Towards a unification of movement ecology and biogeography: conceptual framework and a case study on Afrotropical ducks

Abstract

Aim We present elements of a new conceptual framework for the unification of biogeography and movement ecology, and demonstrate the value of the new framework using a case study of two species of Afrotropical duck (Anatidae) across a latitudinal gradient. Location Southern Africa. Methods The first part of the paper rests on logic and philosophy. For the second (case study) section, we used data from up to 3 years of satellite telemetry for 26 individuals of two species of Afrotropical duck, the Egyptian goose (Alopochen aegyptiaca) and red-billed teal (Anas erythrorhyncha), from three different populations with moulting sites spread across 17 degrees of latitude. We compared quantitative measures of movement patterns using principal components analysis and boxplots. Results We argue that unpacking the concept of dispersal into the fundamental elements of movement (internal drivers, external drivers, navigation capacity, and motion capacity) provides a more solid basis for contrasting competing hypotheses in biogeographical studies. We found, surprisingly, that red-billed teal, a 'highly nomadic' species, moved with a relatively high degree of consistency at each of our three study latitudes, while Egyptian geese, a 'resident' species, showed latitude-dependent variation in their movements. However, much of the latitude-related variation for Egyptian geese was driven by their annual moult migrations, rather than directly by fluctuations in resource availability. Internal factors appear to dominate movements and probably determine the species ranges of both of our study species. Main conclusions The integration of biogeography and movement ecology, through a more sophisticated view of mechanisms formerly lumped together under 'dispersal', offers a fertile area for further research. The biogeography of Afrotropical ducks appears to be strongly influenced by internal factors. Biogeographical patterns in this taxon may thus be best understood (and modelled) as a long-term response to environmental stochasticity, rather than as a deliberate selection of optimal habitat. Latitudinal comparisons emerge as a valuable way of gaining insights into the drivers of movement for widespread species. (Résumé d'auteur

Susceptibility and Status of Avian Influenza in Ostriches

“…Reassortment of the internal gene segments is an indication of the mixing of viral populations, and by extension, mixing of wild bird populations. Southern African waterfowl breed in isolated ephemeral wetlands during the wet season, following which they undertake long-distance annual movements to form large molting aggregations at permanent water bodies (14,20). Moult sites, where birds from different populations share resources in close proximity, provide areas with high potential for virus reassortment.…”

Influence of moult and location on patterns of daily movement by Egyptian Geese in South Africa

“…The existence of moult migrations by waterfowl in southern Africa has long being suspected (e.g. Geldenhuys 1981;Milstein 1993) but has never been proven, not least because of the disparate directions in which migrating individuals move (see Cumming et al 2012). This study, together with our previous larger-scale analysis of the same dataset (Cumming et al 2012), thus provides empirical evidence of such migration and some indication of the distances that birds travel during these migrations.…”

“…The long-distance travel paths summarise these movements and provide compelling evidence that these birds undertaking moult migrations (Table 1, see fig. 2 in Cumming et al 2012). The existence of moult migrations by waterfowl in southern Africa has long being suspected (e.g.…”

“…The study had a sample size of only two, the transmitters functioned for <8 months, and the authors did not evaluate daily movements. More recently, Cappelle et al (2011) used satellite telemetry to study the movement patterns of Garganey (Anas querquedula), Comb Duck (Sarkidiornis melanotos), White-faced Whistling-Duck and Fulvous Whistling-Duck (Dendrocygna bicolor) in parts of central and West Africa in order to understand pathways of influenza transmission, and Cumming et al (2012) have analysed the seasonal movements of Egyptian Geese and Red-billed Teal (Anas erythrorhyncha). Neither of these two studies, however, evaluated daily movements.…”

Focusing Ecological Research for Conservation

“…Viewing dispersal as a product of integrating movement ecology and biogeography (Cumming et al 2012) enables conservation decisions at regional/continental-level. A broad-scale approach is particularly relevant given the mounting need for species to track climate-induced habitat changes across landscapes that are increasingly modified by humans (e.g., Vos et al 2008).…”