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1 May 2011 Latitudinal Variation in Reproductive Strategies by the Migratory Louisiana Waterthrush
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Abstract

We evaluated hypotheses that seek to explain breeding strategies of the Louisiana Waterthrush (Parkesia motacilla) that vary across a latitudinal gradient. On the basis of data from 418 nests of color-banded individuals in southwestern Pennsylvania and 700 km south in the Georgia Piedmont, we found that clutch size in replacement nests and probability of renesting were significantly greater in Pennsylvania (clutch size 4.4; renesting probability 0.66) than in Georgia (clutch size 3.8; renesting probability 0.54). Contrasts of the remaining measures of breeding were not statistically significant, and, in particular, mean daily nest survival in the two study areas was nearly identical (0.974 in Pennsylvania; 0.975 in Georgia). An individual-based model of fecundity (i.e., number of fledged young per adult female), predicted that approximately half of the females in both Pennsylvania and Georgia fledge at least one young, and mean values for fecundity in Pennsylvania and Georgia were 2.28 and 1.91, respectively. On the basis of greater support for the food-limitation hypothesis than for the season-length hypothesis, the trade-off between breeding in a region with more food but making a longer migration may be greater for waterthrushes breeding farther north than for those breeding farther south.

© 2011 by The Cooper Ornithological Society. 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.
Brady J. Mattsson, Steven C. Latta, Robert J. Cooper, and Robert S. Mulvihill "Latitudinal Variation in Reproductive Strategies by the Migratory Louisiana Waterthrush," The Condor 113(2), (1 May 2011). https://doi.org/10.1525/cond.2011.090212
Received: 9 November 2009; Accepted: 1 January 2011; Published: 1 May 2011
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