Showing posts with label urban animals. Show all posts
Showing posts with label urban animals. Show all posts

Sunday 11 August 2013

Birds, bugs and butterflies: attracting nature to your garden

For many years I've tried to attract wildlife to my garden; perhaps there's something extremely relaxing about watching other components of the biosphere go about their business. Even the closest I lived to the heart of London, a largely overgrown garden provided a haven for all sorts of creatures from tiny wrens via boisterous squirrels to the odd, slightly mangy fox. Although I've discussed the behavioural changes seemingly present in urban animals I thought it would be worth exploring the pros and cons of attracting various critters to your garden.

As a child our family supported winter visitors, usually with bread crusts for birds and cow's milk - for some unknown reason - for hedgehogs. I've since learnt that the latter is a very poor choice as hedgehog food, so where the idea came from I don't know. Mind you, much bacon rind is probably too salty for birds, so I wonder how many animals we killed with our kindness! If you want to feed hedgehogs, cat and dog food is apparently among the suitable alternatives. Not that these days we put anything out for the hedgehogs that occasionally appear in our garden, often disappearing behind the wood pile at night when I'm out at the telescope (and startling me with their sudden snuffling). The reason isn't due to being anti-hedgehog, but the food would most likely attract other, less welcome rodents such as rats and mice.

Interestingly, hedgehogs are amongst the survivors brought to New Zealand by acclimatisation societies in the Nineteenth Century, along with many European bird species that also congregate in our garden: sparrows, blackbirds, starlings, song thrushes and various finches. As a side note, it would be interesting to tabulate these against the many imported species that didn't survive their first year in the New Zealand wild, such as robins and emus; clearly, there's some unknown adaption criteria going on here.

One problem I frequently faced in the UK but don't any more is the seemingly inexhaustible ingenuity of squirrels in getting to the content of bird feeders, as described in the post above. However, possums imported from Australia fulfil a similar, if nocturnal role in New Zealand, and are a major pest for numerous reasons. Again, keeping bird food for only birds is a primary consideration. Not that birds don't show cunning when it comes to getting at food: I remember visiting the Zealandia eco-sanctuary near Wellington many years ago and seeing the kaka bush parrot feeding from mini bins opened via foot pedal - that's the parrot's foot, not a human one.

Back to now. So why attract wild animals to your garden? Usually it's a two-way gain - humans watch the antics for minimal expenditure and the fauna get food, shelter or even a bath. It offers children a close up view of nature and the realisation that you don't have to go to zoos and wildlife parks for the experience: nature is all around us. It also introduces them to the diversity of the local biosphere as opposed to just the typical, ‘grand' fauna such as African savannah species or large sharks and rays that are kept in zoos and aquaria. To this end, the UK's Royal Society for the Protection of Birds (RSPB) organised the Big Wild Sleepout last weekend, the idea being to camp in your own garden or at an organised event in order to hear and possibly even see the nocturnal creatures we don't usually come into contact with. I only tend to be outside at night if I'm at the telescope, and must confess to frequently hearing the unmistakeable cry of the morepork, New Zealand's only native owl, but have yet to see one.

Talking of owls, birds are the obvious favourite to attract to your property, since it's easy for them to get around and escape from predators such as domestic cats. According to the RSPB over half of UK adults have fed garden birds. In recent years organisations have started to take advantage of all this previously unrecorded observational data by encouraging the public to submit sighting reports for collation. These projects range from observing familiar creatures such as butterflies and ladybirds, to tracking the growth of invasive species such as New Zealand stick insects in the UK's South West. The RSPB, which is a veteran of collecting such data, utilised a weekend in January this year for their Big Garden Birdwatch, the world's largest wildlife survey.

Following the State of Nature report released in May this year, it sounds like this sort of project hasn't come a moment too soon. The new assessment was compiled by twenty-five British wildlife organisations including the RSPB and makes for a sobering conclusion. It found that 60% of the 3,148 UK species under assessment have declined over the last half century, with slightly over 10% deemed under threat of extinction in the UK. It's impossible to know if the situation is similar in other nations, but such worrying statistics suggest that any help given by the public to aid biodiversity can only be for the better. But as per the hedgehogs and milk example, what other pitfalls are there to befriending fauna?

It is fairly widely known that common foodstuffs such as salted peanuts and desiccated coconut should not be given to birds, but how many people remember to soak white bread before putting it out so that it doesn't swell inside the animals' stomachs? Although you can buy purpose-made bird seed mixtures it is cheaper - and frequently better - if possible to grow a bird-friendly garden yourself. It depends on what species live locally, but some birds like open lawn for insect feeding, others prefer overgrown areas (the goldfinches in my garden are very keen on the latter) whilst other species prefer fruit or nectar direct from the tree or bush.

Silvereyes eating apple

It isn't just birds either: as a child I remember a buddleia bush that attracted at least four species of butterfly whilst here in New Zealand a swan plant (a type of milkweed) plays host to dozens of monarch butterfly caterpillars over the summer. In addition, praying mantises lay their egg sacks on just about any vertical surface in our garden, masonry or timber, so spring sees a profusion of baby mantises heading for undergrowth. The trick is to keep them away from the swan plant; otherwise the caterpillars tend to disappear in their early stages at the expense of the mantises...

In contrast to planting your own, commercial ready-made food mixtures may have large carbon footprints or be grown in developing nations that could better use the land and effort for growing their own food. In addition, messy eaters will cause seeds to drop onto the ground where sterilised seeds can choke native growth and the non-sterilised ones germinate: we once even had a hemp plant that grew several metres in a month or so from some spilt seed!

Therefore having plants or garden layouts that provide food for birds can be as good as leaving out scraps or purpose-bought food. I suppose the main difference with the latter two is that you can place them where you like for ease of viewing. After all, watching birds eat is the primary attraction. Although you can buy bird feeders I prefer to make my own, with a variety of success rates depending on the design. The most popular to date has proved to be table hung from a cherry tree, with half apples spiked on nails attracting a regular stream of silvereyes. Here in New Zealand you can even feed nectar eaters such as tuis via an old wine bottle containing sugar solution.

Bird nectar feeder

One important issue is when you should feed wildlife. The best time of year is obviously winter, when natural foodstuffs are least available. As a general rule, it's probably best to stop feeding once chicks arrive, so that both they and their parents don't start relying on human support. However, in addition to providing food you can also create habitats suitable for assorted wildlife from mammals to invertebrates. As a boy I made a nesting box for a Cub Scout badge, but it was never inhabited, probably being located in too low and too busy a position for birds to consider safe. Today you can buy all sorts of homes and feeders suitable for different species and climates so there's no shortage of easy options. The RSPB recently started supplying a free guide to building animal homes in your garden, ranging from bird box to hedgehog shelter. I can even claim success with my homemade weta motel (current resident: one female tree weta), although it took some time to gain any inhabitants other than numerous, small cockroaches. Note the weta legs poking out of the hole below!

Weta motel

Most of these are generally great aids to wildlife and observing wildlife, although I find the idea of building small ponds not particularly attractive since any standing water in my gardens usually attracts biting insects to lay their eggs in it. When I lived in East London any empty plant pot that collected rainwater swarmed with wriggling mosquito larvae in next to no time. Not nice!

The one thing about this sort of amateur interaction with biology is that you can do as much or little as you like as quickly or slowly as you like, but you are bound to get some form of success. Having said that, there are still plenty of species I'd like to spot in my garden. I have a large pile of volcanic stone that would look good in a far corner of the back garden as a potential lizard home; friends down the road are lucky enough to have skinks and geckos around their grounds. I'm also ever hopeful of various sections of rotting timber serving as home to peripatus -  a.k.a. velvet worm - an ancient form of life that lies somewhere between worms and arthropods. Although I've definitely seen some small white things that might just possibly be very young ones...

Tree weta

Saturday 25 June 2011

Amazed rats and super squirrels: urban animal adaptations

If I was the gambling sort I might be tempted to bet that the most of the large fauna in my neighbourhood was, like much of London, restricted to very few species: namely feral pigeons, rats, mice and foxes. The most interesting visitor to my garden is, judging by the size, a female common toad - the wondrously named Bufo bufo - which makes an appearance every couple of years to feast on snails and leave a shell midden behind.

After spotting a small flock of Indian-ringnecked Parakeets in our local park, I decided to look at the adaptations wildlife has undergone whilst living in an urban environment. After intermittently researching this topic over a month or so, I was surprised to find the BBC Science News website posting an article along similar lines. Synchronicity? I decided to plough ahead, since the subject is too interesting to abandon and I've got my very own experimental data as well, although it's hardly 'laboratory conditions' material.

Your friendly neighbourhood Bufo bufo
It's easy to see why animals are attracted to cities: the ever-present food scraps; the warmer microclimate; and of course plenty of places to use for shelter (my nickname for railway embankments is 'rodent condominiums'). Even the mortar in walls seems to offer smaller birds a mineral supplement (calcium carbonate) and/or mini-gastroliths (A.K.A. stomach grit) judging by the way they peck at them. Then there's also the plentiful sources of fresh water, which in my neighbourhood goes from birdbaths and guttering to streams and reservoirs. Who can blame animals for coming in from the cold? In the case of the London fox they have been arriving since the 1930s, whilst rodents were probably rubbing their paws together in glee as the first cities were being built many millennia ago in the Fertile Crescent.

There seem to be several, obvious behavioural changes that result from urban adaption, particularly when it comes to judging humans. I have found an astonishing lack of wariness in mice, squirrels and foxes, even in daylight, although rats are usually more circumspect. There are an increasing number of stories concerning foxes biting sleeping humans, including adults, even during the day. I was informed by a Clapham resident of how, having chased a noisy fox down the street at night, it then followed him back to his house, only stopping at the garden gate. Clearly there is some understanding of territorial boundaries here, too. This is supported by the behaviour of foxes in my area, which will happily chase cats in the local allotments even during the day, but once the cat emerges onto the street, the fox doesn't follow. Perhaps they have some understanding of connection between cats and humans?

City fauna has become more opportunist, prepared to scavenge meals from the enormous range of foodstuffs available in an urban environment, which around my area seems mostly to consist of fried chicken carcasses, usually still in the box. Even birds of prey such as the Red Kite (no small fry, with up to a one and three-quarter metre wing span) have recently been seen taking food off unwary children. This follows a period of finding food deliberately left out for them, so an association forms between people and food. This then is a two-way connection, with humans helping to generate changes in urban fauna by their own actions. Less time spent foraging means urban animals expend less physical energy, so there may a feedback loop at work here; if surplus energy can aid higher cognition, discrimination of humans and the urban environment increases, and thus even less time is required to source food. A facile conclusion perhaps, but read on for a possible real-life example.

My own experiments on grey squirrels took place about ten years ago, probably at least partially inspired by a television lager advertisement. It started when I found that my bird feeder was being misappropriated by a couple of squirrels. My first idea was to add radial spikes around the bird feeder using garden canes, but the squirrels were more nimble than I had thought, so after adding more and more spikes to create an object reminiscent of the Spanish Inquisition, I had to change tack. I next suspended the bird feeder on the end of a long rod that was too thin for the squirrels to climb on, but they managed to dislodge it at the wall end, causing it to drop to the ground for easy consumption. Rounds one and two to the pesky Sciurus carolinensis. My final design was a combination of spikes on the approach to the rod, the rod itself, then the feeder suspended from a long wire at the end of rod. I went off to work with an air of smug satisfaction that no mere rodent was going to get the better of me, only to find on my return that somehow the squirrels had leapt onto the rod and eaten through the wire!

One point to consider is that the bird food itself was in a transparent perspex tube, which is totally unlike any natural material. So when it comes down to it, are some animals, at least mammals and birds, over-endowed with grey matter when it comes to their usual environment, only utilising more of their potential when faced with artificial materials? Or do the challenges and rewards of being an urban sophisticate cause an increase in neurological activity or actual physiology? The latter gets my vote, if only for the evidence that supports this in human development. After all, the archaeological record suggests that modern humans and our ancestral/cousin species experienced an incredibly slow rate of technological development, with rapid increases only coming after disastrous setbacks such as the population bottleneck around 70,000 years ago, probably following a decade-long volcanic winter.

Experiments using rats in mazes over the past eighty years seem to agree with this thesis. However, there are clearly limits to animals' ability to learn new cognitive skills if they don't have time for repeated interactions, which may explain why most young foxes' first encounter with vehicular traffic is also their last. As for the BBC Science News report I mentioned earlier, research shows that birds with comparatively larger brain to body size ratios are those found to thrive in an urban environment. So it isn't all nature red in tooth and claw after all, but at least on occasion a case of brain over brawn for the city slickers.

Finally, I ought to mention a series of scare stories over the past year about another urban coloniser that seems to be returning after half a century's absence, namely the Cimicidae family of bloodsucking insects. With many of us using weaker laundry detergents at lower water temperatures, some researchers are predicting an imminent global pandemic of these unpleasant critters. So please be careful at night, and don't let the bed bugs bite!