Painting with birds in an old golden frame

Drawing of the birds of our gardens, a nuthatch, a titmouse and, I think, a jay. The drawing is signed amtr (for a marlin?), it is in good condition. The pink and gold marquise is integrated into the design. Its gold frame is original, there is a small ring to hang it on the wall. Featherweight of 300 gr. 22 cm X 14 cm and 1 cm thick.