Reduced Blue Crane Grus paradisea breeding productivity in intensive agricultural landscapes

Abstract

We compare Blue Crane Grus paradisea breeding productivity in the Western Cape wheatlands in Overberg and Swartland (2018–2021), Karoo (2009–2011) and eastern grasslands (2009–2011 and 2013). Productivity was higher in the grasslands (0.95 fledglings/attempt, 95% CI = 0.86–1.30, n = 95) and Karoo (1, 95% CI = 0.79–1.55, n = 90), than in the Overberg (0.55, 95% CI = 0.42–0.80, n = 98) or Swartland (0.48, 95% CI = 0.34–0.75, n = 63). Swartland pairs fledged two chicks half as often as Overberg, grasslands and Karoo pairs. In 2019–2021, juveniles comprised 4.0% (range = 2.8–5.0%) of winter flocks in the Overberg, and 3.6% (3.4–4.0%) in the Swartland, which is approximately half of the estimates from the Overberg 30 years ago. Low breeding productivity and recruitment could explain the declining population in the Western Cape wheatlands and may indicate that the region has become an ecological trap for the species. Breeding productivity could be improved by reducing disturbance at nests, preventing chick drownings in water troughs and reducing fence entanglements.