Differential Timing of Wilson's Warbler Migration in Alaska

Benson, Anna-Marie; Andres, Brad A.; Johnson, W. N.; Savage, Susan; Sharbaugh, Susan M.

doi:10.1676/05-085.1

Cited by 7 publications

(9 citation statements)

References 8 publications

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“…Contrary to our results, Benson et al (2006) reported juvenile Wilson's Warblers migrating before adults at four stopover sites in Alaska. Andres et al (2005) and Benson and Winker (2001) found mixed results in time of passage by age class of neotropical migrants moving through Alaska, though HY birds migrated significantly earlier than older birds in more than 70% of the species.…”

Section: Discussioncontrasting

confidence: 99%

“…Andres et al (2005) and Benson and Winker (2001) found mixed results in time of passage by age class of neotropical migrants moving through Alaska, though HY birds migrated significantly earlier than older birds in more than 70% of the species. These results might be driven by the proximity of the stopover sites to the breeding grounds and by delays in departure of adults of species that undergo a complete molt before fall migration (Carlisle et al 2005, Benson et al 2006. Benson et al (2006) suggested that when age-related differences during migration are evaluated, the location of the research site with respect to the breeding grounds could confound the results.…”

Section: Discussionmentioning

confidence: 99%

“…These results might be driven by the proximity of the stopover sites to the breeding grounds and by delays in departure of adults of species that undergo a complete molt before fall migration (Carlisle et al 2005, Benson et al 2006. Benson et al (2006) suggested that when age-related differences during migration are evaluated, the location of the research site with respect to the breeding grounds could confound the results. Variability in the results of these studies suggests that long-term monitoring at multiple stopover sites along the migration pathways is necessary for agerelated migration patterns to be determined accurately.…”

Section: Discussionmentioning

confidence: 99%

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Geographic Origins and Timing of Fall Migration of the Veery in Northern Colombia

et al. 2011

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confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Geographic Origins and Timing of Fall Migration of the Veery in Northern Colombia

et al. 2011

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“…The timing of arrival at the population level may depend on environmental conditions along the migration route, whereas, at the individual level, it may depend on characteristics such as sex, differences in age, social status, and body condition (Potti 1998, Mitrus et al 2005). Although intraspecific variation in the arrival times of migrants at breeding areas is common and widely reported (Sealy and Biermann 1987, Benson et al 2006), such variation has been poorly studied at wintering areas. Variation in body condition was apparently not the cause for the later arrival of smaller adult birds in my study because condition did not vary for any species throughout the season.…”

Section: Discussionmentioning

confidence: 99%

Fall migration of Empidonax flycatchers in northwestern Colombia

Colorado

2010

Journal of Field Ornithology

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South of Mexico, little is known about the fall migration patterns of most Neotropical migrants. I studied the migration of Empidonax flycatchers using mist-net surveys in northwestern Colombia from late September to mid-October in 4 yr (2003)(2004)(2005) 2008). Empidonax species were identified using linear measurements and color patterns. About 62% of captured individuals were reliably identified to species, with 86% identified as Willow Flycatchers (Empidonax traillii) and 14% as Alder Flycatchers (E. alnorum). No Acadian Flycatchers (E. virescens) were identified. Most birds captured were adults (84.9%) and, due to overlap in measurements, I was only able to determine the sex of 16.3% of the birds. Most Empidonax flycatchers migrated through northwestern Colombia during September and October, with individuals migrating through my study area over a period of at least 1 mo. Willow Flycatchers tended to migrate earlier than Alder Flycatchers, a pattern consistent with the fall movements of these two species at other locations. No captured flycatchers were molting either remiges or rectrices, and most (89%) had either no or slight traces of subcutaneous fat. No Empidonax flycatchers were recaptured, suggesting that stopover duration at my study site was brief. My results show that many Empidonax flycatchers can be identified as Willow and Alder flycatchers during the nonbreeding period, and such identification will enhance our knowledge of their geographical distribution and improve our understanding of possible patterns of segregation on their wintering grounds. RESUMEN. Migración otoñal de Empidonax en el noroeste de ColombiaSe sabe muy poco sobre los patrones de migración de la mayoría de las aves que se mueven al sur de México. Estudie la migración de papamoscas (Empidonax) utilizando redes de niebla para hacer censos en el noroeste de Colombia. El trabajo se llevó a cabo desde tarde en septiembre hasta mediados de octubre durante los años [2003][2004][2005] 2008. Se utilizaron medidas lineales y patrones de coloración para identificar las especies de Empidonax. Un 62% de las aves capturadas se pudieron identificar adecuadamente hasta el nivel de especie. De estos, un 86% resultaron ser individuos de E. traillii, y 14% de E. alnorum. El común E. virescens, no fue identificado. La mayoría de las aves fueron adultos (84.9%) y debido a un solapamiento en las medidas solo pude determinar el sexo del 16.3% de los individuos. La mayoría de los. Empidonax migran a través del noroeste de Colombia durante septiembre y octubre, con individuos migrando sobre elárea de estudio durante al menos un mes. E. traillii tiende a migrar más temprano que E. alnorum, lo que es un patrón consistente con los movimientos otoñales de esta especie a través de otras localidades. Ninguna de las aves capturadas estuvo mudando y la mayoría (89%) no tenía grasa subcutánea. Ninguna ave fue recapturada, sugiriendo que el tiempo de estadía en el lugar de estudio es breve. Mis resultados muestran que muchos Empidonax pueden ser identificados co...

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“…SMI) to show specific details (and effect magnitudes) for males and females in spring and fall. Because arrival dates during migration can vary between males and females in warblers (Francis and Cooke 1986, Yong et al 1998, Morris et al 2003, Smith and Moore 2005, Benson et al 2006, we graphed arrival-date distributions (using ordinal dates) for each species by sex and season to determine whether there were intraspecific differences in arrival time between sexes in our study population (Supplemental Material Figure S1). Some species exhibited sexual differences in arrival date in the fall, but not consistently among species.…”

Section: Data Analysesmentioning

confidence: 99%

Do migratory warblers carry excess fuel reserves during migration for insurance or for breeding purposes?

Holzschuh

Deutschlander

2016

The Auk

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Migration is energetically costly, and many passerines prepare for and maintain migration with hyperphagia and increased fuel or fat reserves. During spring migration, as they approach their breeding grounds, passerines may deposit fat in excess of what is needed to complete migration. Individuals may carry excess fuel reserves as insurance against potentially poor environmental conditions in early spring (insurance hypothesis). If this is true, individuals arriving early at northern stopover locations or their breeding grounds should have greater energy reserves than later arrivals. Alternatively, passerines may arrive in spring with excess fat to help offset the demands of breeding (breeding performance hypothesis). Given the energetic requirements of egg production, females may arrive with greater reserves than males if excess fat directly or indirectly offsets breeding costs. We analyzed the energetic condition of 12 warbler species mist-netted during migration from 1999 to 2012 at Braddock Bay Bird Observatory, Monroe County, New York, USA. This northern stopover location is near the breeding range (in relation to total migratory distance) for most of the parulid species we examined and, therefore, is a likely location to show carryover effects between migration and breeding. In 11 of the 12 species, energetic condition was greater in the spring than in the fall for both sexes; and in all 12 species, condition was greater in females than in males in both seasons. Contrary to the insurance hypothesis, condition increased with arrival date for most species during spring migration. Although better condition in females supports the breeding performance hypothesis, the presence of this difference in both seasons suggests that additional factors influence energetic condition in parulids. Given that males arrive in better condition in the spring than when they depart in the fall, individuals of both sexes may carry excess energy reserves during spring migration to potentially use for reproductive efforts.

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Differential Timing of Wilson's Warbler Migration in Alaska

Cited by 7 publications

References 8 publications

Geographic Origins and Timing of Fall Migration of the Veery in Northern Colombia

Geographic Origins and Timing of Fall Migration of the Veery in Northern Colombia

Fall migration of Empidonax flycatchers in northwestern Colombia

Do migratory warblers carry excess fuel reserves during migration for insurance or for breeding purposes?

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