Dr Jo Venables

Tel: +44 (0) 1223 331 861
Fax: +44 (0) 1223 336 676
Email: jcv29 at cam.ac.uk

Position held: Former PhD student (supervisor: Mike Brooke)

Research
 
My PhD aims to explore the relationship between adult sex ratios and population decline in birds.  Research on adult sex ratios (ASR) has largely been overshadowed in the past by interest in adaptively skewed offspring sex ratios, a subject which has received much attention in the last decade.  However, it is becoming increasingly obvious that our current knowledge on ASRs in a wide variety of taxa is limited.

Recent research (Donald, Ibis 2007) has not only confirmed that male-skewed ASRs are common in wild bird populations but has also highlighted a significant positive relationship between male-skewed ASR and threat status in bird populations.  This tendency for more threatened populations to have more male-skewed ASR is a concern for conservation.  In particular for species that practise polygyny and monogamy, a shortage of females and an abundance of males provides a sub-optimal ASR.  In order to conserve these threatened populations it is important to understand the cause and effect of skewed ASRs.  My research, under the supervision of Dr Mike Brooke, will utilise previously collected data to shed more light on the subject of skewed ASRs in wild bird populations

A brief summary of the aims of my research is included below:
  • Using mark-recapture data I hope to look further into the relationship between skewed ASRs and population decline – is this relationship causal or not?  And if so, does a skew in ASR cause population decline; or does population decline cause a skew in ASR?
  • In contrast to the majority of bird populations, the ASR of mammal populations is often female-skewed (Donald, Ibis 2007).  Given either a polygynous or monogamous breeding system, a population will increase in size quicker if the sex ratio is female skewed.  On this basis, mammals should be at less risk of extinction than birds.  To investigate this idea I will use population viability analysis to look into the affects of skewed ASRs on extinction risk in bird and mammal populations
  • During the course of my PhD I also hope to shed some light onto the possible, and realistic, causes of skewed ASRs in bird populations.  The main arguments are for dispersal, differential predation of the sexes, competition for resources from the larger, dominant sex, and the effect of being the heterogametic sex.  To do this I hope to look at differential seasonal mortality of the sexes and the change in ASR across a species’ range.

Prior to Cambridge:

I studied for my undergraduate degree at University of Bath.  During my course I spent a year working for the Great Bustard Group, a conservation group aiming to establish a self-sustaining population of Great Bustards in the UK.  During this year I had hands on experience of conservation, carrying out practical work such as caring for birds in quarantine, helping with health checks, radio tagging birds before release and monitoring them after release.  I also assisted in a survey of the source population in Saratov, Russia.  Whilst working for the Great Bustard Group I undertook a three month study of predator recognition in Ring-necked Pheasants.  My final year dissertation was a statistical exploration of data I had previously collected from a two month expedition to Indonesia.  The study I had conducted attempted to understand the affect of seagrass density and habitat connectivity of seagrass beds on seagrass bed fish populations.  My final year project included writing a statistical guide for future students as well as an in depth assessment of my previously collected data and data collection methodology using a variety of statistical techniques.

Jo Venables
 
Research

 
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, U. K.