Avian movements in a modern world - cognitive challenges

Different movement patterns have evolved as a response to predictable and unpredictable variation in the environment with migration being an adaptation to predictable environments, nomadism to unpredictable environments and partial migration to a mixture of predictable and unpredictable conditions. Along different movement patterns different cognitive abilities have evolved which are reviewed and discussed in relation to an organism’s ability to respond to largely unpredictable environmental change due to climate and human-induced change and linked to population trends. In brief, migrants have a combination of reliance on memory, low propensity to explore and high avoidance of environmental change that in combination with overall small brain sizes results in low flexibility to respond to unpredictable environmental change. In line with this, many migrants have negative population trends. In contrast, while nomads may use their memory to find suitable habitats they can counteract negative effects of finding such habitats disturbed by large-scale exploratory movements and paying attention to environmental cues. They are also little avoidant of environmental change. Population trends are largely stable or increasing indicating their ability to cope with climate and human-induced change. Cognitive abilities in partial migrants are little investigated but indicate attention to environmental cues coupled with high exploratory tendencies that allow them a flexible response to unpredictable environmental change. Indeed, their population trends are mainly stable or increasing. In conclusion, cognitive abilities have evolved in conjunction with different movement patterns and affect an organism’s ability to adapt to rapidly human-induced changes in the environment

Fastloc-GPS reveals daytime departure and arrival during long-distance migration and the use of different resting strategies in sea turtles

Determining the time of day that animals initiate and end migration, as well as variation in diel movement patterns during migration, provides insights into the types of strategy used to maximise energy efficiency and ensure successful completion of migration. However, obtaining this level of detail has been difficult for long-distance migratory marine species. Thus, we investigated whether the large volume of highly accurate locations obtained by Argos-linked Fastloc-GPS transmitters could be used to identify the time of day that adult green (n = 8 turtles, 9487 locations) and loggerhead (n = 46 turtles, 47,588 locations) sea turtles initiate and end migration, along with potential resting strategies during migration. We found that departure from and arrival at breeding, stopover and foraging sites consistently occurred during the daytime, which is consistent with previous findings suggesting that turtles might use solar visual cues for orientation. Only seven turtles made stopovers (of up to 6 days and all located close to the start or end of migration) during migration, possibly to rest and/or refuel; however, observations of day versus night speed of travel indicated that turtles might use other mechanisms to rest. For instance, turtles travelled 31% slower at night compared to day during their oceanic crossings. Furthermore, within the first 24 h of entering waters shallower than 100 m towards the end of migration, some individuals travelled 72% slower at night, repeating this behaviour intermittently (each time for a one-night duration at 3–6 day intervals) until reaching the foraging grounds. Thus, access to data-rich, highly accurate Argos-linked Fastloc-GPS provided information about differences in day versus night activity at different stages in migration, allowing us, for the first time, to compare the strategies used by a marine vertebrate with terrestrial land-based and flying species

Drought in Africa Caused Delayed Arrival of European Songbirds

A severe drought in the Horn of Africa delayed the spring arrival in Europe of two migratory species.</jats:p

Absolute Consistency:Individual versus Population Variation in Annual-Cycle Schedules of a Long-Distance Migrant Bird

<p>Flexibility in scheduling varies throughout an organism's annual cycle, reflecting relative temporal constraints and fitness consequences among life-history stages. Time-selection can act at different scales, either by limiting the range of alternative strategies in the population, or by increasing the precision of individual performance. We tracked individual bar-tailed godwits Limosa lapponica baueri for two full years (including direct observation during non-breeding seasons in New Zealand and geolocator tracking of round-trip migrations to Alaska) to present a full annual-cycle view of molt, breeding, and migration schedules. At both population and individual scales, temporal variation was greater in post-breeding than pre-breeding stages, and greater in molts than in movements, but schedules did not tighten across successive stages of migration toward the breeding grounds. In general, individual godwits were quite consistent in timing of events throughout the year, and repeatability of pre-breeding movements was particularly high (r = 0.82-0.92). However, we demonstrate that r values misrepresent absolute consistency by confounding inter- and intra-individual variation; the biological significance of r values can only be understood when these are considered separately. By doing so, we show that some stages have considerable tolerance for alternative strategies within the population, whereas scheduling of northbound migratory movements was similar for all individuals. How time-selection simultaneously shapes both individual and population variation is central to understanding and predicting adaptive phenological responses to environmental change.</p>

執筆者

Tracking devices are increasingly used to monitor individual movement patterns continuously and in high resolution. However, carrying a device could potentially compromise an individual's physiology or behaviour, thereby making tracking data unreliable for detailed behavioural measurements. To this end, we assessed the possible consequences of the application of GPS devices on offspring development in an opportunistic seabird species, the lesser black-backed gull (Larus fuscus), by comparing the growth and survival of nestlings of which none, one or both parents were equipped with a GPS device. We found that the developmental trajectories of the nestlings were not affected, and there were no differences in skeletal size and body mass at the fledging stage. A lack of negative effects on offspring development strongly suggests that the parental behaviour, and thus likely the foraging behaviour, did not differ between tagged and non-tagged individuals. The evidence that GPS data can be used to reliably study parental care, as well as other aspects of the bird's behaviour, opens up new possibilities to study behavioural and evolutionary ecological questions in ever-increasing resolution