Fecal consumption by adults of altricial birds in relation to the temporal change in nestling gut microbiota

The Influence of Microbiota on Wild Birds' Parental Coprophagy Behavior: Current Advances and Future Research Directions

This comprehensive review provides an in-depth exploration of the intriguing phenomenon of parental coprophagy in wild birds and its profound implications on the influence of adult avian parents' health. This review investigates the composition and dynamics of avian feces' microbiota, casting light on the various dietary, environmental, and genetic factors that influence its diversity. Furthermore, it emphasizes parental coprophagy, a behavior observed in numerous bird species, particularly among herbivorous and passerine birds. The review investigates multiple hypotheses proposed to explain the occurrence of coprophagy. It delves into its function as a potential mechanism for transmitting microorganisms, particularly feces bacteria, from nestlings to their parents. This microbial transfer may affect the health and well-being of adult avian parents. In addition, the review highlights the current research deficits and debates surrounding coprophagy. These gaps include crucial aspects such as the onset of coprophagy, its long-term effects on both parents and offspring, the nutritional implications of consuming nestling feces, the potential risks of pathogen transmission, and the ecological and evolutionary factors that drive this behavior. As the review synthesizes existing knowledge and identifies areas requiring additional research, it emphasizes the significance of future studies that comprehensively address these gaps. By doing so, we can understand coprophagy's ecological and evolutionary significance in wild birds, advancing our knowledge on avian biology. This information can improve conservation efforts to protect migratory bird populations and their complex ecosystems.

Impacts of coprophagic foraging behaviour on the avian gut microbiome

Avian gut microbial communities are complex and play a fundamental role in regulating biological functions within an individual. Although it is well established that diet can influence the structure and composition of the gut microbiota, foraging behaviour may also play a critical, yet unexplored role in shaping the composition, dynamics, and adaptive potential of avian gut microbiota. In this review, we examine the potential influence of coprophagic foraging behaviour on the establishment and adaptability of wild avian gut microbiomes. Coprophagy involves the ingestion of faeces, sourced from either self (autocoprophagy), conspecific animals (allocoprophagy), or heterospecific animals. Much like faecal transplant therapy, coprophagy may (i) support the establishment of the gut microbiota of young precocial species, (ii) directly and indirectly provide nutritional and energetic requirements, and (iii) represent a mechanism by which birds can rapidly adapt the microbiota to changing environments and diets. However, in certain contexts, coprophagy may also pose risks to wild birds, and their microbiomes, through increased exposure to chemical pollutants, pathogenic microbes, and antibiotic-resistant microbes, with deleterious effects on host health and performance. Given the potentially far-reaching consequences of coprophagy for avian microbiomes, and the dearth of literature directly investigating these links, we have developed a predictive framework for directing future research to understand better when and why wild birds engage in distinct types of coprophagy, and the consequences of this foraging behaviour. There is a need for comprehensive investigation into the influence of coprophagy on avian gut microbiotas and its effects on host health and performance throughout ontogeny and across a range of environmental perturbations. Future behavioural studies combined with metagenomic approaches are needed to provide insights into the function of this poorly understood behaviour.