My research seeks to increase our understanding of migration ecology by connecting migration with other periods of the annual cycle through the use of intrinsic markers such as stable isotopes. Our understanding of the physiology, behavior, and ecology of migratory birds during stopover has been limited by the lack of knowledge of a bird’s point of departure as well as their ultimate destination. Recent advances in the use of intrinsic markers such as stable isotopes have enhanced our ability to discern at broad scales how breeding populations are spatially distributed throughout the annual cycle. Specifically, stable hydrogen isotopes (dD) are a powerful research tool in assigning origin for a migratory species because predictable continental patterns of dD in precipitation are highly correlated with dD of body tissues of birds due to trophic level interactions. This relationship is primarily associated with latitude, as southern latitudes are more enriched in dD than northern latitudes. Since many species of migrant warblers molt their feathers on or near their breeding grounds before migration, the isotopic signature of their feather should reflect the isotopic signature of that breeding site. Utilizing stable isotopes to identify the breeding location of migratory birds during migration enables the examination of in-depth questions about stopover ecology which were previously not possible. We can now integrate information about a bird’s breeding location with factors known to be important to the success of migration for innovative approaches that provide a more comprehensive understanding of stopover ecology of small passerines.

I propose to utilize stable isotopes to identify different breeding populations of Wilson’s Warblers (Wilsonia pussilla) utilizing riparian habitat in the southwestern U.S. during spring migration to examine intraspecific variations in migration stopover strategies.  Migration stopover strategies of interest include fuel deposition rates, stopover duration, orientation, and immune function.  To further our understanding of stopover ecology, results from the proposed research will be integrated with other know factors such as competition, predation, weather, and age of the bird that can all influence migration strategies of birds.

Master’s Thesis

Spatial and Temporal Migration Patterns of Wilson’s Warbler (Wilsonia pusilla) in the Southwest as Revealed by Stable Isotopes

 I used stable hydrogen isotopes (dD) to identify the breeding locations of Wilson’s Warbler (Wilsonia pusilla) migrating through five sites spanning a cross-section of the species’ southwestern migration route during the springs of 2003 and 2004.  At all five migration sites, I found a significant negative relationship between the date Wilson’s Warblers passed through the sampling station and dD values of their feathers. These data were consistent with a pattern of “leap-frog” migration, in which individuals that bred the previous season at southern latitudes migrated through migration stations earlier than individuals that had previously bred at more northern latitudes. I documented that this pattern was consistent across sites and in multiple years. This finding corroborates previous research conducted on Wilson’s Warbler during the fall migration. In addition, mean dD values became more negative across sampling stations from west to east, with the mean dD values at each station corresponding to different geographic regions of the Wilson’s Warblers’ western breeding range. These data indicate that Wilson’s Warblers passing through each station represented a specific regional subset of the entire Wilson’s Warbler western breeding range. As a result, habitat alterations at specific areas across the east–west expanse of the bird’s migratory route in the southwestern United States could differentially affect Wilson’s Warblers at different breeding areas. This migration information is critical for management of Neotropical migrants, especially in light of the rapid changes presently occurring over the southwestern landscape.

Publications: 

van Ripper C III, Paxton KL, O’Brien C, Shafroth P, and McGrath LJ (in press).  Rethinking avian response to tamarisk on the Lower Colorado River: a threshold hypothesis.  Restoration Ecology

Paxton KL, van Riper C III, Theimer TC and Paxton EH.  2007.  Spatial and temporal migration patterns of Wilson’s Warblers (Wilsonia pusilla) in the southwest as revealed by stable isotopes. Auk 124:162-175

Department of Biological Sciences
The University of Southern Mississippi
118 College Drive # 5018
Hattiesburg, MS 39406-0001
(601)266-4394
Kristina.l.paxton@usm.edu 

The University of Southern Mississippi. Last modified: 16 May, 2007 . Questions and Comments?
URL: http://www.usm.edu/mbrg/Kiristina.htm
AA/EOE/ADAI