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1 October 2009 Lipid Reserves of Lesser Scaup (Aythya affinis) Migrating Across a Large Landscape are Consistent with the “Spring Condition” Hypothesis
Michael J. Anteau, Alan D. Afton
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Abstract

The “spring condition” hypothesis (SCH) states that nutrition during spring migration affects survival, reproductive success, and, ultimately, population size of migratory birds. The North American population of Lesser Scaup (Aythya affinis) has experienced a marked decline, apparently because of poor recruitment. An important prediction of the SCH is that female Lesser Scaup have low lipid reserves during spring migration. We previously reported that lipid reserves and body mass of females collected on migratory stopover areas in northwestern Minnesota in springs 2000–2001 were lower than those on the same areas in the 1980s and markedly lower than those collected at Pool 19 of the Mississippi River in 2000–2001, an important preceding stopover area. However, it was unclear whether these findings represented a site-specific result or a landscape-scale phenomenon. Accordingly, we examined lipid and body mass of 641 female Lesser Scaup migrating across seven eco-physiographic regions of Iowa, Minnesota, and North Dakota during springs 2003–2005. We found that lipids and body mass of females throughout the Upper Midwest were similar to or less than the low values documented in northwestern Minnesota in springs 2000–2001 and markedly lower than those of females at Pool 19 in springs 2000–2001. Accordingly, our results are consistent with a prediction of the SCH, because lipid and body mass of females are low throughout this large landscape, lower than at an important preceding stopover area, and lower than all historical values. Finally, our results suggest the potential for cross-seasonal influences of nutrition on recruitment and that a stronger management focus on spring migration habitats may be necessary for conservation and recovery of declining migratory birds, especially Lesser Scaup.

© 2009 by The American Ornithologists' Union. All rights reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press's Rights and Permissions website, http://www.ucpressjournals.com/reprintInfo.asp.
Michael J. Anteau and Alan D. Afton "Lipid Reserves of Lesser Scaup (Aythya affinis) Migrating Across a Large Landscape are Consistent with the “Spring Condition” Hypothesis," The Auk 126(4), 873-883, (1 October 2009). https://doi.org/10.1525/auk.2009.08193
Received: 30 September 2008; Accepted: 8 May 2009; Published: 1 October 2009
JOURNAL ARTICLE
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KEYWORDS
Aythya affinis
body condition
lesser scaup
lipids
migratory fattening
population regulation
stopover area
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