly demonstrating that the two are not mutually exclusive.

 

      

Figure 3: Educational awareness of the choughs in the quarry aided by Ronez and the Insurance Corporation Awards. Photo: Paul Pinel
 

The release phase of the project is at an end. Durrell staff will now focus on monitoring and protecting the species in the wild. We are yet to determine the carrying capacity for the number of choughs in Jersey. We believe we are now seeing the numbers of breeding pairs occupying the quarry reaching its limit. The importance now will be to ensure those pairs breeding in the quarry will continue to have success and the ‘have-a-go’s’ of 2019 will get to bred in 2020.