Journal archives for December 2021

December 18, 2021

Gang-gang Hollow Search study already yielding results.

Thanks to Katie, Chris, Matt, Amber and Susan for their identification and monitoring of nests in Campbelltown and Moruya where Gang-gang chicks have already fledged. This is about 4-6 weeks ahead of the nesting occurring in the twenty observed nests in the Canberra area and one in Cooma (thanks Ange). In terms of the Gang-Gangs total range, Campbelltown and Moruya are at the higher latitude and or lower altitude parts of this range. Thus they achieve higher temperatures than most areas in which Gang-gangs occur.

Peter and Judy Smith in their 2018 Gang-gang survey of Hornsby Shire, (https://www.researchgate.net/publication/340599663), failed to record any Gang-gangs in areas where from 1970-2010 they were commonly sighted. They concluded that Gang-gangs in the Hornsby and Ku-ring-gai Local Government Areas are certainly very close to extinction if not already extinct. They noted that a similar decline had occurred within a 20km radius of their study area and at the lower elevations of the Blue Mountains. They proposed that this pattern of decline suggests a climate change effect. They noted that the Gang-gang is adapted to cooler conditions and has always been more common at higher elevations and more southern latitudes. They hypothesized that as the climate warms up, Gang-gang Cockatoos can be expected to decline at lower elevations in the northern parts of their distribution.

A result of our citizen science study suggests that Gangs-gangs in at least part of the northern lower elevation range may be able to avoid the higher summer temperatures by breeding earlier than more elevated or southern birds. This is a hopeful finding, that will need further investigation.

Some of you are also watching nests in Tumbarumba, on the outskirts of Melbourne and in western Victoria – none of which appear yet to have produced fledglings. Fingers crossed you will be able to observe fledglings and you will add to our knowledge of breeding times across the Gang-gangs range. Now that there is a large band of us looking for nests, we can expect that next season we will have the range well covered.

In addition to climate, the Smith’s mentioned other factors that may be contributing to the decline including competition with other species for nest hollows (particularly the over-abundant Sulphur-crested Cockatoos and Rainbow Lorikeets). Our study is also throwing light on this issue – but reporting of these initial results is for the next Journal report.

Posted on December 18, 2021 08:20 PM by michaelmulvaney michaelmulvaney | 2 comments | Leave a comment

December 20, 2021

Hollow occupancy suggests Brushtail Possums may be a greater concern than nesting bird competitors

Over the last three years citizens have made over 500 image based reports of Gang-gang activity at tree hollows. Thank you, to all those who reported sightings. Trees with multiple records or where Gang-gangs were observed entering or leaving hollows were prioritised for checking. The occupancy of hollows during this Gang-gang breeding season was initially checked by visible observation and if no activity was observed then with a pole camera. To date, one Hundred and ninety hollows of known Gang-gang interest were checked in the Canberra area, fifteen at Cooma and four at Tumbarumba.

The following are the initial results

1 Hollows empty – 109 (52%)

  1. Gang-gang nest hollow – 22 (11%) note two nests seem to be no longer active
  2. Flooded (hollow a likely water source) - 19 (9%)
  3. Brushtail Possum in hollow - 18 (9%)
  4. Hollow lined with many gum-leaves suggesting possum use - 12 (6%)
  5. Now a bee-hive -6 (3%)
  6. Galah nest hollow – 6(3%)
  7. Wood-duck eggs or eggshell in hollow 5 (2%) – woodducks have an earlier breeding season and sometimes woodducks and Gang-gangs can use the same hollow within a year
  8. Sulphur-crested Cockatoo nest hollow 4 (2%)
  9. Crimson Rosella nest hollow 1
  10. Rainbow Lorikeet nest hollow 1
  11. Kookaburra nest hollow 1
  12. Boobook Owl roost/nest hollow 1

At least eight of the empty hollows were known Gang-gang nest hollows in previous years. At least three previous nest hollows were flooded this season. Over half of the hollows in which Gang-gangs were observed entering, leaving, chewing bark around or looking into, were empty. Galahs, Sulphur Crested Cockatoos, Rainbow lorikeets and Corellas have all been suspected as being significant competitors of Gang-gangs for nesting hollows, but between them they only occupied 5% of the inspected hollows.

Brushtail possums were observed in 9% of the hollows, with evidence of possum use found in a further 6% of hollows. No Gang-gang nests were found in trees in which Brush-tail Possums were observed but on a few occasions Gangs-gangs were found nesting in the same tree as Sulphur Crested Cockatoos.

Once completed and nest images checked the results will be subject to further analysis, but your work is already providing valuable insights. It is hoped that the Canberra results (were the Gang-gang population is steady) will be compared to that of areas where they have suffered significant and drastic declines – so please keep those tree hollow activity records flowing in.

Posted on December 20, 2021 07:55 PM by michaelmulvaney michaelmulvaney | 0 comments | Leave a comment