Interseasonal and intersexual resource partitioning in hairy and white-headed woodpeckers

Foraging behaviour in the closely related hairy (Picoides villosus) and white-headed (P. albolarvatus) woodpeckers was examined in an area of sympatry in California. Similar foraging heights were observed for each species-sex sample during summer, but significant differences were evident during winter. Male and female white-heads maintained similar relative foraging heights between season; male and female hairies foraged relatively higher during winter. Use of tree species differed significantly for each class between seasons, except for male hairies. All foraged at similar times of day during summer, but negative relationships occurred between times of foraging during winter; foraging times were significantly different between male hairies and white-heads. A general trend toward decreased overlap in foraging behaviours during winter was a reflection of concentration of foraging activities on live incense cedar Calocedrus decurrens, especially by female white-heads. This change apparently was due to the presence of an abundant and accessible prey (incense cedar scale Xylococculus macrocarpae) on cedar. Behavioural shifts in foraging activities may be related to the differential ability to extract prey as a function of bill morphology. Segregation of foraging activities may be attributed to morphological differences and habitat complexity rather than to competitive interactions dictated by resource limitations. -from Authors

Interseasonal and intersexual resource partitioning in hairy and white-headed woodpeckers Academic Article