A Review of the Use of Pacific Madrone by Nesting, Pollinating and Frugivorous Birds

This paper reviews ecological interactions of birds with Pacific madrone (Arbutus menziesii). Results from a tree inventory in the Magnolia area during 1994–95 and a literature search are summarized. We surveyed 126 trees and found 2 Northern flicker (Colaptes auratus) cavity nests and 35 cup nests. American Crows (Corvus brachyrhynchos) occupied the cup nests. Madrone is a substrate for nesting and is a nutrient resource. Birds provide pollination service to the plant and disperse seeds. Madrone berries are consumed by numerous bird species. The role of frugivores as a mechanism for flower pollination and seed dispersal is discussed. Knowledge of the nutrient content of madrone berries may be useful for managing madrone-dependent frugivores. The presence of antifungal chemicals in madrone berries may be a factor in understanding the spread and control of madrone diseases. Successful management of the Pacific madrone entails protecting not only the trees, but also the wildlife that use it. The Pacific madrone (Arbutus menziesii) provides habitat for nesting and nutrients for foraging birds. Madrone also serves as habitat for other wildlife, providing protection from predators and harsh weather, structures for nesting and sources of food (Benyus 1989). Pollination of flowers determines the size of fruit crop production that, in turn, influences foraging behavior of frugivore populations and dispersal of seeds (Meeuse 1961). Pollination and seed dispersal benefit the tree by increasing genetic variability through minimization of inbreeding and intraspecific competition (Dirzo and Dominguez 1986). Healthier trees may result because dispersed seeds germinate in areas distant from diseased stands. The purpose of this paper is threefold: we report on a study of bird nests found in Pacific madrones growing in the Magnolia area of Seattle, Washington; we review information relevant to ecological interactions of birds with Pacific madrones; and, we present research ideas relevant to madrone wildlife use and management.