International Journal of Molecular Zoology 2024, Vol.14, No.3, 141-153 http://animalscipublisher.com/index.php/ijmz 146 the zebra finch (Taeniopygia guttata), social isolation has been shown to delay the onset of adult plumage, indicating that social environment plays a critical role in triggering hormonal changes necessary for plumage maturation (Choi et al., 2022). Additionally, environmental stressors such as predation pressure and competition for resources can influence the evolution of DPM. Birds in high-predation environments may benefit from retaining cryptic juvenile plumage longer to avoid detection, while those in competitive social settings might delay plumage maturation to reduce aggression from dominant adults (Berggren et al., 2004). Understanding these environmental impacts helps elucidate how DPM is an adaptive strategy that enhances survival and reproductive success in varying ecological contexts. 6 Implications for Survival and Reproduction 6.1 Advantages of delayed plumage maturation Delayed plumage maturation (DPM) offers several advantages that can enhance the survival and reproductive success of juvenile birds. One of the primary benefits is crypsis, where juvenile birds retain a non-adult-like plumage that makes them less conspicuous to predators and less likely to be targeted by aggressive adult conspecifics. This cryptic plumage allows young birds to avoid conflicts and focus on survival during their early life stages (Figure 2) (Ferreira et al., 2023). Additionally, female mimicry is another adaptive strategy where juvenile males resemble females, reducing the likelihood of being perceived as a threat by dominant adult males. This mimicry can facilitate access to resources and safe territories without incurring the costs associated with direct competition (Lyu et al., 2015). Another significant advantage is the status signaling hypothesis, which posits that juvenile birds use their subadult plumage to signal their subordinate status. This honest signaling reduces aggressive interactions with dominant adults, allowing juveniles to coexist peacefully within established territories. By minimizing conflicts, juvenile birds can conserve energy and allocate more resources to growth and development, improving their chances of survival and future reproductive success (Lyu et al., 2015). Moreover, DPM can be particularly beneficial in environments with high competition for breeding sites and resources, where avoiding early-life confrontations can enhance long-term fitness (Allen et al., 2022). 6.2 Disadvantages and risks Despite its advantages, DPM also carries certain disadvantages and risks. One of the primary drawbacks is the potential delay in reproductive opportunities. Juvenile males with subadult plumage may be less attractive to females compared to fully mature males, resulting in reduced mating success during their first breeding season. This delayed mating can decrease the overall reproductive output of individuals, especially in species where early breeding is crucial for maximizing lifetime reproductive success (Doucet et al., 2018). Furthermore, the retention of juvenile plumage might lead to higher predation risks if it fails to provide adequate camouflage in certain habitats or seasons, thereby compromising the bird's survival (Ferreira et al., 2023). Another significant risk associated with DPM is the increased vulnerability to environmental stressors. Juvenile birds with subadult plumage might face challenges in securing high-quality territories and resources, especially in habitats where competition is intense. This can lead to lower body condition and reduced survival rates during critical periods such as winter or migration (Berggren et al., 2004). Additionally, subadult plumage may not offer the same level of social acceptance within flocks, potentially leading to exclusion from group benefits such as cooperative foraging and predator detection (Kiat and Sapir, 2017). 6.3 Impact on mating success The impact of DPM on mating success is multifaceted and depends on various ecological and social factors. In many species, subadult males with delayed plumage maturation are less successful in securing mates compared to their fully mature counterparts. Females often prefer males with definitive adult plumage, which is typically associated with higher fitness and better genetic quality. This preference can result in lower mating success for subadult males during their first breeding season, delaying their reproductive contributions (Doucet et al., 2018).
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