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Orange breasted Sunbird. Cape Sugarbird Visitors to Cape Town with an interest in birds often head for Kirstenbosch Gardens to see the emblematic and endemic Cape Sugarbird (773) and the Orange breasted Sunbird (777), amongst others. They are often disappointed. So what has happened? In the 1960's and 70's, before the upper garden (south western sector) was developed horticulturally, the area was covered with extensive stands of proteas and ericas typical of montane fynbos, accessed only by a few rough tracks. The sugarbirds were present throughout the year, and nested extensively in the proteas in April and May. In the last decade, the situation has changed. During the monthly BIRP counts in the Gardens, the actual numbers of sugarbirds seen were recorded, rather than just their presence. Over a period of 2.5 years commencing in July 2002, a clear pattern is emerging (see table below). In the months of January, February and March the birds are easily seen, displaying and perching prominently in the protea beds. Then, almost as if a curtain has dropped, in April they disappear from the Gardens, and are virtually absent for the subsequent four months, April - July. A few more are sighted from August to December, but numbers are still low and some diligent searching is often required. Then, quite suddenly, in January they are back again in force; up to 30 birds have been recorded in the south western protea beds which comprise a fairly small area. This pattern is almost the direct opposite of that noted by Broekhuysen (1)(2) who stated that " in the late spring and summer the birds leave the protea clad slopes and move to other areas where other plants then in flower, attract them". He goes on to say that "the birds move to the lower regions in the bushes around the lawns near the central pond: but not so today, as the birds appear nowhere in the garden outside the south western protea beds and occasionally in the montane fynbos between the service road and the upper contour path". I suggest that the sugarbirds have abandoned breeding in Kirstenbosch because of the extensive disturbance by garden staff working in and around the protea beds and the much reduced size of these beds which now form a series of small, isolated pockets. They seem to migrate out of the Gardens to breed elsewhere. This would explain the March exodus, the beginning of their breeding season, which peaks in May, June tailing off in July. Exactly where they go is not known, and possibly may only be determined by ringing. Why the birds do not return in numbers until January, a period of 9 months after the start of the breeding season, is not clear. Even allowing for two clutches, which is fairly common in Sugarbirds (2), the breeding cycle would not last more than two to three months. One possibility is that the return for the three summer months coincides with the flowering of P.speciosa and P.grandiceps, amongst their preferred food sources. The position with the Orange breasted Sunbird is less clear, but sightings and numbers do fluctuate markedly throughout the year. The BIRP records indicate their absence in October and November 2002, October and December 2003; January, February and June, 2004. In the months when they were recorded, the numbers showed a wide variation. If you are taking visitors to Kirstenbosch any time apart from January to March, don't expect to find sugarbirds. Other locations such as the Helderberg might be more productive. A few of the local bird guide-books (3)(4)(5) require updating; the phrase "common all the year round" is no longer accurate.
References: (1) Broekhuysen G.J. 1958 : "Birds of the National Botanic Gardens of Kirstenbosch" (2) Broekhuysen G.J. 1959 "The biology of the Cape Sugarbird Promerops Cafer". (3) Cohen C. and Spottiswood C. 2000 "Essential birding: Western South Africa" (4) Petersen, W. and Tripp M. 1995 "Birds of the South Western Cape" (5) Longrigg, T.D. 1978 "A Guide to the Birds of Kirstenbosch". Cape Bird Club
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