Ruthrauff, Dan

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De populatie Calidris p. ptilocnemis (hierna: ptilocnemis), een ondersoort van de Beringstrandlopers, telt ongeveer 20.000 individuen. Deze ondersoort overwintert in het noorden van Cook Inlet, Alaska (61°N, 151°W). Dit is voor zover bekend het meest noordelijk gelegen overwinteringsgebied voor steltlopers in de gehele Stille Oceaan en het is bovendien het koudste gebied dat regelmatig overwinterende wadvogels herbergt. De extreme condities in het noorden van Cook Inlet zorgen voor hoge verblijfskosten en de jaarlijkse aangroei van zee- en landijs veroorzaken onvoorspelbare en moeilijke foerageer-omstandigheden voor de strandlopers. Op een experimentele manier, door de strandlopers van Alaska naar Texel te brengen, hebben we de energiehuishouding en het foerageergedrag van ptilocnemis vergeleken met een andere ondersoort van de Beringstrandlopers C.p. tschuktschorum (hierna: tschuktschorum). Deze ondersoort heeft een meer zuidelijk gelegen overwinteringsgebied rond de Stille Oceaan, langs de noordwest kust van Noord Amerika, waar de omstandigheden aanzienlijk milder zijn. De twee ondersoorten vertoonde vergelijkbare toenames in energieverbruik met temperatuurverlagingen, maar in vergelijking met tschuktschorum vertoonde ptilocnemis belangrijke verschillen in foerageer-ecofysiologie die voor een hogere energie-opname en doorstroom van de in de maag gekraakte schelpresten zorgde. Dit is waarschijnlijk het resultaat van fysiologische verschillen tussen de twee ondersoorten in verteringstelsel en niet van verschillen in foeragee gedrag of de begaafdheid in het vinden van prooien. In het wild vergroot ptilocnemis de maag en lever om de stofwisseling sneller en efficiënter te laten verlopen. Tegelijkertijd worden vetreserves opgeslagen die gebruikt worden om perioden van kou en voedselschaarste te kunnen overbruggen. Daarbij maakt de aanwezigheid van buitengewoon hoogwaardig voedsel in de vorm van Nonnetjes Macoma balthica het de steltlopers mogelijk hun winter door brengen in het hoge noorden van Alaska. Samengevat zorgen de aanwezigheid van deze hoogwaardige voedselbron in combinatie met de bovengenoemde fysiologische- en gedragsaanpassingen er voor dat ptilocnemis ondanks de ogenschijnlijke erbarmelijke omstandigheden in staat is te overwinteren in het koude Alaska.The nominate subspecies of Rock Sandpiper (Calidris p. ptilocnemis; hereafter ptilocnemis) numbers about 20,000 birds and winters primarily in upper Cook Inlet, Alaska (61°N, 151°W). This is the most-northerly site to host nonbreeding shorebirds in the Pacific Basin, and is also the world’s coldest site that regularly supports shorebirds in winter. Cook Inlet’s cold temperatures impose high energetic demands on ptilocnemis and create unique foraging hurdles due to the annual formation of extensive sea and shore-fast ice. We experimentally compared the metabolic output and foraging-related behaviors of ptilocnemis to individuals of another subspecies (C. p. tschuktschorum) that winters at more benign, southerly locations along the Pacific coast of northwest North America. The two subspecies exhibited similar metabolic responses to cold temperatures, but ptilocnemis displayed differences in foraging abilities that yielded higher rates of energy intake and food-waste processing compared to tschuktschorum. This was likely due to physiological differences between the two subspecies in digestive capacity and not differences in feeding behaviors or prey finding abilities. In the wild, ptilocnemis increases the size of its gizzard and liver to increase digestive capacity, and accumulates high fat stores to help endure periods of low food availability. In addition to these physiological adjustments, the winter occupancy of upper Cook Inlet by ptilocnemis is further facilitated by an abundance of unusually high-quality food resources, the bivalve Macoma balthica. Taken together, these unique behavioral, physiological, and environmental factors permit ptilocnemis to exploit the seemingly inhospitable conditions along Alaska’s frozen edge

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   University of GroningenOn the frozen edgeRuthrauff, DanIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2014Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Ruthrauff, D. (2014). On the frozen edge: Environmental and physiological constraints in the life history of anortherly-wintering shorebird. ([S.l.] ed.). [S.n.].CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 12-10-2022Stellingen behorende bij het proefschriftOn the frozen edgeEnvironmental and physiological constraints in the life historyof a northerly-wintering shorebirdDaniel Robert Ruthrauff1. Upper Cook Inlet, Alaska, is the world’s coldest site that regularly hosts nonbreeding shore-birds; these birds are almost exclusively Rock Sandpipers Calidris p. ptilocnemis (Chapter 3)2. Ptilocnemis Rock Sandpipers have one of the most restricted annual distributions of anyshorebird species (Chapters 2, 3)3. Ptilocnemis Rock Sandpipers carry unusually high fat stores for a nonbreeding shorebird; adearth of aerial predators in upper Cook Inlet during winter makes this otherwise risky trade-off between energy stores and escape performance feasible (Chapter 4)4. Compared to conspecifics, ptilocnemis Rock Sandpipers exhibit intrinsic adaptations related toresource acquisition but not apparently those related to energetic output (Chapters 5, 6) 5. In the context of energetic expenditure and physiological condition, wintering in upper CookInlet, Alaska, is akin to a months-long migration for ptilocnemis Rock Sandpipers (Chapter 7) 6. A warming climate may not necessarily bode well for cold-hardy sandpipers (Chapter 7) 7. Sometimes characteristics of the prey are more important than those of the predator: ultimately,ptilocnemis Rock Sandpipers are able to inhabit upper Cook Inlet, Alaska, during winter thanksto an abundance of high-quality Macoma (Chapter 7)8. Seemingly simple ecological questions invariably yield complicated results: ‘In many cases it isnot reasonable to expect to be able to make inferences from a single (best) model: biology is notsimple; why should we hope for a simple inference from a single model?’ —Burnham andAnderson 2002. 9. Sometimes the greatest hurdle is the first. ‘At this moment the VWA is still internally fightingover the requirements mentioned in the certificates. I think we will have a solution today.Please note that we also have no clue what agent will clear the birds.’ —quote from KLM agentin Amsterdam to another in Los Angeles regarding the intercontinental transport of RockSandpipers.10. Field efforts during winter in upper Cook Inlet, Alaska, are impractical: waist-deep mud, 10-mtides, remote field sites, 5-hour day lengths, incapacitating cold. A study approach that incorpo-rates natural history perspectives with laboratory experiments can nonetheless yield powerfulinsights in lieu of field observation. 11. Even where dedicated field efforts are possible, an approach combining both perspectives ispowerful and underutilized. Despite our vocation’s ‘almost medieval horror of experiment’(Heinroth, in Stresemann 1975) and the lament that ‘the pure study of nature languishes’(Beehler 2010), each approach obviously strengthens the other.12. Q: Why do ptilocnemis Rock Sandpipers winter in upper Cook Inlet, Alaska?A: Because they can.

On the frozen edge:Environmental and physiological constraints in the life history of a northerly-wintering shorebird

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On the frozen edge:Environmental and physiological constraints in the life history of a northerly-wintering shorebird

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