Trapping methods can bias age ratio in samples of passerine populations

Domènech, Jordi; Senar, Juan Carlos

doi:10.1080/00063659709461070

Cited by 23 publications

(26 citation statements)

References 12 publications

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“…Generally, sex-ratio skews are particularly important if they have net negative ramifications on productivity, where lower bird densities coupled with skewed adult sex ratios result in overall reduced reproductive success. In capture-recapture studies, productivity can be estimated by the ratio of juveniles to adults trapped (Dome`nech & Senar, 1997).…”

Section: Introductionmentioning

confidence: 99%

Demography of an Afrotropical passerine in a highly fragmented landscape

Githiru

Lens

2005

Animal Conservation

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Demographic attributes of discrete subpopulations of animals and plants that constitute a larger (meta)population network may affect the strength and direction of local population responses to habitat loss or degradation. To address this question in an Afrotropical context, we studied survival rates, population densities, sex ratios and age distributions in seven white-starred robin Pogonocichla stellata populations inhabiting differently sized forest remnants in a highly fragmented Kenyan landscape. Sex ratios were strongly male biased, especially during the non-breeding season, but the level of bias did not differ between age groups nor fragment sizes. Juvenile to adult ratios were smallest in the mediumsized fragment, but did not differ between the largest and smallest fragments. Low population density combined with a skewed sex ratio in the medium-sized fragment pointed towards a local scarcity of females, which was supported by the presence of unmated territorial males. Based on capture-recapture analysis, all populations were considered stable on average. When combining demographic patterns with those emerging from a recent population genetic study and removal experiment, our results support the notion that small populations inhabiting tiny habitat remnants may play an important role in augmenting the long-term survival of spatially structured populations.

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Section: Introductionmentioning

confidence: 99%

Demography of an Afrotropical passerine in a highly fragmented landscape

Githiru

Lens

2005

Animal Conservation

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“…Age-ratio analysis assumes that ages can be reliably distinguished, populations are not fluctuating strongly, and immigration or emigration do not occur during the survey period (Ricklefs 1997, Udevitz and Ballachey 1998, Conn et al 2005, Ricklefs and Rohwer 2005. Biased estimates from museum materials could also arise if collectors targeted or avoided a particular age class, if age classes differed in ''collectibility,'' or if collections occurred in areas preferred or avoided by an age class (Domenech and Senar 1997, Ricklefs 1997, Rohwer 2004, Conn et al 2005, Ricklefs and Rohwer 2005, Peery et al 2007). Direct comparisons of demographic estimators developed from age-ratio analysis with conventional measures of fecundity and survival are notably lacking (Newton 1999, Green 2004, Bonenfant et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Reconstructing the Historic Demography of an Endangered Seabird

Beissinger

Peery

2007

Ecology

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Abstract. Reducing extinction risk for threatened species requires determining which demographic parameters are depressed and causing population declines. Museum collections may constitute a unique, underutilized resource for measuring demographic changes over long time periods using age-ratio analysis. We reconstruct the historic demography of a U.S. federally endangered seabird, the Marbled Murrelet (Brachyramphus marmoratus), from specimens collected ;100 years ago for comparison with predictions from comparative analyses and with results from contemporary field studies using both age-ratio analysis and conventional demographic estimators. Reproduction in the late 1800s and early 1900s matched predictions from comparative analysis, but was 8-9 times greater than contemporary estimates, whereas adult survival was unchanged. Historic reproductive rates would support stable populations, but contemporary levels should result in population declines. Contemporary demographic estimates derived from age-ratio analysis were similar to estimates from conventional estimators. Using museum specimens to reconstruct historic demography provides a unique approach to identify causes of decline and to set demographic benchmarks for recovery of endangered species that meet most assumptions of age-ratio analysis.

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“…Siskins were trapped once a week at baited feeders using traps, mist and clap nets (Domènech and Senar 1997) and were marked with numbered aluminium rings. In the Sarrià ringing station, there are two subpopulations of wintering siskins, the residents and the transients (Senar et al 1992).…”

Section: Methodsmentioning

confidence: 99%

Prior residence effect in wintering male Eurasian siskins is not related to resource holding power

Senar

Pascual

2015

Behav Ecol Sociobiol

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Animals competing for resources follow a general rule for which prior residents usually win contests over intruders. This prior residence effect might arise because animals possess a genetically fixed convention so that 'residents always win' (i.e. an uncorrelated asymmetry), because residents have a higher resource holding power (RHP) than intruders or because residents have a higher motivation to defend territories (i.e. pay-off asymmetry). The discrimination between these different hypotheses, though, has proven to be difficult. Eurasian siskins (Spinus spinus) provide us with an adequate opportunity to test for the effect of RHP on the prior residence effect. Siskins show two different strategies while in the wintering grounds: residents remain for several weeks on a given location while transients continuously move and residents are dominant over transients. The black bib area of male siskins signals their RHP. In this study, we compared the black bib area of a large sample of male resident and transient siskins and we found no differences between the two subpopulations. Hence, residence status in this species is not related to black bib size, which is a good proxy for RHP. Our results support the view that asymmetries in RHP are not required to explain the prior residence effect. We discuss the important implications that it has on the evolution of partial migration.

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Trapping methods can bias age ratio in samples of passerine populations

Cited by 23 publications

References 12 publications

Demography of an Afrotropical passerine in a highly fragmented landscape

Demography of an Afrotropical passerine in a highly fragmented landscape

Reconstructing the Historic Demography of an Endangered Seabird

Prior residence effect in wintering male Eurasian siskins is not related to resource holding power

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