Changing wildfires Sierra Nevada may threaten northern goshawks

Thanks to Nick Smith for including this press release in his Healthy Forests, Healthy Communities news roundup today. The paper mentioned is here ($S). Goshawks prefer late-seral forest, but such stands are at greater risk of fire. California spotted owls aren’t the only at-risk species.

Changing wildfires in the California’s Sierra Nevada may threaten northern goshawks

Amsterdam, December 5, 2019 – Wildfire is a natural process in the forests of the western US, and many species have evolved to tolerate, if not benefit from it. But wildfire is changing. Research in the journal Biological Conservation, published by Elsevier, suggests fire, as it becomes more frequent and severe, poses a substantial risk to goshawks in the Sierra Nevada region.

How Northern Goshawks respond to fire is not well understood. The single study to date examined the effects of fire on nest placement and found that the birds avoided nesting in areas burned at high severity. The effects of fire on the birds’ roosting and foraging habitat however may be more complex, because prey populations may temporarily increase in burned areas and improve their quality as a foraging habitat.

“To effectively manage and conserve wildlife, we need to understand how animals use the landscape across their life cycle,” noted corresponding author Dr. Rachel Blakey at The Institute for Bird Populations and UCLA La Kretz Center for California Conservation Science.

Dr. Blakey and her colleagues at the institute wanted to better understand the habitat preferences of Northern Goshawks. In collaboration with scientists at the US Forest Service and the US Geological Survey Missouri Cooperative Fish and Wildlife Research Unit at the University of Missouri, the research team looked specifically at how goshawks use burned areas in the Plumas National Forest, California.

Twenty Goshawks were fitted with solar-powered global positioning system (GPS) tracking devices that monitored the habitats the goshawks chose for foraging and night-time roosting. Goshawks preferred forest stands with larger, more mature trees and higher canopy cover-also called “late seral” forest-for both roosting and foraging.

“While there was individual and sex-based variability in selection of habitat at the finest scales, at the larger spatial scales that are arguably most important for management, goshawks consistently selected for late-seral forest,” added Dr. Blakey.

Unfortunately, late-seral forest is already in short supply in the western US and the attributes that make it attractive to Northern Goshawks also put it at a high risk of large and severe wildfires. Further analysis of the study area showed that 80 percent foraging habitat and 87 percent of roost sites were designated a “High Wildfire Potential Hazard” by the US Forest Service.

Rodney Siegel, Executive Director of The Institute for Bird Populations and co-author of the study said “A lot of work by our organization and others over the past decade has shown that some wildlife species are quite resilient to forest fire and can even thrive in recently burned forests.

“But habitat selection by the Northern Goshawks we studied suggests that these birds, with their strong preference for late seral forest attributes like big trees and closed forest canopy, are jeopardized by changing fire patterns that reduce forest cover,” added Dr. Siegel.

Dr. Siegel also notes that reducing wildfire risk in goshawk habitat will be a major challenge for forest managers. “The treatments to reduce risk of high-severity fire, including forest thinning and prescribed fire, may also reduce goshawk foraging and roosting habitat quality if they decrease canopy cover and fragment late-seral forest,” said Dr. Siegel.

Dr. Blakey expects that the foraging and roosting habitat preferences seen in goshawks in this study are probably common to goshawks throughout the Sierra Nevada region, and perhaps western montane forests in general. Likewise, this preferred habitat is likely at risk of high severity fire across the region as well.

“Given that fire regimes are changing across the range of the Northern Goshawk, both in the US and across the species’ distribution globally, the use of burned habitats by this species should also be investigated more broadly,” concluded Dr. Blakey.


7 thoughts on “Changing wildfires Sierra Nevada may threaten northern goshawks”

  1. Here’s link to the paper (thank you, Dr. Blakey) Blakey_et_al_goshawks_fire
    and here are the management recommendations at the end.
    “4.1. Management implications
    Across the global range of the Northern Goshawk, changing fire regimes are resulting in longer fire seasons and conversion of forest to shrublands and grasslands (Jolly et al., 2015; Karavani et al., 2018). Given the variety of fire regimes and vegetation types across the range of the Northern Goshawk in North America and indeed across its global distribution in Europe and Asia, our findings warrant further regional investigation and are likely to be most relevant to the dry coniferous forests of western North America. As is the case for other late seral forest dependent species (Wan et al., 2019), high-severity fires are likely to increase in areas occupied by Northern Goshawks in western North America and subsequently reduce the extent and/or quality of
    roosting and foraging habitat for Northern Goshawks. Efforts to reduce risk of high-severity fire, including forest thinning and prescribed fire, also may reduce goshawk foraging and roosting habitat quality if they decrease canopy cover and fragment late-seral forest. However, high resolution diurnal tracking indicated that goshawks use areas with smaller trees and medium canopy cover while foraging and two individuals forayed into burned areas. Additional study is required to establish whether mixed severity fire may improve goshawk foraging habitat by creating a mosaic of habitat structures conducive to prey diversity.

    Global declines in late seral and old forests (2.5% per year) are exacerbated in western North America by loss through recent increases in wildfire extent and severity (Davis et al., 2015; Morales-Hidalgo et al., 2015; Ray et al., 2014; Stephens et al., 2016). Forest management
    directed at creating vegetation patterns maintained by wildfire has been proposed in the Sierra Nevada to reduce the risk of large-scale stand-replacing wildfire (North et al., 2009; Sherlock, 2007) and specifically to restore Northern Goshawk habitat in the Southwest U.S.

    (Reynolds et al., 2013). Concentrating relatively larger-scale fuels treatments (forest thinning) and prescribed fire in mid- seral and young forest patches across the landscape may simultaneously reduce risk of large scale high-severity wildfire and promote development and maintenance of wildfire-maintained vegetation patterns, reducing risk to Northern Goshawk roosting and foraging habitat.”

    I know it’s not that simple, but it sounds like “birds like areas of older trees to roost, to protect those areas you might want to do thinning for fuel treatments, but try to do those outside of areas with big trees that these birds like.” Which sounds a bit like the recipe for spotted owls, I wonder if others more knowledgeable might comment.

  2. I’m sure that a California-wide map of actual nest sites could be produced but, I doubt if it would be made available. It is very important that nest sites be protected, as they are parts of a system that both owls and goshawks use, in rotation. They are notoriously lazy, re-using nests, after time cleans up the mess. I’ve always wondered if us humans could set up more nests, in unoccupied habitats. We could even ‘grow’ small acreages of nest sites, complete with bird condo. Their nests need coverage from above, and each patch could have multiple nests. Each patch would be surrounded with ‘regular managed forest’, which makes for good foraging habitat.

  3. I agree that there needs to be careful consideration of whether short term loss of big trees is worth the reduced risk of habitat loss to fire, but I think it would be the exception rather than the rule to be targeting big trees. I question this statement a little: “the attributes that make it attractive to Northern Goshawks also put it at a high risk of large and severe wildfires,” The attributes that make it attractive to goshawks are “late seral forest attributes like big trees and closed forest canopy,” and I’m not sure those are the main causal factors for fire. I assume the recommended treatments in “mid- seral and young forest patches” would address causal factors (and maybe so would removal of small, non-canopy trees in old growth stands if that would line up better with more sustainable conditions).

  4. Here’s a post by the Institute for Bird Populations, who did the work.

    They also study black-backed woodpeckers. Here’s a part of one post.

    “Our findings indicate that, for the most part, Black-backed Woodpeckers don’t colonize forests killed by drought and bark beetles to the same extent that they use burned forests,” says Rodney Siegel, executive director of The Institute for Bird Populations and co-author of the paper. The researchers suspect that this has more to with another type of beetles–the woodboring beetles, which are much larger (and preferred by Black-backed Woodpeckers) than their bark beetle cousins. Siegel elaborates:

    Hungry Black-backed Woodpeckers don’t really care about dead trees per se, they care about the woodboring beetle larvae that live inside the dead trees. Some groups of woodborers are able to rapidly colonize burned forests in large numbers because they can sense fire and smoke from far away. They lay eggs on the dead trees, which soon hatch and provide an all-you-can-eat buffet of super-abundant larvae for the woodpeckers. But without the cues of fire and smoke, forests killed more slowly by drought and bark beetles may not attract as many woodborers. And even where woodborers may be abundant in forests killed by bark beetles, Black-backed Woodpeckers may be less likely to look for them there, as large stands of beetle-killed trees were generally rare in California until very recently.

    In other words, the woodpeckers may also look for burned trunks as a signal that food lies within. The researchers conclude that any benefit of beetle-killed forest stands to Black-backed Woodpeckers may lie more in their flammability than their immediate value as habitat. Bark beetle-killed trees are predisposed to burn, and once they do, the woodboring beetles and their numerous, tasty larvae may arrive.

    But determining exactly how Black-backed Woodpeckers, and other snag-loving species use beetle-killed stands will take more research. “Beetle-killed forests present an unprecedented phenomenon in California that has suddenly covered a vast area. If this forest type is part of the ‘new normal’ of California’s ecology, we need to know what potential role these forests will play in the overall ecology of the Sierra Nevada,” says Tingley.”

  5. This makes me curious about whether NEPA effects analysis for logging beetle-killed trees (since they are “predisposed to burn”) addresses the loss of future burned habitat for black-backed woodpeckers.

    • A random example:
      Hungry Ridge Restoration Project on the Nez Perce-Clearwater National Forest.

      “In general, this project is designed to reduce high fuel loadings that are a result of increased insect and disease disturbance.” Here is the entire effects “analysis” in the EIS:

      “Based on short-term impacts resulting from the project, it is determined that the Hungry Ridge project may impact individuals, but would not lead to a trend toward federal listing or a loss of viability for the … black-backed woodpecker …”


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