Exploring the environmental drivers of waterfowl movement in arid landscapes using first-passage time analysis

dc.contributor.authorHenry, Dominic A W
dc.contributor.authorAment, Judith M
dc.contributor.authorCumming, Graeme S
dc.date.accessioned2021-10-08T07:08:26Z
dc.date.available2021-10-08T07:08:26Z
dc.date.issued2016
dc.description.abstractBackgroundThe movement patterns of many southern African waterfowl are typified by nomadism, which is thought to be a response to unpredictable changes in resource distributions. Nomadism and the related movement choices that waterfowl make in arid environments are, however, poorly understood. Tracking multiple individuals across wide spatiotemporal gradients offers one approach to elucidating the cues and mechanisms underpinning movement decisions. We used first-passage time (FPT) to analyse high spatial and temporal resolution telemetry data for Red-billed Teal and Egyptian Geese across a 1500km geographical gradient between 2008 and 2014. We tested the importance of several environmental variables in structuring movement patterns, focusing on two competing hypotheses: (1) whether movements are driven by resource conditions during the current period of habitat occupation (reactive movement hypothesis), or (2) whether movements are structured by shifts in the magnitude and direction of environmental variables at locations prior to occupation (prescient movement hypothesis).ResultsAn increase in rainfall at a 32day lag (i.e., prior to wetland occupancy), along with tagging site, were significant predictors of FPT in both waterfowl species. There was a positive relationship between NDVI and FPT for Egyptian Geese during this 32day period; the relationship was negative for Red-billed Teal. Consistent with findings for migratory grazing geese, Egyptian Geese prioritised food quality over food biomass. Red-billed Teal showed few immediate responses to wetland filling, contrary to what one would predict for a dabbling duck, suggesting high dietary flexibility. Our results were consistent with the prescient movement hypothesis.ConclusionsUsing FPT analysis we showed that the proximate drivers of southern African waterfowl movement are the dynamics of rainfall and primary productivity. Waterfowl appeared to be able to perceive and respond to temporal shifts in resource conditions prior to habitat patch occupation. This in turn suggests that their movements in semi-arid landscapes may be underpinned by intimate knowledge of the local environment; waterfowl pursue a complex behavioural strategy, locating suitable habitat patches proactively, rather than acting as passive respondents.
dc.identifier.apacitationHenry, D. A. W., Ament, J. M., & Cumming, G. S. (2016). Exploring the environmental drivers of waterfowl movement in arid landscapes using first-passage time analysis. <i>Movement Ecology</i>, 4(1), 174 - 177. http://hdl.handle.net/11427/34580en_ZA
dc.identifier.chicagocitationHenry, Dominic A W, Judith M Ament, and Graeme S Cumming "Exploring the environmental drivers of waterfowl movement in arid landscapes using first-passage time analysis." <i>Movement Ecology</i> 4, 1. (2016): 174 - 177. http://hdl.handle.net/11427/34580en_ZA
dc.identifier.citationHenry, D.A.W., Ament, J.M. & Cumming, G.S. 2016. Exploring the environmental drivers of waterfowl movement in arid landscapes using first-passage time analysis. <i>Movement Ecology.</i> 4(1):174 - 177. http://hdl.handle.net/11427/34580en_ZA
dc.identifier.issn2051-3933
dc.identifier.ris TY - Journal Article AU - Henry, Dominic A W AU - Ament, Judith M AU - Cumming, Graeme S AB - BackgroundThe movement patterns of many southern African waterfowl are typified by nomadism, which is thought to be a response to unpredictable changes in resource distributions. Nomadism and the related movement choices that waterfowl make in arid environments are, however, poorly understood. Tracking multiple individuals across wide spatiotemporal gradients offers one approach to elucidating the cues and mechanisms underpinning movement decisions. We used first-passage time (FPT) to analyse high spatial and temporal resolution telemetry data for Red-billed Teal and Egyptian Geese across a 1500km geographical gradient between 2008 and 2014. We tested the importance of several environmental variables in structuring movement patterns, focusing on two competing hypotheses: (1) whether movements are driven by resource conditions during the current period of habitat occupation (reactive movement hypothesis), or (2) whether movements are structured by shifts in the magnitude and direction of environmental variables at locations prior to occupation (prescient movement hypothesis).ResultsAn increase in rainfall at a 32day lag (i.e., prior to wetland occupancy), along with tagging site, were significant predictors of FPT in both waterfowl species. There was a positive relationship between NDVI and FPT for Egyptian Geese during this 32day period; the relationship was negative for Red-billed Teal. Consistent with findings for migratory grazing geese, Egyptian Geese prioritised food quality over food biomass. Red-billed Teal showed few immediate responses to wetland filling, contrary to what one would predict for a dabbling duck, suggesting high dietary flexibility. Our results were consistent with the prescient movement hypothesis.ConclusionsUsing FPT analysis we showed that the proximate drivers of southern African waterfowl movement are the dynamics of rainfall and primary productivity. Waterfowl appeared to be able to perceive and respond to temporal shifts in resource conditions prior to habitat patch occupation. This in turn suggests that their movements in semi-arid landscapes may be underpinned by intimate knowledge of the local environment; waterfowl pursue a complex behavioural strategy, locating suitable habitat patches proactively, rather than acting as passive respondents. DA - 2016 DB - OpenUCT DP - University of Cape Town IS - 1 J1 - Movement Ecology LK - https://open.uct.ac.za PY - 2016 SM - 2051-3933 T1 - Exploring the environmental drivers of waterfowl movement in arid landscapes using first-passage time analysis TI - Exploring the environmental drivers of waterfowl movement in arid landscapes using first-passage time analysis UR - http://hdl.handle.net/11427/34580 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/34580
dc.identifier.vancouvercitationHenry DAW, Ament JM, Cumming GS. Exploring the environmental drivers of waterfowl movement in arid landscapes using first-passage time analysis. Movement Ecology. 2016;4(1):174 - 177. http://hdl.handle.net/11427/34580.en_ZA
dc.language.isoeng
dc.publisher.departmentFitzPatrick Institute of African Ornithology
dc.publisher.facultyFaculty of Science
dc.sourceMovement Ecology
dc.source.journalissue1
dc.source.journalvolume4
dc.source.pagination174 - 177
dc.source.urihttps://dx.doi.org/10.1186/s40462-016-0073-x
dc.subject.otherWaterfowl
dc.subject.otherNDVI
dc.subject.otherRainfall
dc.subject.otherSouthern Africa
dc.subject.otherNomadic
dc.subject.otherFirst-passage time
dc.subject.otherAlopochen aegyptiaca
dc.subject.otherAnas erythrorhyncha
dc.titleExploring the environmental drivers of waterfowl movement in arid landscapes using first-passage time analysis
dc.typeJournal Article
uct.type.publicationResearch
uct.type.resourceJournal Article
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