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In marine ecosystems climatic fluctuation and other physical variables greatly influence population dynamics, but differential effects of physical variables on the demographic parameters of the two sexes and different age classes are largely unexplored. We analyzed the effects of climate on the survival and recruitment of both sexes and several age classes of a long-lived tropical seabird, the Blue-footed Booby (Sula nebouxii), using long-term observations on marked individuals. Results demonstrated a complex interaction between yearly fluctuations in climate (both local and global indexes, during both winter and breeding season) and the sex and age of individuals. Youngest birds' survival and recruitment were commonly affected by local climate, whereas oldest birds' parameters tended to be constant and less influenced by environmental variables. These results confirm the theoretical prediction that sex- and age-related variation in life-history demographic traits is greater under poor environmental conditions, and they highlight the importance of including variability in fitness components in demographic and evolutionary models. Males and females showed similar variation in survival but different recruitment patterns, in relation to both age and the spatial scale of climatic influence (local or global). Results indicate different lifehistory tactics for each sex and different ages, with birds likely trying to maximize their fitness by responding to the environmental contingencies of each year. Key words: Blue-footed Booby; capture--recapture modeling; climate; demography; life-history trails; population dynamic, seabird; Sula nebouxii.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2009.10.005 Byline: Sergio Ancona, Hugh Drummond, Jaime Zaldivar-Rae Abstract: Simultaneous effects of mate guarding on a male's energy intake and expenditure have not been measured. We tested whether guarding males of the western Mexican whiptail lizard, Aspidoscelis costata, reduce energy intake and increase expenditure of energy on male-male aggression. Also, we tested whether guarding males calibrate their aggressive behaviour and feeding to aggression from male rivals (a proxy of their female's probability of extrapair copulation) and body size of the guarded female (positively correlated with fecundity in this species). Observation during and after guarding showed that guarding males (1) ate 77% fewer prey/h and 54% smaller prey, (2) initiated 87% more agonistic interactions/h and (3) participated in 120% more escalated agonistic interactions/h than when alone. Also, guarding males initiated more aggressions when aggression from other males and female size were greater. These results indicate that mate guarding is costly for males because of simultaneous reduction in energy intake and increased expenditure on aggression, and that males incur higher guarding costs when competition with other males and female reproductive value are greater. These costs of mate guarding probably result in negative energy balances that could reduce male fitness through diminished survival. The evolutionary persistence of mate guarding by males can be explained if the net gain in fitness derived from guarding more than offsets its survival costs. Author Affiliation: Departamento de Ecologia Evolutiva, Instituto de Ecologia, Universidad Nacional Autonoma de Mexico, Mexico Article History: Received 8 May 2009; Revised 2 July 2009; Accepted 10 September 2009 Article Note: (miscellaneous) MS. number: A09-00302

Contradictory patterns of density-dependent animal dispersal can potentially be reconciled by integrating the conspecific attraction hypothesis with the traditional competition hypothesis. We propose a hypothesis that predicts a U-shaped relationship between density and both natal and breeding dispersal distance. Using 10 years of observations on a breeding colony of the Blue-footed Booby (Sula nebouxii), the hypothesis was confirmed by documenting simultaneous positive and negative density-dependent dispersal distances in natal and breeding dispersal of males and breeding dispersal of females within the colony. Point-pattern analyses demonstrated that the breeding sites of Blue-footed Boobies were highly aggregated in all years within a large study area, and aggregation presumably resulted in heterogeneity in patch density throughout the colony. As predicted, at moderate to high densities, dispersal distances showed positive density dependence, with individuals moving to lower density patches. In contrast, at low to moderate densities, dispersal distances showed negative density dependence, with individuals moving to higher density patches. In both sexes of the 1994 cohort, the higher the mean density in patches used by an individual over the long term (up to age 11 years), the fewer fledglings it produced. A positive effect of density on longterm reproductive success was not detected, possibly because birds that failed during pair formation or incubation were not sampled. Density of conspecifics may be an important influence on habitat selection of breeders, and dispersal may tend to carry individuals to patches where pair formation opportunities are better and negative effects of competition on reproductive success are reduced. Key words: Allee effect; Blue-footed Booby; competition; conspecific attraction; density dependence; dispersal; Isla Isabel, Nayarit; patchiness; Ripley's K; Sula nebouxii.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2007.02.034 Byline: Claudia Valderrabano-Ibarra, Ireri Brumon, Hugh Drummond Abstract: Theoreticians propose that trained winning and losing are important processes in creating linear animal dominance hierarchies, and experiments have shown that both processes can occur in animals, but their actual roles in creating natural hierarchies are unknown. We described agonism in 18 broods of three blue-footed boobies, Sula nebouxii, a species for which trained winning and losing have been demonstrated, to infer how these processes generate and maintain a natural hierarchy. Ranks in the linear hierarchy that emerged in every brood were initially assigned by asymmetries in age, size and maturity, which led to differences between broodmates in levels of expressed and received aggression and, consequently, to differences in the training of their aggressiveness and submissiveness. Later, ranks appeared to be maintained by the chicks' acquired aggressive and submissive tendencies combined with ongoing effects of persisting differences in size and maturity. Our results suggest that trained winning and trained losing are important in the construction of booby hierarchies but that these two axes of learning are largely independent. Increase in submissiveness occurs over a period of about 10-20 days, and the level of submissiveness reached varies with the amount of aggression received. After training, submissiveness is apparently maintained by a lower level of aggression and increasing use of threats. Threats become increasingly effective as chicks age, but are never as effective as attacks. Author Affiliation: Instituto de Ecologia, Universidad Nacional Autonoma de Mexico, Mexico Article History: Received 5 June 2006; Revised 9 August 2006; Accepted 14 February 2007 Article Note: (miscellaneous) MS. number: A10466R2

In broods of Crested Ibis (Nipponia nippon), aggressive dominance was unstable over time, even within feeding sessions. All chicks took turns pecking aggressively while broodmates hung their heads submissively, although roles were contested at the start of feeding bouts when chicks were 11-17 days old. In all broods, at least half of all pecks were false pecks, which did not strike broodmates even when within reach. False pecks seem to be ritualized displays that function to solicit food from parents and possibly to threaten rivals. Received 9 July 2002. accepted 24 March 2004., We describe an extraordinary form of agonistic interaction between broodmates of the Crested Ibis (Nipponia nippon), a critically endangered ciconiiform (Liu 1981). Aggression among altricial broodmates occurs in a variety [...]

Cross fostering to pair dominant and submissive chicks with singletons in the blue-footed booby, Sula nebouxii, was undertaken to determine the effects of early social experience on the agonistic behavior in the chicks of this species. Results reveal that the strong influence of early social experiences on the agonistic behavior is reversible. Experiences as a subordinate chick have more persistent effects compared to experiences as a dominant one.

Male Blue-footed Boobies (Sula nebouxii) first nested at an age of two to six years (arithmetic mean of sample = 4.7), and females a little earlier at one to six years (arithmetic mean of sample = 3.6). Both sexes nested selectively close to the natal site in their first reproduction (males 24.1 m, females 28.3 m) and similarly close to the natal site in their second reproduction, despite displacement from first to second site. First sites of both sexes were similarly close to the natal site and the parents' current site, and parents dispersed only 26.2 m between hatching and first reproduction of their offspring. Throughout their lives, both sexes may tend to nest close to the natal site and, hence, close to kin. Nonetheless, given high nest density in the colony (0.0356 nests/m squared) and high variance in natal dispersal (males, SD = 33.1 m; females, SD = 35.2 m), inbreeding and social interactions with kin are unlikely to result. Overall, these results do not support the hypothesis that philopatry in some marine birds and other animals functions to achieve an optimal balance between inbreeding and outbreeding.

An experimental study of the factors affecting direction of sibling dominance in the avian species, Sula nebouxii, was done. Results showed that a chick's social experience determines its aggressive or submissive behavior, although junior chicks may become aggressive when they see a personal advantage. When chicks with a history of subordination become aggressive they were seen to be competitively inferior to smaller chicks with a history of dominance.

The article describes indirect feeding, long nestling periods and small broods in combination with other factors that have tended to favour the evolution of aggressive broodmate competition.

A review of the influence of food as the driving mechanism for the evolution of broodmate aggression is presented. In particular the twin hypotheses of food amount and prey size are evaluated.