One little fact leads to half dozen questions

PHENOLOGY is the study of variations in the timing of events in the natural world.

It might be the date of the arrival of the first swallow, or the first appearance of frog spawn, or noting when a tree loses its leaves in the autumn.

People have been fascinated by these things for a long time, but scientific phenology has become more important recently because it can provide important information about climate change.

There are precise dates for the life cycle of vines in European vineyards that go back unbroken for 500 years, which is a pretty good data base.

It can also be a fascinating area of study for the amateur naturalist and I came across an interesting example about a week ago.

I went to Barcelona but, because I travelled by Ryanair, I actually arrived at the small airport of Girona, an hour and a half by express bus from my destination. I was pleased about this because it gave me an opportunity to see some of the Catalan countryside through the bus windows.

Botanising and birdwatching at 120kmh is a little frustrating, but the route took us through some pretty, wooded hills with fast flowing streams and, as we neared the coast, some Mediterranean maquis. There was a lot of blackthorn and it was in full flower. The interesting thing about this is the blackthorn in Catalonia appeared to be at exactly the same stage of flowering as the blackthorn back home.

My home in the Midlands is 1,200km to the north with a totally different temperature and rainfall regime, but blackthorn flowers at the same time. It seems that some plants react to temperature and soil moisture, but others are hard-wired to the calendar, reacting to day-length. According to my observations through the window of the bus blackthorn belongs to the second category.

Blackthorn is Prunus spinosa and the Genus Prunus contains quite a lot of Irish wild and cultivated trees, including all the cherries and plums. So I wonder if all the trees in the Genus all over Europe flower at the same time. And Prunus is part of the Family Rosaceae, a huge plant family that contains species as different as hawthorn and wild rose. Do they all have this characteristic?

Certainly other plants are different, which is particularly evident this spring because we’ve had such a mild winter. I arrived back from Spain on Apr 2 to find the first cow parsley in flower along the verges of the lane I live on. This is unprecedented. It’s between three and four weeks earlier than I’ve ever seen it before. The cow parsley was obviously reacting to higher than normal soil temperatures and satisfactory soil moisture levels and ignoring the amount of daylight.

There have been other signs of an early spring. There were primroses and dog violets along the lane by the end of February and reports of blackbirds nesting in the middle of winter.

One reader emailed me with a report of frog spawn in a garden pond in December. I wonder if cuckoos or swallows will arrive earlier this year and, if so, how did they get the information that spring was early this year in Ireland while they were making their travel plans in Africa? Do warm-blooded creatures like birds and mammals react less to ambient temperature than cold-blooded animals like fish, frogs or insects? That’s the fascinating thing about natural history. You learn one small fact — that blackthorn flowers at the same time in Catalonia and Kildare — and it leaves you with half a dozen questions still to be answered.

If you notice unseasonal happenings in the natural world this spring I’d be interested in hearing from you.

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