Breeding ecology of the pileated woodpecker (Dryocopus pileatus) in bottomland forests of eastern Arkansas, with reference to the conservation of the ivory-billed woodpecker (Campephilus principalis ).

摘要

The purported rediscovery of the ivory-billed woodpecker (Campephilus principalis) in the Cache River National Wildlife Refuge in 2004 was a monumental moment in conservation biology. Although controversy surrounds this and other sightings of ivory-billed woodpeckers within bottomland hardwood forests, the rediscovery of a species thought to have gone extinct revitalized optimism focused on its conservation. What knowledge we possess about ivory-billed woodpeckers comes from research done by James Tanner in the 1930s and his data are pseudo-replicated from just a few pairs. Tanner suggested that sweetgum-oak forest cover types were better quality habitats for ivory-billed woodpeckers and other woodpecker species than cypress-tupelo swamps. Therefore, to learn more about large woodpecker ecology in bottomland hardwood forests and swamps, I studied pileated woodpecker (Dryocopus pileatus) habitat use and demography in two different cover types of bottomland hardwood forests (cypress-tupelo swamps [Taxodium-Nyssa] and sweetgum-oak forests [Liquidambar-Quercus]) in Arkansas. With the help of coworkers and approximately 16,700 hours of field work in the swamps, I found 100 pileated woodpecker nests, 180 forage trees, and captured 73 pileated woodpeckers from 2007 to 2010.;Overall, pileated woodpecker nest cavities were found between 3.8 and 29.3 m high in dead or decaying trees in both cover types and nest success rates (42.7--50.5%) were lower than what was reported in the literature (55--93%). Daily nest survivorship rates were best predicted by day of year, nest age, basal area, and number of cavities in the nest tree. Contrary to my predictions, predation rates were higher in the sweetgumoak forest cover type, but competition for cavities seemed higher in cypress-tupelo swamps, particularly with wood ducks (Aix sponsa). The primary predator detected at nests was the black rat snake (Pantherophis obsoleta). Specifically, of the 41 nests that failed in bottomland hardwood forests of eastern Arkansas, 31 (80%) were likely caused by black rat snakes.;In addition to nest monitoring and survivorship modeling, 64 pileated woodpeckers (PIWO) were radio-tagged. In my first 2 years of research, I found that the harness attachment, handling time, and possibly capture date reduced the survival of PIWOs after release. After I made several adjustments in these techniques during the last 2 years of the study, all birds radio-marked survived the entire field season (n = 31; 100%). Based on the remaining individuals, between year survivorship estimates were marginally higher in cypress-tupelo swamps (0.84) than sweetgum-oak forests (0.79). However, home--range sizes were significantly smaller in sweetgum-oak forests (x¯ = 37.6 ha) than cypress-tupelo swamps (x¯ = 60.5 ha). Woodpeckers were selecting sugarberry (Celtis laevigata) and water tupelo ( Nyssa aquatica) trees for foraging in bottomland hardwood forests and preferred trees that were larger and more decayed with greater amounts of deadwood in the vicinity compared to random trees.;Collectively, these data suggested ecological trade-offs in these two cover types. Specifically, adult survivorship and nest success rates were higher in cypress-tupelo swamps, but home--range sizes were smaller in sweetgum-oak forests, suggesting resources may have been more abundant in the latter cover type. Regardless of these trade-offs, both cover types represent relatively high quality habitats based on what has been reported in the literature. Pileated woodpeckers can serve as an indicator species for old-growth forests, and large trees that are stressed are important to the persistence of this species in bottomland hardwood forests. Management for woodpeckers and other old-growth species should emphasize restoring bottomland habitats, maintaining old-growth stands, and reducing fragmentation of these habitats to maintain connectivity of bottomland forests.