American Three-toed Woodpecker (Picoides dorsalis) response to spatial patterns of burn severity and prey availability.
Deutschman, Douglas*,1, Reynolds, Elizabeth1, 2, Kotliar, Natasha2, 1 San Diego State University, San Diego, CA, USA2 USGS Fort Collins Science Center, Fort Collins, CO, USA
ABSTRACT- The American Three-toed Woodpecker (Picoides dorsalis) is a rare habitat specialist that colonizes early post-fire forests in response to outbreaks of bark and wood-borer beetles. Burns are highly heterogeneous and patterns of burn severity vary across spatial scales. We describe how Three-toed Woodpeckers respond to burn severity over multiple spatial scales at the Hayman burn, a fire that in 2002 consumed 138,000 ha of the Pike National Forest in Colorado. American Three-toed Woodpeckers were studied in Ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga menziesii) forests during 2003 and 2004. We examined the pattern of settlement by these Woodpeckers into the burned area as a function of burn severity, forest composition, and beetle availability. These same variables were also measured at a fine scale by comparing trees the woodpecker was observed foraging on to nearby control trees. Data were analyzed using simple t-tests, 2-way contingency tests, log-linear models and McNemar's test for symmetry. At the coarsest scale, American Three-toed Woodpeckers settled in mixed-severity burns (a mosaic of low, moderate and high severities) and avoided large contiguous areas of low or high severity. At finer scales, they selected trees that were larger and more likely to be infested with beetles than nearby control trees. This is the first study of Three-toed Woodpecker habitat preferences in the ponderosa pine system and the first to delineate the heterogeneous post-fire landscape by burn severities. The multi-scale design of the study allows us to separate broad-scale habitat choices from fine-scale foraging decisions. Three-toed Woodpeckers appear to be hierarchical and strongly influenced by heterogeneity of the post-fire landscape. This highlights the need for fire management programs that can accommodate high levels of habitat heterogeneity.
Key words: fire, heterogeneity, scale, Picoides dorsalis
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