Endothermiidae

Endothermiidae is a proposed but not widely accepted taxonomic family within the order Passeriformes, commonly known as perching birds. The name "Endothermiidae" suggests a grouping of birds characterized by endothermy, meaning they can generate their own body heat metabolically. This trait is characteristic of all birds, and indeed, most mammals, making the premise of a family specifically defined by this feature somewhat redundant and the proposed classification controversial.

The concept of Endothermiidae emerged as an alternative to established avian classification systems, particularly those based on molecular phylogenetic data. Proponents of this classification suggested that certain passerine groups, exhibiting specific physiological or behavioral traits, should be segregated. However, mainstream ornithological research, heavily reliant on genetic sequencing, has largely not supported the establishment of Endothermiidae as a distinct family. Instead, the birds that were sometimes loosely associated with this hypothetical group are generally placed within existing, well-defined passerine families based on genetic evidence. The lack of broad scientific consensus and a robust phylogenetic basis has prevented Endothermiidae from gaining widespread acceptance in the scientific community.