鸟类第二节燕形态概述:燕分家燕和穴燕两类,家燕又分泥燕与砂燕两种,都是我们常见的,兹分述于后。泥燕的头顶背部,都是铜青色,额和咽喉部都为粟壳色,胸部有黑带,腹部纯白色,颈很短,嘴也短,前端尖细,上嘴略向下弯曲,口裂很大,翼长而狭,尾成义状,脚短,趾端有爪,能(?)壁上。沙燕形态与泥燕颈相似,不过胸部无黑带。 Birds Section II Yan morphological overview: Swallow points and cave acupoints two types of swallows, swallow is divided into two kinds of mud and sand Yan, are common to us, are divided in the post. Muddy’s head back, are copper cyan, the amount and throat are millet color, chest with black belt, pure white belly, the neck is very short, the mouth is short, sharp tip, slightly bent down on the mouth, mouth Cracked large, long and narrow wings, tail into the shape, short legs, toes have claws, can (?) Wall. Sandy swallow shape similar to the neck, but no black belt chest.