This type of migration is normally associated with food availability.

Growth rates vary with environmental conditions, food availability and other factors.

The figures, the commission said, pointed to a huge problem of food availability this year.

They usually reside in cool and damp places with green food availability.

They also are known to deposit feed in times of low current or food availability.

However, they can be very productive in good conditions and high food availability.

Conditions there remain poor in terms of food availability.

The figures point to a massive problem of food availability next year, according to the European commission.

Expanding production brought only a 5 percent increase in food availability per capita over the two decades.

Current trends pointed to a massive problem of food availability next year.