The project leader says some of the birds place pieces of wood on heavy machinery like bulldozers.

VOA: special.2009.10.06

The shield itself, as I've told you is made of a heavy wood, covered by a leather or bronze sheet about three feet across, something in the neighborhood of 16 to 20 pounds worth of shield and gripped as I told you before.

而盾牌,就像我说过的,是由沉重的木材制成,上面包裹有皮革或铜皮,约三英尺宽,大概是十六到二十磅重,就像我刚才所说的,拿起来很费劲

耶鲁公开课 - 古希腊历史简介课程节选

You need to do that to be able to control the shield that's as big as that and as heavy as that, because it is made fundamentally of a heavy wood, typically covered by leather, sometimes with some bronze, a bronze sheet across the front of it as well.

如果你想自如操控这块盾牌就必须得这样,这种盾牌很大并且很笨重,因为它主要是由沉重的木材制成,表面一般覆有皮革,或包上铜皮,就是表面上有一层铜皮

耶鲁公开课 - 古希腊历史简介课程节选