in the smog affected areas there is also probably not that much insects - bird food - giving how insects are breathing (https://en.wikipedia.org/wiki/Spiracle_(

in the smog affected areas there is also probably not that much insects - bird food - giving how insects are breathing (https://en.wikipedia.org/wiki/Spiracle_(arthropods) https://en.wikipedia.org/wiki/Spiracle_(arthropods)), i.e. beside the fire itself, the resulting air pollution may probably clog the insects breathing pores. Even when not dying, some insects stop breathing and fall into kind of hibernation, thus no flying around to be consumed by birds.