On a recent thread [0] there was a lot of conversation around various estimates and news coverage of animal deaths caused by the fires in Australia.

I contacted Professor Chris Dickman [1], the author of the '480 million affected animals' estimate (now revised up to over 800 million).

He mentioned this article he co-authored that was just published. It expands on the impact to animals and their habitats and addresses a lot of the questions people are asking.

He also made some points after I asked him about this extract from the abstract of a paper of his [2] called "The Responses of Mammals to La Niña (El Niño Southern Oscillation)–Associated Rainfall, Predation, and Wildfire in Central Australia":

The responses of vertebrates to wildfires are complex, reflecting the varying food and shelter requirements of different species, their exposure to predation, and other factors. Vertebrates that shelter above the ground and are not particularly mobile are often killed directly by fire (Chew et al. 1959; Newsome et al. 1975; Silveira et al. 1999; Simons 1991). Conversely, species capable of extensive movements such as large predators and birds frequently escape the flames and may increase in abundance after wildfire when food resources become available (Loyn 1997; Newsome et al. 1975).,Burrowing herbivores and omnivores are likely to survive fires and, depending on predation, may increase in abundance after postfire flushes of vegetation (Newsome et al. 1975). Postwild-fire decreases in the abundance of some species have been attributed to a lack of food resources and increased exposure to predation (Groves and Steenhof 1988; Lawrence 1966; Newsome et al. 1975, 1983).

Here are his thoughts, with his permission. I provide them in full, but perhaps the most frightening part is the last sentence "the current fires seem to be overwhelming these [animal responses to fire] owing to [the fires] severity and geographical extent":

The abstract that you have quoted stems from work carried out in the Simpson Desert some years ago by myself and others in spinifex dominated environments. Fires there burn with much less intensity than the fires we have been seeing in eastern Australia recently, as there is very little leaf litter and the major vegetation association that burns is spinifex grassland. To give you an idea of how low intensity and close to the ground the spinifex fires are, you can actually jump over an advancing fire front (not recommended, but I have done it in my younger days ...!). In the current forest fires, of course, you cannot get anywhere close without risk of death.

The consequences for wildlife of these two types of fire are very different, as alluded to in the abstract of the paper. In desert areas fires often leave large unburned patches where animals can escape, and many can go down into burrows or fly away. In the current bushfires, by contrast, few refuge patches of unburned habitat seem to be persisting, the areas of the fires are huge so lack of resources and post-fire predation become very significant for survivors, and even many birds are killed while fleeing by the flames and the smoke.

In other words, the abstract is accurate in talking about the variability in animal responses to fire, but the current fires seem to be overwhelming these responses owing to their severity and geographical extent.

[0] https://news.ycombinator.com/item?id=21985532

[1] https://sydney.edu.au/science/about/our-people/academic-staf...

[2] https://academic.oup.com/jmammal/article/86/4/689/876336