Roach (Rutilus rutilus) live in lakes and partly migrate into freshwater tributaries in winter. When most of the population migrates out of the lakes, zooplankton can thrive and control the abundance of phytoplankton, keeping the lake in a clear-water state. However, when most roach stay in the lakes over winter, they feed on zooplankton, reducing its abundance such that phytoplankton can become overabundant and force the lake into a turbid state. © Jakob Brodersen

African armyworm moths (Spodoptera exempta) flying across Kenya, as seen on an entomological radar display (distance between the range-rings on radar display = 463 m). The dense aerial populations, produced by convergent wind-flows, can result in high concentrations of moths on the ground, mass egg-laying and, ultimately, serious outbreaks of the ‘armyworm’ caterpillars. © Don Reynolds

Approximately 200-250 million Silver Y moths (Autographa gamma) arrive in the United Kingdom in the spring of “mass-invasion” years, which occur roughly every 3-4 years. In these mass-invasion years, between 0.5 and 1 billion offspring migrate south from the United Kingdom to Southern Europe in autumn (see also Chapman et al. (2012) PNAS 109: 14924-14929) © Ian Woiwod

Loggerhead turtles are highly migratory throughout their range with individuals known to cross both the Atlantic and Pacific Oceans. The individual here has been equipped with a satellite tag in Greece to follow its post-breeding migration. © Gail Schofield.

Mallards (Anas platyrhynchus) are partial migrants with populations breeding in northern areas wintering further south. They have been shown to transport freshwater molluscs and plant seeds both externally and internally, potentially over considerable distances. © Andrew Glover

Bewick’s swans (Cygnus columbianus bewickii) breed in Arctic Russia and return to Western Europe in autumn. Avian influenza virus infections have been linked to the swans’ foraging during autumn migration, potentially increasing terrestrial transmission in winter. © Bethany Hoye

Many species of European songbirds breed in (northern) Europe and return to Sub-Saharan Africa in autumn. They have been shown to harbour haemosproidian (avian Malaria) parasites from breeding and wintering ranges, suggesting transmission with residents across the migratory range. © Jonas Waldenström

Several species of geese migrate between breeding grounds in the Arctic and wintering grounds in Central and Western Europe. Most of these goose populations have rapidly increased in size in over the last 20 to 30 years (including populations of Barnacle goose (Branta leucopsis) shown here, foraging in The Netherlands), resulting in immense grazing pressure on wintering, breeding and intermediate stop-over locations that has led to both overgrazing of natural vegetation and conflicts with agriculture. © Hugh Jansman

Similar caption as previous photo. © Bethany Hoye

Northern fulmars (Fulmar glacialus) migrate from the open ocean to breed in large colonies along coastal cliffs in the Arctic, bringing with them vast quantities of marine-derived nutrients that fertilize these otherwise nutrient-poor terrestrial systems. © Bethany Hoye