Causes of nesting losses in the cattle egret Ardeola ibis in eastern Australia with special reference to the pathogenicity of the tick Argas (Persicargas) robertsi to nestlings

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Abstract
In a 3 year study of the cattle egret at a heronry of 3500 nests in south‐east Queensland, 34% of eggs in 711 nests observed failed to survive to become fledglings (11 day old chicks). Fledgling mortality seemed much lower. The main sources of mortality were crow predation on eggs, failure of the incubated egg to develop fully, starvation of nestlings and tick infestation of nestlings. These were of about equal importance overall but their individual magnitudes varied considerably among the three seasons. The pattern of infestation of the cattle egret chick with the tick Argas (Persicargas) robertsi and the effect of this on chick health are described. An account is given of the other sources of morbidity also. The heronry appeared to be producing a net surplus of young despite these losses.