10. Blue Crane monitoring: trends begin to emerge Donella J. Young & J.A. Harrison Avian Demography Unit, UCT, Rondebosch, 7701 The Blue Crane Anthropoides paradiseus, a species which is largely endemic to South Africa, is listed in the recently published Eskom Red Data Book as Vulnerable. The species has declined by 20% over the past three generations, declining most rapidly over portions of its range (Barnes 2000). The ADU, by means of CAR, the Coordinated Avifaunal Roadcounts project, has been monitoring the Blue Crane in the Overberg, Western Cape, since July 1993 when David Allan initiated the project. A history of road counting and earlier CAR results appeared in Bird Numbers 7(2), 1998. In July 1995 Mark Anderson, of Northern Cape Nature Conservation Services, began the Karoo Large Terrestrial Bird Survey (KLTBS) in the De Aar and Hanover districts of the eastern Karoo. James Harrison and Wendy Hitchcock of the ADU started routes in the Swartland, Western Cape, in July 1996. Monitoring in four other provinces was initiated more recently, mostly under Donella Young’s coordination, but it is still too early to detect trends there. However, a comparison of densities between areas does confirm declines in regions which were former strongholds, e.g. the Midlands of KwaZulu-Natal. The graphs accompanying this article show that some trends are emerging. The Blue Crane appears to be thriving in the agriculturally transformed Overberg region in the deep south, where a wheatland/pasture system operates. The birds breed in the summer and the results indicate that the breeding population is steadily increasing in this region. The Swartland results appear to indicate a similar trend, and there is some evidence that birds from the Overberg are colonizing the Swartland as Overberg breeding habitats become saturated, and as agricultural practices in the Swartland become more similar to those in the Overberg (Underhill et al. 1999; pers comm.). The high densities during the Swartland winter 1998 and 2000 counts were largely due to the sighting of two huge flocks of 225 and 216 birds respectively. It is interesting to note that David Allan’s roadcounts, during the 4.5 years prior to this study, showed no significant increase in numbers (Allan 1993). However, the population levels during his study were significantly higher than those during Roy Siegfried’s study in the same area in 1965 (Siegfried 1985; Allan 1993). The KLTBS is monitoring an important area where Blue Cranes still occupy natural vegetation as opposed to land which has been transformed by agriculture. No distinct trend is evident yet, but the summer breeding population appears to be at least stable. Winter densities are consistently higher than summer densities. This was initially thought to indicate seasonal movement of large numbers of cranes, but it is now believed to be a statistical artefact of the fact that Blue Cranes gather in flocks during the nonbreeding season, and flocks are much more conspicuous than breeding pairs of birds. The large fluctuations in the winter densities are a consequence of big flocks being either seen or missed owing to their being located within sight of the road transects, or not. One flock of 200 birds can make a big difference to the results by simply being out of sight over a ridge. This means that the summer counts, when the birds are more evenly dispersed, provide a more reliable indication of trends, despite the fact that fewer birds are counted. In the graph showing mean densities per region, it is striking that Blue Crane numbers are low in areas like KwaZulu-Natal, Free State and Mpumalanga which include large tracts of the species’ original grassland stronghold. CAR data confirm the decline in the grassland biome which was obvious in the Atlas distribution map. Major threats within the grassland biome have been poisoning and loss of habitat to afforestation, urbanization and crop farming (Allan 1997). The decline of Blue Crane in this biome is estimated to be about 90% (Allan 1994). However, the species has increased in the fynbos biome, a region from which the Blue Crane was previously absent but large tracts of which have come to resemble grasslands through the effects of crop agriculture and pastures (Allan 1994). The Blue Crane first colonized the Overberg over 100 years ago. However, numbers remained low until the period between the late 1960s and the early 1980s (Allan 1994). The first large-scale transformation from the natural Renosterveld scrublands to the wheatland/fallow system took place after World War II (1945–50). The second transition, from a wheatland/fallow system to a wheatland/pasture system, took place from 1975–85 (Wicus Leeuwner & Hennie Lötter pers. comm.). It is probable that the huge increase between the late 1960s and the early 1980s is linked to the shift to the wheatland/pasture system. The pie charts indicate the increase in use of pastures by Blue Crane in the winter and the marked increase in use of cereal-stubble fields in the summer. These results confirm the pattern pointed out by David Allan (1994). In the summer they feed mainly on fallen grain and insects in cereal-stubble fields or fallow land, but in winter in planted pastures, fallow land and at feedlots (Allan 1995; Wicus Leeuwner pers. comm.). Breeding occurs in stubble fields and pastures (Allan 1995), as well as fallow land and wetlands (Wicus Leeuwner pers. comm.). The shift to a wheatland/pasture system would therefore have favoured Blue Cranes. It is important to note that the percentage in crops is low. This suggests that Blue Cranes are not a threat to growing crops in January and July. It is indeed fortunate that our national bird has had the ability to adapt to change and thrive in the artificial grasslands of the Overberg and Swartland wheatbelts, and that the Karoo population appears to be stable. There is no doubt that the work of the Overberg Crane Group, Nature Conservation Boards, and the South African Crane Working Group in increasing awareness of this species amongst farming communities, and in addressing the threats of poisoning and collisions with powerlines, has played a significant role in the conservation of the Blue Crane. Thanks are also due to the many farmers themselves who share their land with these graceful birds and use bird-friendly management practices. Acknowledgements We would like to thank all CAR participants and Precinct Organizers who have given freely of their skills, time and petrol in ensuring that routes are regularly covered. Those involved are members of bird clubs, farming communities, schools, Conservancies, Nature Conservation, Free State Department of Environmental Affairs and Tourism, Overberg Crane Group and South African Crane Working Group, Steven Evans (Project Manager of Important Bird Areas) and interested members of the public. BirdLife South Africa and the Tony and Lisette Lewis Foundation are thanked for their financial support, and Mazda Wildlife Fund for the use of their vehicle. Allan D.G. 1993. Aspects of the biology and conservation status of the Blue Crane Anthropoides paradiseus, and the Ludwig’s Neotis ludwigii and Stanley’s N. denhami stanleyi Bustards in southern Africa. MSc thesis, University of Cape Town, Cape Town. Allan D.G. 1994. Haven for Blue Cranes in the southern Cape. African Wildlife 48(4): 8–14. Allan D.G. 1995. Cape Bird Club Blue Crane and Stanley’s Bustard counts. Promerops 217: 13–14. Allan D.G. 1997. Blue Crane Anthropoides paradiseus. In: Harrison J.A., Allan D.G., Underhill L.G., Herremans M., Tree A.J., Parker V. & Brown C.J. (eds). The Atlas of southern African birds. Vol. 1: Non-passerines. Birdlife South Africa, Johannesburg. pp. 314–315. Barnes K.N. (ed.) 2000. The Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland. Birdlife South Africa, Johannesburg. Siegfried W.R. 1985. Relative abundance of cranes (Gruidae) in the Cape Province. Ostrich 56: 101–103. Underhill L.G., Tree A.J., Oschadleus H.D. & Parker,V. 1999. Review of ring recoveries of waterbirds in southern Africa. Avian Demography Unit, University of Cape Town.

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Document posted: 10 January 2001