FIELDS have eyes, and woods have ears
The urban equivalent is
WALLS have ears
.
c
1225
in
Englische Studien
(1902) XXXI. 8
Veld haued hege [eye], and wude haued heare—
Campus habet lumen et habet nemus auris acumen
.
c
1386
Knight's Tale
1. 1522
But sooth is seyd, go sithen many yeres, That ‘feeld hath eyen and the wode hath eres.’
1640
Dodona's Grove
A4
V
Hedges have eares, the rurall Proverb sayes.
1738
Polite Conversation
III. 199
‘O, Miss; 'tis nothing what we say among ourselves.’ .. ‘Ay Madam; but they say Hedges have Eyes, and Walls have Ears.’
1905
Starvecrow Farm
xxviii.
Heedful of the old saying, that fields have eyes and woods have ears, she looked carefully round her before she laid her hand on the gate.
eavesdroppers