From Letter XVII:
 Perhaps, to you, it is unnecessary to expatiate  on the importance of cultivating kindness towards whatever possesses life. Our happiness, our moral improvement, are, in some measure, connected with it. And while we see both birds and beasts exercising the most generous treatment towards each other,) of which there are many remarkable instances,) we, who boast the higher gift of reason, must surely be inexcusable, should we be guilty of the least unkindness or cruelty.
A disposition to inflict pain will not be confined to one set of objects. A boy who suffers himself to torment birds and beasts, will often tease his play-fellows; and, by inattention to the wants and feelings of others, he renders himself troublesome to all around him: and if he grow up thus, it must be in wretchedness; for, while he is cruel, he cannot be happy. But to the benevolent child, who nurtures and who feeds, every living object he sees is a source of pleasure; because he benefits all where he can: and every bird he hears, seems to sing him a song of gratitude.
This recals to my recollection the stanzas you once found on the bracket, after the winter was over, and the birds no longer needed our aid. If they tend to renew pleasant impressions, you may to be sorry to find them here.
 From the Robin,
to the friend who had provided crumbs.
Kind little girl, if such it be,
Who spread the dainty board,
Accept sincerest thanks from me,
Who oft partook the hoard.
When gloomy winter’s frost and snow
Beat on my little head,
Alas! I knew not where to go,
To find one crumb of bread.
Till, as I hopp’d from spray to spray,
A feast I chanc’d to see;
And gentle accents seem’d to say,
“Sweet Robin, ’tis for thee!”
Thy favourite songster’s taste to please,
What bounty didst thou spread!
The little dainty bit of cheese,
And tiny crumb of bread.
Then did I trim my red breast gay,
And meet the storm resign’d;
Chaunting, on many a frosty spray:
“One little girl is kind!”
For this, when summer days appear,
To make thy garden gay,
Thy Robin-red-breast shall be there,
To sing his sweetest lay.
Kind little girl, where’er thou art,
If still thou wouldst be blest,
Go, act aright thy pleasant part,
And succour the distrest.