Jones et al. in "Megafires: an emerging threat to old-forest species" (2016; Front Ecol Environ 14[6]: 300–306), claim their data describe a strong negative impact of severe fire on site extinction rates for spotted owls (Strix occidentalis) and significant avoidance of high-severity fire areas for foraging. Unfortunately, the paper has fatal flaws in the data analyses that render their results unreliable.

First, their owl population has documented long-term trends of decreasing site colonization and increasing site extinction probabilities, before the King Fire (Tempel and Gutiérrez 2013). However, Jones et al. did not account for these important pre-fire trends in their site occupancy analyses. Site occupancy analysis measures, each year, the probability that occupied sites are abandoned (called site extinction), and the probability that empty sites are colonized and become occupied again, and uses those colonization and extinction probabilities to calculate a yearly average probability of site occupancy. The population has had 22 years of documented trends of ever-lower site colonization probability, and ever-increasing site extinction probability, yet the authors simply compared their 1 year of post-fire data against the average of all previous years without accounting for those known year-to-year trends in colonization and extinction probabilities. The pre-fire decreasing trend in occupancy means 2015 (the year after fire) was expected follow the trend of having higher extinction probability and lower occupancy relative to all previous years, even if there was no fire. Fig. 3f clearly shows that the 2015 post-fire year of decrease in occupancy was not significantly different from the 10 previous years of decrease. The ‘trend analysis’ Jones et al. did was not what I just described. Rather, Jones et al. simply took annual estimates of site occupancy and compared a few models to describe the 23 years of annual occupancy rates. This trend analysis is not the same as including the pre-fire trends in extinction and colonization probabilities described above.

The second flaw was, Jones et al. used compositional analysis of foraging habitat use, a method that is inappropriate for central place foragers like spotted owls (Rosenberg and McKelvey 1999; Bond et al. 2009; Bond et al. 2016). Foraging habitat use analysis aims to determine whether a habitat type, for example severely burned forest, was used more often or less often than it would if the animal was foraging randomly and used the habitat type in proportion to its availability in the animal’s territory. Compositional analysis compares simplistic ratios of the proportion of foraging points in a habitat type relative to the proportion of territory area in that type. The proper habitat use analysis is a ‘resource selection function’, a math model that accounts for the fact that spotted owls, as central place foragers, will return to their nest or roost trees many times during the night, so their probability of using habitats near the nest is much higher than the probability of using habitats farther away from the nest. Every spotted owl foraging habitat use paper has found distance from nest is a highly significant effect on a point’s probability of use – but Jones et al. did not account for the distance of a foraging site to the nest. Because Jones et al. did not do a proper resource selection function analysis, they were essentially ignoring each foraging point’s distance from the nest, and the distribution of different habitat types at different distances from the nest, and this fatal mistake makes their radiotelemetry results and discussion unreliable.

Third, Jones et al. reported extinction for a territory in WebFigure 4 when the owls shifted their location by a distance that is less than the diameter of a territory as defined by the authors. The owls’ shift was also less than mean foraging distance reported by the authors. Because the authors ignored their own definition of a territory, they arbitrarily declared the short-distance shift to signify the extinction of the ‘old’ territory and creation of a ‘new’ territory a few hundred meters away. This was an arbitrary reclassification of a continuously occupied territory whose occupants shifted a few hundred meters, an occurrence that happens quite often in spotted owl territories. This decision inflated their ‘burned site’ extinction probability by classifying a normal within-territory movement as site extinction.

The sites that were occupied in 2014 are those most relevant to extinction probability in 2015, the only significant ‘fire-related’ effect Jones et al. found in 2015 and attributed to the King Fire. 2014 occupied site sample sizes indicates Jones et al. make their claim of ‘large extinction effects’ from only 8 severely burned sites that were occupied in 2014. Considering that Jones et al. did not account for the long-term increasing site extinction probability (meaning site extinction probability was getting bigger every year leading up to the fire), and the fact that only 8 sites in the burned area were occupied before the fire in 2014, and at least one site that they declared extinct from the fire actually just moved a few hundred meters, means their results are not correct.

Given the analytical shortcomings we described, and the fact that their conclusions contradict eight previous studies on the topic of spotted owls and fire, we suggest the results reported by Jones et al. be viewed with caution and not used to justify management actions that harm spotted owls.

Spotted owls exist in landscapes with a long evolutionary history of large, severe fire disturbances (Noss et al. 2006), and existing data mostly show no serious harm to spotted owl populations from mixed-severity fires with substantial areas of high-severity burn, including megafires. To summarize existing data: spotted owls forage in severely burned, unlogged stands (Bond et al. 2009; Bond et al. 2016; Comfort et al. 2016); breeding site (hereafter ‘site’) occupancy rates are not different between mixed-severity burned and unburned sites (Jenness et al. 2004; Roberts et al. 2011; Lee et al. 2012); and mixed-severity fire does not affect survival or reproduction (Bond et al. 2002; Jenness et al. 2004; Tempel et al. 2014).

The only Before-After-Control-Impact (BACI) study with large sample sizes that found negative effects of fire on spotted owl site occupancy comes from 71 burned and 97 unburned sites monitored over 9 years in southern California, where forests are drier, and burn more severely than Sierra Nevada forests, providing an example of what a warming climate may induce in the Sierra Nevada. Lee and Bond (2015b) found in higher-quality sites that were consistently occupied and reproductive, the amount of severe fire (even up to 100% high severity burn in the territory core) had negligible effect on occupancy or reproduction. However, in lower-quality sites that were often vacant and non-reproductive, occupancy was negatively correlated with increasing amounts of severe forest fire in the site’s core. High-quality sites may have been the type of territories that were 87% pair-occupied after the Rim Fire (Lee and Bond 2015a).

Additionally, errors of scholarship in Jones et al. include: Pg. 304 “The observation that lower-severity fire is benign, and perhaps even moderately beneficial, to spotted owls is consistent with previous studies (Roberts et al. 2011; Lee et al. 2012)” Both those studies found mixed-severity fire (rather than lower-severity fire) had no effect on occupancy. Mixed severity fire is common historically and currently in the Sierra Nevada and explicitly includes low, moderate, and high severity burned patches.

Pg. 305, “because owls were not individually marked in the Rim Fire study, some detections at “occupied” sites may have involved individuals from neighboring territories or non-territorial “floaters” (Lee and Bond 2015), both of which may have contributed to inflated estimates of territory occupancy.” This exact same situation exists in the data analysed by Jones et al. Data were collected as described in Tempel and Gutiérrez (2013), “We included both nocturnal and diurnal surveys in our occupancy analyses.” During nocturnal surveys leg bands were usually not resighted, therefore detections at occupied sites would have been similarly inflated by individuals from neighboring territories or non-territorial floaters.

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