Hototogisu mare ni naku yo wa yamabiko no kotauru sae zo ureshikarikeru - Kinyo Wakashu(English Translation & Meaning)

ほととぎす稀に鳴く夜は山彦の
答ふるさへぞうれしかりける

Roma-ji: Hototogisu mare ni naku yo wa yamabiko no kotauru sae zo ureshikarikeru
English Translation: O little cuckoo,
on the rare night when you sing,
the mountain echo
that answers back your call
fills my heart with happiness
Meaning: On the rare nights when the cuckoo sings, even the mountain echo answering its call fills me with joy.
Commentary: Book Two Summer Poems 120

On a night when the seldom-heard cuckoo sings, even the echo returning its call from the mountains is a delight. The poem conveys a heart that cherishes even the reverberation, precisely because the voice is rare.
From poem 104 through poem 126 in this book, poems on the cuckoo follow one another, expressing every mood around the bird: waiting for its first song, seeking it out, rejoicing at hearing it and lamenting having missed it.

First line, 'hototogisu', opens by naming the theme.
Second line, 'mare ni naku yo wa', means on nights when it rarely sings, showing how precious the voice is.
Third line, 'yamabiko no', is the echo in the mountains and valleys, representing the repeated call.
Fourth line, 'kotauru sae zo', uses the additive sae, even the echo's answer, and zo binds with the attributive keru in the final line.
Final line, 'ureshikarikeru', means how joyful it is. It shares this ending with 'kotonoha sae zo ureshikarikeru' in poem 107, and the two share the idea that not the song itself but even what surrounds it gives delight.
Source: Kinyo Wakashu
Prev Poem: Yado chikaku shibashi katarae hototogisu matsu yo no kazu no tsumoru shirushi ni
Next Poem: Yama chikaku ura kogu fune wa hototogisu naku watari koso tomari narikere