Aspects of the ecology of macaroni penguins (Eudyptes chrysolophus) around South Georgia
Author(s)
Hart, Tom
Type
Thesis
Abstract
Macaroni penguins (Eudyptes chrysolophus Brandt) feed when diving during long
foraging trips away from their breeding colony. Their foraging behaviour is
constrained by a number of factors including their physiology, their condition, the
condition of their partner, and the condition of their chick. This thesis concerns
aspects of their foraging ecology in relation to prey availability. Time Depth
Recorders and other archival tags are increasing in their capacity, battery life and
durability at the same time as getting cheaper and smaller and are frequently used to
explore foraging behaviour. However, development and application of techniques to
analyse these resulting data sets lags behind our ability to collect the data. This thesis
develops new methods and uses data from 129 macaroni penguins collected over 6
years to determine patterns of foraging behaviour. In particular:
1. Appropriate identification of sex is essential to any study of foraging ecology,
in particular during the breeding season. In response to an identified problem
with morphometric sexing, I conduct a validation test between molecular and
morphometric sex tests and make conclusions about the nature and identity of
error in these tests.
2. I use summary statistics to characterise dives. This work suggests that time
series techniques may provide insights that have been lacking from previous
analyses. I apply time series techniques to the data to model non-independence
in data sets and to compare results obtained using auto-correlation methods
with findings obtained from (1) above. The time series approach allows a
comparison of different temporal elements of dives, in particular correlations
between features of successive dives and how correlation between dives
decays with time.
3. I use Hidden Markov Models as a clustering algorithm to provide a
statistically robust description of patterns in dives that may outperform the
widely used concept of bouts of dives. I then use this method to determine
whether such clustering of dives exists in my data. Characteristics of bouts and
types of dives vary with year, the stage and sex of the individual.
4. Hidden Markov Models do not provide a direct replacement for the concept of
bouts. Rather than identify bouts as summary statistics of diving activity, I
take daily summaries of activity. I then use these to overcome the nonindependence
of dives and to determine the relative periods of dive activity
and travel or searching. Comparison between the adult and chick fledging
weights revealed a strategy of investment in the chick at the expense of the
adult body mass.
The application of time series techniques has led to new insights about the timing of
decision-making, but this thesis reveals that further advances also require positional
data to be combined with temporal activity data.
foraging trips away from their breeding colony. Their foraging behaviour is
constrained by a number of factors including their physiology, their condition, the
condition of their partner, and the condition of their chick. This thesis concerns
aspects of their foraging ecology in relation to prey availability. Time Depth
Recorders and other archival tags are increasing in their capacity, battery life and
durability at the same time as getting cheaper and smaller and are frequently used to
explore foraging behaviour. However, development and application of techniques to
analyse these resulting data sets lags behind our ability to collect the data. This thesis
develops new methods and uses data from 129 macaroni penguins collected over 6
years to determine patterns of foraging behaviour. In particular:
1. Appropriate identification of sex is essential to any study of foraging ecology,
in particular during the breeding season. In response to an identified problem
with morphometric sexing, I conduct a validation test between molecular and
morphometric sex tests and make conclusions about the nature and identity of
error in these tests.
2. I use summary statistics to characterise dives. This work suggests that time
series techniques may provide insights that have been lacking from previous
analyses. I apply time series techniques to the data to model non-independence
in data sets and to compare results obtained using auto-correlation methods
with findings obtained from (1) above. The time series approach allows a
comparison of different temporal elements of dives, in particular correlations
between features of successive dives and how correlation between dives
decays with time.
3. I use Hidden Markov Models as a clustering algorithm to provide a
statistically robust description of patterns in dives that may outperform the
widely used concept of bouts of dives. I then use this method to determine
whether such clustering of dives exists in my data. Characteristics of bouts and
types of dives vary with year, the stage and sex of the individual.
4. Hidden Markov Models do not provide a direct replacement for the concept of
bouts. Rather than identify bouts as summary statistics of diving activity, I
take daily summaries of activity. I then use these to overcome the nonindependence
of dives and to determine the relative periods of dive activity
and travel or searching. Comparison between the adult and chick fledging
weights revealed a strategy of investment in the chick at the expense of the
adult body mass.
The application of time series techniques has led to new insights about the timing of
decision-making, but this thesis reveals that further advances also require positional
data to be combined with temporal activity data.
Date Issued
2009
Date Awarded
2010-06
Advisor
Coulson, Tim
Tratham, Phil
Sponsor
BBSRC ; British Antarctic Survey
Creator
Hart, Tom
Publisher Department
Biology
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)