Nestling Sex Ratios in Two Populations of Northern Mockingbirds

Schrand, Brett; Stobart, Christopher C.; Engle, Dorothy; Desjardins, Rebecca B.; Farnsworth, George

doi:10.1656/058.010.0215

Cited by 3 publications

(3 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Late in population establishment, when carrying capacity has placed limits on the number of breeding pairs, competition for breeding resources should shift towards production of more of the further‐dispersing sex (Julliard 2000, Schrand et al . 2011, Rutz 2012, Morandini et al . 2019).…”

Section: Discussionmentioning

confidence: 99%

“…As noted above, there is a widespread tendency for younger breeders to produce more cheaper-to-produce male offspring, which could also account for this outcome. Late in population establishment, when carrying capacity has placed limits on the number of breeding pairs, competition for breeding resources should shift towards production of more of the furtherdispersing sex (Julliard 2000, Schrand et al 2011, Rutz 2012, Morandini et al 2019. Additional pressure to avoid inbreeding or competing with the previous years' offspring would also be expected to accelerate the shift.…”

Section: Influence Of Population Dynamicsmentioning

confidence: 99%

See 1 more Smart Citation

Brood sex ratios in Merlins reflect characteristics of the associated breeding male and population density

Warkentin

Brooks

Lieske

et al. 2022

Ibis

View full text Add to dashboard Cite

Population‐level estimates of offspring sex ratios in birds typically approximate parity whereas biased ratios within nests are not uncommon. In sexually dimorphic raptors, the costs and relative fitness benefits of rearing male and female progeny vary with changing environmental circumstances. This may lead to substantial deviations from balanced investment in offspring of a particular sex by individual parents. Based on a 13‐year dataset for breeding Merlins Falco columbarius in Saskatoon, Canada, we used a model selection approach to assess the influence of parents, nest‐mates and nesting area on brood sex ratio during the nestling phase. The best model for predicting brood sex ratio included age of the breeding male and brood size for each nest (n = 127); nests with older male breeders and smaller brood sizes had more female young. The population‐level annualized average proportion of male offspring was 0.472 ± 0.017 (mean ± standard error), but tended towards greater production of female young during an initial period of population growth (8 years, 10–21 pairs; proportion male 0.435 ± 0.031) versus a period when the population fluctuated around a presumed carrying capacity (11 years, 24–33 pairs; proportion male 0.500 ± 0.017). Energetics appears to be a finely tuned mechanism driving sex ratio allocation in Merlins at both brood and population levels. Provisioning food for young in the nest represents the male's ability to successfully capture prey, reflecting his age and/or experience, as well as the availability of prey to the male. Confounding this mechanism to determine sex ratio allocation are the pressures created by population dynamics that dictate competition for resources both within the nest (brood size) and external to the nest (population density).

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Influence Of Population Dynamicsmentioning

confidence: 99%

Brood sex ratios in Merlins reflect characteristics of the associated breeding male and population density

Warkentin

Brooks

Lieske

et al. 2022

Ibis

View full text Add to dashboard Cite

show abstract

“…Fledgling dispersal is sex biased with females more likely to disperse (Curry and Grant 1990). Sex ratios have not been investigated in this species; however, in a congener, the northern mockingbird Mimus polyglottus, nestling sex ratios differ between populations (Schrand et al 2011). Northern mockingbirds may overproduce females (the dispersive sex) in high density populations to avoid competition between parents and offspring for food (Schrand et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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

McNew

Knutie

Clayton

2020

Journal of Avian Biology

View full text Add to dashboard Cite

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.

show abstract

No Seasonal Variation of the Sex Ratio in the Common Kingfisher Alcedo atthis Broods

et al. 2020

View full text Add to dashboard Cite

Nestling Sex Ratios in Two Populations of Northern Mockingbirds

Cited by 3 publications

References 19 publications

Brood sex ratios in Merlins reflect characteristics of the associated breeding male and population density

Brood sex ratios in Merlins reflect characteristics of the associated breeding male and population density

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

No Seasonal Variation of the Sex Ratio in the Common Kingfisher Alcedo atthis Broods

Contact Info

Product

Resources

About