The notes of birds cease to affect us as they did.

February 5

When we have experienced many disappointments, such as the loss of friends, the notes of birds cease to affect us as they did. 

I see another butcher-bird on the top of a young tree by the pond.

H. D. Thoreau, Journal, February 5, 1859

The loss of friends. See February 3, 1859 ("I perceive that we partially die ourselves through sympathy at the death of each of our friends or near relatives. Each such experience is an assault on our vital force. It becomes a source of wonder that they who have lost many friends still live.") Compare   January 21, 1852 ("I never realized so distinctly as this moment that I am peacefully parting company with the best friend I ever had,"); June 11, 1855 ("What if we feel a yearning to which no breast answers? I walk alone. My heart is full. Feelings impede the current of my thoughts. I knock on the earth but no friend appears, and perhaps none is dreaming of me."); March 28, 1856 ("Farewell, my friends, my path inclines to this side the mountain, yours to that."): ; February 8, 1857 ("And now another friendship is ended. I do not know what has made my friend doubt me, but I know that in love there is no mistake, and that every estrangement is well founded. . . . I am perfectly sad at parting from you. I could better have the earth taken away from under my feet, than the thought of you from my mind. ");  February 23, 1857 ('That aching of the breast, the grandest pain that man endures, which no ether can assuage . . . If the teeth ache they can be pulled. If the heart aches, what then? Shall we pluck it out?"); November 3, 1858 ("How long we will follow an illusion! On meeting that one whom I call my friend, I find that I had imagined something that was not there.")

The notes of birds cease to effect us. See  July 5, 1852 ("Some birds are poets and sing all summer. They are the true singers. Any man can write verses during the love season. ")

Another butcher-bird. See February 3, 1856 ("See near the Island a shrike glide by . . . with a remarkably even and steady sail or gliding motion"); March 1, 1855 ("Saw a butcher-bird, as usual on top of a tree, and distinguished from a jay by black wings and tail and streak side of head.") and note to December 24, 1858 ("See another shrike this afternoon, — the fourth this winter!") See also A Book of the Seasons, by Henry Thoreau, The Northern Shrike

the notes of birds cease 

to affect us as they did 

when we lose a friend