Solstice sees the days lengthen

Dick Warner takes a look at the importance of the Winter Solstice to nature and its wildlife.

Well, it’s over. The winter solstice is behind us and the days are getting longer. The solstice is an event that goes largely unnoticed today but was of huge significance to our ancestors.

So significant, that it inspired Neolithic people to huge efforts to construct megalithic monuments such as Newgrange which were aligned to sunrise on solstice morning.

If we go back far enough, we are all Africans. Our species evolved close to the equator, where there is little or no difference in day length year round. When, relatively late in our evolutionary history, we migrated to higher latitudes, the short days and long nights of winter must have been a traumatic new experience.

The solstices, particularly the winter solstice, became central events in our spiritual and intellectual lives and remained so until evangelical Christians hijacked them and gave them new connotations.

However, the winter solstice is still important to our wildlife. Most of our wild birds are diurnal, which means they sleep when it’s dark and only feed in daylight. There are some exceptions, and they’re not just owls. Many waders, including snipe and woodcock, and some wild ducks and geese are nocturnal feeders.

However, all songbirds and most of the rest of our birds are diurnal, which means they face the challenge that, as the weather gets colder and their calorie demands rise, the time available to find food diminishes.

Longer days increase their chances of avoiding death by hypothermia, even if the weather does get colder in the new year, so the winter solstice is as significant for them as it was to the Neolithic farmers of the Boyne valley. And as the daylight increases imperceptibly it affects the whole of nature.

In most cases, day length rather than temperature triggers the hormonal changes that prepare animals for mating in Ireland. Foxes mate in February, which is often the coldest month of the year but also the one in which increasing day length first becomes obvious.

How animals and birds measure day length is not fully understood. Plants can do it too, which is even more mysterious and suggests that the process does not require a brain and a nervous system.

What triggers spring growth in plants is a rather complex mixture of several factors, including temperature and soil moisture, and the importance of one factor over another varies from species to species.

There is plenty of scientific evidence to show that in many species the length of the day is the overriding factor and that plants can measure this with extreme accuracy — not just hours but minutes and even seconds.

The ash tree outside my window will not flower or produce leaves for months. It, too, is affected by the solstice.