The golden orb weaver spider usually eats insects. It is a step up for it to consume a bird. The bird had flown into the spider's web and become weak. Then the spider attacked it.
Golden orb spiders grow much larger than the one shown in the photograph. Though they were not thought capable of eating a whole bird.
http://www.adventure--australia.blogspot.com/
http://www.tysaustralia.blogspot.com/
http://www.feeds.feedburner.com/AdventureAustralia
http://www.technorati.com/blogs/
http://adventure--australia.blogspot.com
http://www.tysaustralia.blogspot.com/
http://www.feeds.feedburner.com/AdventureAustralia
http://www.technorati.com/blogs/
http://adventure--australia.blogspot.com
Science