Brolgas and salinity

On this page Ozcranes looks at the intriguing, but hardly studied, relationship of Brolgas to saline environments. Due to a specialsed gland, Brolgas are the only crane able to drink fresh or saline water, but there are no published studies of Brolgas drinking in the wild to describe or quantify this. Here we present a description and photographs of Brolgas apparently drinking salt water on Sweers Island, Gulf of Carpentaria, north-west Queensland, and observations of Brolgas in some other saline environments.

Also on Ozcranes: Brolga food covers Brolga food (and water in general) and Brolga FAQ 1 covers features, size, location and numbers. An introduction to Brolgas and Sarus Cranes including comparison photos and calls, is in Ozcranes Australia/New Guinea Cranes Intro.


Drinking seawater?

Brolgas use fresh and saline wetlands, and are the only crane to have glands near the eye (or specialised tear ducts) that excrete excess salt (Hughes & Blackman 1973). The glands only kick in to excrete salt if required, so do not operate if Brolgas can consume sufficient water from fresh sources. The reference [1] states that Brolgas ‘roost frequently on saline areas at night, and drink fresh and salt water’, page 515. However the paper deals only with the biological processes studied in two captive Brolgas, and gives no detail on Brolgas drinking in the wild, or the levels of salinity in the waters they drink. Presumably the statement derives from Blackman's experience in ecological studies of northern Brolgas, e.g. ‘The Swamps’ [2]. Ozcranes is pleased to present images and a firsthand observer report on Brolgas apparently drinking sea water.

Brolgas drinking seawater Brolga footprints Brolgas on  beach

↑ L. Brolga family drinking from the sea, and C. their footprints on the beach showing the three front toes. R. Brolgas feeding on the beach, Sweers Island, far NW Qld. Their salt excretion gland enables Brolgas to drink salt water and feed in saline environments (Bob Forsyth)

In April 2008 Bob Forsyth saw three Brolgas – a pair with one young of the season – walk down to the shore on Sweers Island, Gulf of Carpentaria. Each bird took a maximum of two very short drinks of sea water, then they left: so the ‘trip’ was specifically to drink. There were about 40 Brolgas on the island at the time, but no fresh surface water on Sweers Island (drinking water comes from wells). Bob said he forgot to taste the sea water at that spot himself, but he believes with the normal tides it would be saline. Observers report up to 20-30 Brolgas on the island, they often feed on sandbanks.

There is a freshwater lagoon on Bentinck Island, some 8 km from the nearest point of Sweers Island, and elsewhere Brolgas have been recorded flying from 5 to 11 km for fresh water (Walkinshaw 1983, see below). Lyn Battle of Sweers Island resort adds: “We have seen them [Brolgas on Sweers] dig holes at high tide, and the Bentinck ladies have told us that when they themselves are looking for fresh water when camping, they seek out these Brolga 'holes' and they dig deeper and find where fresh water is seeping off the land” (the indigenous people of Bentinck also own Sweers Is).

Salt pans on Princess Charlotte Bay, CYP

Salt pans and saline grasses on Princess Charlotte Bay, CYP (Spelio). More than 300 Brolgas were seen feeding and loafing here in 2000 (cranesnorth)

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Saline habitats

Brolgas in Victoria, south-eastern Australia, use mostly freshwater wetlands for nesting, but records of 29 wetlands used by flocking Brolgas found that eight sites were fresh water (< 500 ppm); 12 were brackish (500 ppm to 18,000 ppm); three were semi-saline (18,000 ppm to 30,000 ppm) and six were saline to ultra- or hyper-saline (30,000 ppm to > 100,000 ppm), [3]. However Brolgas using very saline sites for feeding or loafing may fly to fresher water sources to drink, or use e.g. stock troughs [4]. It's also hard to know how far current choices by Brolgas are their actual preference, or determined by what wetlands are left after substantial clearing and drainage for agriculture in south-eastern Australia. Brackish wetlands can in fact be more productive for waterbird food sources than fresh water swamps [5], but in Townsville, northern Queensland, Blackman [2] reported that Brolgas nesting on saline swamps needed larger territories and home ranges than pairs nesting on fresh water wetlands.

In 1968 crane observer L H Walkinshaw visited northern Queensland [6] and reported that near Townsville, Brolgas often roosted on saline tidal flats, but rarely drank there:

At times I observed Brolgas sipping some of this, but not often. Once as I watched they flew up, circling one to three times for elevation, then flew three to seven miles [5-11km] away for fresh water at some dam or pond...two small ponds on the Pallarenda Town Common were also used. These were only about a mile from where the Brolgas fed.

At Lake Buchanan, 250 km SW of Townsville, Walkinshaw found that Brolgas concentrated more on fresh water as the season became hotter and drier:

In October 1968 we found forty or more Brolgas around [salt] Lake Buchanan, scattered pairs around Cauckingburra Swamp [fresh] in late October and early November 1968, and up to around 700 in early January 1969. At Lake Buchanan cranes fed on a grass that had a small tuber beneath the sandy soil. These birds, although drinking some saline water from Lake Buchanan, periodically went back to Cauckingburra Swamp for fresh water [distance 1.6 km]. Later, when Lake Buchanan began to dry up and become more saline, the birds resorted to a little nearby lake for fresh water entirely.

Flocking Brolgas at brackish Lake Wongan, SW Victoria (Ed Dunens).

Flocking Brolgas at Lake Wongan

As Lake Wongan dries out (below), salinity increases and Brolgas may seek fresher water elsewhere.

Lake Wongan drying out

Websites

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References

[1] MR Hughes & JG Blackman (1973). ‘Cation content of salt gland secretion and tears in the brolga, Grus rubicundus (Perry) (Aves: Gruidae)’ Aust J Zool 21(4): 515-518.

[2] Blackman, J.G. (1983). ‘The swamps: A habitat in motion’. In: Lavery, H.J. (Ed.). Exploration North: A Natural History of Queensland, 2nd edn, pp. 147-184. Currey O'Neill, Melbourne.

[3] RA Sheldon (2004). ‘The characterisation and modelling of Brolga Grus rubicunda flocking habitat in south-western Victoria: Relationships between habitat characteristics, Brolga abundance and flocking duration’. Hons. thesis, Federation University Ballarat.

[4] K King (2008). ‘Behaviour patterns and habitat use of the Brolga Grus rubicundus at two flocking sites in south-west Victoria’. Hons. Thesis, Deakinn University, Geeong.

[5] Halse SA, Williams MR, Jaensch RP, Lane JAK (1993). ‘Wetland characteristics and waterbird use of wetlands in south-western Australia’. Wildlife Research 20, 103-125.

[6] LH Walkinshaw. (1973). Cranes of the World. Winchester, New York.

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