Expression Of Migratory Behavior Research Articles

The evolution of avian migration

The study of avian migration has reached sophisticated levels in many areas, including ecology, behaviour, and physiology. Traditional discussions of the evolution of migration, however, have been compromised for several reasons. Previous ideas concerning the ancestral home of migrant species, southern or northern, and whether a partially migratory stage always precedes a fully migratory stage, were not expressed as testable hypotheses. Plotting migratory behaviour on phylogenetic trees has become commonplace and allows tests of traditional hypotheses. Some of these studies are reviewed, lending some support for almost all of the previous ideas. Although phylogenetic mapping helps to frame questions about the evolution of migration in a testable framework, there are two serious issues. First, experimental and observational studies reveal that the expression of migratory behaviour can change rapidly within a lineage, which can violate assumptions of character mapping. In addition, a species distribution model is used to show that current conditions for obligate migratory populations of the chipping sparrow were much restricted at the Last Glacial Maximum, and that the species might have been considered a partial migrant at that time. The expression of migratory behaviour in an extant species might be an artefact of the current inter-glacial period. Only if the rate of gains and losses of migratory behaviour can be incorporated into a phylogenetic mapping exercise will the actual evolutionary pattern of migration be revealed. For example, reconstruction of the ancestral area and the evolutionary history of migratory categories in a clade of New World warblers depended on the assumptions of character state transitions. A second concern is that the trait ‘migratory’ is too broad for evolutionary analysis and that, if possible, the expression of hyperphagia, Zugunruhe, and navigation could be mapped individually. Loss or suppression of any of these components can lead to sedentary populations, revealing how migratory behaviour can appear and disappear rapidly. A report of low levels of Zugunruhe in a sedentary bird, Saxicola torquata, is reconstructed as derived in a clade of otherwise migratory populations, suggesting that the loss of migration was a result of suppression (but not elimination) of Zugunruhe. When researchers mention the independent origin of migration in a clade, they are most likely referring to the gain or loss of the expression of the ancestral migratory programme, not the de novo evolution of migration per se. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 237–250.

Evolution of bird migration in a biogeographical context

AbstractWe infer from the literature that migratory habits of birds evolved in various phylogenetic lineages and biogeographical contexts, either after gradual range expansion into seasonal habitats, or due to environmental changes within established breeding ranges. Shifts of breeding ranges are the results of interactions between colonization due to dispersal and extinction due to deteriorating conditions. Range expansions provide a platform for the evolution of migration from the newly colonized areas towards seasonally favourable non‐breeding areas. A comparison of palaeoclimatic changes with concurrent evolution and distribution of passerine birds suggests that at least some of the basic genera of the Passerida radiated on the northern continents when quasi‐tropical or subtropical climates prevailed. The Passerida may be a special case, but they suggest that ‘tropical origin’ does not necessarily imply a ‘southern origin’ of migratory species. Climate deterioration required adaptations either towards on‐site survival under harsh conditions or towards escape movements allowing improved non‐breeding survival in less seasonal climates or with reversed seasonality. Taxon‐specific life‐history traits and environmental conditions favoured either sedentary or migratory lines of adaptation. Repeated climate variation induced range shifts and concurrent increases or decreases in the expression of migratory behaviour. Two examples of waders suggest that the principle of range shift, followed by the development of migratory habits, is also applicable for other taxonomic groups.

WING SHAPE IN HOUSE FINCHES DIFFERS RELATIVE TO MIGRATORY HABIT IN EASTERN AND WESTERN NORTH AMERICA

Abstract We investigated whether wing morphology differed between the sedentary House Finches (Carpodacus mexicanus) of western North America and the introduced population of eastern North America, as the latter has developed migratory behavior since its inception. Wing morphology differed between eastern and western House Finches. Eastern House Finches had shorter proximal primaries and a longer outer primary, perhaps reflecting a thinner and more pointed wing, although no disparity in wing length was detected. Since we interpret these differences in wing shape as modifications for flight capability, we believe that initial evidence for morphological divergence relative to migratory habit between eastern and western House Finches has been established here. Confirmatory studies to determine if wing morphology varies according to the gradient in expression of migratory behavior throughout the range of eastern House Finches are now warranted. La Forma Alar en Carpodacus mexicanus Difiere en Relacion a los H...

Population variation in the ontogeny of predator-induced vertical migration of copepods

DIEL vertical migrations (DVM) of zooplankton are nearly ubiquitous and vary widely in timing and magnitude1–5. Predation can be both an evolutionary and proximal ('inducing') agent in promoting this variation6–14. Because aquatic predators are strongly size-selective15, vulnerability to predation changes during an individual's ontogeny. Accordingly, natural selection on photo-taxis, timing and magnitude of migration should also vary during ontogeny. Furthermore, biogeographic variation in the composition, density and behaviour of predators would probably select for different ontogenies of DVM. Whether predator-induced or developmentally fixed (canalized) migrations would be favoured probably depends on the variability of predatory risk16–19. Here I compare experimentally DVMs of calanoid copepods from populations with contrasting histories of vertebrate and invertebrate predation. Results show predator- and population-specific migrations that differed with life history stage/size. Both develop-mentally fixed and predator-induced migrations were found at various life-stages in the same group of individuals. Ontogenetic patterns, however, differed among populations adapted to different suites of predators. Genes coding for differences in phenotypic expression of migratory behaviour seem to have been selected by local predation at each stage/size.

Induction of Zugunruhe by photostimulation of encephalic receptors in white-crowned sparrows.

Daily 20-hour encephalic photophases (DEPP), transmitted (hours 0 to 20) via chronically implanted light-conducting fibers to selected sites in the basal hypothalamus of male white-crowned sparrows, were superimposed on daily 8-hour (hours 0 to 8) external ambient photophases (DAPP). Initially the birds displayed motor activity only during the 8-hour DAPP. After a delay of at least 2 weeks, some of the birds became intensively active during hours 8 to 20. We postulate that this period of "nocturnal" activity is equivalent to the nocturnal Zugunruhe shown by caged individuals of many nocturnally migratory species subjected to long days; such activity is generally regarded as the expression of migratory behavior.