October 2025

Just as an addendum to September Nature Notes, January (named after the Roman god Janus, who was the god of beginnings, endings, doorways, and transitions) and February (from the Latin word februum or februare, meaning “to purify,” and from Februa, a Roman festival of purification and atonement held mid-month). These were added to the monthly calendar by Numa Pompilius, the second king of Rome, around 713 BC. The additions were made to account for the full lunar year and the period of winter that was previously left unassigned. This part of ancient Rome’s lunar calendar considered winter to be a monthless period, which originally only had ten months starting with March. The word ‘month’ should be ‘moonth’ as a lunar month accounts roughly as the period from one ‘new moon’ to the next, which is approximately 29.5 days. This period is also called a synodic month and represents the time it takes for the Moon to go through all its phases and return to the same alignment with the Earth and Sun. A harvest moon is when the moon is particularly bright, such that farmers can harvest crops during the night and usually occurs in September, but sometimes early October.

August, September and October are months when many birds migrate south to escape the short cold days of winter. Maybe the most remarkable of these is the arctic tern (Sterna paradisaea), which breeds in the northern Arctic zones and spends the winter in the Antarctic. I am also fascinated by cuckoos (Cuculus canoris), who never meet their biological parents, but instinctively know where and when to go (Africa) for the winter after fledging in late summer. Other bird species can at least migrate in mixed age groups, often with their parents, but most cuckoo adults leave Europe in June before their offspring have fledged the host’s nest. The other thing to look out for in the autumn is spiders’ webs. They often show up with dew or frost in cold mornings. Most insects die at the end of the summer, and nature is never wasteful, there is always a use for its products. Some insects lay eggs, and then die with the first frosts or are eaten by spiders or birds. Others hibernate as larvae, pupae or adults, and some such as painted lady (Vanessa cardui) butterflies migrate south like some birds.

One of my specialities is the blue tit (Cyanistes caeruleus). I studied how they planned their families to optimise breeding success for my doctorate. What I found has been published in my book called ‘The Blue Tit’. One relevant thing is that female British blue tits often migrate for short distances, maybe 100 miles or so from where they bred, usually southwest and near the coast. The south-west of England is probably the warmest place on our island in the winter due to the relatively warm Atlantic Conveyer current flowing from the Gulf of Mexico to Britain. Male blue tits tend to remain at their nesting sites.