This article is written by Jane Doherty from the Cape Bird Club (CBC). The Friends of the Liesbeek thank the CBC for allowing us to repost it here.
The CBC embarked on a long-term bird survey of the Liesbeek River towards the end of 2020. The survey was coordinated by the Chair of the Conservation Sub-Committee, Dave Whitelaw, and a number of teams conducted 15-minute point counts every two weeks at spots along the length of the river. These spots were selected to represent different physical features of the river, as well as different vegetation types.
The main aim of the survey was to provide a baseline against which to compare future changes caused by urbanisation (such as infrastructure development and pollution) or, on the more positive side, to observe changes due to efforts to conserve and restore the river. A subsidiary aim was to understand seasonal changes, and therefore to conduct the survey for at least one year. (Some sites are aiming to continue for two years). Longitudinal data of this nature are quite unusual.
This article summarises the first year of bird counts by the three teams on the lower reaches of the river, where the environment flattens out and opens up, providing relatively unimpeded views of the water, river banks, and sky. There are more reeds and fewer dense shrubs at these sites than higher up the river.
Five people are involved in counting along this stretch, three from the Cape Bird Club (Penny Dichmont, Lynn Wilkinson and myself) and two volunteers from the Observatory community, Terna Gyuse and Alan Millar. The Club owes these two volunteers a big debt of gratitude as they allowed an important site to be added to the survey, where the final canalised section of the Liesbeek comes to an end, broadens into an area with small inlets and sloping banks, and joins the Black River. This site (which we call Site C) has proved to be particularly dynamic and rewarding, and the only one to be directly impacted during the course of the survey by grading and clearing in preparation for a commercial development.
Site C: Confluence of the Liesbeek and Black Rivers
The first site (Site A) is higher up the river, on a narrow stretch with high banks, across Liesbeek Parkway from the Hartleyvale Stadium. Parking spots and a pedestrian walkway line the edge of this site, and there are many passers-by, including dog-walkers.
Site A: Liesbeek River, Site A, opposite Hartleyvale Stadium
The second site (Site B) is a bit lower down, on the opposite side of the river, near the entrance gates of The South African Astronomical Observatory. Here the river is much wider with a central island and some muddy beaches that allow waders to forage. It is generally a quieter area, but sometimes homeless people use this section for washing.
Site B: Liesbeek Lake near the entrance gates to The South African Astronomical Observatory
Over the year in question (February 2021 to January 2022), we counted 21 times at Sites A and B, and 40 times at Site C. We identified a total of 43, 46 and 54 species at Sites A, B, and C respectively. We feel this is a slight undercount, especially with respect to swifts, warblers, and some seed-eaters: some birds were difficult to identify because they were too distant or hidden in the reeds, while sometimes our identification skills were sadly lacking. The high number of species at Site C was a surprise, as this is presumably the most polluted section of the river, given that it includes the area around the river’s confluence with the Black. The extensive vegetation on both sides of the Liesbeek, including the Raapenberg Bird Sanctuary, may contribute to this diversity. It was also at this site that we saw Cape Clawless Otters on two occasions.
Some species were detected more frequently than others. Species that occurred more than half of the time in one or other of the sites were those that seem to be able to adjust to some degree of urbanisation, namely Red-knobbed Coots, Red-eyed Doves, Yellow-billed Ducks, Egyptian Geese, Hartlaub’s Gulls, Kelp Gulls, African Sacred Ibises, Hadeda Ibises, Common Moorhens and Blacksmith Lapwings. Reed Cormorants and African Darters also occurred at Site C more than 50% of the time, as did Common Starlings in Sites A and B, and Southern Fiscals and Cape Weavers in Site A. A matter for celebration was that African Black Ducks occurred at Site A on 12 out of 21 occasions: we were often anxious that they would zoom past on the fast-moving stream before we could catch them within the time limits of our count.
Apart from the frequency of their presence, some birds also predominated in terms of numbers. We ended up counting Hartlaub’s Gulls on almost every visit and by the time we reached 2,881 at the end of our counting year, were heartily sick of them. Nonetheless, counting them revealed the flux in their numbers over time. At Site B, numbers suddenly swelled from less than 20 per count up to June 2021, to 150 a month later, dropping off slowly thereafter to a third of their peak. We wondered what accounted for these changes.
The example of Hartlaub’s Gulls raises a weakness in our survey method. We were instructed to count each and every bird that we could see well enough to identify, including those flying directly overhead. Clearly, several of these were not actually using the site, but travelling from one more distant area to another. The high seagull count for Site C is thus somewhat misleading, as the birds hardly ever settle. By way of contrast, the high numbers at Site B reflect the fact that many birds land in the wide, shallow area of water at that spot.
A delight to watch were the kingfishers. We spotted Giant Kingfishers on 10 occasions, Malachites on 16 and Pied Kingfishers on 19. On a very recent count at Site C we managed to spot all three species within the same half hour, but sadly not within our time limit. The large majority of Pied Kingfishers were at Site C where the birds usually occurred in pairs, flashing up and down the Black River, perching on the reeds at the confluence or hovering high above the water. At one time or another, we observed juveniles of each species, confirming that the birds must be breeding in the area.
Another joy for the Site C team was when the Black-Crowned Night Herons, including several juveniles, began to roost in a willow tree from April 2021. Their numbers peaked at 17 on 18 May when a loud noise caused them to all fly up into the air, revealing that many must have been hidden from our prying eyes in the centre of the tree during the weeks before. We made fools of ourselves trying to get to the site in the dark before the birds returned to roost, never managing to catch them, and never working out where their feeding grounds must be. By the end of September they had all disappeared.
Apart from these specific details about species and numbers, what have we taken away from this experience of long-term counts on the lower Liesbeek?
- First, returning to the same site repeatedly is more interesting than we had expected – on the one hand it is rewarding to get to know a site well, and on the other hand there always seem to be surprises.
- Second, birdlife is remarkably resilient and it is a privilege to still be able to witness it in all its beauty within an urbanised environment. At the same time, it was painful to witness the start of clearing operations for the new commercial development at the former site of the River Club. Half of the area over which we counted has now been graded, and we no longer see the Black- winged Kite which used to perch on one of the felled trees.
ARTICLE BY JANE DOHERTY – Originally published in Promerops 323 (to view, click here)
