Partial Migration

Biogeography-based optimization (BBO) is a new population-based evolutionary algorithm and is based on an old theory of island biogeography that explains the geographical distribution of biological organisms. BBO was introduced in 2008 and then a lot of modifications and hybridizations were employed to enhance its performance. The researchers found that the original version of BBO has some weakness on its exploration. This paper tries to solve the root problems itself instead of solving its effect by using different techniques. It proposes two modifications; firstly, modifying the probabilistic selection process of the migration and mutation stages to give a fairly randomized selection for all the features of the islands. Secondly, the clear duplication process, which is located after the mutation stage, is sized to avoid any corruption on the suitability index variables of the non-mutated islands. The proposed modifications are extensively tested on 120 test functions with different dimensions and complexities. The results proved that the BBO performance can be enhanced effectively without embedding any additional sub-algorithm, and without using any complicated form of the immigration and emigration rates. In addition, the new BBO algorithm requires less CPU time and becomes even faster than the original simplified partial migration-based BBO. These essential modifications have to be considered as an initial step for any other modifications.

Biogeography-based optimization (BBO) is a new population-based evolutionary algorithm and is based on an old theory of island biogeography that explains the geographical distribution of biological organisms. BBO was introduced in 2008 and then a lot of modifications and hybridizations were employed to enhance its performance. The researchers found that the original version of BBO has some weakness on its exploration. This paper tries to solve the root problems itself instead of solving its effect by using different techniques. It proposes two modifications; firstly, modifying the probabilistic selection process of the migration and mutation stages to give a fairly randomized selection for all the features of the islands. Secondly, the clear duplication process, which is located after the mutation stage, is sized to avoid any corruption on the suitability index variables of the non-mutated islands. The proposed modifications are extensively tested on 120 test functions with different dimensions and complexities. The results proved that the BBO performance can be enhanced effectively without embedding any additional sub-algorithm, and without using any complicated form of the immigration and emigration rates. In addition, the new BBO algorithm requires less CPU time and becomes even faster than the original simplified partial migration-based BBO. These essential modifications have to be considered as an initial step for any other modifications.

The circular distribution of the willow warbler Phylloscopus trochilus around the Baltic Sea shares many features with the classic examples of ring species; however, the system is much younger. It has previously been shown that a secondary contact zone is located in central Scandinavia, where there are narrow clines for several morphological traits coincident with a migratory divide. Here we analyse multiple traits and genes from> 1700 males captured on breeding territories at 77 sites spread around the Baltic Sea to ...

"Understanding the causes and consequences of animal movements is of fundamental biological interest because any alteration in movement can have direct and indirect effects on ecosystem structure and function. It is also crucial for assisting spatial wildlife management under variable environmental change scenarios. Recent research has highlighted the need of quantifying individual variability in movement behavior and how it is generated by interactions between individual requirements and environmental conditions, to understand the emergence of population level patterns. Using a multi-annual movement dataset of 213 individual moose (Alces alces) across a latitudinal gradient (from 56° to 67° N) that spans over 1,100 km of varying environmental conditions, we analyze the differences in individual and population level movements. We tested the effect of climate, risk and human presence in the landscape on moose movements. The variation in these factors explained the existence of multiple movements (migration, nomadism, dispersal, sedentary) among individuals and seven populations. Hence, heterogeneity in the immediate environment can result in multiple movements within a species. Population differences were primarily related to latitudinal variation in snow depth and road density. Individuals showed both fixed and flexible behaviors across years, and were less likely to migrate with age in interaction with snow and roads. For the predominant movement strategy, migration, the distance, timing and duration at all latitudes varied between years. Males traveled longer distances and began migrating earlier in spring than females. Our study provides strong quantitative evidence for the dynamics of animal movements in response to changes in environmental conditions along with varying risk from human influence across the landscape. For moose, given its wide distributional range, changes in the distribution and migratory behavior are expected under future warming scenarios.
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Many salmonids, including brook trout (Salvelinus fontinalis), contain both anadromous (migrant) and nonanadromous (resident) forms within a population (partial migration). Although partial migration is commonly observed, the mechanisms governing the adoption of migration or residency are poorly understood. We used field estimates of fish growth coupled with in situ estimates of food consumption rates to demonstrate that a trade-off exists between the ability to efficiently exploit local environments (resident approach) and the capacity to capitalize from large-scale environmental heterogeneity (migrant approach). We demonstrate that in the year before migration, migrant brook trout have consumption rates 1.4 times higher than those of resident brook trout. However, migrants have lower growth efficiencies (ratio of growth to consumption) than residents, indicating that migrants have higher metabolic costs. Residents and migrants also differed in their stable carbon isotope signature...

ABSTRACT Food availability and acquisition are critical components of a stopover site's suitability, but we know relatively little about how changes in food availability affect the stopover ecology of migrating landbirds. We examined fruit and arthropod availability in three habitats, studied foraging behavior and diet, and investigated use versus availability for passerines migrating through southwestern Idaho in autumn. Hemiptera dominated foliage-dwelling arthropod communities in all three habitats, whereas Hymenoptera were most numerous among ground-dwelling arthropods. Mountain shrubland had relatively high biomass of both ground-dwelling and foliage-dwelling arthropods, whereas conifer forest had high biomass of foliage-dwelling arthropods only and shrubsteppe had high biomass of ground-dwelling arthropods only. Species' foraging behavior varied, but most species foraged in mountain shrubland more often than expected by chance. Diets of most species included a high proportion of certain Hemiptera and Hymenoptera with smaller proportions of Coleoptera, Diptera, and Heteroptera; Coleoptera and some Hemiptera were consistently preferred by most species. Importantly, all 19 bird species examined consumed some fruit, and this is the first documentation of frugivory for two warbler species. These data point to the importance of several arthropod taxa, especially the Hemiptera and Hymenoptera, and fruits to landbirds migrating in mountain shrubland in autumn. Finally, we found no effect of annual variation of fruit or arthropod abundance on migrants' energetic condition, suggesting that food was sufficient for mass gain in all years of this study and/or that foraging behavior may be plastic enough to allow birds to gain mass despite annual differences in food availability. La disponibilidad y la adquisición de alimento son componentes críticos de la calidad de un sitio de parada, pero sabemos relativamente poco sobre cómo los cambios en la disponibilidad de alimento afectan la ecología de parada de las aves terrestres migratorias. Examinamos la disponibilidad de frutos y artrópodos en tres hábitats, estudiamos el comportamiento de forrajeo y la dieta e investigamos el uso versus la disponibilidad para los paserinos que migran en otoño a través del sudoeste de Idaho. Los hemípteros dominaron las comunidades de artrópodos que viven en el follaje en los tres hábitats, mientras que los himenópteros fueron más numerosos entre los artrópodos que viven en el suelo. El arbustal de montaña tuvo una biomasa relativamente alta de artrópodos que viven en el suelo y en el follaje, mientras que el bosque de coníferas tuvo una biomasa alta sólo de artrópodos que viven en el follaje y la estepa arbustiva tuvo una biomasa alta sólo de artrópodos que viven en el suelo. El comportamiento de forrajeo de las especies varió, pero la mayoría de las especies forrajearon más frecuentemente en el arbustal de montaña que lo esperado por azar. La dieta de la mayoría de las especies incluyó una alta proporción de hemípteros e himenópteros con una menor proporción de coleópteros, dípteros y heterópteros; los coleópteros y algunos hemípteros fueron consistentemente preferidos por la mayoría de las especies. De modo destacado, todas las 19 especies de aves examinadas consumieron algo de frutos y este es el primer registro de frugivoría por parte de dos especies de arañeros. Estos datos señalan la importancia en el arbustal de montaña de varios taxones de artrópodos, especialmente de hemípteros e himenópteros, y de los frutos para las aves terrestres migratorias de otoño. Finalmente, no encontramos un efecto de la variación anual de la abundancia de frutos o artrópodos sobre la condición energética de los migrantes, sugiriendo que el alimento fue suficiente para el aumento de la masa en todos los años de este estudio y/o que el comportamiento de forrajeo puede ser lo suficientemente plástico como para permitir que las aves ganen masa a pesar de las diferencias anuales en la disponibilidad de alimento.

Do Reeves make different choices? Meadow selection by spring staging Ruffs Philomachus pugnax in Southwest Friesland

Each spring Ruffs stop over in large numbers in the northern part of the Netherlands, especially in Southwest Friesland. While staging, Ruffs use meadows for feeding and refuelling. A general believe is that they are attracted by the typical Dutch wet peat grasslands, with a diverse vegetation situated in an open landscape. We wanted to test this idea and to explore whether the assumed different flyways of the sexes could be related to sexual dimorphism, e.g. whether the smaller, shorter-billed females use other habitats than the males. This paper describes which meadow characteristics are correlated with meadow use and how meadow use differs between ruffs and reeves. In April and May 2003, 125 meadows in Southwest Friesland were monitored for five weeks. The total number of Ruffs decreased over the season, which is consistent with published region-wide counts. Relatively few females passed through: only in late April, when total numbers were low, the proportion females exceeded 10%. To find correlations with meadow use, 13 scored meadow characteristics were used in a multiple logistic regression model. Grass height and distance to the nearest roost proved most important (included in the model in four weeks): used meadows were closer to a roost and had shorter vegetation than unused meadows. Vegetation type, soil type, drainage level, openness of landscape and fertilisation freshness correlated with meadow use in two or three weeks. Percent flooding, fertilisation method, presence of grazers, vegetation evenness, relief and meadow size were never included in the model. The expected reference for peat meadows was not found: sand and clay soils were used more. As expected, ‘wet’ meadows and meadows in an open landscape were used more often than heavily drained meadows or meadows near buildings or trees from where predators may launch surprise attacks. Grass monocultures were least used, but the most used vegetation type was not rich but intermediately diverse in herbs. Females seem to be more extreme in meadow choice than males: groups with females used meadows that were drained less deep (thus wetter) and situated closer to the nearest roost than meadows with male-only groups. Groups with females were also more common in peat grasslands. We found indications that the sex-related differences in meadow use may be related to differences in feeding behaviour. Females foraged with higher pacing speeds. more females than males ate insects, but females had lower intake rates. Also when eating buried prey like earthworms and leatherjackets, intake rates in females were lower, although probing rates were equal. Females likely use other flyways: the proportion of females passing through this Dutch stopover site was very low compared with an important eastern European stopover site in Ukraine. At this point we can not yet decide whether this results from a difference in habitat preference induced by the size difference between the sexes or whether competition forces the females out of preferred, rich feeding sites.