SPRING has sprung early in Oxfordshire according to The Woodland Trust.

The trust, which runs more than 20 sites in the county, has received thousands of sightings of frogspawn, tadpoles, butterflies, catkins and snowdrops.

In Oxford, scores of nest-building rooks have been spotted earlier than normal.

Trust manager Dr Kate Lewthwaite said natural events were very responsive to warmer temperatures - and while an early spring could be pleasant for humans, it was not always good news for nature.

She said: "There are concerns thrown up by spring's continued advance.

"Species fooled by warmer weather into activity, blossoming or breeding, are very vulnerable. They can get caught out by the sort of freeze not uncommon in February.

"It's also possible that food chains could start to break down. If birds nest and hatch their chicks earlier, is their normal food stock going to be available to them?"

She said another implication was 'competitive advantage'.

The Woodland Trust's Dr Kate Lewthwaite "As the oak tree has started to leaf before ash, does that mean over time that oak will have a greater advantage by virtue of stronger canopy?"

The last few years have witnessed mild springs, while last month's temperatures were two degrees above average.

However, she said it was too early in the year to judge the overall impact of the changes.

The Woodland Trust owns land at Stratfield Brake in Kidlington, Piddington Wood near Bicester, Shillbrook Wood near Witney and Ham Wood in Thame. It has 50,000 people registered as 'nature recorders' across the country.

Dr Lewthwaite said: "Only by ongoing recording can scientists judge the impact of what appears to be a changing spring, so we need all the information we can get from the public."