Backyard Bird Surveys - 2000

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Introduction

The first research module for the Birds in Backyards program consisted of a community survey of backyards across Sydney, co-ordinated by Birds Australia, the University of Wollongong and the Australian Museum.

Volunteers recorded the birds visiting their gardens for twenty minutes each day for seven days in October, 2000. To date, we have investigated twelve species, comprising seven of the small birds that appear to be declining in numbers and five of the large birds that we considered might be involved in this decline.

Participants

Eight hundred and seventy-one people took part in the survey, with good representation from the Illawarra and Central Coast as well as Northern, Southern and Western Sydney.

Results

Confirming the expectations of many of the volunteers who phoned in, the introduced Common Myna (also known as Indian Mynah) was the most frequently encountered bird across urban Sydney, occurring in 80% of gardens during the survey. The most common native species were the Australian Magpie (72%), Pied Currawong (64%) and Noisy Miner (59%). The Willie Wagtail was the most common small bird, occurring in 37% of gardens, and the Eastern Yellow Robin was the rarest (7%).

Several of the more common species, most notably the Common Myna were found in similar numbers right across Sydney, but some of the smaller birds varied in abundance depending on the district. For example, Willie Wagtails were nearly ten times more common in Illawarra gardens (43%) and Western Sydney gardens (47%) than in gardens of Northern Sydney (5%). Overall, the outer districts of Sydney, including the Illawarra, Western Sydney and Central Coast, had more small birds than the inner districts of Northern and Southern Sydney.

Discussion

One of the main aims of this first module was to determine whether there were negative associations between some of the aggressive birds and the smaller birds. For example, we wanted to know whether Superb Fairy-wrens were less likely to be found in gardens with Pied Currawongs. Collecting this information is the first step in determining whether the increase in Pied Currawong numbers has led to a decrease in small birds.

Despite its overwhelming abundance and the fact that it is so widely hated by Sydneysiders, the introduced Common Myna (that's the brown and black one with the yellow feet and beak that walks around in the gutter) was not negatively associated with any native bird species. In other words, it is unlikely that Common Mynas were preventing native birds from living in backyards.

Interestingly, it was the native Noisy Miner (that's the grey and black one with the yellow feet and beak that squawks from the nearest gum tree) that was most negatively associated with small native species. In fact, all seven small native species were less likely to be found in gardens inhabited by the nectar-feeding Noisy Miner. For example, Eastern Spinebills were found in 20 % of gardens from which Noisy Miners were absent, but only in 4 % of gardens in which Noisy Miners were present.

What does this mean? Perhaps the small native birds have different habitat requirements to Noisy Miners and so they don't occur in the same gardens? However, none of the garden attributes that we recorded, explained the distribution of Noisy Miners. They were equally common in gardens with quite different proportions of lawn, shrubs and trees, and they showed no preference for gardens with higher representation of either native or introduced plants. This suggests that Noisy Miners actually exclude small birds from suburban gardens. A similar result has been found in rural areas where Noisy Miners are known to exclude small birds from small remnants of habitat.

Some of the small birds did show preferences for particular types of garden. For example, Eastern Spinebills and Eastern Yellow Robins were more common in gardens with higher proportions of trees, and these species as well as the Superb Fairy-wren were more commonly observed in gardens in which the majority of the plant species were Australian natives. Little Wattlebirds and Red Wattlebirds also preferred native gardens and although they are large honeyeaters like the Noisy Miner, no small birds were negatively associated with the wattlebirds.

Conclusions

So, what is the message from this study for boosting backyard biodiversity? Those people who have switched to native gardens get a big tick. They are more likely to attract a greater diversity of small birds to their gardens. Planting more shrubs and trees will also be beneficial for native species, and converting some of your lawn into shrubs and trees will have the added bonus of reducing visitation by the Common Myna (if you're a Myna hater).

The problem that remains is what we can do to lessen the impact of the aggressive Noisy Miner, which was found in 59% of gardens (even 89% of those in Northern Sydney!) Our habitat assessment in this first survey was very basic, and we hope that finer habitat measurement in future modules of the Birds in Backyards project might enable us to identify the combinations of plant species that discourage Noisy Miners, or allow small species to coexist with them. This pilot study provided some promise in this regard. Silvereyes were present in 25% of gardens from which Noisy Miners were absent, but in only 4% of gardens where Noisy Miners were present. However, this ranged form 1 % in gardens with less than 25% shrub cover up to 7% in gardens with more than 50% shrub cover. Although dense shrubbery might not exclude Noisy Miners, the cover may increase the possibility for small birds to coexist with them. Perhaps we need to think more about planting shrubs that provide dense, protective refuges and nest sites, and not just focus on those plants that provide food.
 

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