Changes in Sex Ratio Occurring with Age in Young California Quail in Central Otago, New Zealand

Bird-Banding ◽  
1957 ◽  
Vol 28 (3) ◽  
pp. 145 ◽  
Author(s):  
G. R. Williams
Keyword(s):  
New Zealand ◽  
Sex Ratio ◽  
California Quail

Feral horse demography and population growth in the Kaimanawa Ranges, New Zealand

2004 ◽  
Vol 31 (2) ◽  
pp. 119 ◽  
Author(s):  
Wayne L. Linklater ◽  
Elissa Z. Cameron ◽  
Ed O. Minot ◽  
Kevin J. Stafford
Keyword(s):  
New Zealand ◽  
Sex Ratio ◽  
Population Growth ◽  
Management Problem ◽  
Feral Horses ◽  
Sex Structure ◽  
Young Males ◽  
Feral Horse ◽  
Adult Sex Ratio ◽  
Female Bias

Although feral horses are a common management problem in numerous countries, detailed and long-term demographic studies are rare. We measured the age and sex structure, and pregnancy, birth and death rates in a population of 413 feral horses in New Zealand during 1994–98 and used them to construct a model simulating population growth. Survivorship increased with age (0–1 years old = 86.8%, 1–2 = 92.3%, 2–4 = 92.4%, ≥�4 years old = females 94%, males 97% per annum). Birth sex ratio parity, a slight female bias in the adult sex ratio (92 males per 100 females) and higher adult male survivorship indicated lower average survivorship for young males than females that was not detectable in mortality statistics. Pregnancy and foaling rates for mares ≥�2 years old averaged 79 and 49%, respectively. Foaling rates increased as mares matured (2–3-year-old mares = 1.9%, 3–4 = 20.0%, 4–5 = 42.1%, ≥�5 = 61.5% per annum). Young mares had higher rates of foetal and neonatal mortality (95% of pregnancies failed and/or were lost as neonatal foals in 2–3-year-old mares, 70.6% in 3–4, 43.2% in 4–5, and 31% in mares ≥�5 years old). Population growth was 9.6% per annum (9.5–9.8, 95% CI) without human-induced mortalities (i.e. r = 0.092). Our model, standardised aerial counts, and historical estimates of annual reproduction suggest that the historical sequence of counts since 1979 has overestimated growth by ~50% probably because of improvements in count effort and technique.

Provenance and sex ratio of Black-browed Albatross,Thalassarche melanophrys, breeding on Campbell Island, New Zealand

2001 ◽  
Vol 101 (4) ◽  
pp. 329-334 ◽  
Author(s):  
Peter J. Moore ◽  
Theresa M. Burg ◽  
Graeme A. Taylor ◽  
Craig D. Millar
Keyword(s):  
New Zealand ◽  
Sex Ratio ◽  
Campbell Island

scholarly journals The sex ratio of babies born after single embryo transfers, Australia and New Zealand, 2002-2006

2009 ◽  
Vol 92 (3) ◽  
pp. S253
Author(s):  
J.H. Dean ◽  
M. Chapman ◽  
E.A. Sullivan
Keyword(s):  
New Zealand ◽  
Sex Ratio

The California Quail in New Zealand

1952 ◽  
Vol 16 (4) ◽  
pp. 460 ◽  
Author(s):  
Gordon R. Williams
Keyword(s):  
New Zealand ◽  
California Quail

scholarly journals Social selection is density dependent but makes little contribution to total selection in New Zealand giraffe weevils

2021 ◽  
Vol 288 (1952) ◽  
pp. 20210696
Author(s):  
David N. Fisher ◽  
Rebecca J. LeGrice ◽  
Christina J. Painting
Keyword(s):  
Body Size ◽  
New Zealand ◽  
Sex Ratio ◽  
Evolutionary Change ◽  
The Body ◽  
Direct Selection ◽  
Social Selection ◽  
Phenotypic Assortment ◽  
Focal Individual ◽  
Total Selection

Social selection occurs when traits of interaction partners influence an individual's fitness and can alter total selection strength. However, we have little idea of what factors influence social selection's strength. Further, social selection only contributes to overall selection when there is phenotypic assortment, but simultaneous estimates of social selection and phenotypic assortment are rare. Here, we estimated social selection on body size in a wild population of New Zealand giraffe weevils ( Lasiorhynchus barbicornis ). We measured phenotypic assortment by body size and tested whether social selection varied with sex ratio, density and interacted with the body size of the focal individual. Social selection was limited and unaffected by sex ratio or the size of the focal individual. However, at high densities social selection was negative for both sexes, consistent with size-based competitive interactions for access to mates. Phenotypic assortment was always close to zero, indicating negative social selection at high densities will not impede the evolution of larger body sizes. Despite its predicted importance, social selection may only influence evolutionary change in specific contexts, leaving direct selection to drive evolutionary change.

scholarly journals Sex ratio of the offspring of New Zealand phenoxy herbicide producers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin

2016 ◽  
Vol 74 (1) ◽  
pp. 24-29 ◽  
Author(s):  
Andrea ‘t Mannetje ◽  
Amanda Eng ◽  
Chris Walls ◽  
Evan Dryson ◽  
Manolis Kogevinas ◽  
...  
Keyword(s):  
New Zealand ◽  
Sex Ratio ◽  
Phenoxy Herbicide ◽  
Tetrachlorodibenzo P Dioxin

scholarly journals Female Scarcity and Natal Dispersal Differences Between Sexes Among Bellbirds (Anthornis melanura)

2021 ◽  
Author(s):  
◽  
Hilary Misha Cresko
Keyword(s):  
New Zealand ◽  
Sex Ratio ◽  
Food Source ◽  
Radio Telemetry ◽  
Intrasexual Competition ◽  
Natal Dispersal ◽  
Supplemental Food ◽  
Dispersal Distances ◽  
Anthornis Melanura ◽  
Sex Ratio Imbalance

<p>Sex ratio imbalances in wild bird populations have been a challenge for wildlife managers for decades. Differences between sexes during natal dispersal has long been thought to promote sex ratio imbalances. Natal dispersal distances may differ between sexes because of competition for food and space, or intrasexual competition and aggression. I investigated natal dispersal and intrasexual competition as mechanisms for a sex ratio imbalance in a small, translocated population of a New Zealand honeyeater, the bellbird (Anthornis melanura) in the Karori Wildlife Sanctuary- Zealandia, Wellington, New Zealand. I analysed long term records of population size and structure to document annual variation in sex ratios since the reintroduction of bellbirds to Zealandia. Radio telemetry was used to track the 2008/2009 cohort of bellbirds for five months after fledging to observe movements and distances travelled from their hatching location. Observations at a supplemental food source that was used by both adults and fledglings, were used to study intrasexual competition and aggression. Dispersal distances did not differ between the sexes for any of the measurement types used. Males did however significantly dominate the use of a supplemental food source and were significantly more aggressive around this food source, which is most likely responsible for the lower feeding rate among females. Therefore, I conclude that the sex ratio imbalance in the bellbird population in Zealandia may not result from a difference in natal dispersal, but from males dominating a supplemental food source, raising their population and fitness over that of females.</p>

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