Control and adaptability of seasonal changes in behavior and physiology of latitudinal avian migrants: Insights from laboratory studies in Palearctic‐Indian migratory buntings

Abstract

Twice‐a‐year migrations, one in autumn and the other in spring, occur within a discrete time window with striking alterations in the behavior and physiology, as regulated by the interaction of endogenous rhythms with prevailing photoperiod. These seasonal voyages are not isolated events; rather, they are part of an overall annual itinerary and remain closely coupled to the other annual subcycles, called seasonal life history states (LHSs). The success of migration depends on appropriate timing of the initiation and termination of each LHS, for example, reproduction, molt, summer nonmigratory, preautumn migratory (fattening and weight gain), autumn migratory, winter nonmigratory (wnM), prevernal (spring) migratory (fattening and weight gain), and spring migratory LHSs. Migration‐linked photoperiod‐induced changes include the body fattening and weight gain, nocturnal Zugunruhe (migratory restlessness), elevated triglycerides and free fatty acids, triiodothyronine and corticosterone levels. Hypothalamic expression of the thyroid hormone‐responsive dio2 and dio3, light‐responsive per2, cry1, and adcyap1 and th (tyrosine hydroxylase, involved in dopamine biosynthesis) genes also show significant changes with transition from wnM to the vernal migratory LHS. Concurrent changes in the expression of genes associated with lipid metabolism and its transport also occur in the liver and flight muscles, respectively. Interestingly, there are clear differences in the behavioral and physiological phenotypes, and associated molecular changes, between the autumn and vernal migrations. In this review, we discuss seasonal changes in the behavior and physiology, and present molecular insights into the development of migratory phenotypes in latitudinal avian migrants, with special reference to Palearctic‐Indian migratory buntings.

Modular switches shift monarch butterfly migratory flight behavior at their Mexican overwintering sites

“… 2 Transitioning between migratory states requires system-wide coordination on different scales—from specific cellular changes to the development of entire organ systems—that are often mediated by differential hormone activity (reviewed in studies by Rankin, Sharma et al., and Cornelius et al.) 3 , 4 , 5 or epigenetic mechanisms. 6 , 7 , 8 Migration initiation involves integrating intrinsic (e.g., circadian and circannual timers) and extrinsic (e.g., environmental, social) factors in vertebrate (reviewed in a study by Cornelius et al) 5 and invertebrate (reviewed in a study by Chapman et al.)…”

Relationship between Fat Status, Stage of Gonadal Maturity and Hormonal Variation of Turdus philomelos (C.L. Brehm, 1831) Wintering in Apulia during 2018–2020

“…The phenomenon of migration, however, has reached its greatest complexity in birds, which are preadapted to migrate due to their capacity for active flight, size, and extraordinarily efficient circulatory and respiratory systems [2]. Endogenous control mechanisms are thought to regulate seasonally appropriate migratory restlessness and orientation [3] and the onset and end of migratory activity, which may have influences through seasonal changes in dietary and habitat preferences [4] such as the circannual pattern of body mass change, including fat deposition [5,6].…”

An introduction to the Special Issue on seasonal rhythms in birds and mammals

“…Most photoperiodic studies used temperate zone animals. The contribution from Sharma et al (2022) describes the role of photoperiodic cues to time seasonal transitions in latitudinal migration by palearctic‐Indian birds. The authors show that a suite of molecular changes including thyroid hormone catabolism achieved by the deiodinase enzymes type‐2 and type‐3, and circadian clock genes, period 2 and cryptochrome 1 in the mediobasal hypothalamus are key molecular correlates of vernal migration.…”