Local weather, food resources and breeding stage influence Thrush Nightingale movement

Insectivorous migrants breeding at northern latitudes often time the breeding period with the seasonal peak of food resources. Whether this general pattern transfers to movement behaviour during the breeding season requires detailed study from a local perspective. We investigated fine-scale environmental correlates of movements by six actively-breeding adult Thrush Nightingales (Luscinia luscinia) at a breeding site in Denmark, using radio tracking and multiple regression models. Overall, the chick-rearing period coincided with the peak of vegetation greenness at the site. Adults flew further from nesting areas during stable weather and as vegetation greenness decreased. Adults were more active at higher environmental temperatures and when fledglings were older but still dependent on adults. These changes in local movements likely reflect adjustments to chick developmental needs and to specific local environmental conditions, including resource availability

Crossing the Logarithmic Barrier for Dynamic Boolean Data Structure Lower Bounds

This paper proves the first super-logarithmic lower bounds on the cell probe complexity of dynamic boolean (a.k.a. decision) data structure problems, a long-standing milestone in data structure lower bounds. We introduce a new method for proving dynamic cell probe lower bounds and use it to prove a $\tilde{\Omega}(\log^{1.5} n)$ lower bound on the operational time of a wide range of boolean data structure problems, most notably, on the query time of dynamic range counting over $\mathbb{F}_2$ ([Pat07]). Proving an $\omega(\lg n)$ lower bound for this problem was explicitly posed as one of five important open problems in the late Mihai P\v{a}tra\c{s}cu's obituary [Tho13]. This result also implies the first $\omega(\lg n)$ lower bound for the classical 2D range counting problem, one of the most fundamental data structure problems in computational geometry and spatial databases. We derive similar lower bounds for boolean versions of dynamic polynomial evaluation and 2D rectangle stabbing, and for the (non-boolean) problems of range selection and range median. Our technical centerpiece is a new way of "weakly" simulating dynamic data structures using efficient one-way communication protocols with small advantage over random guessing. This simulation involves a surprising excursion to low-degree (Chebychev) polynomials which may be of independent interest, and offers an entirely new algorithmic angle on the "cell sampling" method of Panigrahy et al. [PTW10]

Migration of the Common Redstart (<em>Phoenicurus phoenicurus)</em>:a Eurasian songbird wintering in highly seasonal conditions in the West African Sahel

Some species of long-distance migrant birds are thought to follow spatiotemporal patterns of high food availability during the non-breeding season, a strategy termed "itinerancy," instead of being sedentary in one specific site. We tracked the migration of a small Eurasian songbird, the Common Redstart (Phoenicurus phoenicurus), using archival light-level geolocators. The birds showed a distinct counterclockwise loop migration from northern Europe. Fall migration passed west of the Mediterranean Sea and along the northwest African coast before the birds made an abrupt change of direction at the southern edge of the Sahara toward the winter area farther inland in the West African Sahel. Spring migration was more direct: north to the Iberian Peninsula and back to northern Europe. The birds spent more time in only one winter site than they do during the breeding season in northern Europe, and they generally showed no signs of itinerancy-except for one bird that probably avoided an exceptional drought. Their arrival on the winter grounds was well timed with peak vegetation greenness, assumed to reflect food availability, but vegetation greenness declined rapidly during their stay, and resource availability was relatively low throughout most of the non-breeding season. Despite the highly seasonal conditions in the wintering area, itinerancy is apparently not an optimal strategy for the Common Redstart, possibly because of timing constraints. Alternatively, food availability may not be closely linked to vegetation greenness

Autumn migration and wintering site of a wood warbler Phylloscopus sibilatrix breeding in Denmark identified using geolocation

Abstract Background Basic knowledge of detailed spatiotemporal migration patterns is lacking for most migratory bird species. Using the smallest available geolocator, we aim to map autumn migration and wintering areas of north European wood warblers Phylloscopus sibilatrix and compare the spatiotemporal pattern with recoveries of individuals ringed across Europe. Results A tracked wood warbler migrated south-south-east to sub-Saharan Africa in Sudan and then west-south-west to winter in Côte d’Ivoire. The timing and route fits well within the distribution of ring recoveries although the westward movement after the Sahara crossing is not revealed by the ring recoveries, but only few recoveries south of Sahara exist. Conclusions The surprising westward movement south of the Sahara supplements the overall pattern revealed by ring recoveries and aids our understanding of the connectivity and site dependence in this generally declining species

A bird distribution model for ring recovery data:where do the European robins go?

For the study of migratory connectivity, birds have been individually marked by metal rings for more than 100 years. The resulting ring recovery data have been compiled in numerous bird migration atlases. However, estimation of what proportion of a particular population is migrating to which region is confounded by spatial heterogeneity in ring recovery probability. We present a product multinomial model that enables quantifying the continent-wide distribution of different bird populations during different seasons based on ring recovery data while accounting for spatial heterogeneity of ring recovery probability. We applied the model to an example data set of the European robin Erithacus rubecula. We assumed that ring recovery probability was equal between different groups of birds and that survival probability was constant. Simulated data indicate that violation of the assumption of constant survival did not affect our estimated bird distribution parameters but biased the estimates for recovery probability. Posterior predictive model checking indicated a good general model fit but also revealed lack of fit for a few groups of birds. This lack of fit may be due to between-group differences in the spatial distribution on smaller scales within regions. We found that 48% of the Scandinavian robins, but only 31% of the central European robins, wintered in northern Africa. The remaining parts of both populations wintered in southern and central Europe. Therefore, a substantial part of the Scandinavian population appears to leap over individuals from the central European population during migration. The model is applied to summary tables of numbers of ringed and recovered birds. This allows us to handle very large data sets as, for example, those presented in bird migration atlases

Effects of food provisioning and habitat management on spatial behaviour of Little Owls during the breeding season

The population of Little Owls in Denmark is close to extinction. The main cause is food limitation during the breeding season. Efforts to improve breeding success include providing breeding pairs with supplementary food and attempts to improve foraging habitats by creating short grass areas near the nests. In addition to increasing the reproductive output, feeding and habitatmanagementmay cause parents towork less hard improving their future reproductive value. We studied working efforts of five radio-tagged Little Owl pairs in years of absence and presence of food provisioning, and/or access to short sward vegetation areas near to the nest.We quantifiedmovement as theminimumflight distance hour–1 (MFD), using themean distance from the nest (DN) as a supplementary index. Under unmanipulated conditions, males had higherMFD and DN than females. If provided with food and/or areas with short sward vegetation, males but not females reduced their MFD and DN significantly. If MFD was adjusted for DN (the two measures correlated positively), both sexes reduced their DN-adjusted MFD as response to food provisioning but not to habitat provisioning. Food provisioning therefore had similar proximate effects on the foraging effort ofmales and females, whereas provisioning of short sward habitats had an indirect effect onmale but not female MFD, because of decreased commuting distances between nest and foraging sites. The results indicate that food provisioning not only leads to increased reproductive output in an endangered raptor, but also to decreased working effort, which in turn may improve adult survival