Bird numbers in Cairns Botanic Gardens

Barry Muir | Guest Contributor

Cairns, in Northern Queensland’s Wet Tropics, is a significant destination for bird enthusiasts globally, and a central starting point for other Tropical North Queensland birding hotspots, including the Atherton Tablelands, Daintree Rainforest, and Cape York Peninsula.

The Wet Tropics region covers less than 1% of Australia, but supports over 450 bird species, which is more than 45% of bird species recorded in Australia. Fourteen of the Wet Tropics bird species are endemic.

A popular tourist attraction in Cairns is the Cairns Botanic Gardens (CBG) Precinct, and every Tuesday morning through the year, a birdwatching walk is led by volunteer local bird experts from Cairns Birders. More than 50 visitors have been recorded for some of the tours, and the average on any given day is 14. Many visitors are from overseas and represent almost every continent.

Visitors come at every time of the year, though slightly more during the cooler months. However, business is also brisk during the hot, humid wet season, as visitors from cooler climes arrive here (eg. visitors from Iceland, Scotland, Japan, and Alaska have been recorded on the tours).

The Tuesday morning CBG bird tours are of world renown and, although there is no charge to attend, they contribute to a significant portion of tourism income regionally. Many tourists have expressed that they stayed in Cairns, or extended their stay, in order to undertake one (or several) of the bird tours. As well as having educational and conservation value for tourists, groups of students also occasionally attend tours.

Many of the visitors are keen wildlife photographers, and sometimes contribute photographs to a summary of the bird tours published in a free newsletter by Cairns Birders.

Much can be learned from regular reports such as those of the weekly guided tours, by Cairns Birders experts, in the CBG Precinct. These reports prompted this Study, and data from the weekly Cairns Birders reports from January 2020 to early 2026 have been analysed.

Occasionally the Tuesday tours did not occur because they fell on Christmas Day or some other holiday; because of threat of a Tropical Cyclone; or if no visitors came for the tour and it was cancelled. Conditions recorded in the reports varied greatly from warm sunshine to extremely heavy rain to extremely hot and humid, and sometimes activities within the CBG Precinct, such as maintenance works, curtailed or forced rerouting of the tour.

The tour route is about 2.5–3.5 km, and takes about three to four hours, usually in a clockwise direction. If there are two or more groups, or the guides would like a change, the tour sometimes follows the same route in an anti-clockwise direction. Tours roughly follow the route and minor variations shown in Figure 1.

Figure 1. Main route and occasional variations of the bird tours.

Habitats traversed during the tour include constructed gardens, buildings, bamboo forest, water-course with mangroves, open paddock, Melaleuca forest, Saltwater Lake, Freshwater Lake, swamp forest, and rainforest.

Blue-winged Kookaburras move around seasonally, and are recorded occasionally in the CBG Precinct. Photo by Jennifer H Muir.

Average number of people on tours was 14, including from two to four tour guides: bird experts from the local group Cairns Birders. Highest number of people reported was 54, and when such large numbers arrive it is necessary to break the tours into smaller groups, the number depending on the number of expert local birders present. As it is not required to book ahead for the tours, and with no way of predicting the number of tourists, the number of groups depended on the number of local experts available that day.

A consideration in this study was whether there was a relationship between number of visitors and number of bird species sighted. More observers could mean more species records, or more observers could spook the birds, resulting in lower number of species if there were large groups. Results are presented in Figure 2. Note the trend (red line) for more species observed when number of people increases. Also note that mean number of observers is around 14.

Figure 2. Number of bird species recorded plotted against number of observers.

It was found that there is a relationship between number of people on the walks and number of bird species recorded. This suggests that most bird species are not spooked by the large crowd, and that more observers result in more birds sighted. Certainly, most of the birds regularly sighted are most likely those habituated to city traffic, people and noise.

Further, because the number of local expert birders is usually between two and five, it may be that the visitors contribute significantly, probably by spotting birds and alerting the experts. Thus, the visitors themselves play a significant role in recording bird richness within the CBG Precinct.

Number of bird species by month and year

Number of bird species recorded in each month is shown on Figure 3. Numbers are similar in any given month from year to year. Most species recorded were around mid-year, and they were a little lower during the build-up towards the wet season (November to March), but this may reflect less comfortable weather conditions affecting observations, rather than real changes in number of bird species.

Note the quite dramatic decrease between August and September, when conditions often become hotter quite suddenly. Average number of bird species recorded during any tour at any time of year was around 41.

Figure 3. Numbers of bird species by month from January 2020 to February 2026.

Number of bird species and weather

Another aspect was the weather. There were 109 records of weather conditions in the reports, with distribution as shown in Figure 4. Comments were generalised and mostly favourable (eg. “nice weather”), but others ranged from “bucketing down” with rain to unbearably hot and humid.

Numbers of bird species recorded did not vary greatly, and it may be that slightly lower numbers in inclement weather may reflect the comfort and durability of the guides and visitors, rather than any relationship to bird species numbers when conditions were very wet. Notably, very hot humid weather did not appear to deter either birds or visitors.

Figure 4. Numbers of species recorded plotted against comments made in the reports regarding weather conditions at the time of tour.

Is the number of bird species fairly constant?

A consideration is whether bird numbers are declining or increasing over time. We have mean numbers of bird species for full years from 2021 to 2025 (Figure 5).

Figure 5. Number of bird species recorded by year where full years of data are available: trend shown in red.

Data from 2021 is less reliable than that recorded in later years as the new program of tours had only just begun, and numbers of tourists were quite low. However, even if 2021 is omitted from the graph, it is clear that the mean number of bird species recorded each year appears to be increasing.

Possible reasons are:

1

Tour guides and visitors are becoming more skilled at observing and recording.

This may be occurring as the tour guides’ skills continue to improve, and as visitors become more aware that the impacts of climate change, urbanisation and land clearing have reached critical levels. More visitors are found to be skilled in bird watching and bird photography, although they may not know local species. Further, the excellent reputation of the tours may be attracting more skilled birdwatchers.

2

Rapidly increasing urbanisation is pushing species into the CBG Precinct and adjacent bushland.

The CBG Precinct itself is part of a larger area of relatively undisturbed habitat (certainly when compared to the urbanised areas). Mount Whitfield Conservation Park, just north of the CBG Precinct, contains rainforest, eucalypt forest, several popular walk trails, and is 329 ha in area. The CBG Precinct is 485 ha in area, of which 126 ha has no access, making it an excellent wildlife refuge area.

3

The CBG Precinct contains a significant area of Melaleuca Swamp Forest that is included in the tours.

This specialised habitat type has been largely destroyed over the rest of the Cairns regional coastal plain (and does not occur within Whitfield Conservation Park). Some highly habitat-specialised wetland birds, such as the Black Bittern, may have become concentrated in this habitat within the CBG Precinct. The only other large area of Melaleuca Swamp Forest remaining on the coastal plain in the immediate vicinity of Cairns is Cairns Central Swamp, but this is heavily disturbed by public access.

4

Freshwater wetlands near Cairns have mostly been “beautified”, rendering them much less attractive to wetland birds.

The Freshwater Lake in the CBG Precinct, although altered both structurally and floristically, is one of the few remaining near-natural freshwater lakes in the Cairns region. The only other saltwater lakes with mangroves are many kilometres by road away at East Trinity. The CBG Precinct bird tours start at 7:30 am every Tuesday in Flecker Garden (see Figure 1), at the nature tours meeting place near Friends House.