Birds: Did Evolution of Biological Novelties Compromise their Capacity of Effectively Adapting to Extreme Environmental Conditions?

Foremost, the structural-, functional- and behavioural traits of birds relate directly or indirectly to powered flight, an elite mode of locomotion which has importantly made them what they are - ‘specialist and extreme animals’. Placing them at the pinnacle of the evolutionary hierarchy, birds possess exceptional biological specialisations which have conferred profound survival advantages. The adaptive novelties of birds are particularly exhibited by the exemplary morphological and physiological refinements of their respiratory system, the lung-air sac system. To contribute to the ongoing discussions and debates on the impacts of the existing extreme environmental conditions (ECs) on the biology of birds, here, a perspective is posed that the adaptive specialisations which birds acquired ostensibly under different ECs may have undermined their capacity of efficiently adjusting to different ones. To explain the viewpoint, the following aspects are considered: the specialist- and extreme biology of birds; the prevailing harsh ECs which are brutally impacting on birds and; the consequences from their enduring the harsh conditions which include among others global warming and habitat devastation. It is contended that under the existential threats, the adaptive capacities of birds appear to have declined, rendering them more vulnerable to external stressors. It is urged that urgent conservation measures, especially of the most threatened species of birds, are necessary.