Connecting the dotsText by Philip Briggs Tracking Blue migration patterns

Text by James Wakelin† & Andrew McKechnie

In recent years, the distinctive and charismatic Blue Swal- low atrocaerulea has been the focus of considerably more research effort and media coverage than many other threatened African . Despite this, the South African and Swazi population remains precariously balanced on the edge of extinction and is currently thought to number only about 80 breeding pairs (see Africa – Birds & Birding 9(6): 42–46). So dire is the plight of the southernmost Blue Swallow breed- ing population that the has been red-listed as Criti- cally Endangered within South Africa and Swaziland.

he swallow’s troubles arise from African/Swazi population occupy the the fact that during the breeding same winter quarters in as season it is a mistbelt grassland individuals that breed in the Eastern Tspecialist and is thus completely Highlands of ? We simply reliant on a poorly conserved habitat don’t know. This dearth of information type that has been decimated by for­ is reflected in the lack of recoveries of estry and agriculture. Contributing to ringed in the Central African the species’ decline are its very particular wintering range. Until recently, ringing breeding requirements: over most of its was the only way to link wintering indi­ range, it nests exclusively in sinkholes or viduals to specific breeding populations. disused burrows. Without this information, it is impos­ Another factor significantly hamper­ sible to coordinate conservation efforts ing the development of effective con­ between the areas that individual swal­ servation strategies for the local Blue lows occupy at different times of year. Swallow population is a lack of know­ Over the past decade, however, bio­ ledge about the migratory links between chemical techniques that take advantage the various breeding and wintering of the stable isotopes in birds’ feathers populations. Blue Swallows are intra- (see Africa – Birds & Birding 9(4): 17) have African migrants and spend the winter revolutionised the study of avian migra­ in Central Africa, particularly around tion, and to a large extent freed orni­ The biochemical properties of this juvenile Lake Victoria and elsewhere in Uganda. thologists from having to rely on ring Blue Swallow’s feathers may hold the key Do members of the dwindling South recoveries to understand migration  to understanding the migration patterns of this threatened species. † deceased

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wim de groot patterns. A few years ago, we realised used to reliably distinguish individuals he trip to Nyika began with that these techniques were in all proba­ from these two breeding areas. an epic six-day drive through bility the only way to reveal the secrets The missing link in the puzzle, how­ , with a quick stop of the Blue Swallow’s migra­ ever, concerned the third major breed­ in Lilongwe to pick up per­ tion. We therefore set about ing population of Blue Swallows. This mits.T Visitors to Nyika entering the obtaining feather samples population, which is also the largest, park by way of the southern Thazima from South African, Swazi and inhabits the Nyika Plateau in northern Gate experience a dramatic altitudinal Zimbabwean swallows, with the and the highlands of south­ transition between habitats. Beyond intention of establishing whether ern . Nyika’s montane grass­ Thazima, the road climbs through a these populations differ from each lands alone are thought to hold close to belt of pristine miombo woodland, other in terms of the isotopic proper­ 300 breeding pairs. Fortunately, this which demands regular stops for ties of their feathers. In order to make population enjoys substantial protection parties that include Rufous-bellied Tit, certain that we did not analyse feath­ as the entire plateau falls within the bor­ Cabanis’s Bunting and Miombo Rock- ers that had grown elsewhere prior to ders of the Nyika National Park. Thrush. The most sudden application migration, we collected specimens only In early 2009, a group of researchers of the brakes, however, is reserved for from nestlings and first-year juveniles. from the Universities of Pretoria and the Anchieta’s , a red, blue and Wintering site Working with Dr Stephan Woodborne Witwatersrand visited Nyika with the yellow jewel of a bird that is without Breeding site at the CSIR in Pretoria, we measured goal of obtaining feathers from the Blue doubt the highlight of this drive. As the the relative abundance of two stable Swallows there. Analyses of feathers from road continues upwards, the miombo isotopes of hydrogen in the feathers. these Malawian birds would allow us to abruptly gives way to the rolling grass­ the most compact member of the Our initial results were encouraging: compare the isotope signatures from lands of the plateau. The mean annual team was assigned the portfolio of the hydrogen stable isotope ratios of each of the three major known breed­ rainfall of approximately 1 600 mil­ feathers from South African and Swazi ing populations, and hopefully provide limetres on the plateau ensures that feather collector, swallows were distinct from those of the basis for future studies that identify reaching the main camp at Chelinda in which involved crawling head Zimbabwean birds, with no overlap in the origins of wintering birds from their late summer is a lively experience, with values. This approach can therefore be feather biochemistry. many of the roads reduced to muddy first into a burrow until he could tracks that can only be negotiated by a remove the chick four-wheel-drive vehicle. The grassland-covered hills of the straightforward, if somewhat muddy Nyika plateau stretch from horizon to procedure. Ben Smit, the most com­ horizon, providing a vivid backdrop for pact member of the team, was assigned summer thunderstorms fuelled by evap­ the portfolio of feather collector, which oration from nearby Lake Malawi. The involved crawling head first into a bur­ grasslands are punctuated by patches of row until he could gently remove the afromontane forest, innumerable crystal- chick(s) from the nest and pull a single clear streams and marshy, bracken- feather from each bird. The fact that covered wetlands. The Blue Swallows Nyika boasts healthy populations of occur throughout the grasslands, but leopards and warthogs, both decidedly seem to be most common in the deeper partial to denning in aardvark burrows, valleys east of Chelinda. made Ben’s task all the more challeng­ Above Blue Swallows typically breed in During the visit, the team conducted ing. The success of the method relied disused aardvark burrows, and reaching intensive searches of two valleys and heavily on the continuing goodwill of their nests can require gravity-defying found nine active or recently active the other team members, since the near- teamwork. nests in disused aardvark burrows. vertical profile of many of the burrows Interestingly, the single nest located by a meant that the only feasible way for Ben Top Nyika’s vast grasslands are dotted Zambian group during a survey in 2005 to be extricated was to be hauled out in with patches of afromontane forest. was not in an aardvark burrow, but in a reverse by his boots. During the rainy season, storms roll shallow sinkhole instead. We visited it The trip also yielded some interesting across the plateau almost daily. and it appeared to still be active, show­ observations. On one occasion, a group of ing signs of having been used earlier approximately 30 Blue Swallows, together Opposite Two Blue Swallow chicks in the 2008/2009 breeding season. Our with Banded Martins and White-headed in one of the active nests we found trip, which took place in late February, Saw-wings, was seen foraging over a at Nyika. seemed to have missed the breeding marshy area, probably attracted by large peak, as many of the nests we found numbers of insects. Another observation were empty and there were large num­ involved a Blue Swallow very nearly end­ bers of juvenile swallows foraging in ing up as a meal for a stooping Eurasian the valleys. Hobby – the swallow lived to see another When we did find nests containing day only because of some frantic evasive chicks, feather collection involved a manoeuvres.  andrew mckechnie (3)

38 blue swallow africa – birds & birding october/november 2009 blue swallow 39 Besides being a site of major conservation significance to the global Blue Swallow popu- lation, Nyika is a rewarding and accessible birding destination

three major breeding populations, name­ ly South Africa/Swaziland, the Eastern Highlands of Zimbabwe, and northern Malawi/southern Tanzania. Population- specific isotopic signatures would pro­ vide the basis for a biochemical map of the Blue Swallow’s breeding range. Once we have such a map, we plan to travel to the swallows’ wintering grounds in Central Africa. By collecting and ana­ lysing a single feather from any Blue Swallow we mist-net there, we will be able to deduce the breeding area from which it originated and thus identify migratory connections between various tim jackson breeding and wintering populations. If adam riley (2) this approach works for Blue Swallows, it Above White-headed Saw-wings esides being a site of major con­ will open the door for similar research on Psalidoprocne albiceps are common servation significance to the glo­ other threatened African species whose at Nyika, and may be seen foraging in bal Blue Swallow population, conservation is hampered by a lack of the same habitats as Blue Swallows. Nyika is a rewarding and acces­ knowledge of migration patterns.  Bsible birding destination. The grasslands Right Bronzy Sunbird kili- and wetlands are home to a number We thank Ben Smit and Bryan Maritz for mensis is one of several sunbird species of species that do not occur in south­ their able assistance and sense of humour in that forage along the edges of Nyika’s ern Africa, including Churring Cisticola, the field, and Dr Roy Bhima and the staff of afromontane forests. Montane Widowbird, Yellow-browed Nyika National Park for their support. Seedeater and Baglafecht Weaver. There are also large numbers of Montagu’s and Pallid harriers, as well as Denham’s Bustards. In addition to this host of grassland specials, Nyika offers stimu­ lating afromontane forest birding. The grasslands are interspersed with patches of primary forest, with the largest and best-known areas located in the western parts of the park along the border with . Excursions to the gloomy in- terior of Chowo Forest provide stunning views of Bar-tailed Trogon and Brown- headed Apalis, while walks along the forest edges yield Malawi Batis and Forest Double-collared, Bronzy and Green- headed . After a week of hiking Nyika’s valleys and searching several hundred burrows, we had obtained feathers from nine young swallows. These feathers will now be analysed at the CSIR and we are hoping to be able to identify a unique isotopic ‘featherprint’ for each of the

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