This verse plays with two poetic conventions of an avian nature. The first is that haṃsas, the all-white birds that act as the vehicles of Brahma and Sarasvatī, can, among other things, separate a mixture of milk and water into its constituent parts. The second is that cakravākas, monogamists par excellence, are fated to be with each other only by day; every night they are forced to part at the rise of moon, to their great distress.
क्षीरयोरकृत हन्त विभागम् ।
सायमेष सितरश्मिमरालः ॥
It is evening.
The moon, arrayed in white, is a haṃsa.
Gliding through the sky that is his lake,
water from milk –
cakravāka from wretched cakravākī.
10.31 of Nārāyaṇācarya’s Rāghavendravijaya