Woodpecker nest survival, density, and a pine beetle outbreak

Abstract

Mountain pine beetle (Dendroctonus ponderosae) outbreaks in western North American coniferous forests are increasing in size and severity. An understanding of wildlife population responses to pine beetle outbreaks is needed to inform habitat conservation strategies. We monitored 355 nests of 5 woodpecker species during 2 sampling periods, before (2003–2006) and after (2009–2014) the peak of a pine beetle outbreak in dry mixed conifer forest of Montana, USA. Three of 5 woodpecker species represented the beetle‐foraging group: American three‐toed (Picoides dorsalis), hairy (Dryobates villosus), and downy (D. pubescens) woodpeckers. The other 2 species studied were northern flicker (Colaptes auratus), a foraging and habitat generalist, and red‐naped sapsucker (Sphyrapicus nuchalis), a sap forager and bark‐gleaning insectivore. We analyzed daily survival rate of nests in relation to pine beetle outbreak (445,000 ha) severity and timing, along with covariates unrelated to the outbreak (temp, nest height, and nest tree diameter). Our results provided stronger evidence for relationships between woodpecker nest survival and the non‐outbreak variables than those associated with outbreaks. Our results indicated limited support for nest survival relationships with beetle severity (annual and cumulative pine tree mortality at 0.81‐ha and 314‐ha scales). Nevertheless, we observed a significant increase in densities of hatched nests for beetle‐foraging woodpeckers following the outbreak. Our results suggest that woodpeckers, particularly beetle foragers, respond numerically to pine beetle outbreaks through increased nesting densities more so than functionally via nest survival. © 2019 The Authors. Journal of Wildlife Management Published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.

Forest birds exhibit variable changes in occurrence during a mountain pine beetle epidemic

“…Information on other factors, including nest density, nest success, fecundity, and survival, is necessary to determine whether species experienced greater fitness during the mountain pine beetle epidemic (Saab et al. ).…”

“…Saab et al. () found that an eventual decline in the pulse of mountain pine beetles may result in decreases of nest densities for woodpeckers several years after the peak of a beetle outbreak. In addition, dramatic changes in understory growth, downed wood, and canopy cover in the years following the epidemic (Stone and Wolfe , Page and Jenkins , Jenkins et al.…”

“…Increased occurrence may not be related to increased densities or more importantly, fitness of these species. Information on other factors, including nest density, nest success, fecundity, and survival, is necessary to determine whether species experienced greater fitness during the mountain pine beetle epidemic (Saab et al 2019).…”

“…While our study yields short-term information on avian responses, long-term responses must also be considered. Saab et al (2019) found that an eventual decline in the pulse of mountain pine beetles may result in decreases of nest densities for woodpeckers several years after the peak of a beetle outbreak. In addition, dramatic changes in understory growth, downed wood, and canopy cover in the years following the epidemic (Stone and Wolfe 1996, Page and Jenkins 2007, Jenkins et al 2008) might result in occupancy increases for ground-and shrub-nesting and foraging species on a longer time horizon than what we studied (Janousek et al 2019).…”

The influence of climate and habitat on stable isotope signatures and the isotopic niche of nestling White‐headed Woodpeckers (Dryobates albolarvatus)

“…Insect populations are directly influenced by climate because temperature determines rate of larval development, as well as survival and reproduction of adults (Brown, Gillooly, Allen, Savage, & West, 2004; Chuine & Régnière, 2017). Because many birds, especially woodpeckers, respond positively to outbreaks of insects (Edworthy, Drever, & Martin, 2011; Morris, Cheshire, Miller, & Mott, 1958; Norris, Drever, & Martin, 2013; Saab, Latif, Dresser, & Dudley, 2019), changes in climate may alter the diet of these species.…”