Because they need large trees for nesting and roosting and forage primarily on dead or declining wood substrates, long-term conservation of pileated woodpecker populations may depend on maintaining these key structural elements in forest landscapes (Bull 1987, Bull and Jackson 1995). Large dead and declining trees are associated mainly with mature and older forests (McClelland 1979, Bull 1987, Renken and Wiggers 1989, Mellen et al. 1992). However, they are also found in young forests as remnant structure following a natural disturbance or logging. Although use of younger forests with remnant structure has been documented, many authors consider that young or fragmented forest habitat may not sustain pileated woodpeckers (Robbins et al. 1989, Bull and Holthausen 1993, McClelland and McClelland 1999). Others believe that pileated woodpeckers may be able to prosper in young and fragmented forests with abundant remnant structure (Mellen et al. 1992, Savignac 1996, Rolstad et al. 1998). In addition to their ecological role as predators of wood-dwelling forest ants, especially carpenter ants, pileated woodpeckers are thought to fill a keystone function (Power et al. 1996) as producers of large tree cavities that support cavity-using wildlife communities (Hoyt 1957, McClelland 1977, Bull and Snider 1993, Bull and Jackson 1995). Although there are numerous anecdotal accounts of secondary cavity-users using pileated woodpecker cavities, there have been no quantitative studies. Relative rarity, association with late seral forests, and ecological importance justify concerns about the long-term effects of timber management on pileated woodpeckers. This concern, together with the poor understanding of pileated woodpecker ecology in western boreal and cordilleran forests, was the catalyst for my research to gather knowledge that could be used to determine habitat conservation strategies and incorporate them into forest management planning. RESEARCH QUESTIONS Ecological theory holds that the fitness of an individual will increase as the quality of occupied habitat increases. Fitness is related to survival and reproduction of an individual and habitat quality is related to the ability of an individual to obtain essential life requisites from its environment. Animals living in high quality habitat should have high relative rates of survival, reproduction, and vitality of their offspring, when compared to animals living in low quality habitat (Van Horne 1983, Morrison et al. 1992). Relationships between habitat quality and species fitness have both theoretical and practical significance because they can be used to predict species response to changes in habitat quality (Kennedy and Gray 1993). In wildlife ecology the concept of habitat selection refers to the relative proportion of activitydependent use of habitat units compared to the relative availability of habitat units. Use depends on activity type and must be defined for each measure of habitat selection. The null hypothesis is that use is proportional to available habitat (no selection). Positive selection occurs when an animal uses a habitat unit more often than expected and negative selection occurs when an animal uses a habitat unit less often than expected. Animals select habitat at various scales and may show selection at some scales but not others (Johnson 1980). An example is shown for pileated woodpecker nest trees in Table 1.1. For reproduction to occur, a territory must contain at least some trees suitable for nesting. One of the factors governing territory location at a landscape scale must therefore be the presence of potential nest trees. Within a territory, pileated woodpeckers may select particular types of forest stands (areas of relatively distinct vegetation when compared to other adjacent areas), particular types of very local sites within stands, particular trees within sites, and particular locations on trees. Alternatively, birds may select trees and locations on trees and show no selection for sites or stands.
Published on Feb 9, 2014