I read with interest a response to a post from a while back ('bats on the beach in 40,000 years?', which listed the many advantages that birds have compared to mammals when it comes to flight. Those listed included the superiority of feathers over hair/skin, a method of locomotion more suited to freeing up the forelimbs (as opposed to mammals who tend to become quadrupeds) and a much more efficient respiratory system. These all sound like formidable barriers, but that got me wondering - given birds were already well established, how was it that bats managed to evolve? Were they exploiting a niche birds had not taken advantage of (the example that comes to mind is their nocturnal lifestyle) or did some other factor or factors play a part?

Hi Bruce,

I think you've got it when you mention the nocturnal niche.

Birds are largely diurnal animals, relying mainly on their excellent eyesight to navigate. Mammals are generally better suited to nocturnal activity, with their well developed sense of smell and hearing.

It seems reasonable to assume that the lack of competition for aerially accessed resources at night would provide sufficient benefit to drive the evolution of a nocturnal flying animal. Some birds have gone down this route, but remarkably few - and of those most don't engaging in active aerial pursuit at night, due to the limitations of their sensory system.

Bats probably initially evolved flight as a mechanism to avoid predators on the ground, but their preadaptations to nocturnal living probably made it much easier for them to adapt to fill a more active nocturnal niche.