Scientific information is conditional on the approach to the study (framing), discipline(s)involved, methodology used, and the specifics of time and place. The more information expands, the more we know, even though it might feel like we are the blind person dealing with the elephant. Yet there is a balance between accepting the conclusions and understanding that for most topics, what you know is a a function of the step you’re on and not the final story. And as the climate (and people and whatever) changes, there may never be a “final story.” Just note the ubiquity of the expression in scientific papers “previous studies concluded x, but we have found y.”
Here’s one example of Stillman et al.’s work from Bird Pop!. There a link to the paper on the blog site.
But the simple assumption that more fire always equals good news for a post-fire specialist wasn’t holding up. Stillman’s earlier work, in collaboration with IBP, his PhD advisor UCLA Professor Morgan Tingley, and the US Forest Service, showed that Black-backed Woodpeckers prefer to nest near the edge of severely burned patches. Now fledgling woodpeckers, hatched in nests within burned forests, were moving out of the burn and into adjacent forest that burned at low severity or sometimes hadn’t burned at all.
A new story began to emerge. Perhaps Black-backed Woodpeckers nest close to the edges of burned patches so that, upon fledging, their young can take cover in unburned or less severely burned patches nearby — presumably to take advantage of greater vegetation cover and avoid predation. “We started thinking of the food-rich high severity burn as a grocery store and the high-cover low severity burn as a nursery,” says Stillman. “If you’re going to build a home, you want to place it close to both the food source and the nursery!” But if this was indeed what was going on, you’d expect survival of juvenile woodpeckers to be higher in the less severely burned areas with more live vegetation.
To test this prediction, Stillman and collaborators tracked the habitat use and survival of 84 fledgling Black-backed Woodpeckers from 39 nests in seven different recently burned areas in the Sierra Nevada and Cascade Mountains of Washington and California. Tracking during the first 35 days was done the hard way — hiking many rugged miles with handheld receivers. As the juveniles got older and dispersed, tracking was done by driving and with the generous help of the skilled volunteer pilots of LightHawk Conservation Flying. “We expected survival to be lower in the high-severity patches compared to low-severity patches — and that’s what we show in this paper. However, it was surprising to us just how much of a difference it made,” says Stillman. “If you’re a fledgling Black-backed Woodpecker, you have a 53% chance of surviving 35 days if you spend your time in low-severity burned patches — about average for a baby bird. But if you instead choose to spend all your time in the high-severity burn (which is good habitat for adults), your chance of surviving 35 days plummets to just 13%.” Most fledgling deaths were due to predation.
Another surprise: the identity of the predators. Most juvenile Black-backed Woodpecker deaths could be attributed to birds of prey including Cooper’s Hawks, Northern Goshawks, Red-tailed Hawks, and even a Western Screech-owl. Apparently if you are a bird of prey, fledgling woodpeckers in open stands of burned snags are the easy-to-grab, juicy hamburgers.
Previous research has shown that increased pyrodiversity yields more diverse habitat types across the landscape, which in turn increases diversity in the bird community. But this study and Stillman’s other dissertation research shows that pyrodiversity can be a good thing even for a single species. This is an example of habitat complementation: when a species has different habitat requirements for different parts of its life history. Forest managers can support and enhance pyrodiversity through management practices before fire, and by protecting pyrodiverse areas after fire.
8 thoughts on “Take Cover: Even a post-fire specialist needs a break from the burn for part of its life cycle: from BirdPop!”
For whatever it’s worth, I reached out to two Phd experts in post-fire ecology related to birds and this is what they had to say:
That research has a major flaw, in that it did not exclude post-fire logged areas and, of course, we know that post-fire logging is heavily concentrated in high-severity fire patches. So, the Stillman et al. study is fatally confounded by post-fire logging, since black-backed woodpeckers heavily avoid post-fire logged areas, while they strongly *select* high-severity fire areas (snag forest habitat) in the absence of post-fire logging. When research subsequent to the Stillman et al. article was conducted either in snag forests that had no post-fire logging, or before post-fire logging occurred, it was found, once again, that black-backed woodpeckers in the Sierra Nevada strongly select mature/old forest that burns at high severity–see White et al. (2019) (surveys conducted prior to post-fire logging: http://www.ace-eco.org/vol14/iss1/art17/ ) and Hanson and Chi (2020) (surveys conducted in areas with little or no post-fire logging).
Yes…this is nothing new, but has been pitched in a way to sound as if it differs from what folks previously understood. Severe fires have always burned in a patchy manner (as any severity map will show), so BBWO have always needed severe fire for nesting and feeding, even if the young feed primarily on the edges of those patches. Nobody ever claimed that the birds do better in large, homogeneous patches of severely burned forest! The young of most all bird species move to feeding sites (often riparian areas) that are quite different from breeding sites—that’s pretty common knowledge. Good study, but doesn’t reduce the need for severe fires, which automatically create a patchwork of severities (unlike understory or most lower-severity prescribed fires).
Thanks Matthew. It appears that your folks and Stillman agree that (1) BBWO need both kinds of habitat. (2) No one said that this study said that need for severe fires is reduced. To me it was just saying that patchy is better for the bird (pyrodiversity).
If the mechanism is “fledglings get et in open areas” I’m not sure what difference salvage logging would make in severely burned areas? If we imagine standing blackened trees that will fall down, does their presence or absence make a difference? Can fledgings effectively hide around spaced dead trees?
No mention of the vast streambuffers, protected from logging? Plus, I wonder what style of salvage logging was used in the study. Did that style exclude 50% of the entire burned area? Did that style leave snags in all of the cutting units (minus hazard trees, of course)? Did that style have large streambuffers? Did that style have rigid mortality guidelines?
Questions, questions, questions.
One of the authors was kind enough to reply to my questions. Here’s what he said.
“Post-fire logged areas were excluded from this study by way of the study design, which was focused on learning about ecological relationships rather than responses to management. There was no salvage logging at the Washington study sites where the authors collected half of their data, but salvage logging did occur in portions of the California fires. However, as we might expect, the fledgling woodpeckers avoided these areas and instead used areas with intact forest burned at low, medium, or high severity. The survival analysis investigates the effect of “used” habitat only, and logged areas weren’t used. Thus, tracking bouts classified as high severity in the dataset represent intact, high-severity burn rather than salvage-logged areas. The negative relationship the authors found between high-severity burn and fledgling 35-day survival is not an artifact of logging.
As the comment states, it is well known that black-backed woodpeckers largely avoid salvaged logged areas, and there is plenty of research documenting negative responses to post-fire logging particularly in high-severity areas. In the future it would be interesting to specifically test for an effect of logging on demographic rates, but that would first require a large sample of birds using logged areas (which is unlikely given this well-documented avoidance).
Last, it is important to clarify that this study certainly does not indicate that high-severity burn is “all bad” for black-backed woodpeckers. Rather, it adds nuance based on the differences in habitat use between adults and young. Past work from the same authors has found evidence for strong, positive relationships between *adult* habitat use (including foraging areas, nesting areas, statewide occupancy patterns) and burn severity.”
So the authors found that’s what good for adults is not necessarily good for fledglings and people should keep both kinds of habitat around (within flying distance) if they want the birds to thrive. Like the folks Matthew quoted said, this is not particularly surprising. I don’t know why this struck them the wrong way, unless it’s getting academic credit for something already known? But we see this all the time, so…
Some other facts to remember:
Woodpeckers only use such habitats for about 6 years of their 8-year lifespan. After that, their prey is gone.
Salvage projects often leave huge portions of the wildfire out of the timber sales. The last one I worked on only proposed cutting on 55% of the burned acreage. This is done in consultation of the Wildlife Biologist.
Re-burns in California are particularly-devastating to overcrowded forests. They inhibit the return of forests useful to wildlife.
“Flying distance” for these kinds of woodpeckers are probably measured in many dozens of miles.
There are over a hundred million dead trees in California. WAY more than the handful of BBWOs can use.
Many California forests are at-risk to complete stand replacement. That does not bode well for many forest-dependent species.
I understand the concept of wildlife flourishing when we see a mosaic burn pattern in wildfires but my question is at what scale? The wildfires of the last 2-3 decades often are reported to have mosaics such as 20% severe, 35% moderate, 30% light with remaining % unburned, which sounds fine until you realize that it is over 150,000 acres where severe burn patches are contiguous 10,000 acres. Is that a mosaic in which wildlife species will prosper??
And in terms of salvage in burned forests, here in Oregon we see a high percentage of burned forestland salvaged. Even in stands that make no economic sense to salvage in efforts to reduce the future fuel loads prior to reforesting the ground. But when it comes to salvage on US Forest Service lands 0% to 5% is the norm, 5% to 15% on BLM lands is ever proposed for salvage.
My point was that there are plenty of snags left for snag-dependent species. The trend is to not salvage where volume is low and scattered, especially when it is on steep helicopter ground. In California, it doesn’t make sense to replant where there are lots of snags, due to the inevitable re-burns. It does make sense to replant salvaged areas of wildfires. Everything needs to be site-specific, IMHO.
I totally agree, Larry. What I was saying is that when it comes to Federal forestlands 90% or more of the dead, burned trees are left on the landscape–whether snags or down logs. Contrary to some assertions made on this blog site and other publications, there is no shortage of snags on our western federal lands,.