International Journal of Molecular Zoology 2024, Vol.14, No.5, 281-289 http://animalscipublisher.com/index.php/ijmz 283 limited plumage differentiation, suggesting that vocalizations play a crucial role in species recognition and differentiation (Gwee et al., 2020). The genetic basis of song characteristics has also been explored, with certain genomic regions being associated with migratory orientation and song traits in Swainson's thrushes, indicating a potential link between these behavioral traits and speciation (Delmore et al., 2016). Figure 1 Genes underlying plumage coloration and elevational adaptation. (A) Five primary candidate plumage genes and their function in rosy-finch phenotype. Variation in Mitf and Edn3 result in cheek patch differences, while variation in Ap3b1, Tyrp1, and Asip result in crown patch differences. (B) Four candidate elevation genes showing shared variation at Egln1 and Aldh1a1 among high-elevation birds, and unique variation inAggf1andJmy in brown-capped rosy-finches (Adopted from Funk et al., 2022) Nesting behavior is another critical behavioral trait that can impact reproductive success and survival. Although specific studies on the heritability of nesting behavior in birds were not provided in the data, it is well-known that nesting site selection, nest construction, and parental care behaviors are influenced by both genetic and environmental factors. These behaviors can vary widely among species and populations, contributing to their ecological adaptation and evolutionary success. 3.3 Physiological Traits Metabolic rate is a key physiological trait that affects energy expenditure and overall fitness in birds. While the provided data did not include specific studies on the heritability of metabolic rate, it is understood that metabolic rate can be influenced by genetic factors, environmental conditions, and individual health. For example, the adaptation to high elevations in North American rosy-finches involves genetic regions associated with hypoxia-related genes, which likely impact their metabolic rate and ability to thrive in low-oxygen environments. The stress response is a physiological trait that can influence an individual's ability to cope with environmental challenges. Although the data did not provide specific studies on the heritability of stress response in birds, it is known that stress response can be affected by genetic predisposition, early-life experiences, and current environmental conditions. Understanding the genetic and environmental factors that influence stress response can provide insights into how bird populations adapt to changing environments and cope with stressors. 4 Factors Influencing Heritability 4.1 Environmental influences Environmental factors play a significant role in shaping the heritability of phenotypic traits in bird populations. For instance, in a study on Great Lakes piping plovers, it was found that environmental factors such as breeding site had a major influence on traits like natal dispersal distance and female breeding time, which were not significantly heritable (Saunders and Cuthbert, 2014). Similarly, in house sparrows, early-life telomere length was primarily driven by environmental variance, including annual and brood effects, rather than genetic factors (Pepke
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