The White Winged Chough [pronounced chuff and sometimes known as Black Jay locally] is still fairly common in our area although we see them less now than we used to, perhaps they are having to enlarge their food gathering areas so take longer to complete the circuits. A Chough is a large black bird that has a white under-wing patch that is only visible in flight or when the bird is displaying. Another feature is the down curved bill and the red eye of birds over 4 years old.
In over 20 years I have only received one or two young Choughs in the shelter for care. Once the bird has been checked to ensure it is healthy and not injured the only way to ensure its survival is to return it to its family or find another group and persuade them to take the young bird under their wing, so to speak. It is rare the offer of a new member for the family is rejected, the young birds are usually quickly accepted into the new group.
Choughs have a very interesting and tough life, an article published in the Australian Nature magazine several years ago gave us a peek into the lives of these large, gregarious birds.
Life for a Chough is particularly hard and a pair simply cannot breed without help. This explains why Choughs are found in groups of 4 to 20 birds during the breeding season. When not breeding more than one group of Choughs’ may come together to a regular food source. A lot of their food comes from beneath the ground and therefore the birds spend a lot of time digging holes, some up to 20cm deep. Digging uses a lot of time and energy and old birds learn that digging around grass tussocks is more likely to yield a beetle larvae or something else edible. More importantly, mature birds learn when to give up digging in an unproductive patch whereas young birds will continue to dig and end up with nothing for all the energy expended. Choughs are interesting to watch as they search for food on the forest floor, often they are so engrossed in their search that they don’t notice an observer and will carry on tossing leaf litter from side to side in search of their elusive meal.
Choughs build a large bowl shaped mud nest approximately 35cm across. Four eggs that take 3 weeks to hatch are laid by the breeding pair, the young then take 4 weeks to fledge; young are fed for up to 8 months. Many songbirds only look after their young for twice the nesting period but Choughs continue their support for up to 8 times the nesting period. The young must have this support until they master their basic survival techniques. The time and experience needed to find food means that one pair alone cannot supply all that is required to feed a clutch of young.
Of the few recorded attempts by single pairs of Choughs to nest they have lost their young to starvation. The minimum viable group size is 4 and even so these 4 will only raise one chick. Each additional helper increases the chances of a chicks survival to where a group of 10+ can occasionally raise all 4 chicks.
The offspring from previous years help in all instances from building the nest through to caring for the fledglings.
Neighbouring groups of birds will sometimes destroy each others nests, intruders peck at the foundations of the nest in an attempt to dislodge it, if this is unsuccessful they will destroy the eggs.
If the nest is destroyed it often stops a group from breeding again that season as the mud needed to rebuild may not be available at the time. These delaying tactics reduce the competition for food from groups close by giving the intruders young a better chance of survival.
Kidnapping also occurs amongst Choughs with large groups ganging up on smaller groups. Some birds from a large group will engage members of a smaller group in battle whilst others approach a juvenile and attempt to entice it away using a tail-wave and wing-wave maneouvre. If the enticement is successful the young bird is fed immediately and within a short period it acts as if it has always been with the group. Young Choughs appear to be easily confused and perhaps have not developed a bonding with their group so early in life. Kidnapping doesn’t occur later than a month or so after fledging when the birds have more than likely bonded to their home group. A group of birds willing to feed someone elses offspring for 7 months must surely be an indication just how desperate a group is to gain another helper. Does this show how hard life is for a Chough?
DNA fingerprinting has found that when the structure of a group of Choughs is stable one pair dominates the reproduction year after year but when deaths in the family have fragmented groups, helpers try out different combinations with others that they meet in their travels until they work out who is likely to produce the best offspring.
Chough groups are highly inbred, often the breeding pairs are closely related. Disasters such as droughts that cause members of groups to die may well be the way new blood is brought into family groups.