Gang-gang nesting behavious

Gang-Gang Nesting
Tell-tale Behaviours.

Mulvaney M.J., Tyrrell T., and Davey C. A, 2022
This guide was prepared by Red Hill Regenerators for those undertaking Gang-gang observations by Sam Nerrie

Purpose
These guidelines detail Gang-gang behaviours associated with nesting. Their primary aim is to assist in the search and identification of nesting hollows. It is hoped that through finding and observing hollows across its range a better understanding of the Gang-gangs nesting ecology will emerge. This knowledge will assist conservation of this endangered bird. The guidelines outline what observers should be looking out for both when watching a hollow and using a pole camera. It should be noted that the behaviours mentioned are usually not unique to Gang-gangs with most being shared with other Cockatoos such as the Sulphur Crested and Galah.

Male chewing bark on a nearby limb and depositing new bark material in the nest.

Hollow Checking

Gang-gangs peer into hollows all year round and will enter hollows to access pooled water. A pair that had fledged chicks the day before, were observed cleaning out a hollow in a nearby tree (passing out material to each other beak to beak and kick-scratching lose material out of the hollow mouth). They where also chewing bark on a nearby limb and depositing new bark material in the nest. Thus observations of potential hollows can be made all year round, though August –October is the time when Gang-gang hollow searching is busiest.
Sightings of Gang-gangs looking into or entering hollows can be made on the iNaturalist or Naturemapr platforms.

Gang-gangs nests in Turtons creek, Victoria have been found in large Mountain ash trees over 100 years of age. One nest was found in a Chinmey hollows and the other in a dead branch.

The recorded sightings within a region, guide the relevant citizen researchers where to focus their observations and camera pole checking.
In the Canberra area about 10% of all hollows reported, across the year, as hollows of Gang-gang interest, were found to be nest trees.

Hollow in Mountain ash with Male Gang-gang stripping bark below.
Photo Stuart Inchley - Turtons Creek

Nest Site Selection

(August -September- October) 

Gang-gangs are most active around hollows they are examining as potential nest sites in the weeks before egg laying commences. This is a good time to actively search for Gang-gang pairs in and around hollows. Timing of breeding may be influenced by weather and is related to both altitude and latitude. The lower and more northern a site the earlier egg-laying will commence. Egg-laying in coastal NSW may begin in early September while that of higher/southern areas may not begin until early November.

In the weeks prior to egg-laying Gang-gangs are easy to see anytime during the day, are sometimes quite noisy and need to fight off other bird species for the hollows; these encounters can be very noisy. Some other birds, which seem to challenge for the hollows are sulphur crested cockatoos, rainbow lorikeets and galahs.
Once eggs have been laid Gang-gangs are very circumspect around the hollow and much more difficult to spot.

Female sitting inside at the top of the  hollow, looking out.

Incubation

(September - October –November)

The female spends the night on eggs, while during the day the male and female share incubation responsibilities. Thus there is always one bird in the nest. Incubation takes about 4 weeks. There is very little activity at all around the hollow and this may involve as little as two nesting sitting change-overs in a day but this varies depending on individual pairs. The non-nesting bird spends very little time around the nest site.

Behaviours/signs to look out for during incubation
Male or female seen sitting inside at the top of the  hollow, looking out.

Change-over
The incoming Gang-gang gives a very  small call on the way in which gives the one on the egg(s) time to be prepared. The adult then comes in and change-over occurs. During this period the Gang gangs are very quite, change-over happens in a matter of minutes or much less. Best time to observe an incubation change-over is within the hour after dawn or at dusk when the female takes on incubation duties. Dusk change-overs can occur as late as one hour after sunset.
- Jacky Fogarty

Note: There is very little Gang-gang activity around the hollow at this time.

Male Gang-gang (Callocephalon fimbriatum) - feeding young.

Chick Rearing

The female continues to spend the night on the nest. Both partners feed chicks during the day, but initially only a few feeding visits are made each day. Young leave the nest about eight weeks after hatching.

Behaviours/signs to look out for:

> Female leaving or entering hollow at times other than early morning or  late evening.

> As chick-rearing proceeds, visits to the site become more frequent and  often the sitting partner is reluctant to leave.

> Chicks begging from inside the hollow can sometimes be heard and you  may also hear them being fed.

>Both partners visit the site during the day to feed the chicks and at times  both adults may be in the hollow at the same time and may leave hollow together.

> Other Gang-gang couples may accompany a returning adult and be present during change-over. These birds may help “guard” the hollow when both adults are away.

> Other pairs may visit the site but they do not enter but may spend some time looking into and presumably listening to the begging chicks.

> Adult birds from other nearby nests will drive other species like lorikeets and Sulphur- crested Cockatoos away from a neighbour’s nest.

> Gangs-gangs may also aggressively drive off other Gang-gang pairs, so not all pairs co-operate.

> Birds calling to and joining other nearby nesting Gang-gangs on foraging flights  

Gang-gang chicks sit at the hollow entrance for on average a week before fledging.

Fledging

(December - January - February) 

The average depth of a Gang-gang hollow in Canberra is  55cm (range 15-129* cm, n=27).
*Note the  maximum ‘depth’ was of a site situated in a spout.

The  deepest measurement in a trunk was 75cm. When  chicks are getting near fledgling, parents encourage  them to climb to the hollow entrance by feeding them  there. Chicks will stay perched at or just below the  hollow entrance and are visible over a 3-11 day period, just prior to fledging. The average is 7 days per chick.  Longer visibility times usually involve multiple chicks. Thus the window in which a nest hollow and number of chicks raised can be confirmed purely by observation is  short.

In Canberra most chicks are first observed  between Christmas and 15 January but has occurred  from 8 December to 26 February. Time from laying to  fledging varies from 61 to 79 days. In Campbelltown and  Moruya, chicks were observed in the first week of December, while in Melbourne a pair of chicks was first observed in the first week of January.

South Gippsland, Turtons creek area has seen fledglings as late as the end of January.

Behaviours/signs to look out for:
Chicks begging from inside hollow can sometimes be heard.
Parents perched on hollow with head in hollow, body or at least head  rocking rapidly.
Heads of chicks appearing above hollow entrance. Gang-gangs usually  have between 1-3 chicks per nest with two being the most common. Chicks can develop at different rates so not all may be visible at one time. Thus determining the number  and gender of chicks at a nest hollow should include multiple visits – preferably two a day once chicks are visible.

At least one adult and usually both are present at  fledging, seemingly encouraging the young to leave the hollow through calling, being close by, making repeated short flights from the hollow and if the young follow, rewarding them with food. This process can take a number of days.

Chicks do not return to a hollow once fledged.  

Galahs compete for hollows in Turtons Creek, South Gippsland, Victoria.

Other Species

Sulphur-crested Cockatoo •(SCC)
In Canberra they don’t seem to do much nest preparation so eggs/chicks are on bare wood or soil collected at hollow base. However HANZAB Vol 4 p 172, indicates that they can have a base of wood chips 2-10 cm deep. The woodchip if present seems to usually be longish strips, rather than the Gang-gangs bite sized chunks. Some Cockatoo droppings are normally present in an active nest. 

If a nest is active SCC will usually appear and protest during poling, while chicks or eggs may be present. SCC nests earlier that the Gang-gang but breeding times overlap. In Canberra SCC have been observed driving Gang-gangs away from a hollow tree, but Gang-gangs and SCC have also be observed nesting in the same trees.

Wood Ducks are early breeders and both Wood Ducks and Gang-gangs may use the same hollow in the same year. Wood Duck down is a prominent feature of nests they utilise. Unhatched Wood Duck egg(s) may remain in a hollow being used by a Gang-gang.

Galahs line nests with a mixture of a few woodchips, single leaves and grass. If a nest is active Galahs will usually appear and protest during poling,  while chicks or eggs may be present. Nests earlier that the Gang-gang but breeding times overlap .

Rainbow lorikeets line base of nest with feathers and usually utilise a smaller hollow entrance size than Gang-gangs.

Gang-Gang Nesting Tell-tale Behaviours.