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- An ontogenetic perspective on migratory strategy of a long-lived pelagic seabird: Timings and destinations change progressively during maturationPublication . Letizia, Campioni; Dias, Maria P.; Granadeiro, José Pedro; Catry, PauloThe processes that drive the ontogeny of migratory strategies in long-lived animals with slow maturation remain enigmatic. While some short-lived migrants are known or believed to repeat the same migratory patterns throughout their lives, little is known on the time required for immature long-lived migrants to progressively acquire adult-like migratory behaviours, or which aspects take longer to refine during the maturation process. Here, we studied the ontogeny of long-distance migratory strategies and related patterns of spatial distribution in a long-lived seabird species during the annual cycle. To do so, we deployed light-level geolocators on 4- to 9-year-old immature Cory's shearwaters (Calonectris borealis) and on breeding adults. We revealed that migratory timings and destinations of young shearwaters progressively changed with age. The effect of ageing was remarkably evident on spring migratory performance and phenology. Birds gradually shortened the duration of the non-breeding period by advancing departure date and reducing travelling time, which resulted in a sequential arrival at the colony of the various age contingents. Ageing immatures gradually changed from a more exploratory strategy to a more conservative way of exploiting resources, reducing both their year-round spatial spread across oceanic domains and the total distance travelled. Immatures always performed a trans-equatorial migration to the Southern Hemisphere, contrasting with 17% of the adults which remained in the North Atlantic year-round. Finally, during the breeding season immatures were widely dispersed through the North Atlantic reducing their overlap with breeding adults. Our long-term study provides empirical support to the hypothesis that in long-lived species, the refinement of migratory behaviour and year-round spatial distribution is a progressive process mediated by age and experience, where life stage constraints and competition for resources may also play a role. The emerging pattern suggests that for some avian taxa, the ontogeny of migratory strategy is a prolonged, complex and dynamic process.
- Citizen science data reveal possible multi-decadal phenological changes in the arrival time of a migratory tropical seabird species at the breeding groundPublication . Letizia, Campioni; Madeiros, Jeremy; Becciu, Paolo· Changes in climate and weather variability are having global impacts on the lives of organisms, particularly on upper trophic-level predators such as pelagic seabirds. In the North Atlantic, migratory seabirds are expected to respond to climate variability by adjusting their seasonal events, including the timing of migration and arrival at the breeding site. The timing of these events may be infuenced by large-scale atmospheric phenomena such as the North Atlantic Oscillation (NAO) and the Atlantic Multi-decadal Oscillation (AMO) that gauge temporal and spatial variation in environmental conditions across the North Atlantic. In the Bermuda Islands (32° 17′ 58″ N, 64° 47′ 25″ W), the White-tailed tropicbird (Phaethon lepturus catsbyii) is one of the few breeding seabird species which returns every year between February and March after migration. According to local belief their return announces the arrival of Spring, and this cultural importance means that the event is noticed. Only recently, early tropicbird returns have been recorded and associated with unusual climate/weather conditions experienced across the region. This raised the question of whether the species is showing some change in its phenology and whether it might be afected by changing climatic conditions. To answer this question, we investigated tropicbird arrival dates at Bermuda using current and historic observation data retrieved from the eBird citizen science platform. After accounting for biases inherent to opportunistic data collection, we selected and used the frst annual observation as a proxy for bird arrival time at the Bermuda breeding ground from 1953 to 2023. We found that tropicbird observation dates advanced substantially over the past 70 years suggesting that arrival time has been likely shifting of ca. 20–25 days. However, frst observation dates were not related to the variation in annual or winter NAO and AMO Indices, and further investigation is required to understand the underlying causes of these progressively early arrivals. Overall, the study highlights that citizen-science data can be used to unveil hidden phonological patterns when a standardized long-term data collection is missing.
- A framework for mapping the distribution of seabirds by integrating tracking, demography and phenologyPublication . Carneiro, Ana Paula B.; Pearmain, Elizabeth J.; Oppel, Steffen; Clay, Thomas A.; Phillips, Richard A.; Bonnet‐Lebrun, Anne‐Sophie; Wanless, Ross M.; Abraham, Edward; Richard, Yvan; Rice, Joel; Handley, Jonathan; Davies, Tammy E.; Dilley, Ben J.; Ryan, Peter G.; Small, Cleo; Arata, Javier; Arnould, John P. Y.; Bell, Elizabeth; Bugoni, Leandro; Letizia, Campioni; Catry, Paulo; Cleeland, Jaimie; Deppe, Lorna; Elliott, Graeme; Freeman, Amanda; Gonzalez-Solis, Jacob; Granadeiro, José Pedro; Grémillet, David; Landers, Todd J.; Makhado, Azwianewi; Nel, Deon; Nicholls, David G.; Rexer‐Huber, Kalinka; Robertson, Christopher J. R.; Sagar, Paul M.; Scofield, Paul; Stahl, Jean‐Claude; Stanworth, Andrew; Stevens, Kim L.; Trathan, Philip N.; Thompson, David R.; Torres, Leigh; Walker, Kath; Waugh, Susan M.; Weimerskirch, Henri; Dias, Maria P.1. The identification of geographic areas where the densities of animals are highest across their annual cycles is a crucial step in conservation planning. In marine environments, however, it can be particularly difficult to map the distribution of species, and the methods used are usually biased towards adults, neglecting the distribution of other life-history stages even though they can represent a substantial proportion of the total population. 2. Here we develop a methodological framework for estimating populationlevel density distributions of seabirds, integrating tracking data across the main life-history stages (adult breeders and non-breeders, juveniles and immatures). We incorporate demographic information (adult and juvenile/immature survival, breeding frequency and success, age at first breeding) and phenological data (average timing of breeding and migration) to weight distribution maps according to the proportion of the population represented by each life-history stage. 3. We demonstrate the utility of this framework by applying it to 22 species of albatrosses and petrels that are of conservation concern due to interactions with fisheries. Because juveniles, immatures and non-breeding adults account for 47%–81% of all individuals of the populations analysed, ignoring the distributions of birds in these stages leads to biased estimates of overlap with threats, and may misdirect management and conservation efforts. Population-level distribution maps using only adult distributions underestimated exposure to longline fishing effort by 18%–42%, compared with overlap scores based on data from all lifehistory stages. 4. Synthesis and applications. Our framework synthesizes and improves on previous approaches to estimate seabird densities at sea, is applicable for data-poor situations, and provides a standard and repeatable method that can be easily updated as new tracking and demographic data become available. We provide scripts in the R language and a Shiny app to facilitate future applications of our approach. We recommend that where sufficient tracking data are available, this framework be used to assess overlap of seabirds with at-sea threats such as overharvesting, fisheries bycatch, shipping, offshore industry and pollutants. Based on such an analysis, conservation interventions could be directed towards areas where they have the greatest impact on populations.
- No evidence of inbreeding depression despite a historical severe bottleneck in the endangered Bermuda petrel (Pterodroma cahow)Publication . Afonso, Rita O.; Pina-Martins; Friesen, Vicki; SUN, ZHENGXIN; Letizia, Campioni; Madeiros, Jeremy; Silva, Monica C.The Bermuda petrel Pterodroma cahow is an island endemic seabird that belongs to the Procellariiformes, one of the most endangered orders of birds. Historical records suggest a significant population size decline following human settlement in Bermuda, bringing the species to near extinction. Since the 1950s, the population has been recovering aided by the implementation of an ongoing conservation plan. However, it still faces several threats, and negative genetic effects resulting from that drastic decline are to be expected, including inbreeding and genetic drift. We studied genetic diversity and levels of inbreeding, and their effects on individual fitness and mating choice. We also tested for a genetic signature of the recent demographic bottleneck. For this, we analyzed variation in thousands of nuclear single-nucleotide polymorphisms derived from double digest restriction site-associated DNA sequencing and 1 mitochondrial gene (cytochrome oxidase I). The results revealed that the Bermuda petrel suffered a recent genetic bottleneck and shows low mitochondrial diversity compared with other petrel species. Conversely, nuclear diversity was similar to that of other endangered petrels. Inbreeding levels were not high overall, although some individuals were highly inbred. However, we found no evidence that individual inbreeding or relatedness between mates affected hatching success, or that mate choice is influenced by kinship in this very small population.