Fecundity, egg size and the influence of rainfall in an isolated population of malleefowl (Leipoa ocellata)
David Priddel A B and Robert Wheeler AA Department of Environment and Conservation, PO Box 1967, Hurstville, NSW 2220, Australia.
B Corresponding author. Email: david.priddel@environment.nsw.gov.au
Wildlife Research 32(7) 639-648 https://doi.org/10.1071/WR04041
Submitted: 17 May 2004 Accepted: 12 August 2005 Published: 24 November 2005
Abstract
An isolated population of malleefowl (Leipoa ocellata) at Yalgogrin in New South Wales, Australia, was studied intensively between 1986–87 and 1998–99. During this period the population produced 124 clutches, comprising a total of 1705 eggs. The number of clutches per annum varied between 5 and 15. Eggs were laid between mid-August and mid-February, with 90% laid between the last week of September and the first week of January. The mean date of laying of the first egg of each clutch (±s.d.) was 21 September ± 13 days and the mean date of the last egg was 23 December ± 19 days. The mean duration of egg laying varied significantly between years (range 70–117 days) and was negatively correlated with the daily maximum ambient temperature in December. Cool temperatures and rain in early summer prolonged the laying season. The mean interval between laying was 6.4 ± 1.1 days (range 3–12 days), with eggs laid at a faster rate during the first half of the laying period. Overall, mean clutch size was 14.1 ± 5.8 (range 1–28). Large clutches were the result of an extended period of laying rather than an increase in the rate of laying. Mean clutch size was greatest when laying extended into mid-February. The best predictor of clutch size was rainfall between May and December – the interval spanning both nest construction and egg laying. The mean volume of all measured eggs (n = 1362) was 162.1 ± 9.0 mL (range 99–200 mL). Egg volume varied during the laying period, with those eggs laid early or late in the breeding season being smaller. Eggs at Yalgogrin were, on average, 10.5% smaller than those recorded at nearby Pulletop.
Acknowledgments
We thank the many volunteers that assisted in the arduous work of excavating malleefowl nests. Geoff Ross organised and participated in the original survey to locate malleefowl nests. We thank Roy Woods, Lindsey Darrington and Alan Jones for granting us access to their properties. This project was conducted under the NSW National Parks and Wildlife Service Animal Research Authority No. 8; NSW National Parks and Wildlife Service Scientific Investigation Licences A269, A2635 and C147; and Australian Bird Banding Scheme Authority 1208.
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