SLIP SLIDING BIRDS ONaway THE MOVE n 1963, when Bob Dylan recorded his classic album ‘The times they are Ia-changin’, he had little idea of quite how prophetic his lyrics were to be. His song referred to the social and political revolution of the times, but almost 50 years later we are witnessing arguably the most rapid environmental revolution the world has experienced since the mass extinction at the end of the Cretaceous, 65 million years ago. Signs of this trans- formation abound in the natural world and are linked to habitat modification and climate change. Among birds, there are many examples of marked alterations in species’ abundances, ranges, breeding The Sanderling is one of the migrant seasons and migration patterns. shorebird species that has become scarce on the south Peninsula over the past two decades, probably as a result of global TEXT & PHOTOGRAPHS BY PETER RYAN population decreases as well as local increases in human disturbance. POPULATION DYNAMICS 31 a square at 120 kilometres per hour contributed running for just on three years. SABAP1 had on the northern Peninsula). By contrast, Forest as much weight to ‘reporting rates’ (the propor- 93 818 species records on 1 407 cards for the Canaries, Swee Waxbills, Amethyst Sunbirds, tion of cards on which a species is recorded) as south Peninsula, compared to 18 208 species Buff-spotted Flufftails, Black Sparrowhawks and did a card gathered over an entire month by on 372 cards to date for SABAP2. As a result, African Harrier-Hawks have all either arrived or someone based in a square. vagrants and species that irrupt into the area greatly increased. Records of Forest Buzzards In an attempt to address these issues, SABAP2 infrequently are less likely to have been record- are also more numerous, although they are records are gathered at the ‘pentad’ level (5 x 5’ ed during SABAP2. However, sufficient data possibly being confused with the ‘mystery’ blocks, approximately 9 x 7 kilometres) and have accumulated to assess changes in the buzzards now breeding in the area (see Curtis cover at most a period of five days. The spatial more common birds of the region, and some and Koeslag 2007, Africa – Birds & Birding resolution is thus nine times and the temporal very striking patterns have emerged. 12(3): 48–50). Cardinal and Olive woodpeckers resolution six times finer than in SABAP1. Each remain rare, but there have been more records observer has to spend at least two hours bird- here have been no marked changes of both during SABAP2 than SABAP1. This ing each pentad and should attempt to survey in species with wide habitat toler- increased diversity and abundance of forest all the main habitats in the pentad (incidental ances (generalists such as Cape Robin- birds is interesting given the ongoing debate records can be submitted, but they don’t con- Chat, Cape White-eye, Cape Bulbul, around the relative merits of the clearing of tribute to reporting rate calculations). Species KarooT Prinia and Common Starling). Aerially pine and eucalypt plantations in the area. It are recorded in the order observed, giving some feeding swallows and swifts also appear little remains to be seen whether these birds’ pos- index of their relative abundance in the area. changed, with the possible exception of the itive trends will continue as the areas of planta- The improved resolution of SABAP2 comes at a arrival of Common Swifts. Among fynbos tion decrease. cost: it is tricky to compare reporting rates with species characteristic of the Peninsula’s moun- Not surprisingly, birds characteristic of low- Thanks to the project’s online data-capture system, it is possible those obtained during SABAP1. The simplest tain chain, several appear to have decreased in land areas of the Cape Flats are less than to interrogate the data as they are submitted to assess how bird solution is to lump together all records for the abundance. In the case of some localised ones, enthusiastic about the changes resulting from pentads in a quarter-degree square and calcu- this may be as a result of reporting biases (for continued urban sprawl. As open spaces on the populations have altered over recent decades late the overall reporting rate for SABAP2. example, Cloud Cisticola, Cape Clapper Lark flats adjacent to the southern Peninsula have But this can lead to biases. For example, on and Plain-backed Pipit), but in others there been lost, records of African Hoopoes, Black- he South African Bird Atlas Project the Cape Peninsula, African Penguins are only is little doubt that species have either disap- shouldered Kites, Lanner Falcons and Barn (SABAP) offers a great tool to assess regularly observed in one of the 11 pentads peared entirely (African Stonechat) or become Owls have decreased. Birds of coastal thicket, how local bird populations are shift- that include some land area, the one around much more scarce (Grey-winged Francolin). such as Karoo Scrub-Robins, Long-billed ing. Data collection for the first SABAP Simon’s Town that contains the Boulders pen- Verreaux’s Eagles have become rare, whereas Crombecs and Chestnut-vented Tit-babblers, Twas conducted mostly in the 1980s and it guin colony. (If you’re wondering why the Booted Eagles have increased in abundance have been hard hit. Several species that used culminated in the 1997 publication of the south Peninsula has 11 not nine pentads, that’s and now breed on the Peninsula. to irrupt fairly regularly onto the flats, such two-volume Atlas of the Birds of Southern Africa. because in SABAP1 some coastal quarter-degree In general, the south Peninsula’s forest birds as Namaqua Doves and Pied and Wattled The atlas team at the University of Cape squares with only a small land area, such as have fared better than their fynbos counter- starlings, have not yet been recorded there in Town’s Animal Demography Unit then took the southern tip of the Peninsula, were lumped parts. The only species that have probably SABAP2, and it will be interesting to see if they a well-deserved rest before launching SABAP2 with their neighbouring square.) Most SABAP1 declined are Lemon Doves and Red-chested are still willing to venture so far south. Other Above A colour-ringed in 2007. After a rather slow start, SABAP2 has atlas cards for the area should have reported Cuckoos (although both are still doing all right species have invaded the urban landscape, White-fronted Plover at taken off and has already amassed more than penguins because the species is easy to see at Kommetjie. Researcher two and a half million records from 45 000 Boulders, whereas in SABAP2 only cards from Penn Lloyd’s study showed checklists. Thanks to the project’s online data- the Simon’s Town pentad are likely to have the key role that dogs play capture system, it is possible to interrogate the penguins. In fact, only 11 per cent of SABAP1 in reducing recruitment of data as they are submitted to assess how bird cards had African Penguins, partly because this species. populations have altered over recent decades. penguins only colonised Boulders in the mid- As an enthusiastic supporter of both atlas 1980s and partly because many ‘incomplete’ Opposite, above projects, I thought it would be interesting to cards were submitted. But the pooled reporting African Stonechats have see how things look in my home square, the rate for African Penguin in SABAP2 is less than disappeared from the Cape southern Cape Peninsula, which extends from two per cent, because only eight of the 372 of Good Hope section of Constantia Nek south to Cape Point. Before cards submitted for the region to date have Table Mountain National reporting the results, however, there are a few been for the Simon’s Town pentad. Clearly Park over the past 20 technical details that need to be understood. Simon’s Town needs a resident atlaser! The years, despite this being a SABAP1 was conducted at the spatial resolution moral of this story is that one has to be cau- protected area. of the quarter-degree square (15 x 15’ blocks, tious when interpreting the apparent seven- roughly 28 x 22 kilometres in extent) and a fold decrease in African Penguin reporting rates Opposite, below Even temporal resolution of one month. Although from SABAP1 to SABAP2, when in fact there are with habitat restoration, this vastly improved our understanding of bird now many more penguins at Boulders than such as here along the distributions in southern Africa, both in space there were when SABAP1 was conducted. lower Silvermine River, and time, it was soon apparent that an even The other big difference between SABAP1 several wetland bird species finer resolution would be valuable to detect and SABAP2 is the duration of the two studies. have disappeared or subtle changes in birds’ ranges. Also, in SABAP1 SABAP1 built on the Western Cape Bird Atlas become less common on there was no attempt to standardise search Project, so data for the Cape Peninsula spanned the south Peninsula. effort. A card completed while driving through more than a decade, whereas SABAP2 has been 32 POPULATION DYNAMICS AFRICA – BIRDS & BIRDING on average 33 times lower than they were in SABAP1. Reporting rates of resident Kittlitz’s and White-fronted plovers have also decreased, but not to the same extent. For largely coastal species such as Ruddy Turnstones, Sanderlings and Common Whimbrels, increased human activity along the coast has probably exacer- bated their decreases. Two migrant terns have also suffered: White-winged Terns have not been recorded during SABAP2 (down from 14 percent of cards in SABAP1) and Antarctic Terns have largely disappeared (due at least in part to increasing disturbance at their tradi- tional roost site at Kommetjie).