When is Autumn?
I’m starting to notice changes around me. When I wake for work, it’s still quite dark out. When I get home, it’s not long before the sun is setting. Does this mean it’s Autumn?
Meteorologists divide the seasons pretty evenly into three month chunks. From their perspective, Autumn is September, October and November. So on that basis Autumn started 1 September.
There is also an ‘Astronomical Autumn’. This starts from the point where the day and night are of exactly even length, which this year fell on 23 September. Autumn by this measure lasts till the Winter Equinox on 21 December.
There is a more organic way of considering Autumn though, and that’s ‘Phenological Autumn’.
We’ve discussed phenology before here. It is the way we use natural events to track the seasons. Tracking these over time can indicate changing response of the natural world to broader events, such as climate change.
This can include migrant species such as swallows, warblers, and thrushes coming in or out of the country.
Recent trends have put Phenological Autumn around the middle of the month, so now on 23 September we can probably say, by all methods, we are indeed in Autumn.
Swifts went ages ago, in August, still summer by anyone’s measure. But the likes of Swallows, House Martins, and Chiffchaffs may still be hanging on. Meanwhile, the first autumn influx of smaller finches like Siskin and Redpoll, and thrushes like Redwing and Fieldfare are underway.
It can also include the appearance of many species of fungi, usually most bountiful in Autumn, and the really obvious changing of the colour of leaves on trees from greens to a firework riot of oranges, golds, reds and browns.
Some of the changes can be subtler, harder to spot. We actually get movement of birds that we see all year round. So for example, the Blackbirds you see in winter are not necessarily the same ones you saw in Spring.
You may also see familiar species moving into larger, mixed flocks. This is particularly the case for Tits who, having spent the summer as pairs feeding young, now mix freely to roam between food sources. It’s not uncommon to wake and discover Blue, Great, Coal and Long-Tailed in one big bunch invading your feeders. Similarly Goldfinches and Greenfinches may mix, and may even be joined by the likes of Chaffinch, Siskin and Redpoll.
Soon, urban winter roosts for Pied Wagtail will fill, along with the rarer Plover roosts in places around Greater Manchester, where Lapwing and Golden Plover will spend the night on the roofs of buildings.
These big flocks may seem counter-intuitive. After all, if you move into a period where food is more limited, aren’t you better alone?
There are a few reasons why flocks work. Firstly, more sets of senses give a better chance of finding food. A denser flock is better for defence, and that’s valuable when plenty of hungry predators are on the lookout. Even more crucially, numbers mean body heat, and in a roost on a cold night that can be the difference between life and death.
One of my personal favourite signs of Autumn comes most mornings, and ties back to the image at the top of the page; singing Robins.
We think of birdsong as a Spring thing for attracting mates. But Robins sing extensively in Autumn and Winter, proclaiming a territory as theirs. This can be a territory a female is holding after breeding, or a territory a bird is new to and trying to occupy, even if only for the colder seasons.
Considering it’s purpose is technically menacing, it’s one of the most beautiful sounds in British wildlife.
So what are your favourite signs of Autumn? What have I missed?
One other note on Autumn, for birders the speculation begins about irruptive migrants. After all, don’t we all live in hope of a ‘Waxwing Winter’?