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- Gulls can change their migratory behavior during lifetimePublication . Marques, Paulo A. M.; Sowter, David; Jorge, PauloMigration is a widespread phenomenon among birds and is likely to be subject to strong selective pressures. Birds’ annual routines and behaviors might be expected to change during their diff erent life history stages, resulting in diff erent, agerelated migration patterns. However, although migration has been the subject of many publications, age-related diff erences in migration have received little attention. Th e present study examined age-related changes in individual migration habits in lesser black-backed gulls, Larus fuscus. We analyzed data from 10-year (1998–2007) color-ringing project in NW England, comprising more than 10 000 ringed individuals. Our results showed a latitudinal cline in age structure across the wintering range, with adults and gulls in their fi rst breeding year wintering closer to the breeding grounds. Supporting this result we observed that individuals, as they get older, changed the migration behavior and winter closer to the breeding areas. Interestingly, we found no diff erences in survival rates across the wintering grounds. Th us diff erences in survival rates can not account for the latitudinal cline in age structure, and the observed fi ndings seem to be best explained by the arrival time hypothesis, based on a mechanism whereby individuals are able to change their migratory behavior as result of the onset of sexual maturity and associated mating pressures.
- Light-dependent magnetic compass orientation in amphibians and insects: candidate receptors and candidate molecular mechanismsPublication . Phillips, John B.; Jorge, Paulo; Muheim, RachelMagnetic compass orientation by amphibians, and some insects, is mediated by a light-dependent magnetoreception mechanism. Cryptochrome photopigments, best known for their role in circadian rhythms, are proposed to mediate such responses. In this paper, we explore light-dependent properties of magnetic sensing at three levels: (i) behavioural (wavelength-dependent effects of light on magnetic compass orientation), (ii) physiological (photoreceptors/photopigment systems with properties suggesting a role in magnetoreception), and (iii) molecular (cryptochrome-based and non-cryptochrome-based signalling pathways that are compatible with behavioural responses). Our goal is to identify photoreceptors and signalling pathways that are likely to play a specialized role in magnetoreception in order to definitively answer the question of whether the effects of light on magnetic compass orientation are mediated by a light-dependent magnetoreception mechanism, or instead are due to input from a non-light-dependent (e.g. magnetite-based) magnetoreception mechanism that secondarily interacts with other light-dependent processes.