INFLUENCE OF FOREST STRUCTURE ON THE DENSITY AND DISTRIBUTION OF THE WHITE-BACKED WOODPECKER DENDROCOPOS-LEUCOTOS AND BLACK WOODPECKER DRYOCOPUS-MARTIUS IN QUINTO REAL (SPANISH WESTERN PYRENEES)

The nesting areas of 13 pairs of Black Woodpecker (0.41 pairs/km(2)) a nd 12 pairs of White-backed Woodpecker (0.38 pairs/km(2)) were mapped in the Quinto Real forest (Spanish western Pyrenees). Nearest-neighbou r analysis indicated a uniform spacing of Black Woodpecker territories and, as both species occupied the most developed beechwoods. White-ba cked and Black territories showed an aggregated distribution. The loca l distribution appears to be determined by forest structure. Principal components analysis indicated that forest plots occupied by the woodp eckers had a high percentage of beech in old forest (with a total basa l area of tree boles above 20 m(2)/ha) and with many large frees (diam eter at breast height, dbh, over 60 cm).