International Journal of Molecular Zoology 2024, Vol.14, No.3, 141-153 http://animalscipublisher.com/index.php/ijmz 145 males and allows subadult males to coexist within the territories of adults, thereby gaining valuable foraging and learning opportunities (Lyu et al., 2015). The Winter Adaptation Hypothesis argues that DPM is an adaptation to increase survival during the non-breeding season. The less conspicuous plumage helps juveniles survive harsh winter conditions by reducing the risk of predation and competition for limited resources (Kiat and Sapir, 2017). 4.3 Evolutionary significance The evolutionary significance of delayed plumage maturation lies in its contribution to lifetime reproductive success. By delaying the acquisition of adult plumage, juvenile birds can navigate the challenges of early life more effectively. This strategy allows them to avoid the high costs associated with adult-like plumage, such as increased predation risk and social aggression. Instead, they can focus on survival and gaining experience, which can enhance their future reproductive success when they eventually acquire adult plumage (Morales-Betancourt and Castaño-Villa, 2018). DPM also allows for a flexible response to environmental conditions. In species with variable resource availability and social structures, retaining juvenile plumage can provide a survival advantage in fluctuating environments. For instance, in cooperative breeders, subadult plumage can signal non-breeding status, reducing conflicts and promoting group cohesion (Bentz and Siefferman, 2013). Overall, delayed plumage maturation represents a complex interplay of ecological, social, and evolutionary factors that optimize survival and reproductive strategies in birds. By understanding these mechanisms, researchers can gain insights into the adaptive value of plumage development and the life history strategies of different bird species (Lyu et al., 2015). 5 Mechanisms of Delayed Plumage Maturation 5.1 Genetic factors The genetic basis of delayed plumage maturation (DPM) involves the interaction of multiple genes that regulate the development and expression of plumage traits. Research has shown that variations in specific genes can influence the timing and pattern of feather development. For instance, studies on the house finch (Carpodacus mexicanus) have identified that certain alleles are associated with the retention of juvenile-like plumage in subadult males (Makarova et al., 2019). These genetic variations are often subject to natural selection, where those that confer survival and reproductive advantages are more likely to persist in the population. The inheritance patterns of these traits suggest that DPM is a heritable characteristic, though the exact genetic mechanisms can be complex and influenced by environmental factors. Additionally, molecular studies have identified candidate genes involved in feather pigmentation and structure, providing insights into the genetic regulation of DPM (Lyu et al., 2015). 5.2 Hormonal influences Hormones play a crucial role in the regulation of plumage maturation, with testosterone being a significant factor. Testosterone levels influence the expression of adult plumage characteristics, and fluctuations in hormone levels can delay or accelerate the development of definitive plumage. Research on black redstart (Phoenicurus ochruros) males has shown that higher testosterone levels during the molting period are associated with the development of adult plumage, whereas lower levels result in the retention of subadult plumage (Schwarzová et al., 2010). The endocrine system's response to environmental cues, such as changes in day length and social interactions, can modulate hormone production, thereby affecting the timing of plumage maturation. Hormonal regulation ensures that plumage changes occur at optimal times for survival and reproductive success, aligning with ecological conditions and life history stages (Perfito et al., 2015). 5.3 Environmental impacts Environmental factors, including habitat quality, food availability, and social interactions, significantly impact the timing and nature of plumage maturation. Poor nutritional conditions can delay plumage development, as adequate resources are necessary for the energy-intensive process of molting and feather growth. In species like
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