燕子为什么会把自己孵化的蛋丢掉

如果是空的那肯定是浮出来了，如果不是，则可能是无精蛋或者死胎蛋导致燕子弃蛋了。

应该要掉下来在，不是燕子自己丢掉在吧。

我找到一篇文献研究了鸟类丢弃空蛋壳的原因，文献整理了5条假说，包括担心锋利的裂口可能会伤害鸟宝宝、影响巢穴的舒适性等，但最后验证的唯一一条假说是“nest-camouflage hypothesis”，即“鸟父母认为裂开的蛋壳会降低巢穴的隐蔽性，而选择移除他们”。 

文献：THE ADAPTIVE SIGNIFICANCE OF EGGSHELL REMOVAL BY NESTING BIRDS:
TESTING THE EGG-CAPPING HYPOTHESIS

5条假说的原文：

(1) sharp shell edges
could injure newly hatched chicks, (2) unhatched eggs
could become trapped inside hatched shells, thereby
reducing hatchability, (3) hatched shells could interfere
with brooding, (4) hatched shells could reduce nest
hygiene and increase the risk of bacterial infection, and
(5) hatched shells could reduce nest camouflage, thereby increasing the risk of predation by visually-oriented
predators

1条假说被验证的原文：

Tinberaen (1963) and colleaaues
(Tinbergen et al. 1963) found considerable suppo; for
the nest-camouflage hypothesis, but they did not test
any of the other four hypotheses.