Valmiki Ramayana Sundara Kanda Sarga 14 Shloka 17

सर्वे all, ते द्रुमाः those trees, मारुतेन by Hanuman, विनिर्धुताः laid bare, अगमाः इव trees unable to move, विहङ्गसङ्घै: by flocks of birds, हीनाः deserted, स्कन्धमात्राश्रयाः only resting on the trunks, बभूवुः became.

Deserted by the flocks of birds resting on them (flowers and leaves also dropped from branches), the trees were left bare with trunks unable to move.