HILBRANDS J (1965) Oölogische nidologische and Communications, 1964 (and earlier). Grey Partridge Perdix perdix Laying Together with Black Grouse Lyrurus tetrix. LIMOSA 38 (1): 85-85.

Grey Partridge Perdix perdix Laying Together with Black Grouse Lyrurus tetrix Grey Partridge Perdix perdix Black Grouse Lyrurus tetrix

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