Stopover Ecology of Autumn Landbird Migrants in the Boise Foothills of Southwestern Idaho

Abstract

Published as "Stopover Ecology of Autumn Landbird Migrants in the Boise Foothills of Southwestern Idaho" in The Condor 107(2):244-258. © 2005 by the Regents of the University of California. Copying and permissions notice: Authorization to copy this content beyond fair use (as specified in Sections 107 and 108 of the U. S. Copyright Law) for internal or personal use, or the internal or personal use of specific clients, is granted by the Regents of the University of California for libraries and other users, provided that they are registered with and pay the specified fee via Rightslink® on Caliber (http://caliber.ucpress.net/) or directly with the Copyright Clearance Center, http://www.copyright.com. DOI: 10.1650/7808[244] Abstract. The topography of western North America provides a complex landscape for landbird migrants, and stopover patterns in this region are poorly understood. We examined seven years of stopover data (1997)(1998)(1999)(2000)(2001)(2002)(2003)) from a montane area in southwestern Idaho to determine whether this area provides suitable stopover habitat. We compared the proportion of birds recaptured, stopover duration, and changes in energetic condition within and among species and between two mist-netting sites located in different habitats. The proportion of birds recaptured ranged from zero to over 20%, and fewer than 5% of individuals were recaptured in most species. Mean minimum stopover durations from recapture data ranged from 1 to 10 days; most species averaged less than 6 days. Stopover duration estimates from open-population models were comparable but generally greater than estimates from recapture data. As found in stopover studies from other regions, stopover metrics varied within and among species in Idaho. However, most migrants in this study exhibited an ability to gain mass, evidenced both by recapture data and by regression of energetic condition against time since sunrise. These data imply that montane habitats in Idaho are suitable stopover sites. It follows that these habitats might serve an important role for many landbird migrants during the period of late summer molt and autumn migration, a time when many lowland areas of the West, including some riparian systems, are especially arid. We suggest that including montane nonriparian habitats in future stopover ecology studies will allow for a more complete understanding of migrant habitat needs in the West.Key words: habitat suitability, Idaho, Intermountain West, landbird migration, stopover ecology. Ecología de Aves Migrantes de Otoño Durante Períodos de Escala en el Piedemonte de Boise, Suroeste de IdahoResumen. La topografía del oeste de Norte América representa un paisaje complejo para las aves terrestres migratorias, y los patrones de escala migratoria en esta región son poco conocidos. En este estudio examinamos datos de escalas migratorias colectados a través de siete años (1997)(1998)(1999)(2000)(2001)(2002)(2003) en un área montana del suroeste de Idaho para determinar si esta área provee hábitats de escala adecuado...

Landbird Migration in the American West: Recent Progress and Future Research Directions

“…Both Carlisle et al (2004) and DeLong et al (2005) discussed the possibility that montane woodlands in and around the Great Basin may provide cooler microclimates and higher food availability during late summer and early autumn than surrounding lowlands and thus provide more favorable habitat to migrants at those times of year and Patten et al (2003) suggested the same pattern for the Sonoran Desert. In fact, Carlisle (2005) found that whereas arthropod and fruit availability at an autumn stopover site in southwestern Idaho differed significantly among years, most migrant species were able to gain mass in each year, indicating the presence of adequate food sources for re-fueling at this montane site. Recently, Wightman et al (2007) showed that ponderosa pine forests with a deciduous component were also important for autumn migrants.…”

“…In particular, applications of established techniques (mist-netting and associated analyses) to previously unstudied areas, and use of an important and novel technique (plasma metabolite sampling), have contributed to a growing body of literature pertaining to stopover ecology and habitat suitability (Wang et al 1998, Kelly et al 2002a, Cerasale 2004, Carlisle et al 2005b, Guglielmo et al 2005, Paxton et al 2007b.…”

“…Interestingly, the arrival condition indices for immature birds were significantly lower than those for adults, suggesting that their need for mass gain was greater. Also, Carlisle et al (2005b) investigated autumn stopover ecology at a southwestern Idaho montane site with deciduous shrubs adjacent to conifer forest and found that most species were able to gain mass, suggesting the potential importance of montane habitats to southbound migrants (see above).…”

“…Although mass changes among recaptured birds provide valuable insights into the suitability of stopover sites, such data require intensive (ideally daily) sampling, and recapture rates are low, often less than 10 % (e.g., Carlisle et al 2005b). An emerging technique, plasma metabolite profiling, enables investigators to make among-site and between-season comparisons of fuel deposition rate with reduced sample size requirements (Guglielmo et al 2005).…”

Effects of Regional Cold Fronts and Localized Weather Phenomena on Autumn Migration of Raptors and Landbirds in Southwest Idaho

“…Each method of counting, capture of landbirds in mist nets and counts of raptors, is widely recognized as valid for monitoring avian migration. Unlike raptor counts, however, landbirdcapture data are not a measure of birds actually migrating at the time of observation, and Lucky Peak is a productive stopover point (Carlisle et al 2005). Though our primary goal is to study birds during their migration, not all birds caught on a given day have necessarily been migrating that day or the night before, evidenced by the fact that up to 15% of individual birds are recaptured up to several days after initial capture (Carlisle et al 2005).…”