Making a home for native birds in your garden
Birds were until 800 years ago the majority of residents in Aotearoa. Since human arrival, their area of residence and their food security has continually eroded. Native birds have evolved for an environment dominated by forest and wetlands. These forests are not evolved for disturbance and are unlike forests that have evolved with browsing land mammals. If our forests are disturbed or destroyed by logging or fire they take hundreds of years to return to the stable forest they once were. However, the forests can return. We are fortunate to have areas untouched by humans acting as living seed banks and examples for us to study.
Central Otago, however, lost virtually all of its forest cover from man made fire followed by continued grazing (domestic and wild). We have lost our seed bank and, without human intervention, the forest plants will not return for hundreds or thousands of years. Native plants planted here will have a very tangible effect on the density and distribution of our native birds. Native birds are limited by their evolved physiology to the places they can nest, the food they can digest, and how they can defend themselves. They are tethered to native plants. For us, choosing between garden plants is an aesthetic choice. For a native bird it can be the difference between whether they can afford to build a nest, raise their young to adulthood or even survive winter.
Having said that, it is extreme to expect anyone to convert their garden to 100% native. While many native birds do need the complex ecosystem of a healthy forest to thrive, this is unlikely to be achievable or desirable in a garden environment. According to the garden bird survey, between 2018 - 2023 backyard birds are in decline nationally - but on closer inspection, most native birds are stable with many exotic birds declining. However there are a couple of much loved native birds in moderate to rapid decline in Otago during the last 5 years, the silvereye and the kereru. The bellbird is stable but ideally would be increasing. Tui and fantail are moderately increasing in Central Otago so we won’t focus too much on them. With some wise choices managing our garden ecology we can help these native birds.
Kereru are relatively common as you travel towards the west coast, but are absent inland in Otago. At our nursery it is one of our long term goals to see kereru flying weightily above - a goal which will take many years, being largely surrounded by farmland and exotic infested mountains. This is not an unreasonable goal, however; we are roughly 40km from the closest population of kereru along the Glenorchy Road near Queenstown, and kereru have been recorded to fly 60km to reach a good autumn food source (Powlesland et al, 2011 Satellite tracking of kereru in Southland, New Zealand). This is also a good example of why they are so important for distributing seeds. The plan is simple: we add the correct plants and remove predators via trapping. We need plants for food and nesting.
Kereru will not nest in areas which lack food, with that the abundance of food triggering nesting (Schotborgh, 2005, An analysis of home ranges, movements, foods, and breeding of kereru in a rural-urban landscape on Banks Peninsula, New Zealand). Kereru eggs are precious, with only one egg laid at a time, although they can continue laying from September - April, raising a total of three or four chicks a year. Kereru seem to build nests in a variety of places 2 - 20m from the ground. They do prefer a dense canopy cover of trees, hiding their chicks from harriers by constructing a platform of well selected branches.
It has been suggested that totara and kanuka are favourite sources for nest building material (Mander et al, 1999, Monitoring and management of kereru) but they do adapt to other materials. Food sources are key for kereru, with kowhai species being the key food to kick off the breeding season. Compared to other plant species, kowhai are filled with protein, especially the new leaves. They will consume other exotic leaves like willow and tree lucerne but these do not serve the bird community as well as native kowhai (Sophora microphylla). By late spring kereru move onto a diet of berries and will consume even the largest native fruit. Cabbage trees, totara, Griselinia, Mrysine divaricata are just some of the berries they will consume. Once their chicks have fledged they will travel far and wide to find good sources of food through the autumn and winter.
Here are some plants you can use in your Central Otago garden to attract kereru:
Myrsine australis
Sophora microphylla
Podocarpus hallii
Cordyline australis
Corokia cotoneaster
From a bird's eye view gardens merge with ‘wild areas’. If each garden planted at least one bird friendly native tree or shrub a network of support would be created.
Silvereyes are a relatively recent addition to the New Zealand bird population. They are believed to have flown to the south island from Tasmania in the 1850s. Smoothly spreading throughout the whole of New Zealand, it is a surprise that garden numbers have declined in recent years. One explanation could be that with warm winters, silvereyes can find adequate food out of town without needing to visit bird feeders. Therefore counts are lower in the June garden bird survey.
Silvereyes are omnivorous, eating insects, fruits and nectar. One benefit of luring silvereyes to the garden with a nectar feeder is that they will likely give your garden a once over for much prized aphids. Silvereyes are not difficult to accommodate - the only terrestrial environment you won’t find them in is grassland. If you edge a lawn or paddock with fruit bearing shrubs you should soon find silvereyes flittering through. They will feed on flower nectar such as kowhai and cherries in spring, tree fuchsia and insects in summer (so don’t spray those aphids), and in autumn and winter it’s important to have a range of fruiting natives so fruit is available all through the season. Corokia cotoneaster berries last the longest through the winter. By the end of winter and early spring food can be very scarce depending on how cold the season has been. It’s at this time when exotics can be used to bridge that gap. Shrubs such as flowering quince, Daphne bhoula and wintersweet provide sustenance for nectar feeders during late winter.
Silvereyes will need shrubs to build their nests, but they are not picky, building their 20cm bowls within a couple of metres of the ground. They like to use old leaves of grass lined with softer material like wool or moss. Planting small shrubs and grasses like Corokia cotoneaster and Carex testacea should provide nesting space and material. If you have a dog leave their fur out after grooming, as this can make a luxurious nest lining.
Silvereye mix
Sophora microphylla
Kunzea ericoides
Fuchsia excorticata
Corokia cotoneaster
Coprosma lucida
Bellbirds are a familiar sight throughout most of New Zealand with the south island boasting a higher population than the north, yet they are reported as absent in areas of inland Otago and Canterbury. Their melodies are a welcome soundtrack to outdoor activities. Bellbirds and Tuis are rightly grouped together as nectar feeders, with the bellbird having a more diverse diet than the Tui. Bellbirds feed on nectar, fruit, honeydew (sugary insect excretions) and insects. It’s been observed that bellbirds will feed their fledglings exclusively on insects, gleaning them from bark crevices. Flaky barked plants like kanuka, tree fuchsias and thin barked totara are perfect for housing these insects.
Bellbirds weave a bowl shaped nest from grass, lined with feathers or moss. Nests have been found between 1.5 - 12m above ground in dense evergreen shrubs and trees. Unhedged Pittosporum tenuifolium and Myrsine australis have great density and structure for housing bellbird nests. When the nest is built they do not go far so reliable food is required for a bellbird to start nesting. A bellbirds diet will vary throughout the year with food availability and breeding. They will feed predominantly on flowers in spring, switching to fruit in autumn and finally insects in late winter when fruits run low. All the while they will supplement with honeydew if it is available.
During spring, kowhai (Sophora microphylla) is a beacon of light for the nectar feeder, showing the degree to which these plants and animals have co-evolved. In summer flax (Phormium tenax, Phormium cookianum) shows that it too is a solid counterpart to the bellbird. The bellbird is even more ecstatic when the Tree fuchsia begins flowering, greedily visiting multiple flowers and receiving a fashionable purple pollen face mask, all the while pollinating the Tree fuchsia. Once the fanfare of spring and summer flowers subsides, bellbirds will turn to the emerging berries of Coprosma lucida, Myrsine australis and Pseudopanax species, among others.
Bellbird mix:
Sophora microphylla
Phormium cookianum
Fuchsia excorticata
Kunzea ericoides
Myrsine australis
If we are to make tangible efforts to support our feathered friends then it would be remiss to not consider trapping. When mammals are removed the effects are stark. Predator proofed areas provide us an example of how our birds can thrive without the excessive predation and habitat destruction of introduced mammals. From these areas birds begin to overflow to surrounded areas - for example, residents of Wellington are witnessing substantially more bird numbers and species thanks in large part to the Zealandia ecosanctuary.
Quite understandably for many the idea of trapping can be challenging but the effects of introduced mammals on native birds are not overstated. Trapping can begin small with mice and rats, which have a huge effect on native birds. They will will eat eggs and chicks, and rats also can eat small adult birds. In addition to predation they are a major food source for larger predators such as weasels, stoats and ferrets.
In years of abundant seed and fruiting rodents will breed exponentially. Once the seed and fruit is expended the rats and mice turn to native birds but without vast food availability their numbers will crash. The stoat population rises in conjunction with the rats and when the rats decline, stoats then turn to birds with greater effect and ferocity. Outdoor traps for rats are easy to obtain, bait and maintain. They can be kept in long rat tunnels with rat sized entrances that make it safe for other beings enjoying your backyard. Visit here for more information on traps.
Thankfully few or none of the birds observed here are nationally threatened even if they may be locally rare. However, as these birds share the forest and shrub habitat with threatened birds, by taking steps to encourage non-threatened birds we may be aiding, to some degree, threatened birds. On another note, just because these species are not threatened doesn’t mean that they don’t deserve to thrive, or that we shouldn’t aspire to raise our avian fellows to pre-human population levels.
There is a well known phenomenon called ‘shifting baseline syndrome’ - humans struggle to remember historical abundance. We may see a large flock of birds in current times and believe they are doing well but not remembering the flock 10 years ago was two to three times the size. We believe what we experience in the present is the norm. We may very well have this syndrome even with our common backyard birds. This is one reason why the garden bird survey and similar citizen science projects are so important.