Pair of Brolgas with chicks. Image: Bob McPherson.
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Brolga flocking counts in south-west Victoria recent history and updates
The Brolga Grus rubicunda is a light-grey coloured crane, standing about 1.8 metres high, it has a long, straight bill, long dark coloured legs and a wing span of about 2 metres. Appearance changes with age. Immature birds (up to 10 months of age) have a grey, fully feathered head. Juveniles (11 to 22 months) gradually lose their head feathering and attain a pale orange-red head colouring.
Adults have a conspicuous orange-red head, which contrasts with the bare crown of greenish-grey skin and have a black dewlap under the chin. Adult males and females appear similar, although males are larger.
Genetic research conducted in 2016 via the Nature Glenelg Trust found a genetic differentiation between the Victorian and northern Brolga populations. It is now considered that the Victorian population should be treated as an independent management unit isolated from the northern populations of brolga.
In Victoria, Brolga numbers are highest in the south-west (907 adult birds in the 2013 count), compared with northern irrigation areas (Est. population 60-70). The higher numbers in the south-west are probably due to higher rainfall and the occurrence of suitable freshwater habitats.
Historic distribution of the Brolga in Victoria. Source: Victorian Biodiversity Atlas, Department of Environment, Land, Water & Planning. Accessed: September 2015.
During the breeding period between July to December the main habitat is freshwater meadows or shallow freshwater marshes, although they have been known to nest in deep freshwater marshes and in the shallows of permanent open water in association with vegetation. During the non breeding period from late December to early May habitat comprises deep freshwater marshes, vegetated areas in permanent open water and feeding areas in pasture, seed and stubble crops. The Brolga is omnivorous and utilises a diverse range of food items on a seasonal basis, including vegetable material, amphibians, sometimes small fish and a wide range of invertebrates, including freshwater molluscs, crustaceans and insects.
Brolga pairs bond for life and have been known to utilise the same nesting areas for up to 20 years
Brolga pair with chick in south west Victoria, September 2016. Footage courtesy Bob McPherson.
One of the major threats is loss of freshwater habitats through drainage and removal of wetland vegetation. The cropping of swamps has been shown to result in a reduced diversity and density of plants compared with uncropped swamps (Casanova 2012). At a landscape level the widespread cropping of swamps could reduced the quantity and quality of Brolga habitat in the landscape.
The Red Fox is a serious predator, taking eggs and killing chicks. Failure to achieve sustainable levels of recruitment through constant mortality of young Brolgas could have serious impacts for the population in Victoria. Image: Bob McPherson.
The small (200-250 breeding pairs) in the Victorian population is considered to be an isolated and self-recruiting breeding unit but likely to be particularly prone to loss of genetic diversity and the negative effects of inbreeding.
Conservation efforts in Victoria should be geared toward securing and restoring suitable wetland habitats, increasing local population sizes, and preserving genetic diversity.
The protection of wetlands, particularly on private property is crucial in retaining suitable breeding habitats. This includes predator control around and on public and private land which are breeding areas. Improved management of grazing on public wetlands will ensure habitat is retained at Brolga breeding sites. Surveys to determine population trends, identification of nest sites and breeding success are necessary to monitor the population.
Breeding success is highly dependent upon the availability of suitable habitat. Drought conditions combined with a more permanent loss of wetlands due to drainage may have been major contributing factors low breeding success in 2005 when only a handful of nests were counted in south-west Victoria and the success of these in doubt. Results from the 2006 & 2008 flocking surveys in south-west Victoria also found poor recruitment with no immature birds being identified in these years.
Since 2010 there has been an improvement in the number of nests and evidence of young birds in the flock e.g. 50 young (1& 2 year old) birds recorded in 2011. In addition there is evidence the total flock count has risen since 2007 when the south-west Victorian population count was in the order of 600-700 birds compared with the 2013 count of 907 adult birds. The increase could be due to successful breeding, improved counting methodology or movement of Brolgas from adjoining areas in South Australia, therefore some caution needs to be applied when evaluating the overall status of the population.
The Brolga Recovery Group was formed in March 2010 and is supported Birdlife Australia, Trust for Nature, Glenelg Hopkins CMA and Greening Australia. It also has connections with people from Universities, and the Department of Environment, Land, Water & Planning.
Department of Environment, Land Water & Planning
Parks Victoria
Corangamite CMA area
North East Victoria
Winton Wetlands - Goulburn Broken CMA area
North Central Victoria
Image: Richard Hill, DELWP, Casterton
Flocking counts were conducted in May 2010 with numbers down on previous counts. A good sign was that 6 out of 8 chick banded the year before were recorded in the flocking counts.
This year eight chicks have been colour banded (2 in the Skipton, 4 in the Darlington/Derrinallum/Mortlake and 2 in the Minhamite areas). Two individuals from the Willaura area have been colour-banded and fitted with satellite transmitters. These birds are currently in the Digby/Dartmoor area. Two individuals at Penshurst have also been colour-banded and one of these has a satellite transmitter. One bird has travelled 125 km.
Flocking counts were conducted in May 2011 with numbers similar to previous counts considering the count did not include all known sites. The flocking counts of 2011 indicated a positive sign of 50 young birds (1 & 2 year old). The largest flocking sites were at Penshurst with up to 121 birds recorded and Kaladbro Swamp with 76 birds.
With high rainfall over the last two years many wetlands have been replenished and it is hoped the 2012 breeding season will be a success.
Michelle Casanova, Botanist, Royal Botanic Gardens, Melbourne has undertaken a study to examine the effect of cropping on swamps (Casanova 2012). She found that the flora (community of water plants) that establishes when swamps wet-up after cropping is different from swamps that were not cropped. Cropped swamps have more species that respond to disturbance, a lower plant density and fewer perennial grass species. The seed bank of cropped swamp samples was different from the seed banks of uncropped swamp samples with fewer species and less dense vegetation. Cropping swamps reduces their capacity to respond to water when wetter seasons occur which is likely to affect the quantity and quality of Brolga habitat in the landscape.
Information provided by Richard Hill, DELWP, Casterton
In late April this year, observers again spread out across south-west Victoria to count brolgas at their annual flocking sites. The count had two aims: to get a better estimate of total population size, and to estimate the proportion of young birds in flocks to give an idea of the amount of successful nesting that had occurred in the previous two years. Young brolgas can be aged with confidence to about 2 years old.
Counters searched previously known flocking sites in the following areas: Willaura, Penshurst, Lake Bolac, Streatham, Darlington, Camperdown, Strathdownie, and Bool Lagoon. Bool Lagoon near Naracoorte in South Australia was included because brolgas are known to move between south-west Victoria and South Australia.
A total of 907 birds were counted on the day. The largest flock recorded on the day was a massive 320 birds at Strathdownie counted by Richard and Ros Collins. Numbers for Penshurst were also high, down from a maximum count of 268 earlier in the season to 241 on the count day. A flock of 100 birds were counted at the Willaura flocking site.
The first estimate of the Victoria brolga population was 600-650 birds by Arnol et al. (1984) with approximately 550-600 birds in south west Victoria. The smallest total reported in previous flock counts in south-west Victoria was 402 by Philip Du Guesclin in 2002, and the largest was 675 from 2004 by Rebecca Sheldon. This is only the second year in which counts have been undertaken systematically by having different sites counted on the same day across the state. Previous counts from the late 1980s to 2000s are thus not comparable to the counts from 2012 and 2013. Nevertheless, the large number of young birds in flocks in the past three years and highly unusual sightings of several flocks of sub-adult Brolgas during the breeding season of 2012 both support the conclusion that there has been a substantial increase in total brolga numbers in south-west Victoria in this period.
Large numbers of juveniles and sub-adults were found in this year’s counts, with an estimated 17% of all birds counted being either juvenile or sub-adult (less than two years old). This number is at the upper end of values found for south-west Victorian flocks and is similar to last year’s result. Such high proportion of juveniles and sub-adults in flocks also suggests that breeding success has been higher over the past two years than in previous years. In contrast, the count in 2009 recorded a proportion of only 3% birds less than two years old in counted flocks. These age structure counts are helping us gain a better understanding of breeding success in the southwest and in the longer term, the viability of this south-west Victorian population.
This year all counts were done on a single day, following the advice of Inka Veltheim, PhD candidate at University of Ballarat, who has found that flocking brolgas can move quickly between flocking sites. A simultaneous count of sites across the region gives greater confidence that the number did not include any individuals counted twice. Although the vast majority of birds are considered to flock to these traditional sites, some brolgas can be resident year round at their breeding wetland if they retain water and food resources. Breeding sites are not counted in annual flock counts, and thus these counts represent an underestimate (presumed small underestimate) of the total population size in south-west Victoria.
In conclusion, these counts are allowing us to produce a more accurate picture of the population size and status of our iconic brolga population. Recent results showing substantial increase in successful breeding suggest that breeding success is markedly increased in years of good winter-spring rainfall, and that securing or improving wetland filling for brolga nest sites should be a key focus of brolga conservation in south-west Victoria.
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.
Brolgas can be a welcome sight on farmlands. Image: Stuart McCallum
Brolga with chick near Casterton, Victoria. September 2016. Footage courtasy Bob McPherson.
Brolga breeding success counts in south-western Victoria 2016 and 2017, information provided by the Department of Environment, Land, Water and Planning, Barwon South West Region.
In late April 2016 and again in 2017, experienced counters visited the main brolga flocking sites in south-western Victoria. The purpose of these visits, which have been repeated annually since 2008, is to estimate the amount of successful breeding and recruitment that has occurred in the previous two years by documenting the proportion of juvenile and sub-adult birds in the flocks.
In 2016, a total of 348 birds were detected on one day. From a subset of these birds where age structure could be determined, 8% were juveniles or sub-adults. In contrast in 2017, the estimate of recruitment was taken from 278 birds, with 18% of birds being juveniles or sub-adults. The contrast in these two results is consistent with the belief that rainfall is a major driver of breeding success with the 2016 breeding season being a very wet year with many wetlands filling and holding water throughout winter, spring and into early summer.
Of particular note from these counts was the very large flock of 373 birds recorded in the Strathdownie/Mingbool area on the Victorian/South Australian border the day before the 2016 count. Due to logistical issues this site could not be visited on the day of the formal count.
Victorian brolga census 2018. Source: Department of Environment, Land, Water and Planning, Barwon South West Region.
On 14 April 2018, observers spread out across Victoria and south-east South Australia to count brolgas at their summer-autumn flocking sites. The count this year had two aims: to get an estimate of the population size through a population census, and to estimate the level of successful breeding from the previous two years through the proportion of young birds counted.
Estimating population size is difficult in nomadic species that range over large geographical areas such as brolga. This is because these species tend to be hard to detect i.e. may be dispersed over numerous locations, and hence large portions of the population may not be counted in one census. This has been evident in the large fluctuations in estimated brolga population size from censuses in the past. The results from a population census are therefore only a ‘snap-shot’ of the population at the time of the count.
This year a team of 15 experienced counters searched known brolga flocking sites in south-western and north Victoria and south-east South Australia including: Willaura, Penshurst, Lake Bolac, Streatham, Darlington, Camperdown, Strathdownie, Bool Lagoon, Rutherglen, Nagambie and Corop.
Unfortunately, 14 April was most memorable for its terrible weather, as a very intense cold front drove very strong winds and heavy rain across south-east South Australia and Victoria. Brolga flocks which had been reported regularly just prior to the count vanished or fragmented and the count results suffered. For example, 150 birds had been reported from Penshurst, but only 54 were found on the day. One hundred and fifty-seven birds were then detected at the same site in the week following the census. Similarly, a reported flock of 100 birds at Bool Lagoon disappeared on the census day, with only six birds detected. The weather also made visibility to see brolgas poor and access at some sites difficult.
In total 377 birds were counted on the day. This figure is well below the last population estimate recorded, however it’s also below or similar to the total birds counted in recent annual recruitment counts, which are only taken from a subset of flocking sites in south-western Victoria (449 birds in 2015 and 348 in 2016). The best explanation for this small population estimate is that the very poor weather meant that many birds were not detected on the day. Poor weather, particularly rain and wind, are recognised factors that impact and reduce detectability during monitoring for many types of birds and hence the outcome here is not surprising.
The results of the breeding estimate (taken from a subset of birds counted where the counter was experienced and confident of identifying different age groups) from the day were encouraging with 13% (32 out of 247) of birds either juveniles or sub-adults (less than two years old). This figure is a relatively high value for Victorian flocks, suggesting that there has been good breeding success over the past two years.
In conclusion, although the population estimate was much lower than expected, it isn’t evidence of a significant reduction in population size, but rather a direct result of the very poor weather. As such, the population census will be repeated in autumn 2019. The positive news from this count is that the Victorian brolga population appears to have again had good breeding success.
See also
International Crane Foundation
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