Monday, 16 June 2014

Lining Time

It's nest lining time at Lorna Glen!

Wedge-tailed Eagles begin their breeding cycle early in the year, timing events perfectly so the chicks hatch at a time when the surrounding ecosystem is rich with prey, maximising their chance of survival. Often this prey comes in the form of young mammals that are 'bite size' and naive enough to catch easily - especially young macropods (kangaroo family) and rabbits, which are the preferred prey items across Australia. The first stage of nesting is preparing the chosen nest, which normally begins in May and June. Eagles spend quite a few weeks lining their nest with sprays of fresh green leaves, most often using Eucalyptus, but where this species is not available, Acacia is a commonly used alternative. In the lead up to laying, the lining probably helps advertise that the nest and surrounding territory are occupied. More importantly it creates a soft bed on which the female can sit on and depress into a small cup to cradle her eggs, when eventually she is ready to lay.

The above photo shows an eagle nest that was freshly lined with Mulga (Acacia aneura) sprigs in June 2013. Here the same nest photographed at the end of the breeding, that shows the faded lining and a slight cup:

 There was no evidence of eggshell in the nest which would be expected if eggs were laid. The owners were a young, inexperienced eagle pair that didn't end up laying eggs. While we often think all birds should nest every year, it is normal for some not to, and for others to attempt but fail. Such is life in the arid outback!

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