Phenology - A Study of the Changing Seasons

Phenology is the study of natural events that occur in nature, with particular regard to their timing. To study phenology you will need to keep a nature diary and record when you see different events occurring.

Your records provide information for a long-term study as the timing of events each year are compared with previous years to see if there are any trends.

Phenology is mostly studied in countries where there is a definite change of seasons throughout the year. So it is well suited to countries that have a spring-summer-autumn/fall-winter cycle. Although there is nothing to stop you studying phenology in a country with a different climate. All you need are some annual events that occur at particular times of the year.

Where I live, in the UK, we have a spring-summer-autumn-winter cycle and the two main seasons studied are spring and autumn. This is because these are the two seasons where the most changes and natural events take place.

In spring you can study:

Mammals, reptiles & amphibians

When hibernating animals are first seenFor particular animals, when they change to their summer coat

Birds

When winter residents leaveWhen migratory birds arriveWhen male birds start singing or performing rituals to attract femalesWhen birds start building nestsWhen birds start feeding chicksWhen juveniles are first seen out of the nest

Insects

When particular insects are first seen

Trees

When trees are in bud and ready to produce leaves (an event called budburst)When the first leaves appearWhen flowers appear

For wild flowers

When the flower is first seen, in full bloom.

In the UK, spring phenology has been studied for over 200 years. People have always been very interested in the first signs of spring, as they bring the promise of warmer weather to come.

The first sightings of a Cuckoo or Swallow are well-received. The first Peacock or Orange-tip butterflies are anticipated. With trees, the first flowers on Blackthorn and Hawthorn are very welcome and the first leaves on Oak and Ash trees are keenly noted.

In autumn you can study:

Mammals, reptiles & amphibians

when hibernating animals are last seen

Birds

Trees

When leaves are first tinted yellowWhen leaves fall offWhen trees are bare

Trees and Shrubs

When fruit first appearsHow much fruit is produced

Fungi

When different fungi are first seen

Autumn phenology has been studied far less, so there is still much to learn about autumn events and which factors influence their timings.

Not all birds, insects, trees or flowers show a clear seasonal variation in their life-cycle, but most do, so studying phenology helps you to learn a lot about the wildlife that lives in your local area.

Why study phenology?

Studying phenology helps you to learn about the events that occur in the wildlife around you. It helps you to appreciate the changing seasons and makes you aware of the effect weather can have on wildlife. It brings to your attention 'early' and 'late' years and helps you to understand why this happens. In the long term it helps to see if our climate is changing and if this will have an effect on the wildlife around us.

You can study phenology on your own and keep your personal annual diary if you wish. However, the information you collect is very useful and you can join a national scheme that collects data from many other people throughout your country. These larger data sets are useful in studying our climate on a national and global scale.

Most of all, though, studying phenology helps you to understand the yearly cycle that wildlife goes through, the different events that occur and how everything fits together and is dependent on so many other things happening at the right time. Although, at first glance, studying phenology seems little more than recording a series of dates, it provides an insight into the complex and detailed ecosystems of the organisms we share our planet with.

Michael Knaggs is a keen and enthusiastic naturalist from Yorkshire, England. He has been observing birds, butterflies and wild flowers since he was 12 years old. He has been studying phenology since 2006 and contributes to Natures Calendar, a phenology study run by the Woodland Trust in the UK.

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