Wildlife Watching - September

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Mammals

A female Japanese Sika deer (Cervus nippon). In parts of the Highlands, introgression between this introduced species and the native Red deer is threatening the Red's bloodline. - Credit: Marc Baldwin

Autumn is the season for deer watching, because September marks the start of the autumn rutting season. The weather conditions have a significant impact on the timing of the rut; mild and wet conditions delay it, while cool and dry conditions advance it. Indeed, it has recently been suggested that climate change is advancing the red deer rut on the island of Rum off the coast of eastern Scotland. In 2013, Dan Nussey at Edinburgh University and colleagues published data suggesting that, perhaps because of warmer springs and summers, the birth of calves and the time that males start rutting is now as much as two weeks earlier than when the study began almost 40 years ago.

Another disturbing finding by Nussey and his team was the amount of introgression (mixing of characteristics as a result of inter-breeding) between red and the closely-related sika deer, which roam wild in many parts of Britain. Based on data collected from Scotland’s Kintyre Peninsula, it appears that red deer are getting smaller, while sika are growing larger. What it appears we’re seeing is a blending of traits, providing what some consider a “mongrel” deer. Hybridisation between these species is a problem wherever they co-exist in the wild; in many parts of the country, especially here in the New Forest in Hampshire, red and sika deer are shot if they encroach on each other’s ranges in a bid to prevent such interbreeding.

Problems aside, red, fallow and sika all rut in the coming weeks, and each have their own rutting behaviour and unique call. Red stags (Cervus elaphus) roar/bellow/bolve, fallow bucks (Dama dama) ‘belch’, and sika stags (Cervus nippon) ‘whistle’. Well worth checking out if you have the opportunity.

Rutting activity starts as the nights draw in and the temperature drops. This stimulates a rise in testosterone in the bucks and stags, and what was formerly a relatively good-natured bunch of guys hanging out together starts descending into conflict, leading to the breakup of bachelor groups.

Fallow bucks, being a woodland species, tend to set themselves up in a good spot and proceed to ‘belch’ or groan, scrape the ground and nearby trees, and generally spread their scent around in an attempt to advertise their presence to any females the area. This method of mating is called lekking. Research on fallow rutting suggests that females can judge how big a male is from the acoustics of his belch. Males that belch constantly are perceived as the fittest individuals (i.e. those with the greatest stamina) and are the ones more likely to mate.

A Red deer (Cervus elaphus) stag roaring at hinds during the rut. The familiar "bolving" of Red deer has many functions, including deterring other males, attracting females and even spurring the females into estrus. - Credit: Marc Baldwin

Red deer, by contrast, being a species of more open moorland habitats, are usually ‘showier’ in their rutting. Red stags move to traditional rutting grounds in pursuit of the females. The females move to areas of best grazing to rebuild their fat reserves following a summer of producing milk for their calves, and the males follow. We used to think that a male rallied up a collection of hinds and held them until either they started coming into oestrous or he was deposed by another stag. Thanks to some fascinating in-depth studies conducted by the Red Deer Research Group on Rum, however, we now know the situation is much more flexible. The males do follow the females around and the largest/strongest stag tends to have unrestricted access to the largest group of hinds, roaring to advertise his prowess both to the nearby females and any stags thinking of challenging him. We now know that females may move between different harems if they’re impressed by a neighbouring stag or to get away from smaller stags pestering them. We also know that if the matriarch decides to move to another area, there is little the attending stag can do but watch his harem disappear. A female may also duck briefly out of a harem to mate with a nearby stag and return to her group afterwards.

Sika are slightly different again, tending to set up leks in areas between the feeding and resting grounds chosen by females, from which they stand and whistle.

What’s particularly interesting about rutting deer is that the chosen behaviour can vary with habitat. Fallow, for example, may adopt a more harem-based rutting plan in open habitats and clashes – where two males lock antlers, each trying to push the other back – are more common in open areas than in woodland. Presumably, open habitat allows the deer to see rivals and might make them more prone to fight than in woodland where they can generally only be heard.

Japanese sika deer (Cervus nippon) stags clashing in the New Forest. - Credit: Marc Baldwin

Deer aside, other mammal action this month comes in the form of fox fights, as the family unit starts to break down. This is a protracted process that results in most cubs dispersing between October and January. Another mammal for which September involves much fighting, squeaking and squealing in this case, is the common shrew, and September is a good month to go looking for them in undergrowth and deciduous woodland because their population is at its peak. Grey seals are also very active, September also marking the beginning of their breeding season.

Many other mammals are starting to prepare for winter. There are still a few bats on the wing, so a walk with a bat detector can still prove rewarding, and squirrels are busy caching as much of nature’s bounty as they can to see them through the lean winter months. Hedgehogs and dormice are both in the process of trying to build up sufficient fat reserves to see them through hibernation. Despite the impending winter hiatus, it is not uncommon to find juvenile hedgehogs about in this month; these late-born hoglets (sometimes called “autumn orphans”) often struggle to survive the winter if they’re born too late to lay down sufficient fat reserves. You can help by leaving out food and water for them and, if you happen to find a hedgehog out during the daytime or a hoglet in distress, please check out my Helping Hedgehogs article.

During late August and early September many of our garden birds, such as this blackbird, undergo their annual moult and because this can make them less agile they spend most of their time hiding out in cover. - Credit: Marc Baldwin

Birds

You may have noticed that many of your garden birds seem to have vanished, but don’t fret – it’s perfectly normal behaviour. As we come to the end of summer, most of our garden birds will be moulting; either replacing their juvenile plumage with their first adult plumage, or shedding feathers worn and damaged while raising the chicks for a new set to see them through winter. While moulting, birds tend to be more secretive because the loss and re-growth of the primary wing feathers makes them less agile in the air and thus more vulnerable to predators. If we couple this moult with the breeding season being over and the males having no need to sing to attract a mate now, the birds are also less obvious when they are around and more of their activity goes unnoticed. Furthermore, you may have noticed that many of the berries in your garden are now ripe and this intimates a further reason why you may be seeing fewer birds: they simply don’t need your garden as much at the moment, because food is relatively abundant in fields, parks and woodlands. Don’t worry though – come winter, they’ll be back.

Outside of our gardens, September marks the start of the “passage season” that many ornithologists regard as the most exciting part of the year. Many of our summer visitors will now head further south for the winter, while a variety of species come in from colder parts of Europe or down from the Arctic to spend winter in our milder climes. Most chiffchaffs will head south, and whitethroats tend only to be found around the south coast during the autumn, where they swap their usual diet of insects for one of fruit. Most swallows have now left, although you may still see juveniles lined up on telegraph wires, as have most martins.

Invariably, this is a good month to visit the coast, estuaries in particular, which will be starting to receive geese from the Arctic. There are six migratory species of geese commonly seen in the British Isles, and greylags are the largest. Having spent a pretty intense breeding season on Iceland’s tundra, they migrate south to spend the autumn and winter in our estuaries, lakes and reedbeds, where they roost before flying off to feed in grass fields during the day. The first of our winter visitors and migrants start to arrive this month and many will first appear at southern estuaries. Ring ouzels, red-breasted flycatchers and the striking Union Jack waistcoat of the bluethroat are all highlights this month.

As the days get shorter and cooler, jackdaws (Coloeus monedula) can often be found huddled around chimney stacks. These not only provide a source of warmth but the birds may also use the sooty exhaust to rid their feathers of parasites. - Credit: Marc Baldwin

There are also a lot of corvids around, with jays particularly noticeable in our parks and deciduous woodlands at this time of year as they collect and bury (cache) up to 3,000 acorns a month. Other species to keep an eye out for this month include ospreys as they stop off at lakes and fish farms in the south of England en route to their summering grounds off the African coast, kingfishers in coastal regions, and redwings and chaffinches, both of whose numbers are swollen by visitors from Europe at this time of year. September is also a good month to listen for the calls of tawny owls, which are becoming increasingly vocal as they start re-establishing their territories now the chicks have fledged.

Reptiles & amphibians

Typically, autumn brings cool nights and sunny days, resulting in reptiles needing to spend more time basking in the morning than they did over the summer. A quiet dawn walk in the right habitat with the sun on your back can reveal basking adders and grass snakes. If this autumn follows the pattern of recent years, however, with temperatures remaining mild, snakes and lizards may become more difficult to spot. Nonetheless, there are still many smooth snake and slowworm births during September, along with juvenile lizards, adders and grass snakes to be found.

As the breeding season comes to an end newts start migrating to their hibernation ponds. - Credit: Marc Baldwin

Newts, which hibernate close to breeding ponds, will be on the move, so head out on a dark wet night to look for them. Most ponds are now home to far fewer frogs and toads than six months ago, with the adults and recently metamorphosed froglets/toadlets now spending much of their time on land in leaf litter, long grass and under logs. Indeed, frogs and toads, along with a host of insects, often overwinter in patches of long grass, so please take extra care when mowing your lawn and, if possible, leave it (or a section of it) to grow longer and help support your local wildlife.

Invertebrates

Those of you who are arachnophobic probably arrive at the start of autumn with a sense of dread, because it signifies the start of the spider home invasion season. September is the month when large, hairy, eight-legged critters start being seen indoors. In most cases, these are male “house spiders” (those of the genus Tegenaria or Eratigena) and they’re on the hunt for breeding females. The males follow scent trails produced by the females and tend to follow the same routes each night, which is why you often see them in the same places. Also, spiders aren’t particularly energetic animals and tire easily. If you watch a spider run across the living room carpet (perhaps from on top of the dining room table while screaming) you might notice it stop for a minute before carrying on; it’s not eyeing you up, it’s catching its breath. Despite their size, these spiders are no threat to you. They’re often drawn to bathrooms and kitchens seeking water and frequently end up in the bath or sink, the sides being too smooth for them to climb. If you want to reduce the chance of finding a spider in your bath take a toilet roll and unravel a short length; place the roll on the side of the bath and trail the sheets down into the bath to provide a surface spiders can get traction on and use to get themselves out.

September is start of "house spider season", during which males frequently turn up in baths and sinks, having fallen in trying to get a drink. The sides are too smooth to crawl out. If you want to help, simply leave a length of toilet roll running down into the bath that the spider can use to get himself out. - Credit: Noel Coates (CC BY-NC-ND 2.0)

September is the month that people sometimes find dainty green crickets in their house of an evening. We don’t quite know why, but these oak bush crickets are attracted to light. Out in the fields there is still some stridulation to be heard, with the speckled bush crickets being the last of the chirpers, lending their relaxed chirrups to damp dewy evenings. Dark bush crickets are busy this month, the females pulling back the bark of dead wood to lay eggs that will hatch next year, while the males utter well-spaced chirps from bramble patches. Indeed, if you’re out picking blackberries, keep an eye out for these crickets along with harvestmen, which are also abundant. There are about 23 species of harvestmen in the UK, some of which have hugely exaggerated legs attached to a tiny body, making them look something akin to the Fighting Machines of H.G. Wells’ imagination.

There are a few butterflies still on the wing, including the odd speckled wood, brimstone and gatekeeper. September is the main flying month of the red admiral and small copper butterflies, and some painted lady, clouded yellow and even purple hairstreak butterflies are around. The unmistakable pale tussock moth caterpillar, with its luminous yellow tufts and bristles, can still be found during this month as it prepares to retire into the cocoon in which it will spend the winter.

Plants & fungi

September marks the start of meterological autumn and the "berry season", with rowan, bramble and hawthorn (above) smothered in fruit for wildlife to take full advantage of. Hawthorn is a particuarly important hedgerow species, providing shelter and food for at least 150 species of insect. - Credit: Marc Baldwin

September is the start of nature’s season of bounty, with fruit, seeds, berries and fungi becoming apparent. In countryside lore, loads of berries in the autumn signifies we’re in for a cold winter – it being nature’s way of providing plenty of food for wildlife. In reality, however, autumn’s berry crop tells us more about the weather we saw during spring than what we’re going to experience in a few months’ time. Indeed, cool springs delay flowering while mixed spells of wet and warm, dry and sunny weather boost plant growth and pollinator activity.

A whole host of species take advantage of this glut of fruit, from wasps to foxes and badgers. At this time of year, I often find jet-black fox droppings, chock-full of seeds and drupels, suggesting the fox had gorged on blackberries. Other berries around this month include the bright red rowan, dog rose and honeysuckle, the dark red of hawthorn and the clusters of dark purple elder berries.

Fungi is also to be found in abundance at the moment. This month, keep an eye out for the striking but poisonous sickener in pine woodlands – this fungus has a bright red smooth cap and white stem. The brilliant yellow flute-like chanterelle can be found in coniferous and deciduous woodlands during September and is, I’m told, delicious. The delicate fronds of yellow stagshorn fungi can be found on rotting logs and stumps in pine woodlands, while stinkhorn, giant puffballs and red-cracking bolete can be found in broadleaf woodland. The scarce violet webcap is found mainly in birch woodlands and is a large mushroom with a beautiful rich violet cap that browns with age. The grey-brown and white blotched cap of the magpie fungus is also to be found in beech woodland.

There is a distinct pink tinge to the countryside in September, with heather in bloom on the New Forest and other moorlands. Elsewhere, in fens, marshes and wet woodland, hemp agrimony can be found, with flowerheads containing five of six tufts or reddish-pink tubular florets. Late-flying insects are attracted to the nectar of the pink flowers of Himalayan balsam (originating in Asia, this plant is now a highly invasive species in Britain’s waterways) this month, while vivid pink blooms of rosebay willowherb also add a splash of colour.

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