The nest boxes used at Paradise Park, are based on an original design by Tony Cross. This type of box has been used by almost 5% of the breeding choughs in Wales, and has contributed to maintaining a stable population in some areas. For more details click here (BTO News June 2008 .pdf absract).
Wild choughs in coastal areas often choose a ledge deep within a cave for their nests. There you would expect a lot of space around the nest and a steady, cool, temperature.
Over the course of several years, we have modified and adapted the nest boxes we use for our captive choughs, to promote improvements in breeding success, and also to allow better access. (Both for physical interaction, and monitoring using webcams).
The main change is an overall increase in size, to the dimensions shown. As well as giving more space for a large brood of up to five chicks and a camera, we believe the improved airflow is beneficial in an aviary setting to keep the temperature more even, and reduce the incidence of diseases such as aspergillosis.
The nest should be in the highest point of the aviary and it is most important that it is not in direct sunlight. (In the wild chough nests are very cool, and often quite dark). The box must be shaded to prevent overheating, and some form of roofing should be built into the aviary to provide this. There should be a gap between the nest box and the roofing to allow further cooling air flow.
Ideally the back of the box should be in contact with the aviary wall. This allows for an inspection hatch into the nest so that the adult birds are not alarmed by people entering the aviary and interfering with their nest. The chicks can be easily reached for medical treatment, supplementary food or to be ringed.
The best place for a nest camera is a couple of inches in from the back wall, situated on the roof. The birds cannot reach this, so no extra protection is necessary (Our original cameras were housed in domes, but we found the birds would sometimes peck at their reflection). The camera location has been modified over several years, allowing for observation from initial nest-building, through the egg-laying stage to fledging.
One or two large rocks approximately 10 centimetres tall should be placed in the front of the box. This provides a good perching point for the adults, and juveniles almost ready to fledge. It also forms a barrier for the nest to be built against and prevents chicks from falling out when young.
The nest box incorporates a natural overhang effect by having a downward facing entrance. Boxes are made of 12millimetres-thick exterior plywood – marine plywood is preferable.
We introduce nest material in three phases, starting with large twigs approximately 15-20 centimetres long, up to 1 centimetre thick. These can be put in the aviary over the course of a few days.
The next phase consists of smaller twiggy material, especially heather, which the birds weave into the basic structure.
Finally, add fern fronds, moss, lichens, teased sheep wool and horse hair for the nest lining. Choughs seem to prefer shortish (3-5 centimetres) horse hair, and they show a preference for hair which is light coloured.
Nest Box in the wild
The original design has been used to increase nest site opportunities for wild choughs. In this case the box is half buried in a cliff face – either, supported on a ledge and secured by fixing the back in cement, or with large rocks. Alternatively, it can also be used in abandoned houses, barns and outbuildings.
Several of these boxes have now been installed in the cliffs on Jersey by our partners at the Birds on the Edge project, should natural sites be found lacking.