Migratory Behavior and Endocrine Mechanisms in Birds

Migration in birds represents one of the most striking examples of seasonal adaptation, involving tightly regulated interactions between environmental cues and internal physiological processes. Seasonal changes in day length, or photoperiod, entrain endogenous circannual rhythms that govern both migratory timing and reproductive readiness. At the heart of this regulation lies the hypothalamo-pituitary-gonadal (HPG) axis, which mediates gonadal growth and steroid hormone secretion, and the hypothalamo-pituitary-adrenal (HPA) axis, which modulates energy balance and stress responses. Prior to migration, birds accumulate fat stores under the influence of gonadal steroids and metabolic hormones, while nocturnal migratory restlessness emerges as a behavioural proxy for migratory disposition. Navigation and orientation are further refined by interactions among melatonin, thyroid hormones and neuropeptides within key brain regions. Recent advances have illuminated how variation in receptor sensitivity and hormone receptor expression can differ between obligate and facultative migrants, and between resident and migratory populations within the same species. Such insights are critical for forecasting shifts in migratory phenology under global change, for designing targeted conservation strategies and for understanding the role of migration in disease transmission and ecosystem connectivity.

Research from Nature Portfolio

Work on wintering whooper swans has linked fluctuations in faecal glucocorticoid metabolites to variations in ambient temperature and day length, revealing that rising glucocorticoid levels precede phases of heightened vigilance, preening and locomotion characteristic of migratory restlessness. Behavioural principal component analysis identified distinct activity phases, and one phase—dominated by aggression and calling—showed a marginal effect on expansion of winter home range. These findings confirm an integrated hormonal and behavioural programme underlying the onset of migration, emphasising how glucocorticoid signalling and behavioural shifts interact to prepare birds for long-distance journeys.

Migratory Behavior and Endocrine Mechanisms in Birds publication trend

The graph below shows the total number of articles in migratory behavior and endocrine mechanisms in birds across all publications each year (not limited to Nature Index journals).

Technical terms

Photoperiod: The duration of daylight in a 24-hour period, acting as a primary cue for seasonal timing.

Hypothalamo-pituitary-gonadal (HPG) axis: A hormonal cascade from the brain to the gonads that regulates reproductive development and steroidogenesis.

Migratory restlessness (zugunruhe): Nocturnal activity exhibited by captive migratory birds, reflecting the endogenous drive to migrate.

Glucocorticoid metabolites: Breakdown products of adrenal glucocorticoid hormones measured in excreta, indicative of stress and energy mobilisation.

Gonadotropin-releasing hormone (GnRH): A hypothalamic neuropeptide that stimulates pituitary secretion of luteinizing hormone, initiating gonadal steroid production.

References

1. Extrinsic factors, endocrine mechanisms, and behavioral indicators of migratory restlessness in wintering whooper swans (Cygnus cygnus). Scientific Reports (2021).
2. Increasing photoperiod stimulates the initiation of spring migratory behaviour and physiology in a facultative migrant, the pine siskin. Royal Society Open Science (2018).
3. Early spring sex differences in luteinizing hormone response to gonadotropin releasing hormone in co-occurring resident and migrant dark-eyed juncos (Junco hyemalis). General and Comparative Endocrinology (2016).