As I discuss in this question, by far the most popular school of Hindu philosophy is the Vedanta school, which bases its tenets on the doctrines laid out in the Brahma Sutras, a work by the sage Vyasa that summarizes and systematizes the philosophical teachings of the Upanishads. You can read the Brahma Sutras here. In any case, in his commentary on Adhyaya 2 Pada 1 Sutra 25 of the Brahma Sutras, Adi Shankaracharya discusses the objection that Brahman cannot be the cause of the Universe because an intelligent being can't create anything without external help. Adi Shankaracharya responds by giving various examples of intelligent beings creating things without external help:
As gods, fathers, rishis, and other beings of great power, who are all of intelligent nature, are seen to create many and various objects, such as palaces, chariots, &c., without availing themselves of any extraneous means, by their mere intention, which is effective in consequence of those beings' peculiar power--a fact vouchsafed by mantras, arthavâdas, itihâsas, and purânas;--and as the spider emits out of itself the threads of its web; and as the female crane conceives without a male; and as the lotus wanders from one pond to another without any means of conveyance; so the intelligent Brahman also may be assumed to create the world by itself without extraneous means.
My question is, what scriptures describe the notion that "the female crane conceives without a male"? If it helps, Adi Shankaracharya gives a bit more detail later on as to how the female crane achieves this:
For the material causes operative in the production of palaces and other material things are the bodies of the gods, and not their intelligent Selfs. And the web of the spider is produced from its saliva which, owing to the spider's devouring small insects, acquires a certain degree of consistency. And the female crane conceives from hearing the sound of thunder. And the lotus flower indeed derives from its indwelling intelligent principle the impulse of movement, but is not able actually to move in so far as it is a merely intelligent being; it rather wanders from pond to pond by means of its non-intelligent body, just as the creeper climbs up the tree.
This all seems rather bizarre to me, so does anyone know what Adi Shankaracharya is talking about? By the way, Adi Shankaracharya repeats his claim in his commentary on Adhyaya 3 Pada 1 Sutra 19, in discussing examples of unconventional births:
There are, moreover, traditions, apart from the Veda, that certain persons like Drona, Dhrishtadyumna, Sîtâ, Draupadî, &c., were not born in the ordinary way from mothers. In the case of Drona and others there was absent the oblation which is made into the woman; while in the case of Dhrishtadyumna and others, even two of the oblations, viz. the one offered into woman and the one offered into man, were absent. Hence in other cases also birth may be supposed to take place independently of the number of oblations.--It is, moreover, commonly known that the female crane conceives without a male.
Well, it's not commonly known to me! So I'd like to see if Hindu scripture records this common knowledge.
On a side note, if this is true, it would arguably refute the argument of Madhvacharya given in my question here.
EDIT: The Sanskrit word for crane that Adi Shankaracharya uses here is balaka, so I searched balaka and thunder, and this book says Kalidasa alludes to idea of thunder making balaka birds pregnant in his poem Meghaduta:
The egret balaka breeds in the rains, which establishes the season : as Kalidasa notes (MeghasandeSa 10), the female egrets become pregnant during the rains, there being a poetic fancy that the thunder made them so (see Vallabhadeva's commentary).
And this book says that the Buddhist philosopher Buddhaghosa also alluded to this idea:
No less influential a systematizer than Buddhaghosa can proclaim with a straight face that a woman can get pregnant by looking at a man; or by hearing, like the balaka bird who gets pregnant by hearing thunder; or by smell, like the cow who gets pregnant by smelling the breath of a bull.
So it seems like this was a common idea in ancient India, which is all the more reason to see if it's mentioned in scripture.