Female-biased sex ratio, polygyny, and persistence in the endangered Southwestern Willow Flycatcher (<i>Empidonax traillii extimus</i>)

Kus, Barbara E.; Howell, Scarlett L.; Wood, Dustin A.

doi:10.1650/condor-16-119.1

Cited by 12 publications

(15 citation statements)

References 39 publications

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“…Much like other songbirds with a tendency for conspecific attraction, Willow Flycatchers in California have exceptionally short breeding seasons, lasting less than three months (Sedgwick 2000); Willow Flycatcher territories are often clustered within larger habitat patches (Walkinshaw 1966); and polygyny is observed when population densities are sufficiently high (Prescott 1986, Hahn and Silverman 2006, Mathewson et al 2013, Kus et al 2017. For these reasons, providing social cues at restored…”

Section: Introductionmentioning

confidence: 99%

Using conspecific broadcast for Willow Flycatcher restoration

Schofield¹,

Loffland²,

Siegel³

et al. 2018

ACE

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ABSTRACT. Willow Flycatcher (Empidonax traillii) populations have been in decline across the western United States for decades. California populations are especially vulnerable with fewer than 500 pairs remaining in the state. Declines and local extirpations continue despite extensive habitat restoration and improved management designed to help conserve Willow Flycatchers. Such efforts may have failed to help reverse these trends in part because Willow Flycatchers rarely recolonize habitat after extirpation, regardless of present habitat suitability. Failure to recolonize habitat may be because prospecting Willow Flycatchers, like many other songbird species, assess habitat suitability based on the presence of conspecifics, making them unlikely to consider unoccupied habitat as potential breeding grounds. If true, broadcasting conspecific vocalizations in suitable but unoccupied habitat could help facilitate recolonization. During the 2016 and 2017 breeding seasons, we assessed the effectiveness of providing artificial social cues as a means of restoring Willow Flycatchers to suitable but unoccupied restored meadows in the Sierra Nevada mountains of California. We selected 14 experimental meadows where conspecific songs were broadcast during the settlement and breeding periods and 19 control meadows where no broadcasts took place. All the meadows were recently restored, contain high-quality habitat with hydrological characteristics and vegetation similar to meadows where Sierra Willow Flycatchers successfully breed, and were confirmed to be unoccupied in the year prior to their inclusion in the study. We observed Willow Flycatchers at five of 14 experimental meadows (35.75%) during the breeding season and at one of 19 control meadows (5.3%). We found that habitat characteristics also play a role in the efficacy of this technique, as Willow Flycatcher presence was highly significantly related to the combination of both the experimental treatment and meadow size. These results demonstrate that within large, restored meadows, conspecific broadcasts may be an effective strategy for restoring Willow Flycatchers. Utilisation de la diffusion de chants de conspécifiques pour le rétablissement du Moucherolle des saulesRÉSUMÉ. Les populations de Moucherolles des saules (Empidonax traillii) sont à la baisse dans tout l'ouest des États-Unis depuis des décennies. Les populations californiennes sont particulièrement vulnérables, comptant moins de 500 couples. Les baisses et les disparitions locales se produisent toujours malgré les efforts importants de restauration d'habitat et d'aménagement ciblant la conservation de ces moucherolles. Ces efforts pourraient avoir failli à renverser les tendances, en partie en raison du fait que le Moucherolle des saules recolonise rarement un habitat qu'il a abandonné, sans égard aux conditions actuelles propices. L'échec de la recolonisation d'habitat est peut-être attribuable au fait que les moucherolles qui prospectent, tout comme de nombreuses autres espèces d'oiseaux chanteurs, évaluen...

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Section: Introductionmentioning

confidence: 99%

Using conspecific broadcast for Willow Flycatcher restoration

Schofield¹,

Loffland²,

Siegel³

et al. 2018

ACE

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“…Sex ratio manipulation has been documented across avian orders, including Bucerotiformes, Ciconiiformes, Columbiformes, Psittaciformes, Strigiformes, and within various Old and New World passerine families, such as Acrocephalidae, Estrildidae, Icteridae, Mimidae, Muscicaptidae, Paridae, Sturnidae, Troglodytidae and Tyrannidae (Sheldon 1998, Hasselquist and Kempenaers 2002, Komdeur and Pen 2002, Benito and González-Solís 2007, Goerlich-Jansson et al 2013, Kamiński et al 2015, Kus et al 2017. This pattern, coupled with a conserved physiological mechanism linked to sex determination (stress hormones), suggests that the ability to manipulate sex ratios exists broadly across avian linages.…”

Section: Discussionmentioning

confidence: 99%

No evidence of sex ratio manipulation by Galápagos mockingbirds in response to environment

McNew

Knutie

Clayton

2020

Journal of Avian Biology

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Birds can adjust investment in reproduction by altering the sex ratios of their broods. When one sex is more costly to raise than the other, producing either more male or female offspring can lower the costs of reproduction. Biasing sex ratios can also be advantageous if the expected fitness of male versus female offspring differs. Here, we investigated whether Galápagos mockingbirds Mimus parvulus bias sex ratios in response to variation in rainfall. Female mockingbirds are smaller and thus females may reduce the costs of reproduction by biasing sex ratios in favor of female offspring. We quantified sex ratios in 131 mockingbird broods over four years with variable rainfall (2012, 2013, 2015 and 2016). We found no evidence that mockingbirds adjusted sex ratios in response to environmental conditions. Mockingbirds may not adjust sex ratios either because they lack the ability to do so, or because the costs of manipulation outweigh its benefits.

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“…Accordingly, birds can adjust their mating behavior in response to variation in the ASR (e.g., Kus et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…When the ASR is female-biased (or even), females care for the young and males compete for females, whereas species with male-biased ASR often exhibit sex-role reversal and female competition for males (Sz ekely et al 2014, Jennions et al 2017. Accordingly, birds can adjust their mating behavior in response to variation in the ASR (e.g., Kus et al 2017).…”

Section: Discussionmentioning

confidence: 99%

“…Adult sex ratios are key variables influencing population demography, breeding systems, and many aspects of the behavior of birds (Donald 2007, Sz ekely et al 2014. Variation in the sex ratios of adults has been linked to the social environment (Liker et al 2013), parental quality (Ellegren et al 1996), sex roles and mating systems (Emlen and Oring 1977, Liker et al 2013, Sz ekely et al 2014, Kus et al 2017, Gomes et al 2018, cooperative breeding (Komdeur et al 1997), and size dimorphism (Weatherhead andTeather 1991, Sz ekely et al 2014), and may have conservation implications (Venables andBrooke 2015, Ramula et al 2018).…”

Section: Introductionmentioning

confidence: 99%

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Skewed adult sex ratios inColumbinaground doves from Venezuela

Bosque

Pacheco

2019

J. Field Ornithol.

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Although sex ratios at conception are close to 1:1 in most species of birds, skewed adult sex ratios (ASRs) are not uncommon in populations of birds, and occur frequently at local and temporal scales. ASRs are a key variable influencing population demography, breeding systems, and many aspects of the behavior of birds. However, factors contributing to variation in ASRs, particularly for tropical species of birds, remain poorly understood. By compiling information from field sites and records from bird collections, we found that the ASRs of four species of Columbina ground doves from Venezuela deviated significantly from parity. Males of all species outnumbered females at all field sites and in all museum samples. ASR, expressed as the proportion of males, ranged from 0.59 for Common Ground Doves (Columbina passerina) to 0.65 for Plain‐breasted Ground Doves (Columbina minuta) in the overall samples. Males outnumbered females by ~ 44% in Common Ground Doves and by 85% in Plain‐breasted Ground Doves. Our samples included birds collected as specimens over many decades and across broad geographic areas, suggesting that skewed ASRs are characteristic of Venezuelan ground doves. Because these ground doves do not exhibit pronounced sexual size dimorphism and have socially monogamous breeding systems, selection would be expected to favor equal investment in males and females at hatching. As such, we argue that greater post‐hatching mortality of females, rather than deviations in the sex ratio of embryos, is the main cause of the biased ASRs of Venezuelan ground doves.

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Female-biased sex ratio, polygyny, and persistence in the endangered Southwestern Willow Flycatcher (Empidonax traillii extimus)

Cited by 12 publications

References 39 publications

Using conspecific broadcast for Willow Flycatcher restoration

Using conspecific broadcast for Willow Flycatcher restoration

No evidence of sex ratio manipulation by Galápagos mockingbirds in response to environment

Skewed adult sex ratios inColumbinaground doves from Venezuela

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