Barred owls and megafire hit native owls differently

What two co-occurring stressors did the owl study separate?

Severe wildfire and invasive barred owls, using acoustic occupancy before/after megafires and lethal removals.

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

How large was the study area and the two megafires?

>6000 km2 in the northern Sierra Nevada; North Complex 1220 km2 (49% high severity) and Dixie 3740 km2 (56% high severity).

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

How many barred owls were removed, and did occupancy collapse?

80 total (67 barred, 13 hybrids); occupancy fell from 0.19 to 0.03, a 6.3-fold reduction.

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

How intensive were the acoustic surveys?

517 ARUs in 265 cells (2018 and 2021), then 477 and 401 ARUs in later years; tens to hundreds of thousands of recording hours.

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

How did severe fire affect flammulated owls?

Occupancy fell 71% in near-complete high-severity burns for at least 3 years, though sites with some high-severity fire had higher occupancy than unburned sites (0.29 vs 0.16).

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

What happened to flammulated owls after barred owl removals?

Occupancy at removal sites rose from 0.09 before to 0.18 after (about a twofold increase).

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

Did pygmy or great horned owls show the same fire and removal responses?

No strong support for postfire or post-removal occupancy changes in either species.

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

Was there a fire × barred-owl interaction?

No: interaction models found no interactive effect for any of the three native owls.

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

How did terrain ruggedness sort flammulated versus barred owls?

Flammulated occupancy was 196% higher in the most versus least rugged areas; barred owls declined 84% under the same contrast.

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

Why might barred owls suppress flammulated owls despite little diet overlap?

Authors infer predation or fear effects: flammulated owls are small and nocturnal, and occupancy rose after removals even though barred owls eat mostly vertebrates.

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

What management actions do the authors recommend?

Limit high-severity fire spread while keeping large trees and some live canopy; remove barred owls early while densities are still low.

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified

Why act at the invasion front rather than after barred owls densify?

Removals work best when populations are sparse; high densities expand habitat overlap and make control costly and less effective.

Source: Divergent responses of native predators to severe wildfire and biological invasion are mediated by life history · DOI · quote verified