canberrabirds

Bold eagles take flight

To: Tony Lawson <>
Subject: Bold eagles take flight
From: Robin Hide <>
Date: Sun, 17 Jul 2011 13:55:42 +1000
Between Burra Rd and Tin Hut this morning...there were three WTE in the air, but only two were grappling...and of course up sun from us!- but a magnificent sight.

WTE

At Tin Hut, besides male Musk Duck, Grey Butcherbird and several Flame Robins, the highlight was a family of feral/wild pigs - in several years keeping a close eye, and measuring tape and scales, on free-range village domestic pigs in the New Guinea highlands I never saw such fat c.1 yr ? old young - they seemed to roll away rather than ran, and for a moment we wondered if they were wombats.

Robin Hide

On 13/07/2011 10:08 PM, Tony Lawson wrote:

If you spot two enormous birds locked together in what appears to be a soaring, tumbling battle for dominance of the sky, then look again! You're most probably watching a pair of wedge-tailed eagles re-igniting their passion prior to breeding.

Wedge-tail eagles are among the world's largest eagles with a wingspan of up to 2.5 metres. They are relatively common all over the Australian mainland, in Tasmania and southern New Guinea, except in densely populated areas.

To get off the ground they use an active flapping flight, but once airborne these eagles use thermal updrafts to carry them effortlessly aloft and gracefully spiral upwards to great heights.

Australia has three species of eagle, the Little Eagle (Hieraetus morphnoides), the White-bellied Sea Eagle (Haliaeetus leucogaster) and the largest, the Wedge-tailed Eagle (Aquila audax - literally 'bold eagle'). Wedge-tails prefer open woodland, but are found exploiting a range of habitats from arid desert to grasslands, mountainous areas, and even rainforest.

Easily identified by their size (up to 3.2 kg for males and 4.2kg for females), Wedge-tails are known as booted or trousered eagles thanks to the heavy feather 'trousers' covering their legs. They are also characterised by finger-like wing feathers and, of course, a long wedge-shaped tail. Young birds can be distinguished by their light brown plumage and golden highlights; the plumage of older birds tends to darken to near black at sexual maturity between five and seven years.

Fiery courtship

According to Dr Penny Olsen, a research scientist and raptor expert from the ANU, Wedge-tails appear to be monogamous, mating for life. "They certainly form long-term pair bonds," she says, "although if one bird is killed the survivor will take a new mate."

The time of breeding depends on temperature to some extent. In Tasmania, Wedge-tails breed later than their northern counterparts, but all breed between June and October.

"Breeding season is the best time to see Wedge-tails because of their highly visible soaring and diving displays," says Olsen. Males may also mark their territorial boundaries by flying in a series of showy descending loops, or 'pothooks'.

In another dramatic manoeuvre known as talon grappling, two birds lock talons with one being forced to flip over and fly upside-down, which although spectacular can be fatal if one bird refuses to let go. Olsen says the research community is divided on whether this is an aggressive display aimed at warning off potential interlopers, or just two birds showing off as part of their courtship ritual.

...............

Special thanks to Dr Penny Olsen and Peter Merritt.

http://www.abc.net.au/science/articles/2006/07/06/2041996.htm 

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