Aim  Climate limits the ranges of many animals, but the mechanism whereby it does so remains poorly understood. One explanation is that climate (e.g. temperature or rainfall) affects energy expenditure, eventually limiting where a species can occur. We propose that climate can also affect energy uptake through its effect on foraging efficiency. We examined this idea for the case of the hadeda ibis (Bostrychia hagedash) which has considerably expanded its range in southern Africa over the past 80 years. Hadedas forage mainly by extracting earthworms and other invertebrates from soft soil. Soil moisture, in the absence of irrigation largely determined by climate and soil composition, may therefore be a factor limiting feeding efficiency in hadedas. Location  We tested this hypothesis by observing foraging hadedas in Cape Town, South Africa. Results  We found that soil moisture limited the rate at which hadedas caught prey items, with an optimum on relatively moist ground. We further measured the energy content of the hadedas’ main prey, earthworms. Using published physiological relationships, we estimated that hadedas need to forage for about 6.3 h to meet their daily energy requirements under optimal soil moisture conditions. On dry soils, they need to forage for >12 h, thus showing that soil moisture has the potential to limit the range of this species. Main conclusions  Hadedas originally only occurred in the wettest parts of South Africa, but gradually colonized drier areas, and are now absent only from the driest parts of the country. Our results support the view that climate (determining soil moisture) originally limited the hadedas range and that irrigation has been an important factor facilitating their range expansion. The hadeda is an example for a species whose range expansion is driven by interactions between climate and land‐use change.

A mechanistic understanding of species' geographic range dynamics requires an understanding of the dynamics of populations at the edge of that range. Several ibis species are currently expanding their ranges, and the Hadeda Ibis (Bostrychia hagedash) has increased its southern African range more than 2.5 fold over the past century. We studied the demography of a Hadeda population near the expanding range edge. Estimating survival on a quarterly time interval we found that it was lowest over the first 3 months of life, and then slightly higher over the rest of the 1st year (annual survival: 0.27, SE = 0.04). After the first year, survival was constant (0.75, SE = 0.09). Breeding success increased from 1.5 to 3 fledglings per year with increasing experience of the breeding pair. A matrix population model showed that the growth rate of this population was most sensitive to changes in adult survival and least sensitive to variation in reproduction. Hadedas in our study population thus showed characteristics of long-lived birds but were also able to achieve a high reproductive output in good conditions. Together with their ability to take advantage of a human modified landscape, this may explain the remarkable success of this species in expanding its range. ZusammenfassungDemographie und Populationsökologie des Hagedadsch-Ibises (Bostrychia hagedash) an der Front seines expandierenden Verbreitungsgebietes in Sü dafrika Für ein mechanistisches Verständnis der Dynamik von Verbreitungsgebieten braucht es Kenntnis der Dynamik von Populationen am Rande des Verbreitungsgebietes. Mehrere Ibis-Arten erweitern momentan ihr Verbreitungsgebiet und das des Hagedasch-Ibises (Bostrychia hagedash) hat sich in Südafrika im Laufe der letzten hundert Jahre um das 2.5 fache vergrößert. Wir untersuchten die Demographie einer Hagedaschpopulation am Rande des Verbreitungsgebietes. Die Ü berlebensrate je Quartal ist in den ersten drei Lebensmonaten am niedrigsten; für das gesamte 1. Lebensjahr beträgt sie 0,27 ± 0.04 (s.e.). Nach dem ersten Lebensjahr war die Ü berlebensrate altersunabhängig 0,75 ± 0.09. Mit wachsender Erfahrung des Brutpaares erhöhte sich der Bruterfolg von 1.5 flüggen Jungen pro Jahr auf 3. Ein Matrix-Populationsmodell zeigte, dass die Wachstumsrate dieser Population am empfindlichsten auf Veränderungen in der Ü berlebensrate von erwachsenen Vögeln reagiert und am wenigsten empfindlich auf Veränderungen im Bruterfolg ist. Der Hagedasch in unserem Studiengebiet zeigte deshalb Eigenschaften von langlebigen Vögeln, war aber auch in der Lage, gute Communicated by P. H. Becker. Electronic supplementary material The online version of this article (

Aim: Protected areas are key conservation tools intended to increase biodiversity and reduce extinction risks of species and populations. However, the degree to which protected areas achieve their conservation goals is generally unknown for many protected areas worldwide. We assess the effect of protected areas on the abundance of 196 common, resident bird species. If protected areas were beneficial to avian biodiversity, we expect landscapes with a higher proportion of protected areas will have higher densities of species compared to landscapes with no protection.Location: Greater Gauteng region, South Africa. Methods:We analysed bird survey data collected over regular grid cells across the study area. We estimated bird abundance in relation to the proportion of a grid cell that was protected with the Royle-Nichols model and fitted the model once for each of the species. We examined variation in estimated abundance as a function of avian guild (defined by the type of food a species preferentially ate and its foraging mode) with a regression tree analysis. Results:Abundance was significantly positively related to the proportion of protected areas in grid cells for 26% of the species, significantly negatively related in 15%, and not significantly related in 59% species. We found three distinct guild groups which differed in their average abundance, after accounting for associated variance. Group 1 consisted of guilds frugivores, ground-feeders, hawkers, predators, and vegivores and average abundance was strongly positively related to the proportion of protected areas. Group 2 included granivores, and average abundance was strongly negatively related to proportion of protected areas. Group 3 included gleaners only, and average abundance was not related to proportion of protected areas. Main conclusion:We conclude that the network of protected areas within the greater Gauteng region sustained relatively higher abundances of common birds and thus perform an important conservation role. K E Y W O R D S Avian conservation, citizen science, hierarchical models, protected areas, species abundance B I OS K E TCH E S Gregory D. Duckworth has interests in conservation and ecological modelling. Res Altwegg's interests are in population ecology and statistical ecology.