EFFECTS OF AGE, GENDER, AND CONDITION ON THE REPRODUCTIVE EFFORT OF CASSIN'S AUKLETS (Ptychoramphus aleuticus) ON TRIANGLE ISLAND, BRITISH COLUMBIA.

Hugh Arthur Knechtel B.Sc., Evergreen State College, 1993

THESIS SUBMllTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of BIOLOGICAL SCIENCES

O Hugh Arthur Knechtel 1998 SIMON FRASER UNIVERSITY December 3 1998

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The primacy goal of my research was to determine the effects of age, gender, and individual phenotypic quality (body reserves and immune function) on reproductive effort (egg size and laying date) in Cassin's Auklets (Ptychoramphus aleuticus) on Triangle Island, British Columbia. Breeding individuals were categorized as 'young' or 'oIdl based on iris colour. Two rneasures of condition were related to reproductive effort: body reserves (mass corrected for structural size) and immune function (heterophil :lymphocyte ratio or H:L ratio, an index of stress or infection). Although Cassin's Auklets exhibit a low degree of sexual dimorphism, I confirmed, using a molecular sexing technique, that bill depth is a reliable indicator of sex within breeding pairs. Using bill depth data from 115 pairs, 1 showed that 85% of randomly caught individuals could be accurately sexed. The ability to sex individuals is of value for determining gender in an ongoing mark-recapture study examining adult survival on Triangle Island. I further utilized the molecular sexing technique to show a male-biased offspring sex ratio close to fledging. Egg size variation was related to offspring 'quality': larger eggs produced hatchlings of greater mass and structural size. Although this effect did not persist beyond 5 days post- hatch, hatching from a large egg may lower starvation probability in years of poor food availability. 1 found significant age effects in some measures of female reproductive effort and condition, but not in others. Old females laid significantly earlier, but no age-related differences were found in egg size. By laÿing Iate, young fernales may have incurred greater fitness costs, since conditions are usually unfavourable for raising young later in the season. I found no age effect on female body reserves, however, the H:L ratios of young fernales were significantly higher, indicating greater stress or infection. Elevated H:L ratios in young females, but not in young males, may reflect the greater gametic effort of females (egg production). Variation in effort was related to condition in old breeders, but not in young breeders. Optirnization theory suggests that for individuals to maxirnize lifetime reproductive success, they should base reproductive effort on their condition, and maintain that level of condition throughout the breeding cycle. There was a positive correlation between laying date and H:L ratios in old males and fernales, but not in young breeders. This positive relationship in old males may mean that male 'quality' is important in determining laying date. Similarly, old fernales showed a positive correlation between body reserves and egg size, while young fernales did not. Since individual condition was measured late in incubation, the positive correlations between effort and condition in old, potentially more experienced individuals suggests that they are better at optirnizing current reproductive effort. Acknowledgments

Many people contributed in various ways to rny research and the production of rny thesis. First and foremost, I thank rny supervisor, Fred Cooke, for this opportunity and for his support and patience throughout my journey. I am grateful to Tony Williams for introducing me to physiology, and for making valuable comments on the many drafts of this thesis. I thank Doug Bertram for his humour and advise since his arriva1 in the lab, and Ian Jones for passing on his bountiful knowledge of alcids and for his vision of a research station on Triangle Island. 1 will always be grateful for the enthusiasm shown to me by both Dov Lank and Evan Cooch; Dov in teaching me about behavioural ecology, and Evan in giving me statistical guidance. 1 also acknowledge the tireless work of Connie, Barb, and Joanne in keeping the lab on track and finely tuned. My research was funded by the CWS/NSERC Wildlife Ecology Research Chair and would not have been possible without the logistical support of the Canadian Coast Guard and West Coast Helicopters. 1 would like to thank the many people who have assisted me in the field. Foremost, 1 thank my volunteers, Uli Stiener and Edith Albertz, for their good humour and hard work grubbing burrows, measuring eggs, and bleeding birds through the hurricanes, storms, and cold of the early spring of '96. Thanks also to the colleagues who helped later that season: Alan Burger, Laura Cowen, Colleen Cassady St. Clair, Laura Jones, Suzzane Romaine, Mike WiIey, and Kerry Woo. Recognition is due to John Ryder and Kerry Woo for coliecting egg volume data for me the following year. Thanks also to Xia-Hua Xue and Brett Vanderkist for the many hours of lab work they put in to sex my birds. My time at Simon Fraser University was greatly enriched by the friendship and assistance of my lab mates and fellow grad students, for this 1 will always be grateful. My research benefited from discussions with Julian Christians, Chris Guglielmo, Brent Gurd, Anne Harfenist, Dave Moore, Patrick OIHara, Greg Robertson, Roxana Torres, and Brett Vanderkist. I also benefited from the many helpful comments on various drafts of this thesis provided by: Marion Blake, Ira Chaikin, Julian Christians, Chris Guglielmo, Brent Gurd, Cindy Hull, Lynn Lougheed, Dave Moore, Patrick O'Mara, Greg Robertson, Cyndi Smith, and Brett Vanderkist. Thanks to my family for the support they gave throughout my years at grad school. In particular, I thank my mother, Marion Blake, who showed me by example that anything is possible if you put your mind to it. Table of Contents

APPROVAL ...... ii ABSTRACT ...... ,,,...... iii ACKNOWLEDG EMENTS...... v TABLE OF CONTENTS...... vi LIST OF TABLES...... viii LIST OF FIGURES ...... ix CHAPTER 1. GENERAL INTRODUCTION...... 1 Study Species ...... 6 Study Site...... 9 Objectives...... ,...... 1 1 CHAPTER 2. SEXING CASSIN'S AUKLETS: METHODS AND PRELlMlNARY SU(-RATIO

DATA ...... ,,...... 1 3 Abstract ...... 1 3 Introduction...... 1 3 Methods...... 1 4 Results...... 1 6 Discussion...... 1 6 CHAPTER 3. AGE-RELATED DIFFERENCES IN THE RELATIONSHIP BETWEEN REPRODUCTIVE EFFORT AND MATERNAL BODY RESERVES, AND THE INFLUENCE OF EGG SlZE ON HATCHLING SlZE AND MASS IN CASSIN'S AUKLETS ...... 2 3 Abstract ...... 2 3 Introduction...... 2 3 Methods...... 2 8 Results...... 2 9 Discussion...... 3 O Summary ...... 3 9 CHAPTER 4. A WHITE BLOOD CELL COUNT AS A MEASURE OF CONDITION: THE RELATIONSHIP BETWEEN HETEEROPHllrLYMPHOCYTERATIOS AND LAYING DATE IN CASSIN'S AUKLETS 4 O Abstract...... 4 O Introduction...... 4 0 Methods...... 4 3 Results...... 4 5 Discussion ...... 4 5 CHAPTER 5 . GENERAL CONCLUSION...... 5 6 Synthesis...... 5 6 Future directions ...... 5 9 Conservation implications...... 6 1 LITERATURE CITED...... 6 4 List of Tables

Table 11-1. Morphological measurements of breeding male and fernale Cassin's Auklets from Triangle Island sexed using Griifiths et al.'s (1996) molecular technique (n=16 pairs for al1 tests)...... -20

Table 11-2. Results of a stepwise discriminant function model for morphological rneasurements predicting adult sex (n=16 pairs)...... -...... 20

Table 11-3. Bill depth (mm) for breeding individuals sexed using a molecular technique (n=16 pairs) compared with breeding individuals sexed using bill depth (n=99 pairs). 20

Table 111-1. Mean SE (range) number of days after laying and time during day body reserves were assessed in old and young Cassin's Auktet fernales...... 32

Table 111-2. Results of a stepwise multiple regression model for parental phenotypic characteristics influencing egg volume (n=1 13)...... ,...... --..-...---.-..--....~. 32

Table 111-3. Mean ~t_SE (range) body reserve index and egg size for two different age classes of breeding Cassin's Auklet femafes...... --...-..32

Table 111-4. The influence of egg size on Cassin's Auklet hatchling mass and structural size (wing chord). The hatchling variables were mass (M), structural size (SS), mass controlling for structural size (MCSS), and structural size controlling for mass (SSCM)...... ~...... ~...... ~...... ~...... ~.....-..----.---.....31

Table IV-1. Ancova's looking at the effect of time of day (time bled), and time in relation to laying date (time) on heterophi1:Iymphocyte ratios within and between the different sexes (sex) and agekex classes (group) of breeding Cassin's Auklets...... 51

Table IV. Mean kSE) Iaying date, heterophil:lymphocyte ratio in two different age classes of male and female Cassin's Auklets...... -51 List of Figures

Figure 1-1. Map of Triangle Island showing place names...... -...-....-..-...IO

Figure 11-1. Bill depths of 16 pairs of breeding Cassin's Auklets sexed using Griffiths et a1.k (1996) molecular technique...... -17

Figure 11-2. Frequency distribution of Cassin's Auklet male and female bill depths combining pairs sexed using Griffiths et al.'s (1996) molecular technique and pairs sexed using bill depth (n=115 pairs)...... 18

Figure 11-3. Probability of being a male or female based on the assumption that within pairs, male bill depth is always larger than the fernale's bill depth...... --19

Figure III-1. Correlation between female body reserves and egg volume in old females (FI,,o=5.60, r2=0.12, P=0.02), and in young females (F1,~,=1.33, r2=0.02, P=0.25)...... 31

Figure IV-1. Relationship between H:L ratios and reproductive effort measured as Iaying date in female Cassin's Auklets (y = 64.51 t 0.30~)...... --.A6

Figure IV-2. Relationship between H:L ratio and reproductive effort measured as laying date in male Cassin's Auklets (y = 74.69 + 0.20~)...... 47

Figure IV-3. Mean H:L ratios and laying dates for different agekex categories of breeding Cassin's Auklets (rnean t 1 SE, sample size above error bars)...... 48

Figure IV-4. Relationship between H:L ratios and reproductive effort measured as Iaying date in old (y = 34.08 + 0.49~). and young (y = 97.84 + 0.09~)female Cassin's Auklets.

Figure IV-5. Relationship between H:L ratios and reproductive effort measured as laying date in old (y = 57.61 + 0.31~)~ar?d young (y = 113.4 - 0.09~)male Cassin's Auklets- ...... -50 Chapter 1 Generai Introduction

'Reproductive effort' is defined as the time and energy parents expend that is necessary and sufficient for the production and rearing of young (Winkler and Walters 1983; Lessells 1991). That reproductive effort is costiy constitutes a core assumption in life history theory (Williams 1966a.b). lndividuals must therefore balance the energy expended during the current reproductive season against that required for adult survival and successful future reproduction (Williams 1966a,b; Chariesworth 1980; Stearns 1992; Roff 1992). When clutch or brood size is enlarged in short-lived passerines to demonstrate reproductive costs from increased reproductive effort, reductions in adult survival and future female fecundity mây result, but the consequences will usually be modest in fitness terms (Gustafsson 1990). In longer Iived species the effects of increased reproductive effort on adults have greater consequences (Raskaft 1985; Reid 1987). In order to rnaxirnize Iifetirne fitness, individuals are expected to optimize their reproductive output within each breeding atternpt. Relative to other taxa, the life histories of seabirds are characterized by long lifespans, delayed sexual maturity and low offspring production per breeding attempt (Furness and Monaghan 1987). As a result, the tradeoff between investing in current reproductive effort or future reproduction should be pronouficed. Increased investment in current offspring should be rarely favoured, since a small reduction in survival probability will inordinately reduce the number of subsequent breeding attempts (Curio 1988; Pugesek 1990; Stearns 1992). Seabirds adjust their reproductive effort in response to both current environmental conditions and to their own phenotypic 'quality' which in turn may be considered an adjustment to the environment (Monaghan et al. 1992). To optimize current reproduction, parents are also thought to make behavioural 'decisions' throughout the reproductive cycle. These 'decisions' concern the timing and magnitude of reproductive effort, and the apportionment of time and energy to each component of reproductive effort (Saither et al. 1993; Erikstad et ai. 1997). In seabirds, breeding success (Ryder 1981, Saether 1990) and aduit survival (Thomas and Coulson 1988; Wooller et al. 1989) generatly increase with age and experience. To increase their reproductive success within a breeding season, older birds increase their reproductive effort by laying more eggs (Pugesek and Diem 1983), larger eggs (Croxall et. al 1992), or initiate breeding earlier in the season (Sydeman and Emslie 1992). Although older individuals are able to increase their reproductive effort, they still have greater survivorship than younger breeders, suggesting that older individuals are better able to optimize their current reproductive effort and therefore incur lower reproductive costs. Most seabirds are socially monogamous (Silver et a1.1985) with males assuming up to 50% of parental reproductive effort (Le., incubation, brooding, chick feeding). However, in terms of gametic effort, females invest more energy to the clutch, due to the high nutrient content of eggs compared to males who only invest sperrn (Trivers 1972). Being able to differentiate the sex of paired individuals is therefore important in measuring individual variation in the cost of reproduction. Most seabirds, are sexually rnonomorphic in plumage and size making identification of sex difficult in the field. Through the use of a molecular sexing technique developed by Griffith et al. (1W6), 1 was able to identib a reliable morphological character for sexing individuals within pairs. Clutch size is often used as a measure of effort to try to quantify the cost of reproduction (Partridge 1989). Studies in which clutch or brood size have been experirnentally altered demonstrate that fernales lay clutches that maximize individual reproductive success based on their differing abilities to raise young (Pettifor et ai. 1988; Pettifor 1993). Other studies in which brood sizes were experimentally eniarged demonstrate a cost of reproduction through decreased adult survival, future reproduction or offspring fitness (Nur 1990). However, the rnost common clutch size in seahirds is a single egg (Nelson 1980). Since there is no increase in offspring number with increased effort, the effect of egg size or quality on offspring and adult fitness becomes important, The strong relationship between reproductive effort and an individual's ability to raise young is further demonstrated by rnany life-history studies where reproductive effort is positively correlated to measures of adult 'condition' or 'quality' prior to breeding. For instance, clutch size (Coulson and Porter 1985), egg size (Galbraith 1988) and laying date (Weidinger 1996) are often found to be correlated with female body reserves prior to breeding. A bird's condition may simply act as a constraint, preventing poor 'quality' individuals from increasing their effort (Godfray et al. 1991). Alternatively, selection may favour individuais that base their allocation of effort to reproduction on their 'condition' or 'quality' (Nur 1988). Nur (1988) predicted that, if individuals expend the same amount of effort during reproduction (e.g., same clutch size), individuals of better phenotypic 'quality' will have an increased probability of survival. Individuals of better "quality" are therefore predicted to invest relatively more in reproductive effort, but not to the extent that they lessen their survival probability below that of individuals of poorer quality. If the 'condition' (e.g., body reserves) of an individual worsens during the course of reproduction, a cost of reproduction is often inferred (Drent and Daan 1980; Ricklefs 1983). As a result, if higher 'quality' individuals invest more in reproductive effort, but not enough to lessen survivorship below that of poorer 'quality' individuals, a positive correlation between quality and effort at the end of breeding should reflect that individuals are optirnizing reproduction, as long as the measure of condition influences both the survival and fecundity of the individual (Nur 1 986). Generally, the cost of reproduction can only be dernonstrated by manipuiating one of the involved traits (Le., ciutch size, brood size) (Partridge 1989; Lessells 1991). However, experirnents that increase reproductive effort rnay create a novel situation which itself rnay influence parental behaviour (Monaghan et al. 1995) or rnay fail to elicit a response in long-lived species (Sæther et al. 1993). Furthermore, many experiments where brood or clutch size is enlarged fail to show a cost of reproduction because they do not include the cost of egg production nor most of the cost of incubation (Heaney and Monaghan 1996). Correlational phenotypic studies also fail to find costs of reproduction. Populations contain both 'high' and 'low' quality individuals and these differences affect both fecundity and longevity feading to positive correlations between reproductive effort and condition indices, thus obscuring the cost of reproduction (Reznick 1985; van Noordwijk and de Jong 1986). However, if confounding variables such as differences in parental age are controlled, the cost of reproduction can be measured, thus providing a way to detect the effects of natural selection on Iife-histories (Partridge 1989; Clutton-Brock 1991). In this study, age was controlled for in phenotypic correlations, therefore negative associations between reproduction and su~ivalshould be found (Clutton-Brock 1991). This method of assessing age-related costs of reproduction allows for the inclusion of most costs of reproduction, but does not allow the cause and effect of reproductive costs to be determined. Individual variation in reproductive success is dependent on the interaction between the environment and an individual's p henotypic 'quality' (Monaghan et al. 1989). Reproductive effort is therefore expected to respond directty to environmental variability, as well as indirectly to individual phenotypic 'quality' characteristics (Winkler and Walter 1983). In seabirds, stochastic variation in marine environments has a direct effect on breeding success, because of fluctuations in prey populations (e-g., Anderson et al. 1982; Furness 1982; Hunt et al. 1986). As a result, food supply probably acts as the main proxirnate factor influencing the reproductive decisions of individuals (Monaghan et al. 1992). Supplemental feeding experiments verify the influence of food supply on the reproductive effort of seabirds; increased food availability positively affects laying date (Bolton et al. 1993), egg size (Hiom et al. 1991), and clutch size (Bolton et al. 1992; Bolton et al. 1993). Other direct environmental effects on reproductive effort include the effect of weather on foraging success (Boersma et al. 1980), predation risk (Nelson 1989) and intraspecific cornpetition for nesting territories (Manuwal 1974b). Furthermore, the nutrition an individual receives during developrnent rnay affect its reproductive effort; stunted growth during development is Iikely to persist throughout an individual's Iife thus lessening its effort (Le. delivering smaller food loads to its offspring, Partridge 1989). lncreased breeding experience enables older individuals to reduce the influence of the environment on their reproductive effort. For instance, the improved foraging efficiency associated with older individuals can compensate for poor food supplies (Sæther 1990). Higher sociaI rank (earIy arrival, dominance), rnay decrease the effect of intraspecific competition for nesting sites (Forslund and Part 1995; Martin 1995). Greater mate familiarity rnay allow older individuals to increase coordination of shared effort (Le. incubation shifts, Forsiund and Part 1995; Martin 1995). Additionally, oider individuals rnay be better at predicting future environmental conditions because of increased experience. Phenotypic plasticity, the ability of a single genotype to produce a range of phenotypes (Lessells 1991) can be advantageous in stocastic environments if individuals can predict future environmental conditions (Godfray et al. 1991). There is evidence in seabirds of phenotypic plasticity; individuals lay smaller clutches in years of poor food availability and are able to adjust the timing of breeding so that hatching corresponds with the start of peak of food availability (Ainley et al. 1990). The increased access to resources and greater experience of older breeders rnay therefore lessen the cost of reproduction, possibly facilitating greater ease in optimizing reproductive effort. Although age is a measure of an individual's phenotypic 'quality', the effect of age on reproduction is a consequence of underlying phenotypic 'quality' characteristics (McNamara and Houston 1996). For example, increased access to resources enables older individuals to increase their energy intake, thus improving their energy balance and nutritional status (Weimerskirch 1992). Conversely, younger breeders have poor access to resources due to poor foraging ability and Iow social rank (Forslund and Part 1995; Martin 1995), this suggests that reproduction rnay adversely affect their health and nutritional status. Many methods to assess individual 'condition' or 'quality' have baen developed for birds (reviewed by Brown 1996). To examine age-related differences in the relationship between individual effort and 'quality', I used 'quality' characteristics shown to influence the allocation of reproductive effort: body reserves (Drent and Daan 1980), and immune function as measured by white blood cell counts (Gustafsson et al. 1994). An individual's body reserves are a morphological indicator of an individual's nutrient reserves (Brown 1996) and is assessed by measuring rnass, then controlling for structural size (Piersrna and Davidson 1991). This rneasure is preferable over body rnass alone because it corrects for individual differences in structural size. Nutrient stores measured is this way represent mainly fat and protein available for birds to expend when needed, or to survive during periods of negative energy and nutrient balance (Piersma and Davidson 1991; Brown 1996). The maintenance of body reserves throughout incubation and chick feeding may act as insurance against natural fluctuations in food availability (Phillips and Furness 1997). An individual's white blood cells form the basis of its immune systern and increase in response to infection or stress (Sturkie and Griminger 1986). Because immune system function interacts with the general health state of an organism and cornpetes for the resources that can be allocated to other activities, white blood cell counts (WBC1s) offer a powerful tool for expiaining how reproductive effort links to reproductive costs (Gustafsson et al. 1994). Furtherrnore, WBC's have the potential for explaining why individuals differ from each other in respect to their reproductive decisions (Ots et al. 1998). Individuals with i-iigh WBC's may decrease current reproductive effort to Iessen the cost of reproduction, suggesting a tradeoff between reproductive effort and immune system response (Gustafsson et ai. 1994). Specificalfy, in this study I used the ratio between lymphocytes (specific immune cells) and heterophils (non-specific immune cells) to index relative physiological stress or infection. lncreased heterophi1:lymphocyte ratios in chickens have been associated with stress, infection and starvation (Gross and Siegel 1983; Dohrns and Metz 1991; Maxwell 1993). Phenotypic 'quality' can affect an offspring's fitness through non-heritable variation associated with nutrition or through genetic components which could indicate heritable variation in fitness. For instance, although an individual's body reserves are often associated with its foraging efficiency (Drent and Daan 1980), an individual's level of body reserves can also have a large heritable factor (e.g., Schluter and Gustafsson 1993). Egg size, which is often correlated with body reserves, also has a large heritable component (van Noordwijk et al. 1981; Hendriks 1991). However, the positive correlations found between egg size and maternai age (Coulson 1963; Furness 1983), and egg size and maternai body reserves (Galbraith 1988; Wiebe and Bortolotti 1995) suggest that at ieast some variation in egg size can be attributed to the non-heritable cornponent of the female's phenotypic 'quality' (Le., nutritional status prior to laying). The same holds true for measures of immune function; although they are an indicator of an individual's health andlor stress level (Sturkie and Griminger 1986), immune function also has a heritable component (Gustafsson et al. 1994). Two aspects of reproductive effort were used in this study: egg size and timing of Iaying. Egg production is both energetically and nutritionally expensive to the female (Clutton-Brock 1991; Robbins 1993; Carey 1996). If the female devotes too much of her body reserves to the production of the egg or if there is a reduction in food availabitity after laying, body reserves may be too depleted for her to continue incubation (Ankney and Maclnnes 1978) or offspring andor adult survival may be compromised (Heaney and Monaghan 1996). In seabirds, early laying is advantageous because conditions for raising young deteriorate late in the season (e.g., Ainley and Boekelheide1990). Fernale phenotypic 'quality' characteristics such as age (see Sæther 1990 for review), and body reserves (e-g., Drent and Daan 1980) enable high 'quality' fernates to lay earlier. Individuals of poor 'quality' lay later, decreasing reproductive success (reviewed by Perdeck and Cavé 1992). The timing of egg laying is therefore a result of the interaction between the evolutionary advantages of early breeding and the physiological constraints influencing individual females during the period of egg formation (Perrins IWO). However, most seabirds are colonial nesters (Nelson 1980); this sometimes results in intense intraspecfic cornpetition for nesting sites (e-g., Manuwal 1974b). Males rnay play a large role in the defense of the nesting territory (i.e., Ainley et a[. 1990) making the male's phenotype quality important in intraspecific cornpetition for nests and therefore likely influencing the timing of breeding. In this thesis 1 examine phenotypic correIations between parenta1 'quality' characteristics measured late in incubation and reproductive effort (fernale body reserves and egg size, female and male heterophi1:lymphocyte ratios and laying date) in two age classes of Cassin's Auklets to infer age- and sex-related differences in the cost of reproduction.

Study species Most information on Cassin's Auklets come from Southeast Farallon Island (SEFI), California where a colony of approximately 20,000 pairs has been studied extensively since the early 1970's (Manuwal 1974a, 1979; Ainley et al. 1990). In British Columbia during the 19801s,studies were conducted on feeding and reproductive ecology of Cassin's Auklets (Vermeer 1984, 1985, 1987; Vermeer and Lemon 1986). After extensive surveys during the 19801s, Rodway et al. (1990) estimated that the Scott Islands, which stretch northwest from the northern tip of Vancouver Island, house 58% of the world's population of Cassin's Auklets, with one of the islands, Triangle Island, holding 40% of the world's Cassin's Auklets. With the building of a research station on Triangle Island in 1994, studies on variability in nestling growtn and fledgling behaviour (Morbey 1995; Morbey and Ydenberg 1997; Morbey et al. in press) and colony attendance (Bertram et al. in press) have been cornpleted. Gaston (1992a) estimated aduk survival for Cassin's Auklets on Reef Island, which will soon be followed by survival estirnates for both Triangle and Fredrick Islands. Reviews by Manuwal and Thoresen (1993), and Gaston and Jones (1998) present aspects of Cassin's Auklet natural history. Cassin's Aukfet are small (190g), short-winged members of the order Charadriiformes in the farnily Alcidae. A structure cornmon to the 5 extant species of auklet is the specialized throat pouch or gular pouch (Ainley et al. 1990). A bag-like extension of the bucoal cavity, the gular pouch allows auklet parents to deliver prey-loads containing numerous small zooplankton from the feeding areas to waiting chicks in the breeding colony. Four of the 5 auklet species are confined to the Bering Sea, while the Cassin's Auklet is the only auklet that occurs in waters not influenced by winter pack ice (Ainley et al. 1990). The Cassin's Auklet breeding range extends from Buldir Island in the Western Aleutians south to the Baja California peninsula (Manuwal and Thoresen 1993). Cassin's Auklets are basal to the rest of the auklet species (Friesen et al. 1996) and biogeographical evidence suggests that their breeding range was moved south to avoid the glacial climates of the Late Pleistocene (Udvardy 1963). Cassin's Auklets are socially rnonogamous and sexually monomorphic in size and plumage, although females on SEFI have a shailower bill cornpared to males (Nelson 1981). At fledging, Cassin's Auklets irises are dark brown, but gradually turn white over a 3- to 4- year period making iris colour usefuf in determining age classes (Speich and Manuwal 1974; Manuwal 1978; Emslie et al. IWO). Cassin's Auklets nest colonially on offshore islands mainly in burrows dug by the birds thernselves or sometimes in natural cavities (Manuwal and Thoresen 1993). Males assume 50% of incubation, chick brooding and chick feeding duties (Manuwal and Thoresen 1993). On SEFI a population of 'floaters' exists, some of which are physiologically capable of breeding but unable to do so due to a lack of nesting sites (Manuwal 1974b). Because the availability of nesting sites tirnits breeding, Cassin's Auklets are highly territorial in defense of their nesting site, with males taking an active role in nest defense (Ainley et al. 1990). Males are also assumed to take a larger role in burrow excavation, possibly fo compensate the female for energy spent in egg formation (Ainley et al. 1990). On SEFI, breeding usually begins at age 3, although some individuals start breeding at 1 or 2 years of age (Speich and Manuwal 1974). SEFI Cassin's Auklets have a Iifespan of 10 to 20 years (Ainley et al. 1990). Cassin's Auklets are a highly pelagic species, generaliy foraging well offshore (Gaston and Jones 1998) at the shelf break (Vermeer et al. 1985), or off the shelf (Briggs et al. 1987). Cassin's Auklet use their wings to propet thernselves through the water colurnn to capture prey concentrated in upwelling water that occurs over the continental shelf break (Gaston and Jones 1998). Birds breeding on SEFI are found in large feeding concentrations near the continental shelf up to 50 to 60 km from the island (Briggs et al. 1987; Ainley et al. 1996). ln British Columbia, nestlings are fed primarily euphausiids (Thysanoessa spinifera, Thysanoessa longlpes, Euphausia pacifica) and calanoid copepods (Neocalanus cristatus) and secondarily juvenile and larval fish Ammodytes hexapterus, Hemillepidotus sp., Sebastes sp. and Hexagrammos sp., with prey types delivered to chicks varying both within and between years and between colonies (Vermeer 1981, 1984, 1985). Breeding adults depend on annual springkumrner phytoplankton bloorns to supply energy for reproduction and to complete their rnolt. Adult molt overlaps with breeding, with primaries being molted over an extended period so individuals are not rendered flightless (Emslie et al. 1990). Adults can alter the timing and rate of rnolt in relation to breeding effort, apparently as a means to balance the energetic demands of both (Emslie et al. 1990). Hodum et al. (1998) showed that SEFI Cassin's Auklets feeding their chicks are estimated to consume 117g of euphausiids per day to meet their energy demands, suggesting that Cassin's Auklets are constrained to one-egg clutches due to the high energy costs of foraging and the need to commute between the feeding grounds and the breeding colony. Food availability has a major influence on productivity with clutch initiation, the nurnber of individuals laying, and breeding success being strongly influenced by the occurrence of upwelling in waters near the coiony (Manuwal 1979; Vermeer 1981). Emslie et al's (1992) study on SEFl indicates that mate retention and breeding experience positively influence breeding performance with experienced pairs tending to breed earlier. Cassin's Auklets are sirictIy nocturnal in their visits to the nest which, in conjunction with their need to travel to distant offshore foraging grounds, limits breeding birds to one return trip per night to feed their chick (Manuwal 1974a). Sealy (1968) suggested that nocturnal colony visitation in Cassin's Auklets has evolved primarily in response to the diurnal vertical migration of suitable prey items, facilitating ease of prey capture, and only secondarily as a predator avoidance tactic. Cassin's Auklets lay a single-egg clutch. In British Columbia, egg laying begins in late March or early April (HK pers. obs.), with the date of the first laid egg having become progressively earlier over the last 20 years (Bertram pers. comm). Most laying tends to be skewed towards the beginning of the laying period, with early-laying individuals having greater reproductive success (Ainley et al. 1990; HK unpubl.). Astheimer (1986) suggested that early laying individuals on SEFI may use environmental cues such as zooplankton density or sea temperature to time breeding so that hatching coincides with zooplankton bloorns, Replacement eggs and second clutches have been reported on SEFI, probably due to the extended breeding season in the lower latitudes. In British Columbia, second clutches have not been reported, however replacement eggs have been documented (HK pers. obs.). In general, alcid eggs have a disproportionately high energy content, slow embryonic growth rates, and long incubation periods. Parents switch incubation duties at night every 24 hours (Manuwal and Thoresen 1993; HK unpubl.). Incubation lasts for -38 days, the longest of any alcid in relation to egg size (309, Rahn and Ar 1974). The serni- precocial chick is brooded for the first 5 to 8 days of life (Manuwal 1974a; HK unpubl.). After brooding, the chick remains alone in the burrow, being fed once a night by each parent. At 41 to 50 days of age chicks fledge by flying to the sea were they are apparently independent. (Manuwal and Thoresen 1993). On SEFI, the Western GulI (Larus occidentalis ) is the major predator of Cassin's Auklets (Manuwal 1974a). On Triangle Island, the main predators of adults are Perigrine Falcons (Falco peregrinus) and Bald Eagles (Haliaeetus leucocephalus) (HK pers. obs.). On Triangle lsland chicks are predated by Common Ravens (Corvus corax) (HK pers. obs.), while Keen's mouse (Peromyscus keeni isolatus) has been implicated in the predation of eggs (Bertram pers. comm.).

Study Site This study was conducted on Triangle Island, the outermost of the Scott islands located 46 km northwest of Cape Scott, Vancouver Island, (500 52' N 12g0 05' W, area = 44 ha) from March to July 1996 (Fig. 1-1). Historically, Triangle lsland was the most northern point of traditional Kwakwaka'wakw territory that stretched from Triangle lsland south to central Vancouver Island. A village site and extensive shell middens are reminders of the former occupation of the island by the Kwakwaka'wakw (Yasui et al. 1995). A concrete lighthouse base at the top of the island stands as a testirnony to the Iightkeepers who suffered through wind, and fog in the early 1900s until the lighthouse was closed after 9 years of operation. Except for a few visits from fishermen and biologists the island has rernained relatively undisturbed. Designated an ecological reserve in 1971 the Canadian Wildlife Service/Sirnon Fraser University/NSERC Wildlife Chair built a research station at South Bay in 1994, primarily to monitor the population dynamics and productivity of the nesting seabirds An inventory of al1 plants and animals on Triangle Island is provided by Cari et al. (1951). Triangle lsland is treeless, with the predominant plant species being salrnonberry Rubus specfabalis. The roots of Tufted Hairgrass Deschampsia caespitosa and the rhizomes of Lady Fern Athyrium felix-femina likely play a major role in holding the soi1 in place on the fragile slopes which have been extensively burrowed by seabirds. Rodway et al. (1990) describe Triangle Island's seabird abundance and distribution. Triangle lsland is the most important breeding grounds for seabirds in British Columbia supporting the largest population of Cassin's Aukiets in the world (547,000 breeding Figure 1-1. Map of Triangle Island showing place names. pairs) and the vast majority of Cornmon Murres Uria aalge (4.077 breeding pairs) and Tufted Puffins Fratercula cirrhata (26,000 breeding pairs) in British Columbia. Triangle lsland also supports large breeding populations of Rhinoceros Au klets Cerorhinca monocerata, Glaucous-winged Gulls Larus glaucescens. Pigeon Guillemots Cepph us columbia, and Pelagic Corrnorants Phalacrocorax pelagicus; and srnaller populations of Brandt's Cormorants P. penicillatus, Thick-billed Murres U. lom via, Horned Puffins F. corniculata, Fork-tailed Storrn-petrels Oceanodroma furcata, and Leach's Storm-petrels 0. leucorhoa. Triangle lsland and its offshore rocks afso form British Columbia's largest Northern Sealion Eumetopias jubatus breeding colony. Triangle lsland is located in the transition zone between two oceanographic regions; the upwelling zone of the California current to the south and the downwelling zone of the Alaskan current to the north (Ware and McFarlane 1989)- Thomson (1981) shows that the continental shelf is 20 km wide at the northern end of Vancouver lsland with Triangle lsland lying on the eastern edge of the continental slope. Tidal activity, and coastal winds are the main oceanographic influences in the west side of Vancouver Island, with the strong tidal activity around the Scott Islands being linked to the abundance of sea Iife found there (Thomson 1981). Strong tidal activity and coastal winds are factors likely to positively influence the upwelling occurring at the continental slope, and therefore the food availability for Cassin's Auklets.

Objectives This thesis has two main objectives. The paramount objective is to examine the influence of age- and sex-related differences in the cost of reproduction by looking at phenotypic correlations between components of reproductive effort and individual phenotypic 'quality' characteristics. The second is to provide a reliable method of sexing breeding Cassin's Auklet on Triangle lsland using morphofogical characteristics. In Chapter 2 1 use a molecular sexing technique to verify that bill depth is an accurate rnethod to differentiate the sex of individuals within Triangle Island breeding pairs. Bill depth has been used to sex Cassin's Auklets within pairs on SEFI, but because of clinal variation in body size this sexing technique was in need of verification on Triangle Island. I also examine the utility of using bill depth to sex breeding individuals within the population for possible use in differentiating gender in an ongoing dernographic study to estimate adult survival based on mark-recapture analyses. The molecular sexing technique was further employed to examine the pre-fledging sex ratio of chicks. Chapter 3 is presented in two sections. ln the first, 1 compare differences in egg size and body reserves measured late in incubation between two age classes of fernales. I atso examine age-related differences in correlations between egg size and fernale body reserves. For the second section of Chapter 3, I present data looking at the relationship between offspring fitness and egg size by examining the influence of egg size on hatchling size and mass, and the length of time the influence lasts. In Chapter 4 1 compare age-retated differences in reproductive effort (laying date) and condition (heterophi1:Iyrnphocyte ratios) measured late in incubation in both males and females. To Iook at age and sex related differences in the cost of reproduction, I compare correlations of laying date and heterophil lymphocyte ratios of both age classes and sexes. In Chapter 5 1 summarize the most important findings of this study and discuss the conservation implications of this research, Chapter 2 Sexing Cassin's Auklets: methods and prelirninary sex-ratio data

Abstract Alcids, in general, are sexually monornorphic in size and plumage, making them difficult to sex in the field. By determining the sex of 16 breeding pairs of Cassin's Auklets using a rnolecular sexing technique, I was able to show that bill depth is a reliaMe method for differentiating gender within pairs; male bill depth was always deeper than the female. Vsing bill depth data from 115 pairs, I determined that 85.6% of breeding individuals could be sexed at a population level. This result should prove valuable for differentiating gender in an ongoing mark-recapture study examining adult su~ivalon Triangle Island. I further utilized the molecular sexing technique to sex offspring close to fledge. Although a male- biased sex ratio was found, it could not be determined whether the skewed sex ratio was caused by more female offspring dying prior to being sexed, or because mothers were facultatively adjusting the sex of offspring at fertilization.

Introduction While the gender of many bird species can be determined by differences in size or plumage characteristics, adults in sexually monomorphic species cannot be sexed reliably in this manner (Lessells and Mateman 1996). An individual's gender may have important consequences for many features of its ecology, physiology, behaviour, and Iife history traits, such as its developmentai rate (Clutton-Brock et al. 1g85), natal dispersal (Komdeur et al. 1996), differences in energy expenditure during reproduction (Carey 1996), and sut-vival probability (Dereth and Sepik 1990; Francis and Cooke 1992). The ability to determine the sex of an individual is therefore essential in understanding demography (Lessells and Maternan 1996). As a case in point, alcids of different gender cannot be sexed easily in the field since males and fernales are very sirnilar in plumage and body size (Bedard 1985). However, external measurements can sometimes provide clues about the sex of the bird in the hand. For example, sex has been determined with 95% certainty for 98% of individual Crested Auklets (Aethia cristatella, Jones 1993) using bill shape; for 94% of individual Cassin's Auklets (Ptychoramphus aleutkus, Nelson 1981) and 70% of individual Ancient MurreIets (Synthliboramphus antiquus, Gaston 1992b) using bill depth; and for 65% of individual Atlantic Puffins (Fratercula arctica, Corkhill 1972) using an index combining bill depth and culrnen Iength. However, sorne species of alcid cannot be sexed using morphological measurements (e-g., Comrnon Murres Uria aalge, Threlfall and Mahoney 1980). Although a sexing method using bill depth has been verified for Cassin's Auklets breeding on the Southeast Farallon Island (SEFI), California (Nelson 1981), this technique may not be applicable for Cassin's Auklets at other breeding sites. First, since Nelson (1981) salvaged carcasses preyed on by Western Gulls (Larus occidentalis), his sarnple rnay not be representative of the breeding population as a whole. Second, there is a clinal increase in Cassin's Auklet's body rnass frorn the southern boundary of its range in Baja, California to the northern limits of its range in Alaska (Manuwal and Thoresen 1993). Bill depth may therefore differ among populations, and sexual differences in bill depth may not scale atlometrically th roughout the species' range. In this chapter, I examine the utility of using morphoIogica1 measurements for determining the sex of individual Cassin's Auklets in breeding pairs on Triangle Island, British Columbia. In particular, I look at whether bill depth is a reliabfe method of sexing individuals within pairs. Using a random sample of burrows, I verified the sex of individuals within pairs using Griffiths et a1.k (1996) recently developed rnolecular sexing technique, I also discuss the utility of using bill depth to sex breeding individuals within the population and compare morphological measurements of breeding male and female Cassin's Auklets on Triangle Island, British Columbia with those on the SEFI, (Nelson 1981). Finally, 1 present some preliminary data on tertiary (fledging) sex ratio for chicks, which suggest a male-biased sex ratio.

Methods Field Pro toco1:a dults Prior to egg laying, access holes were excavated to rneet the burrow entrance tunnei in front of the nest chamber; the holes were re-covered with pieces of cedar shingle. Each burrow was marked with a numbered flag and its location mapped. Late in incubation, 115 breeding pairs were removed from their burrows to measure bill depth, culmen length, and tarsus length to the nearest 0.1 mm using vernier calipers; flattened wing chord to the nearest 1 mm using a wing ruler, and mass to the nearest gram using a 300 g Avinet spring scale. Bill depth was measured proximal to the fragments of rhamphotheca (beak furrows) (Knudsen 1976) at the base of the culmen to the angle of the gonys on the underside of the bill. Culmen was measured frorn the tip of the bill to the edge of the feathering at the bill base, while tarsus was measured frorn the rnid-point of the tibiotarsal joint on the back of the leg to the blunt of the tarsornetatarsal joint on the underside of the foot. Of the 115 pairs, I collected 1 ml of blood frorn the brachial vein of both individuals in 16 pairs. Wood samples were centrifuged within 2 hours of collection and the red blood cells e,utracted and later frozen. Field Protoco1:chicks Individual Iaying dates were determined by checking burrows every 3 to 7 days. When an egg was found, the mid-point date between the current and the previous check was used as the laying date. Thirty-five days after laying, burrows were checked every 3 days for hatch, so chicks could be reliably aged. Of the 47 chicks that survived to 35 days of age, blood samples for 43 of the chicks were collected and prepared in a simifar way to the adults. Molecular sexing At the chromosomal level in birds, males have homozygous Z chromosomes (ZZ) and fernales are the heterogarnetic sex (ZW).As a result, ail DNA sequences found in males also occur in females, but DNA sequences on the W chromosome may be unique to females. The avian CHD gene occurs in 2 copies, one copy called the CHD-W gene is linked only to the W chromosome (Griffith et al. 1996), thus providing a nearly universal technique for sexing birds (Ellegren and Sheldon 1997). A second copy of the CHD gene, the CHD-NW gene, is located on one of the other chromosomes, so is found in both females and males. We used a modified sexing technique developed by GriffÏths et al. (1996) to sex birds from DNA extracted from red blood cells. The enzyme Haelll was used to digest PCR products resulting in the following banding patterns: mates are represented by one band (400 bp) because they lack a copy of the CHD-W, while females have two bands, one for the CHD-W gene (400 bp) and one for the CHD-NW gene (470 bp). The CHD-NW gene has a restriction enzyme site for Haelll, so is split into 2 bands, one of 400 bp and one of 70 bp, but the 70 bp band can not be seen. The CHW-W gene has no restriction enzyme site, so remains one band. S ta tis tics 1 used T-tests to determine if mass, tarsus length, culmen length, wing chord, or bill depth differed between known sexed birds within pairs. A sequential Bonferroni test was perforrned on significant results to adjust for the number of independent tests included in the analysis (Rice 1989). In a stepwise discriminate function analysis al1 morphological measures were used to determine which were the best predictors of sex. I used pairs sexed using the molecular technique and pairs sexed using bill depth to determine if bit1 depth is a good predictor of sex using a logistic regression to mode1 the probability of being male or female as a linear function of bill depth. The parameters were estimated on a logit scale. The predicted probability for a given bill depth was derived by back transforming from the logit scale. I used a Chi-squared test to determine if there were differences in the offspring sex ratio at 35 days of age.

Results Differentiating known-sexed adults using morphological measurements The 1:1 sex ratio found within each breeding pair confirmed that Griffiths et al's (1996) molecular sexing technique works. Males and females differed significantly for two of the five external meaçurernents: culrnen and bill depth, with bill depth showing the greatest sexual dimorphism (Table 11-1). Within breeding pairs, male bill depth was atways larger than the female (n=16, Fig. 11-1). There was considerable overlap between males and females in culmen length (18.5-21.8 mm), so this univariate measure is unlikely to be useful for sexing a large proportion of breeding individuals. A stepwise discriminant function mode1 using mass, culmen length, tarsus length, and mass revealed that bill depth explained 69% of the differences between the sexes (r2=0.69, L66.9, P=0.0001, n=16 pairs). Addition of any of the other morphological variables did not improve the predictive power of the rnodel (Table 11-2). Predicting the sex of individuals in the general population using morphological rn easuremen ts Similar means and ranges for male and female bill depths in the sampfe sexed by the molecular technique (n=16 pairs) and the sample where sex was predicted by bill depth (n=99 pairs) suggest that the bill depths of birds sexed by the molecular technique are representative of the breeding population as a whole (Table 11-3). Bill depth is a good predictor of an individuai's sex (iogit scale, xz1 =19.23, P=0.0001, n=115 pairs, sex=13.967x -136.168, Fig. 11-2). After back transforming the data, sex can be determined with 95% certainty from bill depth for 85.6% (197f230) of the birds. The 33 birds that cannot be sexed with 95% accuracy fall within a range of bill depths between 9.54 mm and 9.96 mm (Fig. 11-3). Offspring sex ratio Overall, the sex ratio of chicks near fledging differed significantly from an equal sex ratio (~2~=6.61, P=0.01) and was skewed towards males (30 of 43 chicks, 69.8%).

Discussion Differen tiating sex within breeding pairs Based on Nelson's (1981) study, several authors have assumed that bill depth is an accurate method of differentiating males from females within pairs for Cassin's Auklets nesting on SEFI (Emslie et al. 1992; Sydeman et al. 1996). Using Griffith's et al's 1996 O 2 4 6 8 1O 12 14 16 Pair Number

Figure II-1. Bill depths of 16 pairs of breeding Cassin's Auklets sexed using Griffths et al.'s (1996) molecular technique. - -- -

Female bill depth

Male bill depth

Bill Depths (mm)

Figure 11-2. Frequency distribution of Cassins Auklet male and female bill depths combining pairs sexed using Griffiths et a1.k (1 996) molecular technique (n=16 pairs), and pairs sexed using bill depth (n=99 pairs). 8.0 8.5 9.0 .O 10.5 11.0 1.5 12.0 95% female 95% male

Bill depth (mm) Figure 113. Probability of being a male or female based on the assumption that within pairs, the male's bill is always deeper than the fernale's bill. Table 11-1. Morpholo@cal measurernents of breeding male and fernale Cassin's Auklets fiom Triangle Island sexed using Gntfths et. al.'s (1996) molecular technique (n= 16 pairs for ali tests)- Character Femaies Males Mean+ SE SD Mean2 SE SD (Range) (Range) ta P Bill depth (mm) 93420.07 0.27 10.4020. 11 0.44 -8.18 O.OOOlb (8.7-9.7) (9-7-1 1-4)

Culrnen (mm) 19.6420-19 0.74 20.49+0.20 0.8 1 -3.07 O.OOjb (18 -5-2 1.2) (18.7-2 1.8)

Tarsus (mm) 25.5820.22 0.87 25.54k0.21 0.85 -0.84 0.41 (24.0-27.0) (24.3-27.3)

h4ass (g) 184.6t2.08 8.33 189.7+2.10 8.39 -1.71 0.10 (17 1-199) ( 172-203) 't-test of diference between maIe and fdevalues, signiîicmt dersquentiai Bonkrrani test (Rice 1989).

Table 11-2. Resuits of a stepwise discriminant function mode1 for rnorphological measurernents predicting addt ses (n=l6 pairs). VariabIe Partial R' F P Bill depth 0.69 1 66.9 0.000 1 Culmen 0.003 0.08 11s Wing 0.005 O. 14 ~ls Tarsus 0.005 O. 13 11s Mass 0.008 0.23 ~ls

Table 11-3. Bill depth (mm) for breeding individuals sexed using a molecular technique (n= 16 pairs) compared with breeding ïndividuals sexed using bili depth (n=99 pairs). Ses Ses known' Ses uredicted' .we(tangel me(range) male 10.40+0.11 (9.7 to L 1.4) 10.3650.03 (9.5 to 1 1.2) fernale 9.3420.07 (8.7 to 9.7) 9.2620.03 (8.5 to 9.8) ' birds sesed using rnolecular technique. = birds sexd using bilI deptk molecular sexing technique 1 have verified that this assumption holds true for my sarnple of Cassin's Auklets on Triangle Island: the male always has a deeper bill within pairs. In Cassin's Auklets, careful removal of each parent from the burrow causes minimal nest abandonrnent. especially once an egg has been laid (Emslie et al. 1992; HK pers obs.) Therefore, with relatively little disturbance breeding pairs can be sexed and separated into age-classes (Manuwal 1978)- This method would allow for an understanding of the relative age-related costs of reproduction for each sex. For exarnple, determining the sex of individual birds by comparing relative bill depth within pairs (Nelson 1981) was used by Emslie et al. (1992) in their study on the importance of mate retention and experience on breeding success. Using bill depth as a predictor of sex at a population level Since 1994, a large scale dernographic study has been ongoing on Triangle Island to estimate adult Cassin's Auklet suwival based on rnark-recapture techniques. Being able to sex a large percentage of breeding individuals may facilitate survival estimates for both breeding females and males. Sexual differences in survival rates are of theoretical interest for understanding the life history of a species, determining the factors that limit population growth, and developing a realistic model of populations dynamics (Francis and Cooke 1992). This study dernonstrates that bill depth is a useful tool for differentiating gender in breeding Cassin's Auklets on Triangle Island since 85.6% of birds could be accurately sexed. Since bill depth can be easily rneasured, it provides a relatively rapid method for sexing individuals. For the 14.4% of individual adults that could not be sexed using bill depth (bill depth range 9.54-9.96 mm), Griffiths et al's (1996) molecular technique could then be employed. Since only small amounts of DNA are needed, a single contour feather would suffice to sex an individual (Griffiths and Tiwari 1995). Comparing morphology among populations In this study, bill depth and culmen length differed between the sexes, while Nelson (1981) showed that bill depth and tarsus length differed between the adult sexes on SEFI. The mean wing chords and culmen lengths were higher for both sexes for Triangle Island (Table 1) than for the SEFl (standard deviation presented, wing: males 125.8&!.5 mm, range 120-129 mm, n=14; females 125.7~3.7 mm, range 119-130 mm, n=18); (culmen males 19.8kl .l mm, range 17.9-21 -6 mm; females l9.5+O.6, range 18.4-20.5 mm, Nelson 1981) suggesting that males and females breeding on Triangle Island are larger in body size than individuals breeding on SEFI. No between-island cornparison can be made for tarsus length since two different methodologies were used, or for mass since Nelson (1981) did not report il. The mean bill depths for both adult sexes differed between Triangle Island (Table 1) and SEFI, (standard deviation presented, males 10.89t0.44 mm, range 10.4-1 1.7 mm; fernales 9.51fl.41 mm, range 8.9-10.3 mm, Nelson, 1981). Although bill depth may be a useful indicator of sex within pairs throughout the range of Cassin's Auklets, because sex- related differences in bill depth are specific to different populations, the sex-specific bill depth differences used to sex adult Triangle Island Cassin's Auklets at a population level are unlikely to be useful in other populations. This study verifies that Cassin's Auklet bill depth is a good morphological feature for differentiating the adult sexes on Triangle Island. Gêographic variation in Cassin's Auklet mass (Manuwai and Thoresen 1993) likely reduces the usefulness of Triangle Island bill depth measurements for sexing breeding individuals at other sites. Griffiths et al's (1996) simple and applicable rnolecular sexing technique provides an unobtrusive way of sexing birds in the field. lt is, therefore, a valuable management tool for helping to assess the adult survivorship for both sexes in species were sex cannot be determined by external features. Te rtiary (chic k) sex-ra tio Until recently, there were few data on pre-fledging sex ratios (e-g., Howe 1977; Blank and Nolan 1983), but with the advent of molecular sexing techniques (see Ellegren and Sheldon 1997 for review) many studies have been undertaken (e.g., Ellegren et al. 1996; Svensson and Nilsson 1996; Sheldon and Ellegren 1996; Komdeur et a1.1997). However, Iittle data exists for pre-fledging sex-ratios for seabirds (Meathrel and Ryder 1987; Griffiths 1992; Graves et al. 1993; Bretagnolle and Thibault 1995) and none for alcids. Pre-fledging sex-ratios in alcids are especially interesting since only one egg is laid; therefore the sex ratio of offspring would be an "al/-or-nothing" decision for the female. In this study, since significant rnortality occurred prior to the sexing of chicks (14 chicks died, 4 chicks were not sexed and 54 eggs did not hatch) I was unable to conclusively demonstrate whether the male-biased sex ratio resuited from an adaptive primary sex ratio adjustment or from non-adaptive sex-specific rnortality during the egg or chick stage (Fiala 1980; Clutton-Brock 1986; Ellegren and Sheldon 1997). Chapter 3 Age-related differences in the relationship between reproductive effort and materna1 body reserves, and the influence of egg size on hatchling size and mass in Cassin's Auklets

Abstract In many bird species, female body resewes (mass controlling for structural size) are built-up prior to egg laying as capital energy for clutch formation, and decrease after egg laying. Fernales who allow their reserves to drop too low after egg laying may decrease their probability of survival or future reproduction. Optirnality theory therefore suggests that a positive relationship between ciutch size and female body reserves should be apparent at the end of the reproductive cycle, if individuals are making the tradeoff between current reproductive effort and future reproduction. In this study, I examined age-related differences in female body reserves, assessed late in incubation, egg size, and correlations between the two, in Cassin's Auklets, a srnaIl alcid that lays a single-egg cltltch. Due to increased access to resources, older females were expected to lay larger eggs, have more body reserves, and to exhibit a stronger positive correlation. There was no age-related differences in body reserves or egg size, but the older age class did show a positive correlation between egg size and body reserves, white the younger age class did not, suggesting that older females are better able to optimize current reproductive effort. The second aspect of this chapter was concerned with the relationship between egg size and offspring fitness in the first few days of life. Larger eggs produced hatchlings of greater mass and structural size. lncreased mass provides more nutrient reserves to the hatchling, so may prevent starvation in years of poor food avaiiability. Increased structural size may be of a fitness benefit, since chicks hatch in advanced stage of development. Although egg size only influenced hatchling mass and size for less than 5 days after hatch, the influence of egg size is of importance, since the greatest chick mortality tends to occur in the first few days of Iife.

Introduction Optimal life history theory is based on the idea that parents should balance their investment in current reproductive effort against their investment in future reproduction and survivat (Williams 1966a,b; Charlesworth 1980). To achieve this balance, it is assumed that parents make decisions, duting every stage of the breeding cycle, on how much they should invest in current offspring production at the expense of a reduction in the probability of their own future reproduction and survival (Sæther et al. 1993; Erikstad et al. 1997). Parents are expected to weigh the effect of continued investment in current offspring production against future reproductive success to rnaximize the reproductive success, from both current and future offspring (Sargent and Gross 1985; Clutton-Brock 1991) In many studies. clutch size has been used as a measure of reproductive effort to try to identify reproductive costs in birds. Some studies in which clutch or brood size has been manipulated give results consistent with the individual optimization hypothesis (Perrins and Moss 1375). In these studies, clutch size was related to the female's ability to raise Young. Females were maximizing their individual reproductive success by laying the largest clutch they could rear to recruitment (Pettifor et ai. 1988; Pettifor 1993). In studies where broods have been experimentally enlarged the cost of reproduction has been shown to affect different Iife history traits (Nur 1990). Effects on future reproduction and survival have been documented in the forrn of reduced parental survival (Askenmo 1979; Nur 1984; Reid 1987), delayed laying (Rmkaft 1985; LesseIls l986), reduced ciutch size (Gustafsson and Sutherland 1988) and decreased fledging success (R~skaft1985) in the year following the manipulation. Increased reproductive effort can also have a negative effect on within-year reproduction. For exarnple, in Heaney and Monaghan's (1995) study where Cornmon Terns Sterna hirundo were made to Iay an additional egg, parents reduced chick provisioning effort causing reduced chick growth and survivai. A core assumption of life history theory is that reproduction is expensive (Williams 1966a,b). Parental phenotypic 'quaiity' characteristics, such as age or body reserves, result in individual differences in the effort needed to successfully rear offspring or in the cost they incur as a result of doing so (Bernado 1996). Many authors recognize that the production of eggs is both nutritionally and energetically expensive to females (Clutton- Brock 1991; Robbins 1993; Carey 1996). A recent experimental study by (Monaghan et al. 1998) on Lesser Black-backed Gulls (Larus fuscus) confirms that egg production is expensive; the capacity of parents to rear a control clutch was substantially reduced solely as a consequence of females producing an extra egg. Some studies demonstrate that older breeders have greater foraging skills (Le., Jansen 1990; Desrochers 1992). suggesting that older females are able to accumulate body reserves earlier in the season, therefore are able to lay larger clutches. Thus older females rnay be able to increase their fecundity without jeopardizing their future reproduction or survival (Sæther IWO). Conversely, younger females often may have poorer foraging skills, and therefore may not be able to accumulate sufficient nutrients to lay a large clutch, resulting in decreased fecundity (Sæther 1990). If younger females attempt to lay a large clutch they rnay increase their current reproductive success, but may do so at the cost of depleting body reserves, which in turn may lower their subsequent survival (Nur 1986). It follows that if the phenotypic quality trait being measured influences a fernale's survival or fecundity, females should alter their reproductive effort, based on that trait: 'high quality' individuals are predicted to lay large clutches while 'low quality' individuals should lay smaller clutches (Nur 1986). This argument is the basis of Nur's (1988) 'phenotypic adjustment of clutch size' rnodel which predicts that individuals can attain an optimal balance between current efiort and future reproductive potential by basing their altocation to current reproductive effort on their assessment of their phenotypic quality. If females base their reproductive effort decisions on their body reserves, Ehey could minimize the negative effect of increased fecundity on survival and future reproduction, thereby optirnizing their lifetime reproductive success (Nur and Hansson 1984; Nur 1986; Nur 1988). Females who do not adjust their reproductive effort accordingly pay a relatively higher cost and will be setected against (Nur and Hansson 1984; Nur 1986; Nur 1988). Reductions in body reserves (mass controlling for structural size) are often associated with the cost of reproduction (Ricklefs 1983; Reid 1987; Martins and Wright 1993). In many bird species (e.g., Herring Gulls Larus argentatus Hario et al. 1991; Common Terns Sterna hirundo Nisbet 1977), female body reserves are built-up prior to egg laying as capital energy for clutch formation, and then decrease during egg laying. Ankney and Maclnnes (1978) showed that Lesser Snow Geese Chen caerulescens females who allow their reserves to drop too low after egg laying, risk losing their clutch and have an increased probability of dying during incubation. This observation lead Nur (1986) tc theorize that, since females of high phenotypic quality produce the largest clutches and survive the best, these females should not let their reserves drop as low after egg laying as females of poorer quality. In other words, with an increase in 'quality', both clutch size and the level of reserves after laying increase, resulting in a positive correlation between post- laying reserve levels and clutch size. The time and energy demands of incubation can be a substantial cost of reproduction leading to loss of body reserves in adults (reviewed by Williams 1996). Although activity is reduced during incubation, the time spent attending the nest will significantly reduce the time available for foraging (Monaghan and Nager 1997). Direct measurements of energy consurnption in incubating individuals demonstrates that energy requirements increase with clutch size (Ward 1996). Furthermore, manipulative studies, where the number of egos was increased, demonstrate a reduction in efficiency of incubation resulting in a prolonged incubation period (Moreno and Carlson 1989; Smith 1989) and reduced hatching success (Siikamaki 1995). In birds that share incubation duties it is likely that the phenotypic 'quality' of both pair rnembers will determine the cost of incubation. In the present study 1 examine age-related differences in the relationship between reproductive effort produced and level of body reserves late in incubation in Cassin's Auklet, a long-lived alcid (10 to 20 years, Ainley et al. 1990) with a fixed clutch size of one. In seabirds species that lay rnulti-egg clutches, egg number often varies in response to food supply (Drent and Daan 1980). For species that lay single-egg clutches, variation in egg size is thought to be analogous to variation in clutch size (Birkhead and Nettleship 1982). Female body reserves in seabirds should affect both adult fecundity and survival. Food supply has a major influence on reproductive effort of seabirds either directly through the amount of resources available or indirectly through body reserves stored by the adult (e.g., Monaghan et al. 1989, 1992; AinIey and Boekelheide 1990). Females who have more body reserves may lay Iarger clutches (Drent and Daan 1980; and rnay be better at provisioning their offspring (Weimerskirch et al. 1993). Adults lose more body resewes in poor food years (Croll et al. 1991), sometirnes resulting in birds not returning to the colony to breed (Murphy et al. 1991) or under extreme circumstances the adults die (Cushing 1982; Schreiber and Schreiber 1984; Vader et al. 1990). Since Cassin's Auklets are a long-lived, low fecundity species, the trade-off between current and future reproductive potential is predicted to be strong (Williams 1966; Charlesworth 1980). Cassin's Auklets should be sensitive to over-investing in current reproductive effort, since even a srnall reduction in an adult's future survival can greatly redxe the number of subsequent breeding atternpts (Curio 1988; Pugesek IWO). Therefore, Cassin's Auklets are expected to optimize their effort by maintaining their body reserves relative to egg size. Thus, Cassin's Auklet rnaternal body reserves are expected to correlate with egg size late in incubation. However, it is possible that other maternal quality traits such as age (Coulson 1963; Furness 1983; Reid 1988; Robertson et al. 1994) or laying date (Birkhead and Nettleship 1982; Harris 1980) rnay influence egg size. Furtherrnore, maternal structural size rnay Iirnit egg size as a consequence of rnorphological constraints (Congdon and Gibbons 1987; McGinley 1989). Paternal phenotypic traits rnay also have an effect on egg size. In Cassin's Auklets, the male's quality can influence reproduction; because it is primarily the male's role to acquire and defend the nest site (Ainley et al. 1990). Overall, individuals are expected to base egg size on their anticipated body reserves after egg laying (Nur 1986), leading to a positive correlation between body reserves and egg size which may obscure the cost of reproduction. One way to break up positive phenotypic correlations is by controlling for confounding variables, such as rnaternal age, in order to expose the costs of reproduction (Clutton-Brock 1991). The increased breeding efficiency of older females should lower reproductive costs, allowing them to allocate more resources to the maintenance of body reserves (Weimerskirch 1992) but still resulting in large eggs (Sæther 1990 for review). They should be better able to optimize their reproductive effort, resulting in a positive correlation between egg size and body reserves late in incubation. However, due to constraints imposed by lack of breeding experience, younger females are predicted to have a weaker correlation between body reserves after laying and egg size, reflecting an increased cost of reproductim. The second aspect of this study is concerned with how egg size affects offspring fitness in Cassin's Auklets. In species with multi-egg clutches females can increase fecundity by laying more eggs. However, in species with single-egg clutches fernales can only increase their fecundity by adjusting the quaiity andor size of the egg. Therefore, establishing a Iink between egg size and offspring fitness is important in understanding Iife history tradeoffs in Cassin's Au klets. Egg size theory assumes offspring fitness increases with egg size (Bernard0 1996), although results of studies relating breeding success to egg size are equivocal. Some studies indicate that parental quality (e.g., Reid and Boersma, 1990) or parental behaviour (e-g., Ollason and Dunnet 1986; Meathrel et al. 1993 ), rather than egg size, influences nesting success. Other studies have shown that egg size perse affects hatching success (e-g., Croxall et al. 1992; Amundsen et al. 1996), chick growth (e.g., Magrath 1992a), and fledging success (e.g., Bolton 1991). However, many studies show a positive effect of egg size on offspring survival only in the first few days of Iife (Williams 1994 for review) with larger eggs resulting in either hatchlings having more nutrient reserves (large yolk sacs), or being structurally Iarger (Bolton 1991; Williams 1994). Since Iarger eggs produce larger chicks, larger eggs could act to prevent early starvation, but are likely to result in fitness advantages only in years of poor food availability or in years of poor weather (Smith et al. 1995). Thus, the length of time after hatch that egg size influences chick size or mass becomes important in terms of early chick survival. If the individuals from smaller eggs survive the critical post-hatching period, the fitness disadvantages of small egg size may disappear before fledging, especially in species such as Cassin's Auklets with long fledging periods. In this chapter I investigate: a) correlations of egg size and phenotypic quality traits that rnay affect egg size (female and male body reserves; female and male structural size; female and male age; and laying date) predicting that materna1 body reserves will be positively correlated with egg size. 6) the correlation between egg size and body reserves in old and young female Cassin's Auklets late in incubation, predicting: i) that older birds wiIl have higher body reserves and larger eggs than younger birds; ii) that the correlation between body reserves and egg size will be stronger in older birds compared to younger breeders. c) the consequences of egg size on hatching mass and structural size of chicks, and the length of tirne the effect of egg size influences the mass and size of the chick, Methods Field pro toc01 Prior to egg laying, access holes were excavated to meet the burrow entrance tunnel in front of the nest charnber, in order to facilitate access to the nests with a minimum of disturbance. Access holes were then covered with pieces of cedar shingle. Burrows were marked with numbered flags and mapped. During the last half of the incubation period, adults were removed from their burrow so that their Ievei of body reserves, sex, and age could be determined. Egg volume Egg length (L) and width (W) were measured early in incubation using Vernier calipers (to the nearest .O1 mm). In a sub-sarnple of thirty eggs, egg volume (V) was measured directly by water displacernent in a graduated cylinder. I determined the coefficient of egg shape (k) to be 0.47 for Cassin's Auklets. Volume vras than calculated using the formula, V = k L w*, (Hoyt 1979). Age of breeders Breeding Cassin's kuklets were separated into two age classes using a rnodified aging criterion based on iris colour developed by Manuwal (1978). Fledging Cassin's Auklet chicks have brown irises, which turn white over a period of 3 to 4 years. I classified adults with completely white irises as "old" breeders, and birds with any brown in their irises as "young" breeders. Hatchling srie and mass Individual laying dates were determined by checking burrows every 3 to 7 days. When an egg was found, the mid-point date between the current and the previous check was used as the laying date. Thirty-five days after each egg was discovered, burrows were checked every 3 days to determine hatch date. Only chicks that were wet when found were inctuded in analyses of the effect of egg size on chick structurâl size and mass at hatch. Wing chord (a measure of structural size) was measured using a wing ruler (to the nearest .1 mm), while rnass was determined using Avinet spring scales (to the nearest 0.5 g). 1 remeasured chicks at 5 days of age to determine if egg size was still affecting chick size and mass. Body reserves 1 derived a single measurement of structural size for each breeding fernale and male by extracting the first principal component (SAS lnstitute 1989) of the correlation matrix of culmen length, bill depth, wing chord length and tarsus length. Body mass is partly the result of structural body size and does not necessarily reflect the quantity of body reserves (Piersrna and Davidson 1991). 1 scaled mass to body size by regressing mass against PC1 producing residuals which were used as a nutrient reserve index. Since an adaptive step- wise mass recession of breeding adults is likely to take place soon after the chick hatches (e.g., Ancient Murrelets Synthliboramphus antiquus, Gaston and Jones 1989; Least Auklets Aethia pusilla, Jones 1994; Thick-billed Murres Uria lomvia, Croll et al. 1991), adults were weighed and measured before hatch to assess body reserves. I used the continuous variables; laying date, female structural size, male structural size, female body reserves, male body reserves and class variables; materna1 and paternal age in a stepwise multiple regression on egg volume (n = 113 burrows), ANOVA's were used for al1 remaining analyses.

Results 1.0 Sampling biases As I rneasured body reserves of females at different times of day and at varying intervals after ciutch completion, I wanted to ensure that the sampling protocol did not result in any systematic bias in estimation of body reserves between female age classes. Neither time of day a bird's body reserves were assessed (t = -1.596, DF = 84, P = 0.1 1, n = 113) nor the date body reserves were assessed in relation to laying date (t = -0.605, DF = 94, P = 0.55, n =109) differed significantly between female age classes (Table 111-1). 2.0 Egg size/Maternal body reserves The volumes of eggs measured in this study ranged from 20.13 cm3 to 31 -85cm3 ( mean = 26.07 + 0.20 cm3 n=114), with the smallest egg being only 63% of the size of the largest. A stepwise multiple regression model using; laying date, female structural size, male structural size, female body reserves, male body reserves, female age, and male age revealed that 7% of the variation in egg size was attributable to variation iri materna1 body reserves (n = 113, F = 7.76, p = 0.006, r2 = 0.07) (Table 111-2). Although materna1 body reserves was the only rneasured parameter that significantly affected egg volume, the effect was not large. 3.0 Egg size/Maternal body reserves/Maternal age Although older females tended to have greater body reserves and lay larger eggs than younger females, the differences were not significant (Table 111-3). When laying date was controlled for the age-related differences in body reserves (F=0.48, p=0.69, n=113), and egg size (E0.29, p=0.83, n=113) became less significant (Table 111-3). I found a positive correlation between egg size and body reserves in old females, but in young females there was no significant relationship (Fig. Ili-1). 4.0 Egg Size/Ha tchling size The effect of egg size on the mass and the structural size (wing chord) of freshly hatched chicks was significant with Iarger eggs producing chicks of a higher mass and longer wing chord (TabIe 111-4). When hatching size (wing chord) was controlled for hatching mass became more strongly correlated with egg size (Table 111-4). Similarly, hatching size (wing chord) became more strongly correlated with egg size when controlling for hatching mass (Table 111-4). When chicks were 5 days old, the effect of egg size on hatching mass (Fi ,7 = 1.43, p = 0.3, r2 = 0.19) and hatching size (Fi ,7 = 0.27, p = 0.6, r2 = 0.04) was no longer detectable.

Discussion l found that: (i) overall egg size increased with the level of rnaternal body reserves, (ii) there were no age-related differences in body reserves or egg size, (iii) egg size and maternal body reserves were positively correlated in old females, but not in young females, (iv) large eggs produced hatchlings with greater mass and larger structural size, and (v) the effect of egg size on chick mass and size persisted for iess than 5 days. Egg sîze and maternal body reserwes As predicted, I found a positive, though weak, correlation between egg size and rnaternal body reserves late in incubation, This result suggests that Cassin's Auklet females are adjusting their egg size to correspond with their accurnulated body reserves late in incubation. Females of higher phenotypic 'quality' produce large eggs because they are able to maintain more reserves until late in incubation, and hence are able to minimize the negative effect of increased fecundity on future suniival and reproduction (Nur 1986). Therefore, by basing egg size on body reserves after taying, individuals 'do the best they can' in the amount of effort they allocate to reproduction. Females with lower fertility (low body reserves) during a particular breeding season have a lower fertility optimum (small egg size) than females with a higher fertility (high body reserves) (Partridge 1989). Positive correlations between reserve levels during incubation and clutch sizelegg size have been found in many species (e.g., Askenmo 1982, Pied Flycatcher Ficedula hypoleuca; Nur 1986, Blue Tit Parus caeruleus; Gaston and Jones 1989, Ancient Murrelet Synthliboramphus antiquus), suggesting that natural selection may rnould the behaviour of Cassin's Auklet sOld Females

Youna Females

-20 -15 -?O -5 O 5 10 15 20 25 female body reserves Figure III-1. Correlation between female body reserves and egg volurne in OM fernales (~,,,,=5.60, r2=0. 12, P=o.o~) and in young fernales (F ,,,, =l.33, r2=0.02, P=0.25). Table 111-1. Mean _+ SE (range) number of days after laying and time during day body reserves were assessed in old and young Cassin's Auklet fernales. Age Davs after laying Time during dav (hr: min) Old females 28.1 2 1 .O (2 1 to 50) 1335 t 0:18 (9:44 to 17:36) Young females 30.2 1+ 0.8 (17 to 49) 13.84 f: 0:16 (9:28 to 20:OO) II (oldyoung) 42,7 1 42,67 -1 -60, p=O. Il r-0.60, p=0.54

Table 111-2. Redts of stepwise multiple regression mode1 for parentai phenotypic - - characteristics infIuencktg egg volume (n=l13). Partial R' Mode1 R' F P Female reservesL 0.066 0-066 7.76 0.006 Female age 0.008 0 .O74 0-93 0.33 Male reserves 0.006 0.080 0.69 0.4 1 Femaie size' 0.006 0.086 0.69 0.4 1 Male age 0.007 0.093 0-83 0.36 Laying date 0.004 0.097 0-5 1 0.47 Male Size' 0.0008 0.098 O-10 0.75 ' hdividual body resrrves derived by refressing mass against PCI produchg sesiduals. ' individual structural size derived Eom PC1 score of rnorphological rn~wemccints-

Table 111-3. Mean eSE) body reserve indes and eg3 size for bvo Werent age classes of breeding Cassin's Auklet fernales. Age Body reserves Egg, size (cm3) Old fernales 0.85 2 1.22(-14.27 to 20.25) 26.33 2 0.3 l(2 1.82 to 3 1.85) Young females -0.50 _t 0.86(-18.03 to 16.00) 35.92 & 0.25(20.47 to 30.17) n (old, young) 42,71 42,71 Age differexes ~0.93,p=0.35 1-1 -03, p=0.30 Age difEerencesl ~0.80,p=0.42 L-0-88,p=0.38 ontr roll in^ for laying date.

Tabte 111-4. The influence of egg size on Cassin's Auklet hatchling mass and structural size (\king chord). The hatchling variables were mass (M), structural size (SS), mass controlling for structurai size (MCSS), and structural size controlling for mass (SSCM). Variable n F P ? M 9 96.20 0.000 1 0.93 SS 9 9 -94 0.02 0.59 MCSS 9 119.0 1 0.000 1 0.97 SSCM 9 17.02 0.009 0.85 Egg sizes ranged Gom 20.95 cm3 to 29.1 5cm3(mean = 25.65 cm3 + 0.97 cm3). females so that they produce the optimum egg size appropriate to their phenotypic 'quality' (Godfray et al. 1991). The relationship between female Cassin's Auklet pre-laying body reserves and egg size, and between pre-laying and post-laying body reserves is unknown. Generally in birds, rnost nutrients deposited by the female in the egg corne from the female's diet (Carey 1996). Nutrients can be stored as body reserves for a period of tirne before being deposited in the egg, or they can be directly transported from the digestive tract to the egg (Carey 1996). In true 'capital' breeders, such as Lesser Snow Geese, females rely on accumulated body reserves for egg formation, as they feed very little between arriva1 on the breeding grounds and egg Iaying (Ankney and Maclnnes 1978). In species that are most dependent on reserves, clutch size is most closely correlated with reserve size (Ankney and Maclnnes 1978; Rohwer 1988). Conversely, 'income' breeders, such as members of the Tetraonidae rely very little on body reserves, acquiring most of the nutrients necessary for egg production frorn daily dietary intakê (Carey 1996). Cassin's Auklets are not likely true 'income' or true 'capital' breeders, but probably fit somewhere in between. Although female Cassin's Auklets feed throughout the breeding cycle, both fernales and males build-up body reserves prior to egg laying (Manuwal 1979; Manuwal and Thoresen 1993). During the pre-laying period Cassin's Auklets pairs visit the breeding colony at night either to prospect for a nesting site or to defend and perform maintenance on a pre-existing nesting site (Manuwal and Thoresen 1993). As Cassin's Auklets are primarily offshore feeders, they rnay need to maintain energy reserves to finance long nightly foraging trips between the breeding colony and the feeding grounds (Chastel et al. 1995). Therefore, if individuals lose body reserves the probability of the rapid restoration of reserves is low (Drent and Daan 1980). Furthermore, since feeding conditions for Cassin's Auklets are poor during the pre-laying period (Ainley et al. 1990) this building up body reserves relieves females of dependance on unpredictable food availability (Carey 1996). It may be necessary, therefore, for Cassin's Auklet females to build-up reserves from which they will draw from for egg production, while continuing to feed enough to fuel the nightly Rights to and from the colony. If Cassin's Auklet females are dependent on reserves for egg formation, then egg size and materna1 body reserves are likely correlated prior to laying. Therefore, low body reserves relative to egg size late in incubation would be an indication of the cost of reproduction (Nur 1986). Although adult Cassin's Auklets start to lose mass soon after egg laying is complete (Manuwal 1979; Manuwal and Thoresen 1993), the possible reasons for female mass loss are many. Female mass loss may be due to the combination of effects such as: the egg passing through the oviduct; some of the tissue of ovaries and oviduct being reabsorbed (Breitenbach and Meyer 1959; Prince et al. 1981); nutrient reserves being used for egg formation (Hario et al. 1991); or mass Ioss resulting from costs incurred during incubation (Williams 1996 for review). Age-related differences in female body reserves and egg size Older females were expected to have greater body reserves and lay larger eggs than younger fernales because of greater breeding experience. AIthough there was a slight trend towards greater body reserves and larger eggs in older females compared to younger femaIes the differences were not significant. The lack of an age-related difference in reserves and egg size may be due in part to the body reserve range in breeding young fernales representing the high end of body reserves of young fernales that were physiologically capable of breeding. The decision whether to breed or not, or to abandon a breeding attempt, is generally assumed to be related to the females' ability to rnaintain their body reserves above a certain threshold level (Drent and Daan 1980). Lack of breeding experience likely results in a greater percentage of young females having body reserves fall below the threshold ievel causing them not to breed or to abandon their breeding attempt, leaving only young females of higher phenotypic quality in this study. When controlling for laying date, the lack of age-related differences in body reserves and egg size does not substantially change, indicating that Iaying date did not have a large effect on egg size and body reserves. However, older females did lay significantly earlier than younger females (Chapter 5), indicating that younger females took Ionger to reach a level of body reserves sufficient to lay a clutch (Drent and Daan 1980). Evidence exists in some species, but not in others that egg size is positively correlated with food availability (see references in Magrath 19925). Even though older fernales should have increased access to food supplies due to increased efficiency in foraging (Szether 1990), their egg size and body reserves did not reflect this. Supplernentary feeding experiments have shown that increased food supply results in earlier laying in most species (e.g., Meijer et al. 1990) or increased egghlutch size in some species (e.g., Boutin 1990; Wiebe and Bortolotti 1995). Magrath (1992b) pointed out a general problem related to the interpretation of data relating egg size to food supply: increased food supply may cause either or both earlier laying and an increase in egg size. AIthough younger Cassin's Auklet females did not lay significantly srnaller eggs or have significantly lower body reserves than older females, late laying may have had fitness consequences for raising young due to unfavorabie conditions later in the season (Ainley et al. 1990). Age-related differences in the re1ationshl;o between egg size and female body reserwes As predicted, I observed a positive relationship between egg size and female body reserves tate in incubation in older fernales but found no such reIationship in younger females. Increased breeding cornpetence may enable older females to lessen the cost of egg formation and incubation, thus giving older females the ability to optimize their egg size according to their body reserve levels late in incubation. Food is the ultimate control on reproduction for most birds (Lack 1968), hence the increased foraging effort and efficiency often associated with increased age andor experience in seabirds (S~ther1990) probably played a major role in allowing older females to maintain the correspondence between their accumulated body reserves corresponding and the size of their egg. Social dominance plays a role in Iessening the cost of reproduction in older females (Martin 1995). Cassin's Auklet generally retain the same nesting site year after year (Ainley et al. 1990) possibly resulting in older femaies being more likely to have a nesting site at the beginning of the breeding season than first-time breeders. Since nesting sites can be a limiting factor for breeding in Cassin's Auklets, inexperienced breeders may be forced to breed in suboptimal or marginal habitats, thus increasing their cost of reproduction (Manuwal 1974b). The period when adults feed nestlings and fledglings is thought to be the most energetically expensive for parents (Walsberg 1983; Murphy and Hankioja 1986; Daan et al. 1990). However, Emslie et al. (1992) have suggested that, in Cassin's Auklets, the potential cost of reproduction may be higher during incubation. During Cassin's Auklet incubation (average 38 days) one adult remains at the nest for a 24-hour period while the other member stays at sea during the day returning at night to relieve its mate. However, during chick rearing (41 to 50 days), it is only during the first 5 to 8 days that parents alternate 24-hour brooding shifts of their hatchling. After brooding, the chick is only visited and fed once a night by each parent; otherwise it is left unattended, allowing each parent to feed during the day. Since the alternating 24-hour incubation shifts only allow each parent to feed half the time, Emsfie et al. (1992) suggest that incubation requires increased foraging effort and more coordination by the pair than during the chick rearing period, qualities that come with age and experience. Cassin's Auklets have long-term pair bonds which are terminated only when one member of the pair dies (Ainley et al. 1990). Emslie et al. (1992) demonstrated that fledging and chick weight at fledging increased with the length of pair bond in Cassin's Aukfets. Although Emslie et al. (1992) found that experience for either sex was not important for successful breeding, the authors suggested that experience and mate retention rnay be important in successfuI incubation. In this study, a larger percentage of older females (76%) were mated with older males than were younger females (57%). Although age does not equal breeding experience, it is reasonable to assume mat, on average, older female Cassin's Aukfets had more experienced mates and had retained their mates for a longer period of time when compared with younger females. Since, female body reserves were assessed Iate in incubation in this study, it is likely that older females paid a lesser incubation cost because of their own breeding experience and because they had more expenenced mates which they have retained for a longer period of tirne. If we assume that body reserves and egg size were correlated prior to egg laying, the younger females who had lower available body reserves in relation to their egg size late in incubation, rnay indicate that these birds are physiologically 'stressed' (Ricklefs 1983; Reid 1987; Martins and Wright 1993) and are paying a higher cost of reproduction. These fernales rnay have difficulty repfenishing their reserves because of the shortened foraging time due to alternating 24 hour incubation shifts and the long distznce between feeding grounds and the colony (Drent and Daan 1980). lndividuals with low reserves rnay abandon their breeding attempt (Drent and Daan 1980), or rnay experience lower survival or reduced reproduction in the future (see above). Females who allocated less to egg production in relation to their resewes rnay only incur negative fitness consequences in poor environmental years due to poor chick survival early in the hatchling stage (Williams 1994). ln one-egg clutches, a reduction in reproductive effort (smaller eggs) reduces the nutritional and enerçetic costs of the female, but does not reduce the number of offspring. Consequently, laying a small egg relative to one's body reserves in years of favourable environmental conditions rnay be a fitness benefit. In this study, the younger age class of Cassin's Auklet represents birds from 2 to 4 years of age, while the older age class represents birds 4 + years of age (Manuwal 1978). Cassin's Auklets can Iive from 10 to 20 years (Ainley et al. 1990), suggesting that there is a much larger individual age variation in the older age class. In long-term studies of Wandering Albatrosses Diornedia exulans, Croxall et al. (1992) demonstrated that egg size increases with maternai experience and Weimerskirch (1992) showed that egg size and fernale body reserves increase with maternal age. Consequently, the positive correlation between egg size and body reserves in the older age class of female Cassin's Auklets rnay represent an age andlor experience effect on egg size. So far I have assumed that egg size was correlated to maternal body reserves prior to egg laying. Astheirner (1986) indicated that Cassin's Auklet females rnay be able to predict future environmental conditions by assessing proximate factors such as water ternperature or phytoplankton density. This hypothesis is supported in Cassin's Auklets breeding on Southeast Farailon Island, California, where correlations have been fourid between the annual timing of clutch initiation and the lowering of sea surface temperatures, an indicator of local upwelling and greater phytoplankton densities (Ainley et al. 1990). If we assume that this cognitive or physiological ability to predict future environment conditions is learned through experience, older females may adjust their egg size based on their predictions about future food supplies. The lack of correlation between egg size and body condition in young females may reffect their inability to accurately predict future food supplies leading sorne individuals to over- or under-invest in the size of their egg. Individual optimization of egg size The individual optirnization hypothesis (IOH) indicates that the size of clutch a female lays is based on the female's ability to raise young (Perrins and Moss 1975). This hypothesis is not likely to apply to Cassin's Auklets since: 1) IOH states that individuals lay the number of eggs which will maxirnize the number of recruits produced in a single season: Cassin's Auklets have a fixed clutch size of one. 2) The influence of egg size on chick mass and structural size lasted less than 5 days, indicating that egg size in Cassin's Auklets had Iittle effect on chick suwival except in years of poor food availability. Nur (1986) suggested that fernales may adjust the size of the clutch according to their abitity to incubate the clutch. For example, Biebach (1984) demonstrated that European Stariings Sturnus vulgaris require more energy to incubate a larger clutch when the ambient ternperature falls below a certain threshold. Although a large egg rnay require more energy to incubate, it seems unlikely that this energy expenditure is as large as that required by an extra egg. A more Iikely adaptive explanation for the phenotypic variation of egg size in Cassin's Auklets is that individual fernales are adjusting egg size according to the levels of reserves they have stored for egg production. Alcid eggs in general have a high energy content (Rahn and Ar 1974), likely making thern expensive to produce. fleaney and Monaghan (1995) demonstrated the cost of egg production in Common Terns Sterna hirundo by making fernales lay an extra egg. The additional egg was not of reduced quality since clutch size was kept within its natural range (see Monaghan et al. 1995). The cost of producing an additional egg reduced chick provisioning and thus caused reduced growth and survival of the offspring. The cost of egg production in the Heaney and Monaghan (1995) study appears to be mediated by a negative effect on parental condition, resulting in a reduced capacity to provision the young. The influence of egg size on hatchling size and mass The first few days after hatch are important since high chick rnortality tends to occur at this time (Lack 1968; Parsons 1970; Galbraith 1988; Rhymer 1988). Many studies have shown a positive effect of egg size on offspring survival during this period (Williams 1994 for review), but large eggs are liable to result in fitness advantages only in years of poor food availability (Smith et al. 1995). The strong relationship between egg size and hatchling rnass and structural size suggests that egg size is a good measure of materna1 reproductive investment in Cassin's Auklets, since investment in a large egg leads to a large chick. In William's (1994) review of the effects of egg size on offspring fitness, he found that egg size explained 65.9+20.8% (range 16-94%, n=35 studies) of the variation in hatchling mass and 30.4+22.9% (range 4-80%, n=18 studies) of the variation in structural size. On average, egg size in this study explained a larger amount of the variation in hatchling mass and size compared to these values. When hatchling size is controlled for, chick mass accounted for more of the egg size variation indicating that for a given body size, large eggs produced heavier chicks. Sirnilarly, when controlling for hatchling mass, chick size explained more of egg size, indicating that for a given body mass, Iarger eggs produced a structurally larger chicks. Egg size explained Iess chick size variation (85%) than chick mass variation (97%); this is similar to results of Reid and Boersma (1990) on Magellanic penguins Spheniscus magellanicus. But in two other studies, for a given hatching mass, large eggs did not give rise to structurally Iarger chicks (Birkhead and Nettleship 1982, Thick-billed Murres Uria lomvia; Jarvinen and Yiimaunu 1984, Pied Flycatchers Ficedula hypoleuca), indicating that egg size did not have an influence on chick structural size. The strong positive relationship between egg size and hatchling mass attests that large eggs produce chicks with targer nutrient reserves, particularly reserves of lipid-rich yolk (Lack 1968; O'Connor 1979). This strong relationship suggests that Cassin's Auklet egg size plays a large role in the determination of chick survival in the first few days after hatch in years of poor environmental conditions since larger nutrient reserves help prevent starvation (Smith et al. 1995). ln seabirds, there is a general trend towards increased albumen content and decreased relative yolk content with increasing egg size (Montevecchi et al. 1983; Warham 1983; Shaw 1985; Meathrei et al. 1987). In alcids, Birkhead and Nettleship (1984) found a similar pattern in Atlantic puffins Fratercuta arctica, but in Razorbills Alca torda and Common Murres Uria aalge the relative amount of yolk rernained constant with increasing egg size. It is the protein in the albumen which limits the structural growth of the ernbryo and hatchling (Freeman and Vince 1974), with the components of albumen, water and protein, being entirely used up by hatching. Females that are able to increase their total investrnent in egg production might do so by making facultative adjustments in egg composition, thus increasing egg quality (Hepp et aI. 1987; Arnold 1992). Therefore, in species where chick structural size is important (Le. species with intense sibling competition, Birkhead and Nettleship 1984) females ought to invest more in the protein content of eggs with increasing egg size (Boersrna 1982). The strong correlation between hatchling structurai size and egg size in Cassin's Auklets suggests that females are increasing the protein content of eggs with increasing egg size. Why chick structurai size may be of importance in Triangle Island Cassin's Auklets remains unclear, although the increased structural size of chicks hatching from large eggs may be a fitness benefit in terms of hatching at a more advanced stage of developrnent (Williams 1994). The short tirne egg size affected chick mass and structural size (< 5 days) combined with the long fledging period in Cassin's Auklets (41 to 50 days) rnakes it unlikely that egg size would influence chick growth rates or fledging success, although egg size rnay influence chick survivai in the first 5 days of life.

Summary ln conclusion, although femafe Cassin's Auklets showed rnarked variation in egg size, female body resewes late in incubation only explained a srnaIl proportion (7%) of this variation. Although there was no difference in egg size or body reserves in the two age classes of fernales, younger fernales laid later indicating possible fitness consequences due to unfavourable conditions later in the season for raising young (Ainley et al. 1990). When breeding females are divided into two age classes, the body reserves of older females accounted for 12% of the variation in egg size, while there was no correlation between egg size and body reserves in younger fernales. These results suggest that older females are optimizing egg size to correspond with body reserves late in incubation due to selection favouring reserve-dependent variation in the alIocation of reproductive effort (Nur 1988). The likely adaptive explanation for the phenotypic adjustrnent of egg size in older Cassin's Auklets is that individuals are adjusting their egg size according to their ability to produce a clutch (Heaney and Monaghan 1995). Younger females were Iikely not able to optimize egg size because of constraints irnposed on them due to an inability to access resources (Partridge 1989). Cassin's Auklet egg size had a strong influence on hatchling mass and structural size, but this effect had disappeared by the time the chicks reached 5 days of age. This study suggests that egg size phenotypes are to some extent a consequence of selection on materna1 fitness, since the influence of egg size on offspring fitness changes from year to year depending on environmental conditions (Bernardo 1996). Chapter 4 A white blood cell count as a measure of condition: the relationship between heterophi1:lyrnphocyte ratios and iaying date in Cassin's Auklets

Abstract White blood cells, the main cellular components of blood that respond to the effects of disease and stress, may be effective in describing how an organism's physiological state influences its reproductive performance. It is energetically expensive for an individual to increase its immune system response to infection due to the direct cost of producing white blood cells and the indirect costs of the metabolic changes caused by the infection, suggesting a tradeoff between immune function and reproductive effort. In this study, I used a white blood cell count called heterophil:lymphocyte ratios (HL ratios) that has been shown to increase in response to infection or stress in chickens, as a measure of individual condition. Individual H:L ratios were measured late in incubation in 2 different age classes of male and female Cassin's Auklets to examine age- and sex-related differences in immune function and laying date, an indirect measure of reproductive performance. Younger females had significantly higher H:L ratios and later laying dates than older females consistent with an age-related difference in the cost of reproduction. No age-related difference in H:L ratios in males suggests that younger fernales may be paying a higher cost of reproduction due to sex- related differences in gametic effort. Optirnization theory suggests that an organism can make the tradeoff between current reproductive effort and future reproduction, by basing its reproductive effort on its condition, and maintaining the relationship throughout the reproductive cycle. Both females and males from the older age ciass showed a positive correlation between Iaying date and H:L ratios, while rnernbers of the younger age class did not, inferring an age-related difference in the optimization of current reproductive effort. A positive relationship between laying date and H:L ratios in older males suggests that male 'quality' may play a role in deterrnining laying date in Cassin's Auklets. H:L ratios appear be a valuable tool for measuring condition in seabirds, since they can detect problerns in a population prior to them having a serious impact.

Introduction Condition indices in birds are most effective when they describe the degree to which an organism's physiologicai state influences its performance (Le., reproduction, activity, or response to environmental conditions; Brown 1996). Many authors suggest that hematological analysis provides an indicator of an organism's physiological response to its environment (e.g., Merila and Svensson 1995; Newman et ai. 1997) and that blood composition positively correlates with health and condition (e-g., Gustafsson et al. 1994; Ots and Hôrak 1996). The main cellular components of blood that respond to the effects of disease and stress are white blood cells (Sturkie and Griminger 1986). In this chapter I look at whether an individual's ratio of heterophils to lymphocytes (H:L ratios), a differential white blood cell count, is an accurate measure of condition. To assess the usefulness of H:L ratios as a quantitative rneasure of an individual's condition, I investigated the relationship between an individual's H:L ratio and its laying date (in the case of males, the laying date of its mate), as a probable measure of an individual's phenotypic quality. Timing of breeding has fitness consequences in many bird species, with early breeders achieving more success at fledging chicks than later breeders (Ainley et al. 1990; Perdeck and Cavé 1992; Perrins 1996). In several species laying date advances with supplernental feeding (Davies and Lundberg 1985, Dunnock Prunella modullaris; Arcese and Smith 1988, Song Sparrow Melospiza rnelodia; Meijer et al. 1990, Kestrel Falco tinnunculus) suggesting a strong iink between individuals of good phenotypic quality (e.g., good nutritional status and/or good foraging ability) and early laying. Conversely, iate breeding individuals are likely to be less experienced or of poorer phenotypic quality, therefore may be energetically or behaviourally constrained in their ability to breed early. Differences in laying date among individuals may therefore be a result of the interaction between the evolutionary advantages of early breeding and the physiological and behavioural constraints influencing individual females during the period of egg formation (Perrins 1970). Alternatively, since late laying individuals are usually younger (S~ther1990), young birds may be showing restraint in reproductive effort. The "residual reproductive value" or "restraint" hypothesis (Curio 1983) suggests that young birds put less effort into breeding because reproductive effort increases mortality (Williams 1966a,b). As birds age they put more effort into current reproductive effort because reproductive potential is small. Another possible hypothesis to explain individual variation in laying date is the "selection" hypothesis. This hypothesis states that poor quality individuals die young (Perdeck and Cavé 1992), therefore the older age cohorts should lay earlier since they have a higher proportion of high quality individuals. The immune system protects the vertebrate body by responding to foreign invaders such as viruses, bacteria, and other pathogens, and combstting their effects (Darnell et al. 1990). White blood cells, or leucocytes, are an important part of the immune system, and the number and proportion of different types reflect the health status of individuals (Cline 1975). Levels of leucocytes increase rapidly in response to various stimuli, including stress and disease (Fox and Solomon 1981; Bubenik and BrownIee 1987). In avian species the most frequently occurring leucocytes are heterophils and lymphocytes (Sturkie and Griminger 1986). In chickens, H:L ratios increase in response to environmental and physiological stressors such as unbalanced diet, food and water restriction, and social disruption; and in response to viral, bacterial, protozoan and fungal infection (Gross and Siegel 1983; Dein 1986; Beuving et al. 1989; MacFarlane et al. 1989; Dohms and Metz 1991; Klasing 1991; Maxwell 1993; Zulkifii et al. 1994). An increase in H:L ratio generally reflects an increase in heterophil nurnbers, with the nurnbers of lymphocytes decreasing or rernaining the same (Dufva and Allander 1995). Although an increase in H:L ratios is indicative of stress or infection and therefore a good indicator of poor condition (Sturkie and Griminger 1986), problems can arise in H:L ratio interpretation. The level of H:L ratios in blood at any given time can be a function of infection, the ability to fight off that infection, and the level remaining &ter the immune system interacts with the pathogen (Dufva and Allander 1995). Therefore, elevated H:L ratios may reflect the immune system's ability or inability to respond to and fight an infection, or both (Sheldon and Verhulst 1996). Dufva and Allander's (1995) study of plumage color and immune response in male Great Tits Parus major is a case in point. Males with brighter plumage were considered to be of higher phenotypic 'quality', but these individuats had higher H:L ratios than dull-plumaged males. Since males with elevated HL ratios displayed brighter colouration the authors concluded that these males had superior immunity to parasites. Dufva and Allander's (1995) finding appears to be atypical however, since most field and laboratory studies relate elevated H:L ratios to poor health. One of the central assurnptions of life history theory is that reproduction is costly (Williams 1966a, b; Lessells 1991). Indirect evidence suggests that an individual's response to an infection or stress by increasing its white blood ceIl numbers is also energeticaliy expensive (Lochmiller et al. 1993), Le., immune function requires resources that could be used for some other function (Keymer and Read 1991). Therefore, an individuai's cellular response to disease and/or stress and the effects of the infection andor stress itself should manifest themselves as a decrease in reproductive effort. Since nutritional status is important in defense against disease and/or stress (Baron 1988), good quality, early-laying phenotypes are likeiy to have low H:L ratios, while low quality, late- laying phenotypes should have high H:L ratios, (Le., there is a positive correlation between laying date and H:L ratios), It is aIso Iikely that in highly socially monogamous species (e.g., seabirds) where males provide substantial care that the positive relationship between H:L ratio and laying date will manifest itself in males as well as females. However, this positive relationship should be stronger in females, since their physiology determines the timing of yolk developrnent in the ovary and therefore the timing of laying. Young birds generally lay later than than other birds (91% of 35 species, Szether 1990). This may in part be due to their lower quality/condition. If sol we might expeci: younger birds to have on average higher H:L ratios. The tower condition/quality of younger breeders rnay result in poor access to resources (Partridge 1989) causing them to become stressed or diseased. It is therefore likely that younger breeders should lay later and have higher H:L ratios than older breeders, but that there will still be a positive correlation between H:L ratios and laying dates in both age-classes. This study investigates the relationship between a measure of reproductive effort (laying date) and a rneasure of immune system function (Hi ratio) in a small socially- monogarnous alcid, Cassin's Auklet Ptychoramphus aleuticus. The objectives of this study were to determine: (i) if laying date and H:L ratios are positively correlated in both fernales and males; (ii) if H:L ratios and laying date are correlated in both younger and older age classes; (iii) if older breeders laid significantly earlier and had significantly lower H:L ratios than young breeders; (iv) the mechanisms that rnay cause age and sex-related differences in the relationship between H:L ratio and laying date; and, (v) the utility of using H:L ratios as a measure of condition.

Methods Field methods Prior to egg laying, we excavated burrows to allow access to the nest chambers. Access holes were re-covered with pieces of cedar shingle to keep corvids and tain out. Burrows were marked with nurnbered flags and mapped in relation to each other so they couid be relocated. During the last half of incubation, adult birds were removed from their burrow to be sexed, aged, and bled. Ageing To separate breeding Cassin's AuWets into two age classes I used a modified ageing criterion based on iris colour (Manuwal 1978). Fledging chicks have brown irises, which turn white over a period of 3 to 4 years. Breeders with white irises are older than breeders with some brown in their irises, so I divided Our sample into two components; white iris birds and those with some brown in their irises. Laying date/R eproduc tjve effort To obtain an index of reproductive effort, burrows were checked every 3 to 7 days to determine individual laying dates. When an egg was found, the mid-point date between the current and the previous check was used as tfie laying date. Immune Measures In the field, a blood sarnple from each individual was smeared ont0 two microscope slides and air dried. Stress levels are known to affect differential white ceIl counts, so care was taken to ensure equal handling time of each individual. Slides were fixed and stained using a Hernacolor Q 65044/93 staining set which corresponds to the staining patterns of the Wright stain and Wright-Giemsa stains. Cells were observed under 1000x magnification (oil immersion) and each cell was classified as heterophil/eosinophiI, lymphocyte, monocyte or thrombocyte (Dein 1984). Fifty fields were counted per slide (one slide per individual) using the rneander rnethod, (Coles 1986) with 25 fields being counted in one area of the slide before moving to another area to count the remaining 25 fields. The order in which the slides were scored was randomized so that no information concerning an individual bird's laying date, age, or sex was known while scoring H:L ratios. ln this study, blood smears were collected at various tirnes of the day (range: 9:28 to 21:f 5 hours) and at varying times during incubation (range: 11 to 53 days after laying date). The time of day when a bird was bled (F = 2.11, DF = 3, P = 0.10, n = 205) and the time of bleeding in relation to laying date (F = 1.98, DF = 3, P = 0.72, n =190) did not differ significantly between individuals. Neither the time of day, nor the tirne relative to laying date had a significant effect on H:L ratio. My sampling proctocol did not introduce any systematic biases in estimates of H:L ratio (Table IV-1). Stafis tics ANOVA was used to determine if the time of day the bird was bled, and bleeding tirne in relation to laying date, were significantly different between individuals. ANCOVA was used to see if there were any differences between sex and age/sex categories based on time of day bled or bleeding tirne in relation to laying date on H:L ratios. Sex and age were class variables, white time of day and time in relatiori to laying date were continuous variables. Using the raw data, t-tests were used to look at differences in mean laying date and H:L ratios between different age classes within each sex. Using ranked data to allow for non- parametric statistics, ANOVA was used to determine if sex and sexfage categories affected the relationship between H:L ratios and laying date, where sex and age were class variables. To include every individual in which white bIood cell counts were assessed, 0.5 was added to each individual's heterophil and lymphocyte count. ANCOVA was used to look for differences in the dope of the correlations of H:L ratios and laying dates between different age classes within each sex. Results 1 found a positive correlation between laying date and H:L ratio (Figure IV-1) when females were pooled- A similar, but weaker, positive relationship was found among males (Figure IV-2). When the sexes are divided into two age classes, both older females and older males showed a significant positive correlation between Iaying date and H:L ratio (Figures IV4 and IV-5). In contrast, young females and males did not show a significant relationship (Figures IV-4 and IV-5). ANCOVA demonstrated that the stopes of old females and males were significantly different from the slopes of young females and males (females, H:L ratio age, F = 5.31, P = 0.03; males, H:L ratio ' age, F = 4.04, P = 0.05). The rnean laying date was significantly earlier for old females than young females (Table IV-2, Figure IV-3). Similarly, the rnean HL ratio was significantly lower in old females Lhan in young females (Table IV-2, Figure IV-3). There was no significant difference in the mean Iaying date of fernales paired with older mates compared to females with younger mates (Table IV-2, Figure IV-3). The mean H:L ratio was not significantly different between older and younger males (Table IV-2, Figure IV-3). Discussion 1 found that: (i) overall laying date was positively correlated with the H:L ratios of both females and males, (ii) laying date and H:L ratios of both mates and females were positively correlated in the older age class, but not in the younger age class, (iii) older females laid significantly earlier, and had significantly lower H:L ratios than younger females, but there was no age-related difference in Iaying date or H:L ratios in males. Observations of pigeons have shown a die1 periodicity of leucocyte abundance due to an increase in heterophils in the afternoon (Shaw 1933). In Cassin's Auklets I failed to find any correlation between H:L ratios and time of day bled. Similarly, the date the bird was bled in relation to its laying date had no effect on H:L ratios. These results suggest that H:L ratios in this study are static within individuals (Table l), and therefore can be used as a reliable indicator of long term immune status. A positive correlation was found between laying date and H:L ratios in both males and fernales, indicating that timing of Iaying may be state-dependant (McNamara and Houston 1996); early laying individuais were in good health, while late layers had increased H:L ratios indicating increased stress or infection. Timing of breeding is an important determinant of reproductive success in Cassin's Auklets (Ainley et al. 1990). Laying early is advantageous for two reasons; zooplankton availability deches Iater in the breeding season and good nesting sites tend to be occupied eariy in the season. Drent and Daan (1980) suggested that individuaI females delay breeding until they have atlained a certain threshold Laying Date (julian date) reproductive effort

Figure IV-1. Relationship between H:L ratios and reproductive effort measured as laying date in fernale Cassin's Auklets (y=64.51+0.30~). Laying Date (julian date) reproductive effort

Figure IV-2. Relationship between H:L ratios and reproductive effort measured as laying date in male Cassin's Auklets (y=74.69+0.20x). Figure IV-3. Mean H:L ratios and laying dates for different agelsex catagories of breeding Cassin's Auklets (rnean + 1 SE, sample size above error bar). P = 0.0003 Old Females A

Young Females ,2 =

Laying Date (julian date) reproductive effort

Figure IV-4. Relationship between H:L ratios and reproductive effort rneasured as laying date in old (y=34.08+0.49~)and (y=97.84+0.09~)female Cassin's Auklets. 49 Laying Date (julian date) reproductive effort Figure IV-5. Relationship between H:L ratios and reproductive effort measured as laying date in old (y=57.61+0.31~)and young (y=113.4-0.09~) male Cassin's Auklets. 50 Table IV-1- Analysis of covariance to assess the effects of time of day (time; &C), and tirne in relation to laying date (date; B,D) on sampling heterop hi1:lymphocyte ratios in breeding Cassin's Auklets, by (sex; A, B) and by age/sex classes (group; C,D). Analpis Effect df F P A Ses 1 O. 13 0-72 Time I 0.4 1 0.52 Time*Ses I O. 19 0.66 B S ex 1 O. 14 0.70 Date 1 2.36 O. 12 Date*Sex 1 0.04 0.84 C Group 3 0.49 0.69 Time t 0.09 0-76 Time* Group 3 1.O6 0.37 D Group 3 O. LS 0.93 Date 1 0.93 0.33 Date'Group 3 O -22 0.88

Table IV-2. Mean @SE) laying date, heterophii : Iymphocyte ratio in tnro different age classes of male and fernale Cassin's aukiets. - Sex Laying Date (julian date) ~et&&il: Lymphocyte ratiop Old Femaies 90.97+0.83 Young Females 93 .89+0.7 1 n (old,young) 3437 t-2-60* Old Maies 92.2750.65 Young Males 93 -2320.86 n (old,~oWd 65,34 n.s. = non-sipnificant level of body reserves. Late laying individuals may have been in poor nutritional status prior to breeding, increasing their susceptibility to stress or infection further delaying their breeding attempt. However, the high H:L ratios in late breeders does not allow us to deduce a causal relationship between these phenornena. It is not clear if high H:L ratios negatively affect laying date or if late laying causes high H:L ratios or if the two variables are influenced by an unknown third factor. Since the measurement of H:L ratios took place late in incubation, it is possible that high H:L ratios were a result of birds on poor territories being exposed to more vectors, or they may have had to work harder for food, thereby increasing susceptibility to disease and/or stress. If, indeed, late breeding caused high H:L ratios, one would expect an increase in H:L ratios the later a bird was bled in relation to its laying date. Since this was not the case, Iate layers must have had high H:L ratios prior to breeding, resulting in them laying late. A study of immune function and reproductive performance in Collared Flycatchers Ficedula albicollis lends support to this idea (Gustafsson et al. 1994, but see Oppiliger et al. 1994). Fernale flycatchers showed a strong positive correlation between white blood cell counts and laying date, but since white blood cell counts were the same as those close to arriva1 time, disease andor stress seems to have caused delayed laying. Since high H:L ratios relate to either stress or infection (Gross and Siegel 1983; Dohms and Metz 1991; Maxwell 1993), the causa! basis for high H:L ratios remains unclear. BIood parasites were not the cause of high H:L ratios, since none was noted during cell counting. They also appear to be absent in alcids on oceanic islands due to the lack of suitable vectors (i.e. blackf1ies Simuliidae, mosquitoes Culicidae) (Greiner et al. 1975; Bennett et al. 1992). Dein (1986) showed that bacterial infection results in increased Ievels of heterophils, indicating that bacteria may be important in this population. The influence of feeding conditions during the pre-laying period in determining the laying date of Cassin's Auklet (Astheimer 1986), strongly suggests that the inability to secure enough food, caused birds to lay later. Poor nutritional status during the pre-laying period may have resulted in elevated H:L ratios in late breeders due to increased susceptibility to infection (Kemper and Read 1992). If tate breeders are of poorer quality, then stress during the pre-laying period may be the cause of high H:L ratios (Gross and Siegel 1983; Dohms and Metz 1991; Maxwell 1993) possibly due to food restriction, or an unbalanced diet, or because of social disruption due to low social rank. Lochmiller et al. (1993) demonstrated that poor nutritional condition and its associated stress cause immune suppression. Young Bobwhite Quails Colinus virginianus with reduced nutritional intake experienced a reduction in the development of organs involved in immune response (the spleen and bursa of Fabricius) and a reduction in rneasures of cell-mediated immune function. Thus, poor nutritional condition and increased stress in Iate breeding Cassin's Auklets rnay have resulted in increased susceptibility to disease through the inability of their immune system to respond to infection. The positive correlation between paternal breeding date and H:L ratios was similar to, but weaker than the correlation found in females, suggesting that energy constraints expressed by the father rnay have had an influence on the determination of laying date. The positive correlation in both sexes rnay be evidence of assortative mating for parental quality or evidence of a common parental environment that could lead to simifar H:L ratios. In Cassin's Auklets, as well as other seabirds, males play a large role in parental care (Silver et al. 1985). Cassin's Auklet fathers assume 50% of the parental care in incubation, brooding, and feeding of the chick; and are thought to play a large role in burrow defense to compensate the fernale for the extra effort she assumes in egg production (Manuwal and Thoresen 1993). Therefore, selection should favour laying date being based on the immune function of both members of a breeding pair. Little is known about the mechanisms that cause lifetime reproductive success to increase in older age classes (Sæther 1990). In long-lived, Iow-fecundity species such as Cassin's Auklets (10 to 20 years, one-egg clutch, Ainley et al. 1990) the trade-off between current reproductive effort and future survival shoutd be pronounced, since a small reduction in adult survival can have a negative effect on life-time reproductive success (Charlesworth 1980; Wooller et al. 1992). To obtain a balance between current reproduction, future reproduction and survival, the individual optimization hypothesis States that parents should adjust their effort in the production and raising of young according to their condition and maintain that level of condition throughout the breeding cycle (Nur 1988: Weimerskirch et al. 1993; Lorentsen 1995; Erikstad et al. 1997). This balance in investment assumes that pzrents make decisions at each stage of the reproductive cycle to maxirnize their lifetime reproductive success (Erikstad et al. 1997). In the present study, the younger Cassin's Auklet age class does not appear to be optimizing its reproductive effort, since H:L ratios did not covary with laying date. Therefore, young, early-breeding individuals with elevated H:L ratios rnay be risking their future reproduction and survival by laying too early based on their health. Conversely, young late layers with low H:L ratios rnay not be taking advantage of their reproductive potential based on their H:L ratio. This lack of balance between reproductive effort and H:L ratio in the younger age class suggests a possible rnechanism for the greater lifetime reproductive success usually found in older breeding seabirds, The lack of optirnization by the younger age class in their breeding attempt suggests that younger Cassin's Auklets rnay have been constrained in their ability to tirne laying so as to base it on their H:L ratio. Manuwal (1974b) demonstrated that on SEFI a population of "floatersu exists, made-up mostly of young inexperienced breeders (but see Nelson 1981) physiologically capable of breeding but constrained in doing so due to lack of burrows. Since breeders tend to occupy the same burrow in successive years Emslie et al. 1992), younger, less experienced breeders rnay have been forced to compete for the remaining, possibly inferior, nesting sites (Manuwal 1974b). It is also possible that the ability to correlate one's health (H:L ratio) with Iaying date and maintain this relationship rnay be gained through experience. Astheimer (1986) suggested that early laying females are able to accurateiy predict future environmental conditions early in the pre-laying period through proxirnate factors such as water temperature or phytoplankton density. Thus, early laying individuals are able to time their laying so that hatching corresponds with increases in food availability. Through increased experience, older individuals rnay be therefore better able to predict future environments. Assured burrow ownership, greater foraging skills, and an ability to accurately predict future environmental conditions rnay make it easier for older individuals to maintain their condition based on laying date throughout the breeding cycle. The significant age-related differences in mean laying date, and H:L ratios in breeding females, but not in breeding males, is consistent with a sex-specific, age-related difference in the cost of reproduction. Since measurements of H:L ratios were taken late in incubation, the additional cost of egg formation incurred by females is the likely cause of high H:L ratios in young femaies. Supplernentary feeding experiments affect the timing of laying (see above) and egg size (Hiom et al. 1991), demonstrating that egg production is an expensive process. The results of such experirnents depend on local food availability and on the quality of any supplement provided (Nager et al. 1997), with the availability of energy (Nager and van Noordwijk 1992), protein (Bolton et al. 1992; Ramsay and Houston 1997) and calcium (Graveland et al. 1996) al1 playing a part. Low food availability prior to, and during egg formation (Emslie et al. 1990) and the possible lack of specialized foraging skitls needed to acquire the nutrients necessary for egg formation (Martin 1995) rnay have caused younger Cassin's Auklets to become stressed, leading to increased H:L ratios and Iater laying dates. Using H:L ratios as a technique for examining immune system function appears to characterize the physiological state of Cassin's Auklet individuals and therefore is potentially valuable as a measure of condition. H:L ratios enable an evaluation of individual performance in a manner that is ecologically relevant and would be valuable in determining reasons for reproductive success. They add rnuch to our ability to understand and predict differences in sex and age-related behaviour. H:L ratios and other hematological baseline data rnay yield insights into changes in the health and viability of populations over time (Gilpin and Soulé 1986; Newman et al. 1997). Traditionally, the health status of wild populations of seabirds has been assessed by measunng reproductive success, annual survival, and popuIation size (Ainley and Boekelheide 1990). While these methods are of value, they only recognize problems after a large number of individuals have been affected (Newman et al. 1997). The combined effort of using H:L ratios with other blood analysis techniques in deterrnining the health of seabird populations has the advantage of detecting problems prior to them having a serious impact (Rosskopf et al. 1982). Chapter 5 Generai Conclusion

Synthesis 1 studied the relationship between individual phenotypic quality and reproductive effort in Cassin's Auklets at Triangle Island, British Columbia. The central aim of this thesis was io examine the effects of age and sex on an individuai's ability to optimize current reproductive effort. I did this by comparing phenotypic correlations of components of reproductive effort and indices of individual 'quality'. I used morp hological characteristics to divide breeders into age and sex categories. Iris colour was used to divide the birds into two age classes (Manuwal 1978), while a molecular sexing technique (Griffiths et al. 1996) was used to verify bill depth as a reliable morphological character for differentiating sex within breeding pairs. I used bill depth measurements of 115 pairs to show that 85% of individual breeders could be accurately sexed. The ability to sex breeders on an individual basis should be valuable in differentiating gender in an on-çoing mark-recapture study to ascertain adult Cassin's Auklet survivorship on Triangle Island. I further utiiized Griffiths et al's (1996) sexing technique to sex Cassin's Auklet chicks close to fledging. A male-biased sex ratio was found, although 1 could not determine whether this was because more female offspring died before fledging, or because mothers were able to facuitatively adjust the sex of offspring prior to laying. The positive correlations found between effort and condition in this study suggests that the capacity of individuais to withstand the demands of increased reproductive effort may be state-dependant (McNamara and Houston 1996), thereby varying with adult quality. In species with parental care, it has been generally assurned that the fitness consequences of reproduction are to be found rnainly in the costs of provisioning after birth or hatching (Lessells 1991; Roff 1992; Stearns 1992). Recent experimental studies, however, where the effects of provisioning have been separated from the effects of offspring production, dernonstrate that the different components of reproductive effort involved in offspring production have fitness consequences (e.g., incubation, Heaney and Monaghan 1995; egg production, Monaghan et al. 1998). Since condition indices were assessed late in incubation in this study, any inferred age- or sex-related differences in the cost of reproduction are due to costs associated with offspring production (Le., burrow acquisition and defence, laying date, egg production, incubation). Significant age-related differences in effort and condition were found in female Cassin's Auklets. OIder females laid earlier than young females. In Cassin's Auklets, early laying individuals having greater reproductive success (Ainley et al. 1990; HK unpubl.). Experience likely plays a role in early laying, since early laying individuals are thought to use environrnental cues to time breeding so hatch coincides with annual zooplankton bIooms (Astheimer 1986). Why timing of laying is important in determining reproductive success of Cassin's Auklets is unclear, however, in the Farallon lsiands zooplankton densities, the main food source of Cassin's Auklets. tend to subside later in the breeding season making conditions worse for raising young (Manuwal 7979). Lower reproductive success in iate 1ayir;g birds rnay, however, just be a consequence of the poorer foraging skills of late laying younger females. Significant age-related differences in heterophil:lymphocyte ratios (H:L ratios) of females demonstrates that older females were in better health than young fernales. The elevated H:L ratios in young fernales signifies increased stress andor infection, and therefore is representative of an increased cost of reproduction. Younger females rnay have used energy that otherwise would have been devoted to reproduction to increase their immune response to infection or stress. A positive correlation between laying date and H:L ratios in older females suggests that older females rnay be better at optimizing current reproductive effort relative to younger females whose reproductive effort and condition showed no such relationship. Although early laying rnay increase within-year reproductive success, and low H:L ratios rnay increase the probability of future reproduction in old females, a positive correlation between the two life history traits suggests that older females have based their effort on their condition and maintained that relationship. Thus, older fernales should have increased lifetime reproductive success relative to younger females. Age-related differences in access to resources likely explains differences in ability to optimize current reproductive effort. Because this study is correlative in nature no causal relationship can be made between corre lated characters. Elevated H:L ratios were found in young females but not in young males, showing that age-related differences in the cost of reproduction rnay be sex-specific. The increased effort and nutrients required by females for egg production, compared to males who invest only sperm towards gametic effort, rnay explain the sex-specific differences in condition. Furthermore, the age-related differences in the correlations between H:L ratios and laying date found in females were also found in males. The positive relationship found between H:L ratios in older males and the laying date of their mate suggests that energy constraints expressed by the male are important in deterrnining laying date. The role male Cassin's Auklets play in burrow defence (Ainley et al. 1990) coupled with intense intraspecific competition for nesting sites (Manuwal 1974) rnay explain this positive correlation, although the similar age-related correlational relationships found in each sex rnay be just a consequence of common parental environments. Since Cassin's Auklets only lay a single-egg clutch, females can only increase their fitness by increasing the quality, not the quantity of offspring. This study showed that large eggs produce hatchlings of greater mass and structural size, although this effect persisted for less than five days. Although egg size rnay have a positive influence on chick survival earIy in chick-rearing, the disadvantage of laying smaller eggs is only likety to manifest itself during years of particularly adverse weather conditions or food conditions (Williams 1994). Assuming that egg size did not influence egg hatchability, the lack of age-related differences in egg size found in this study rnay be explained by fluctuating selection for large eggs; the influence of egg size on offspring fitness rnay change year to year depending on environmental conditions. The behavioural 'decision' of older Cassin's Auklet females to increase reproductive effort by laying early, therefore is Iikely to increase the fitness of their offspring to a greaer extent than allocating of more resources to egg production. It cannot be ruled out, however, that older fernales increased the fitness of their offspring to some extent by increasing the quality of the egg laid as opposed to increasing egg size. Although the influence of egg size on offspring fitness rnay change from year to year, this study shows that egg size phenotypes are to some extent a consequence of selection on materna1 fitness. The positive relationship between egg size and female body reserves likely indicates that the allocation of resources to egg size is dependant on materna1 quality. Although there were no age-related differences in correlations between rnaternal body reserves and egg size, variation in egg size was positively related to body reserves in older females, but not in younger females, further suggesting that older females are better at optirnizing current reproductive effort. There was no age-related difference in rnaternal body reserves, although late laying by younger females rnay have been a consequence of taking longer to reach a level of body reserves sufficient to produce an egg (Drent and Daan 1980). In seabirds, body reserves have been linked to changes in prey abundance or other factors such as diseasepmaking thern useful indices of condition (Monaghan 1996). However, in breeding seabirds, body reserves rnay not be a good measure of individual quality since individuals must maintain body reserves to maximize adult survival, and therefore are likely to abandon their breeding attempt before their resenfes deteriorate too far (e.g., Monaghan et al. 1989, 1992; Watanuki et al. 1993). In seabirds, reproductive success and adult survival generally increases with experience or age. The age-related differences found in condition and reproductive effort associated with offspring production, and in the relationship between these two life history traits in this study of Cassin's Auklets, rnay help to explain why survival and reproductive success increases with age in seabirds. Older fernales were in better fiealth (low H:L ratios) and laid earlier than young females. Furthermore, older fernales exhibited positive relationships between condition and reproductive effort while young fernale did not, suggesting that older females were better able to balance the tradeoff between current reproductive effort and future reproduction, Higher H:L ratios in young fernales compared to young males dernonstrates that age-related differences in the cost of reproduction may be sex-specific. A positive relationship between H:L ratios and laying date in males indicates that male quality rnay play a role in determining laying date. The optimization of reproductive effort is likely to be of more importance in a long-lived species such as Cassin's Auklets since a small reduction in survival probability will excessively reduce the number of future breeding atternpts.

Future Directions In this study I assumed, based on data from many other studies, that individual condition prior to breeding was positively correlated with reproductive effort, thus allowing me to infer a greater cost of reproduction in the younger age class. This was because no correlations were apparent between reproductive effort and individual condition assessed late in incubation in the younger birds. Assessing condition in both age classes prior to breeding would confirm my assumption that condition prior to breeding is positively reIated to reproductive effort, thuv allowing for a causal relationship to be determined between correlations of reproductive effort and condition assessed late in the breeding cycle. For example, in Chapter 5, 1 was unabie to ascertain whether individuals who laid late did so because of elevated H:L ratios, or if iaying late caused elevated H:L ratios. By rneasuring H:L ratios prior to breeding cause and effect can be determined. The elevated H:L ratios found in younger females may indicate that their immune systems are less able to respond to additional infection or stress, since a decrease in lymphocyte numbers signifies immune system suppression (Siegel 1985; Fitzgerald 1988). Studies by Apanius et al. (1994) and Konig and Schmid-Hernpel (1995) demonstrate that antibody response to antigens is adversely affected by increased energy turnover, suggesting that younger Cassin's Auklet females rnay have experienced greater energy turnover rates than older fernales. Age-related differences in energy turnover rates during reproduction were found in Raskaft et al's (1985) study of time budgets of rooks Corvus frugilegus. Younger rooks expended more energy on breeding than older birds, but laid srnaller clutches and fledged fewer young. The findings in this study are similar; elevated H:L ratios may indicate younger females used more energy than older individuals, but younger females had decreased reproductive effort in terms of Iaying date. Using the doubly-labeled water technique to rneasure field metabolic rate in different aged females during reproduction would determine whether young female Cassin's Auklet have increased energy expenditure relative to older females, The age- and sex-related differences found in individual condition, reproductive effort, and the relations hip between effort and condition, merely irnplies differences in age- and sex-related costs of reproduction. Only by determining age- and/or sex-related differences in survival and fecundity can differences in the cost of reproduction be assumed. This could be done by establishing a breeding population of birds in artificial nest boxes and marking chicks in successive years, thus creating a marked population of known-age birds. Data from artificial nest boxes on Southeast Farallon Island shows that Cassin's Auklets exhibit strong nest site fidelity (Emslie et al. 1992), lifetime pair bonds (Emslie et al. 1992), and a mean natal dispersa1 distance of only 15.83 m (Pyle et al. 7998). Thus, the yearly monitoring of a large number of artificial burrows may be a practical means of assessing the effects of age and sex on fecundity and survival. This approach would also allow for an assessment of how breeding experience influences reproductive success, thus allowing for an evaluation of what the optimal age of first breeding is in terms of lifetime reproductive success. In this study, the offspring sex ratio close to fledging was male-biased, however 1 was unable to determine whether the cause was nonadaptive (Le, female offspring were less likely to hatch or to survive), or adaptive (i.e., mothers facultatively rnanipulated the sex of offspring at fertilization). Recent developments in DNA extraction from egg membranes (Pearce et al. 1997) and feathers (Griffiths and Tiwari 1995) allows for the determination of prirnary sex ratios (sex ratio at fertilization). Knowledge of the primary offspring sex ratio, and the age and phenotypic quality of parents would allow for the testing of sex allocation theory. Sex allocation theory predicts that when the benefits of producing either sons or daughters varies among individuals, adaptive variation in sex ratio may result in response to prevailing individual or ecological circumstances (Trivers and Wiliard 1973; Charnov 1982; Gowaty 1991). Cassin's Auklets may provide the ideal rnodel to test sex allocation theory. Firstly, being sexually monomorphic in size, females should adjust the sex of their offspring based on the sex-specific benefits of raising sons or daughters, rather than the sex-specific costs associated with sexually dimorphic species (Svensson and Nilsson 1996). Secondly, Cassin's Auklet females may be better at adjusting the sex of their offspring since they only lay a single-egg clutch (Emlen 1997). In several species that lay multi-egg clutches, the sex ratio deviates more strongly frorn unity in the first egg laid than in later eggs (e.g., Bednarz and Hayden 1995; Dijkstra et al. 1 WO), suggesting that the females of these species may be able only to adjust the gender of the first egg. Furthermore, sex allocation theory may be more appropriately tested in one-egg clutches, since offspring quality in multi-egg cIutches can Vary widely as ô function of both egg order and size, as well as hatching times (Parsons 1970; Pinkowski 1975; Ojanen et al. 1981; Zach 1982). There are a varietÿ of interesting and diverse research questions concerning age- and sex-related differences in the relationship between current reproductive effort and measures of individual condition. This thesis has attempted to address only a small subset of these options, and hopefully helps point the way to future work.

Conservation implications Recent climate variability has resulted in large-scale changes in the oceanic ecosystems of the Northeast Pacific (Mantua et al. 1997). These changes rnay be having a detrimental influence on Triangle Island's Cassin's Auklet population due to clirnate-induced changes in food supply. Declines in seabird abundance along the California coast (Viet et al. 1996; Ainley et al. 1996) have been attributed to a significant decline in the production of zooplankton in the California Current (Roemmich and McGowan 1995). Furthermore, Iow surface nutrient levels off the coast of Vancouver lsland (Whitney et al. in review) and prolonged El Nino events (Trenberth and Hoar 1996) in the early and mid 1990's are Iikely fundamental to the dramatic increase in the ocean mortality of steelhead trout Oncorhynchus mykiss and coho salmon Oncorhynchus kisutch off the coast of British Columbia (Welch et al. 1997). Information collected from the 1970's to the present on Triangle lsland indicates that the reproductive performance of burrow-nesting alcids is in decline (Bertram unpubl.) Furthermore, recent estimates of suwival rztes suggest that the population of Cassin's Auklets on Triangle lsland is diminishing (Bertram et al. manuscript). The 1998 recovery of a banded Triangle lsland Cassin's Auklet in the waters off of Southern California (Bertram unpubl) coupled with Manuwal and Thoresen's (1993) assertion that northern populations of Cassin's Auklets winter in southern waters suggests that Cassin's Auklets from Triangle lsland may winter off the California coast where zooplankton stocks are depleted as already noted. Triangle Island's Cassin's Auklet population may therefore be diminishing due to declining food supplies in both their wintering and breeding grounds. The possibility that the largest breeding colony of Cassin's Auklets in the world may be in decline emphasizes the importance of collecting more information to determine the underlying causes of this suspected decline. The year of this study, 1996, was the poorest on record for Cassin's Auklet nestling production, many chicks either starved or fledged at very tow masses (Bertram unpubl.). This thesis shows that the poor environmental conditions present in 1996 had a greater detrimental impact on young breeders, especially young fernales. The lack of positive relationships between condition indices assessed late in incubation, and reproductive effort, shows that younger breeders were unable to optimize current reproductive effort. Furthermore, elevated H:L ratios in young females rnay signify that females are more susceptible to poor years than males. If low zooplankton densities were the cause of the poor reproductive success in 1996, it is likely that the negative impact was greater on younger breeders due to poorer foraging skills. In years of poor food availability individuals must increase their foraging effort which indirectly rnay influence their su~ival(Wernham and Bryant 1998). Because of poor foraging skills, the indirect effect of increased foraging effort on survival would be expected to be stronger in younger individuals. A population bottleneck rnay result if the survival of young breeders becomes extremely low. Breeding individuals rnay be literally "the living dead" if no new cohorts are able to survive or reproduce successfully. The Tufted Puffins Fratercula cirrhata of Triangle Island appear to be an extreme example of this; breeding individuals have been successful in fledging chicks in only one year of the last five (8ertram unpubl.). Traditionally, the health of seabirds has been assessed by monitoring population status, reproductive success or annual survival. Although these methods are practical and valuable, they fail to detect problems prior to their impact on the colony. This is because behavioural and life-history responses (Le. adjusting laying date or clutch size) buffer seabirds frorn the imrnediate effects of environmental change, and therefore rnay introduce a tirne lag in a population's response to such a change (Wiens 1989). The cornbined use of H:L ratios with other blood analysis techniques to determine the heaIth of seabird populations has the advantage of detecting problems in the health of a colony prior to there being a large impact (Rosskopf et al. 1982). Using sexing and aging techniques to pinpoint different portions of the population coupled with bfood analysis techniques would provide a powerful management tool for determining were problems lie before populations are affected. Comparing mean reproductive effort or individual condition between age classes rnay give an assessrnent of differences in age-related reproductive success and health within a particular breeding season, but does not reveal if each age class is making the trade-off between current reproductive effort and future reproduce success. A more appropriate method for assessing age-related differences in fitness rnay be to compare phenotypic correlations between effort and condition late in the reproductive cycle. By comparing differences in phenotypic correlations between age classes on a yearly basis, trends in the inter-year effect of environmental conditions on the optirnization of current reproductive effort between each age class could be assessed. Management perse is unlikely to reverse the suspected decline in Cassin's Auklets on Triangle Island. Global warming is widely accepted to be anthropogenic in origin as opposed to natural (Trenberth and Hoar 1996) and has been linked to severe declines in ocean productivity (Roemmich znd McGowan 1995). Through the continued monitoring of the health and reproductive effort of Cassin's Auklets on Triangle Island, the effect of global warming Triangle Island's seabirds and surrounding marine environment will become better understood. Literature Cited

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