Breeding season of the Beach Stone-curlews in the Wet Tropics
- Paul Fisk
- 1 day ago
- 5 min read
Paul Fisk | Threatened Coastal Birds Project Leader
Over the past four years, BirdLife North Queensland’s (BLNQ) Threatened Coastal Birds (TCB) project has revealed remarkable new insights into the breeding behaviour of one of Australia’s most secretive shorebirds – the Beach Stone-curlew (Esacus magnirostris). Through hundreds of hours of field observations, motion cameras and patient monitoring, the project has documented almost the complete breeding cycle in the Wet Tropics, from nesting through to fledging.
The Threatened Coastal Birds project monitored shorebird populations and Beach Stone-curlews between 2020 and 2023, with a particular focus on understanding their breeding biology. This involved identifying breeding territories and nests, then following up every breeding attempt that could be located.
Affectionately known as 'Beachies', they are exceptionally good at hiding their nests and newly hatched chicks. Finding them is often a matter of persistence, patience and a little luck, and it can be difficult to know whether a pair has not nested or whether the nest has simply remained undiscovered. Once a nest is found, motion cameras provide an invaluable source of information, but there is still no substitute for regular field observations.
For this reason, almost all of the breeding behaviour data came from the four territories around Cairns Airport in Trinity Inlet. In total, the TCB project identified eight breeding territories and documented 30 breeding attempts.
Breeding season
Our observations show that the breeding season in the Wet Tropics begins in late August and continues for approximately seven months until February. Nests may be established at any time during this period, with a peak in incubation occurring during August and September, followed by smaller numbers of second and third nesting attempts over subsequent months (Figure 1).
Records from elsewhere in Australia suggest that breeding generally begins later in southern populations and progressively earlier towards the north (Figure 1). Although there are relatively few records from far northern Australia, these include incubation records during winter (June–July).
Understanding when Beach Stone-curlews breed is critical for conservation. Knowing the timing of nesting, incubation and fledgling development helps land managers, researchers and volunteers better protect breeding territories during the species’ most vulnerable stages.
Incubation
The nest is little more than a simple scrape in the ground, usually located in an open area above the high tide mark and close to productive intertidal feeding areas. There are many variations on this theme, with nests sometimes found amongst dead mangrove forests on sand banks, among tree roots at the top of beaches, or within saltmarshes behind mangroves.
Most nests contain a single egg, although there are occasional records of two-egg clutches.
One nest provided an unusually precise measure of the incubation period, showing that incubation lasted between 33.4 and 34.2 days. This is likely to be close to the minimum incubation period for the species.
Both parents share incubation duties, regularly exchanging places in what can only be described as a very polite, slow-walking handover ceremony.
Hatchlings
Within hours of hatching, the chick is already on its feet, shakily exploring its surroundings. The adults gently encourage it to leave the nest and begin walking.
Although capable of leaving the nest almost immediately, the chick often remains close by for up to 24 hours before being led to a nearby hiding place amongst vegetation. The chick shown in the video below was located the following day approximately 20 metres from the nest, concealed on the edge of the mangroves.
Downy and feathered runners
This marks the beginning of a remarkable ten-week period during which the chick is entirely flightless. During this stage – known as the “runner” stage – survival depends on camouflage, vigilance and instinct.
Protected by the watchful adults and its cryptic plumage, the young bird instinctively runs, hides and freezes whenever danger approaches. As it grows older and becomes more mobile, it increasingly relies on quietly moving away from threats rather than simply remaining hidden.
Unlike many songbirds, it is the legs that develop first. By around ten days of age, the youngster is already capable of keeping pace with a trotting adult.
Over the following ten weeks the chick grows rapidly, transitioning from a downy runner into a fully feathered juvenile.
We have not undertaken a detailed analysis of plumage development in relation to age. However, a recent paper by Noske et al. (2024) provides an excellent description and notes that the timing of plumage changes can vary depending on factors such as nutrition.
Both adults continue feeding the dependent runner for many months after fledging. Crabs are by far the most common food item, although cameras have also recorded adults returning with other crustaceans, what appears to be a large insect and even a toad.
Fledgling
As fledging approaches, young birds can often be seen running while furiously flapping their wings in preparation for their first flight.
We have one precise record of fledging occurring at 72 days of age. In the video, the 70-day-old youngster, now carrying a complete set of primary feathers, disappears from view at the top left of the screen.
Two days later, it was flushed from marine fern where it had been hiding and managed a rather unsteady flight of approximately 50 metres back towards its parents.
The third bird
Young from a successful breeding attempt usually remain with their parents until at least the following breeding season and sometimes much longer.
We recorded one young bird remaining with its parents for three years and through three unsuccessful breeding attempts before a successful August nesting resulted in four Beach Stone-curlews occupying the territory until January. After that, three birds remained consistently within the territory.
Without individually marked birds, the role of this “third bird” remains uncertain. It is unlikely to participate in incubation and is sometimes chased away from nesting sites. However, observations suggest it plays an important role in territory surveillance and defence during subsequent breeding attempts.
Young birds can be readily recognised until approximately 18 weeks of age by their plumage and their broad, poorly defined eye patch. They also behave differently from adults, often following their parents closely and approaching them with their head lowered.
By around 20 weeks of age they are largely independent and their plumage is virtually indistinguishable from that of an adult. At this point they become the 'third bird', forming a three-bird family group and providing evidence that the previous breeding season was successful.
Next steps for the project
Between now and next August we will continue searching for fledglings and third birds, while also looking for additional breeding territories throughout the Wet Tropics.
Every observation helps build our understanding of this remarkable species, and the birding community can make an important contribution.
We would particularly appreciate reports of:
Three or more Beach Stone-curlews together anywhere in the Wet Tropics. Look for evidence of a young bird and, if possible, include photographs.
Any records – or even memories – of Beach Stone-curlew nests or very young chicks from the Wet Tropics. Historical observations have already helped us identify two previously unknown breeding territories.
If you have any information that may assist, please contact Paul Fisk at pgfisk@yahoo.com.au.
References
Richard A. Noske, Terry Burgess and Brian J. Coates. (2024) Incubation Period, Breeding Success and Juvenile Development of Beach Stone-Curlews on Kakadu Beach, Southeast Queensland. Sunbird Vol 51:25-38.
