SWIFFT - State Wide Integrated Flora and Fauna Teams

SWIFFT - State Wide Integrated Flora and Fauna Teams
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Key Findings

 

 

 

 

 

 

 

 

Key research 2009 & 2010

Since late November 2009, 22 brolgas have been fitted with transmitters. This includes 11 pre-fledged chicks, five adults and six juveniles. Nineteen of these have provided enough data for analysing movements and habitat use. Eight transmitters are still providing data.

The deployment of these transmitters over two and a half years has allowed the collection of data across age cohorts, seasons and years. These data are providing information on several aspects of brolga biology and ecology, including:

  • seasonal movements between non-breeding and breeding sites
  • dispersal of chicks from breeding grounds
  • habitat use, home ranges and spatial requirements
  • survival of chicks, juveniles and adults.

Data analysis is currently under way and the next 12 months will be spent writing a thesis and preparing manuscripts for publication.

Pre-fledged chicks colour-banded in 2009-2010

In 2009, eight brolga chicks in south-west Victoria were colour-banded. Sightings of these bands during the 2010, 2011 and 2012 flocking season confirmed that all eight chicks fledged and dispersed. Two of these were seen for the first time since banding in 2012, despite numerous visits to known flocking sites in 2010 and 2011.

In the second half of 2012, two individuals have paired up and one has attempted to breed at the Macarthur wind farm.

Birds fitted with PTTs in 2010 at flocking sites

During the flocking season in 2010 (April-June), three individuals were fitted with PTTs. This included one adult and juvenile at the Willaura flocking site and one juvenile at the Penshurst flocking site.

These PTTs have ceased operating and have provided approximately 10, 18 and 24 months worth of data. From flocking sites all three birds dispersed towards south west Victoria to the Casterton, Digby and Dartmoor area. The Willaura birds departed in late May to early July 2010 and the Penshurst bird departed in August 2010. All three returned to the flocking site they were captured at originally.

During the 2012 flocking season, two of the birds originally captured at Willaura were observed in flocks there. This indicates that birds return to areas they’ve previously used. The sighting of these birds also shows high survival in juveniles and adults over a number of seasons and seasonal movements.

Pre-fledged chicks fitted with PTTs in 2010-2011

During the 2010-2011 breeding season a total of 11 pre-fledged chicks were fitted with PTTs at breeding sites. Ten of these were captured in the Skipton and Streatham area and one was captured in the Casterton area.

Over the 2010-2012 period nine birds have been using an area, of approximately 35 km (east to west) by 95 km (north to south) in size, between the Western Hwy and Princes Highway. Most of the activity of the nine birds has concentrated between an area bounded north-south by Glenelg and Hamilton Highways and east-west by Lismore-Skipton Road and Mortlake-Ararat Road.

Known flocking sites used included the Blue/Pink/Salt Lake complex south of Carranballac and the Darlington area. Areas around Woorndoo were also intensively used by three birds carrying PTTs.

One of the birds fitted with PTTs in 2010-2011 near Skipton dispersed to the Willaura flocking site in November 2011 and spent two months there. It returned to an area near Carranballac in January 2012, close to where it had dispersed from in November 2011.

Another bird fitted with a PTT near Skipton dispersed from Nerrin Nerrin-Lake Bolac area to the Willaura flocking site in August 2012. This bird now appears to be heading south west and is currently between Penshurst and Hamilton.

The bird captured as a pre-fledged chick near Casterton has spent the last 21 months between Mt Gambier, South Australia and Casterton, Victoria.

Birds fitted with PTTs in 2011 at flocking sites

Two birds were captured at the Penshurst flocking site in 2011. This included one juvenile and one adult. The adult bird moved to the Willaura flocking site a few days after release. It dispersed from Willaura south west, 120 km from the flocking site and stayed between Strathdownie and Dartmoor until the PTT stopped transmitting regularly in October 2011. This individual was seen at the Willaura flocking site in early 2012.

The juvenile dispersed from the Penshurst flocking site south, towards Heywood, in June 2011. It continued north west and stayed between Mount Gambier and Casterton, moving between South Australia and Victoria. It began to move north east in December and spent the flocking season at the Willaura flocking site. It departed from Willaura towards south west in May 2012. It flew to the same areas between Mount Gambier and Casterton that it used in 2011.

Three birds were captured and fitted with PTTs at the Willaura flocking site in 2011. This included two adults and one juvenile. All these birds moved south west, following similar paths as all other birds captured at the Penshurst and Willaura flocking sites in 2010 and 2011. One adult bird returned north a day later and spent winter and spring near the Rocklands Reservoir, west of the Grampians. The PTTs ceased transmitting prior to the birds reaching flocking sites in 2012. However, all three birds were observed at the Willaura flocking
site in April 2012.

Habitat use, home ranges and spatial requirements

Birds fitted with transmitters have provided data on habitat use, home ranges and spatial requirements at breeding and non-breeding sites. Up to four GPS locations per day are being logged for each individual, providing detailed information about feeding and roosting habitats. Three birds fitted with PTTs in 2011 are providing more detailed information about day and night habitat use.

Survival of chicks, juveniles and adults

Nineteen pre-fledged chicks have been banded during the project, 11 of which have been fitted with transmitters. All these chicks survived to fledging and dispersal, indicating that chick survival can be high if breeding sites have water for the duration of the hatching to fledging period.

The data from birds fitted with transmitters indicate that adult and juvenile survival is also generally high.  However, survival appears to be lowest in the juveniles, particularly during dispersal from breeding to non-breeding areas.

Data from colour banded pre-fledged chicks indicates that brolgas can pair up and breed when they are almost three years old. This also suggests that survival of chicks to fledging is important, as the chicks can become breeding adults and contribute to maintaining the population.

Analysis of data, thesis preparation and writing for publication

Preliminary analyses for the data have been undertaken and will continue for another two months. Concurrently, I will be undertaking detailed analyses and writing up results towards thesis submission and publications.

I will be presenting the results of the seasonal movements at the Wind and Wildlife Conference to be held in Melbourne on 6 October 2012.

Recommendations for continued data collection

The results from the study so far have shown that colour banding and fitting of transmitters on brolgas of different ages is highly valuable in determining movements at different life stages of brolgas (chicks, juveniles and adults) and during all parts of their annual cycle (breeding to non-breeding).

Chicks colour-banded in 2009-2010 indicate that brolgas can begin to breed at just under three years of age. Birds still carrying operational PTTs are almost two years old, and would therefore be expected to begin to breed from 2013 onwards.

Number of the birds with PTTs have utilised areas where wind farms are being proposed. For example, seven of the birds with PTTs that are still transmitting have used areas around the Dundonnel and Darlington area. One juvenile originally captured as a pre-fledged chick is showing dispersal towards southwest to similar areas as adults and juveniles captured at the Penshurst and Willaura flocking sites. This juvenile has also used habitats around the currently operating Oakland Hill wind farm near Glenthompson.

Use of transmitters

In December 2011 and January 2012 three more transmitters were fitted on birds at flocking grounds.

Further data on survival was collected in 2012 from the transmitters and observations at flocking sites.

In depth analysis of the data was carried out during 2012.

Key brolga count findings to July 2010:

  • 401 Brolgas were found at five flocking sites in May, of which between nine and 16% of flocks were young birds less than one year old.
  • This compares favourably with the previous year 2008 when only 3% of flocks were juveniles, and indicates that the breeding season of 2009 was a very good one. This was due to the good rainfall in southwest Victoria in winter and spring of 2009.

 

Key research findings to November 2011:

Seasonal movements between non-breeding and breeding sites

Eight individual brolgas provided data on seasonal movements. These birds departed the non-breeding grounds of Willaura and Penshurst in late May to early July in 2010 and 2011. Seven of these moved approximately 100 km west and south west to an area near Casterton and Dartmoor. One individual also moved to this area, but flew back north east and settled near the Grampians.

Dispersal of chicks from breeding grounds

Leg band mounted transmitters were fitted on 11 pre-fledged brolga chicks between November 2010 and March 2011. All survived to fledging and dispersal. Nine of these have survived to date. Two individuals died shortly after leaving their breeding site.

Most of the chicks remained near their breeding grounds through the flocking period. The first fledglings began leaving their breeding area in March, with most fledglings leaving between June-August. Two individuals still remained near breeding sites in August.

Habitat use, home ranges and spatial requirements

Up to four GPS locations per day are being logged for each individual, providing detailed information about feeding and roosting habitats. Analysis of this data will begin in early 2012.

Survival of chicks, juveniles and adults

Nineteen pre-fledged chicks have been banded during the project, 11 of which have been fitted with transmitters. All these chicks survived to fledging and dispersal, indicating that chick survival can be high if breeding sites have water for the duration of the hatching to fledging period.

The data from birds fitted with transmitters indicate that adult and juvenile survival is also generally high.

Brolga counts

The Department of Sustainability and Environment has been coordinating counts of brolgas in southwest Victoria for the past three years to get a better understanding of how many brolgas there are in the southwest and how much successful breeding is happening.

 

Key research findings to January 2012:

Identifying and tracking the birds

Chicks and adults are being colour-banded and fitted with satellite transmitters. Two colours identify the bird’s broader region (one of four regions) and specific area, and each bird has a specific letter/ number code. Satellite transmitters collect locations using GPS technology four times per day and send these data back to the researcher via satellite once a week.

Research progress to date

Prior to December 2009 an aerial survey to find brolga nest sites was undertaken. Since late November 2009, 22 brolgas have been fitted with transmitters. This includes 11 pre-fledged chicks, five adults and six juveniles. Fourteen transmitters are still providing data. Introducing these transmitters over a year and a half means data has been collected across age cohorts, seasons and years.

Key research findings 2015

Brolga counts 2015

Brolgas flock count in south-west Victoria 2015 - Information provided by Department of Environment, Land, Water and Planning, Barwon South West Region. 
 

In late April this year, ecology student and PhD candidate with Federation University Inka Veltheim, and DELWP Senior Biodiversity Officer Richard Hill, visited key Brolga flocking sites in south west Victoria.  The objective was to determine the proportion of juvenile and sub-adult birds within the flocks to provide an estimate of the amount of successful breeding that had occurred in the previous two years. This work has been undertaken annually since 2009.

Large flocks of Brolgas were found at regular sites at Strathdownie west of Casterton, north-east of Penshurst, south of Willaura, Darlington, and Lake Wongan while surveys in South Australia failed to detect any flocks.

A total of 449 birds were observed on the one day. The largest flock recorded was of 130 birds north of Penshurst. Of the 449 birds observed, ten percent were juveniles (birds born in spring  2014) or sub-adults (birds born in spring 2013).

In 2014, seven percent of flocks contained juveniles or sub-adults. The lowest estimate since the counts began was three percent in 2009, while in 2012 seventeen percent of flocks were sub-adults or juveniles.

These age structure counts are useful in gaining a better understanding of breeding success in the south-west Victorian population and are considered a better indicator of long term population trends than annual population size estimates.

From these results we are slowly building up a better picture of the population trend and status of our iconic Brolga population and the factors that influence breeding success.  This will help in making better informed decisions for their conservation in the future.