F eathering their nests

Ht ea her McGinness, Kate Brandis, Veronica Doerr, Richard Kingsford, Getting ‘event ready’ We know from our discussions with Ralph Mac Nally and John Martin are collecting data to provide water managers that they want to improve more information on how the success of waterbirds breeding water provision, vegetation and feral management to ensure ‘event readiness’ c an be improved in the Murray–Darling basin. at waterbird breeding sites. Maximising the recruitment of young into the adult Environmental watering events in the Murray– population depends on having the largest Darling Basin (MDB) target a range of possible number of chicks fledging from environmental outcomes, including supporting each site. Understanding and maintaining the habitat and breeding of waterbirds. Through appropriate nesting site characteristics is previous research and observation, we know crucial, so the questions our research is where the key waterbird breeding locations are answering are: in the Basin, and the flows required to trigger 1. How do nesting-habitat preferences and complete nesting events. However, there differ among , sites and events? is limited information about the rates of ‘nest 2. How do nesting-habitat characteristics success’ — which is the number of eggs that influence the numbers of fledglings hatch into chicks, and the number of chicks produced? that survive to leave the nesting site and join – How much does predator access the rest of the population. (nest position, water level) affect As part of the MDB Environmental Water fledging rates? Knowledge and Research (MDB EWKR) – How much does nesting habitat project, we are investigating both rates and influence the exposure of chicks to determinants of ‘nest success’, by examining extremes in temperature or weather? the relative influence of flow, habitat and other 3. Where do the first arrivals at a colony pressures, as well as threats like predation, site decide to start nesting? Are there habitat changes and weather extremes arising relationships between site vegetation and from climate change. This knowledge will water characteristics and these choices? enable managers to focus limited resources For example, how much does the ratio on maximising nest success and the recruitment or distribution of water and vegetation of young birds into the population. affect the initial locations of nesting birds? 4. How can environmental flows be managed to support better nesting habitats?

Above: Cameras monitor the progress of Australian White nests. Photos throughout courtesy of the authors.

Rp i Rap, Edition 40 9 Feathering their nests

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Photos in film strip from left: [frame 2] Royal display and gift, [3] Royal Spoonbills display to one another, [4] Royal parents with eggs, [5] with egg, [6] Royal Spoonbills with chicks, [7] In a good year Royal Spoonbills can raise four chicks successfully, [11] shades its chicks on a hot day. Photos from CSIRO monitoring cameras. Note: Film strip is for graphic purposes. Photos in egg shapes: Straw-necked Ibis chick and eggs (left), slightly older chick (right).

To answer these questions, we are working on: Our discoveries • Measuring egg and chick development and A pilot study was conducted in 2015–16 and survival rates using analysis of images from analyses are underway for data collected in remote motion-sensing and time-lapse 2016–17, with a final year of data collection cameras. planned for 2017–18. The nests of three species • Monitoring predation (predator species, are being monitored: Australian White Ibis impacts, timing, and location) and waterbird ( molucca), Straw-necked Ibis behaviour using analysis of images from (Threskiornis spinicollis), and Royal Spoonbill remote motion-sensing and time-lapse (Platalea regia). So far we have found that: cameras focused on nests. • Australian White start new nests • Colony mapping, nest counts, and throughout the breeding season (spring– fortnightly monitoring of eggs and chicks summer). Straw-necked Ibises start nesting at a subset of tagged nests. later than white ibises and tend to be more • Surveys of nesting habitat characteristics concentrated spatially and temporally. Royal (e.g. species, nest position, nest materials, Spoonbills spend time courting, establishing water depth, vegetation type and territory and trampling rushes for several distribution or density, nest density, weeks before starting to lay. Consequently location within colony, exposure). spoonbills may appear to be nesting when • Analysis and modelling of relationships observed from the air, but may not in fact between flows (water-related variables), have nests, eggs or chicks. Young spoonbills nesting habitat characteristics (particularly are generally present in nests much later vegetation type and structure), predation, than ibis chicks. It is easy to confuse Royal temperature and weather variables and Spoonbills with Australian White Ibis when nest success variables. viewed from the air because both are white. • Clutch sizes differ among waterbird species and among years, with Royal Spoonbills in 2016–17 generally laying more eggs (two to Straw-necked Ibis with four; mean 3.7) than Australian White Ibises chicks in the . (one to four; mean 2.9) and Straw-necked Ibises (two to three; mean 2.4). Abnormally large clutches of five or six eggs are For further information sometimes seen. Heather McGinness — [email protected] https://research.csiro.au/ewkrwaterbirds/ MDB EWKR Story Space — www.ewkr.com.au

10 Rp i Rap, Edition 40 McGinness and colleagues | waterbirds

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• Hatching rates are quite low (30–60 per • Nesting-habitat choices differ within and cent). Royal Spoonbill eggs are more likely among sites. In Barmah-Millewa forest and to survive to hatching than Straw-necked parts of the Macquarie Marshes, both ibis Ibis eggs, while Australian White Ibis eggs species appear to prefer tall common reed are the least likely to survive to hatching. (Phragmites australis) with ‘water views’ in • Most egg mortality is from predation, the centre of regularly-inundated wetlands. with some from parental rejection or Straw-necked Ibises in Barmah-Millewa abandonment of nests. forest also nest in large numbers in giant • Most predation events in Barmah-Millewa rush (Juncus ingens) surrounded by water. forest are in daylight by native species, Royal Spoonbills appear to prefer giant including Purple Swamp Hens (Porphyrio rush surrounded by water at Barmah- porphyrio), Swamp Harriers (Circus Millewa, but nest in trees in other sites. approximans), Australian Ravens (Corvus Lignum is important in other systems such coronoides) and White-bellied Sea-Eagles as Narran Lakes, the lower Murrumbidgee (Haliaeetus leucogaster). Anecdotally, and lower Lachlan rivers. Although Royal predation by feral such as pigs, Spoonbills congregate, they do not nest in foxes and cats is more of a problem in as close proximity to one another like other breeding sites like the Macquarie the ibises do, maintaining at least a Marshes. Most predation events occur couple of metres between nests. in limited areas of the colony, while other Data analyses to be conducted as part areas are not affected much. Entire clumps of the broader MDB EWKR project of nests are typically affected within short will explore these results in more periods (minutes to days). detail with recommendations for • Once hatched, chick survival (fledging) land and water managers during rates are generally high and similar among the next stage of this project. the three species (88–92 per cent). • Nest-attendance patterns differ significantly between species and years. Royal Spoonbills are the most attentive to their nests, which may explain the relatively low mortality

rates for their eggs and chicks. Australian Straw-necked Ibis attending White Ibises are the least attentive, and to a nest in the Macquarie Marshes. the most erratic in their nest-attendance patterns. Differences in attendance T he MDB Ewkr project is funded by the Australian between years may reflect food availability. Government’s Commonwealth Environmental Water Office.

Rp i Rap, Edition 40 11 Australian River Restoration Centre

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Edition 40