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Blue-footed boobies (Sula nebouxii) are socially monogamous, colonial seabirds exhibiting intra-specific nest parasitism and extra-pair copulations. Prior DNA fingerprinting assays failed to detect extra-pair offspring in the nests of congeners, and the rate of intra-specific nest parasitism has not been estimated using molecular techniques. We describe the development and characterization of 11 microsatellite DNA loci, tested using 31 individuals collected on Isla Isabel, Nayarit, México. The number of alleles per locus ranged from three to 22, averaging seven; total exclusionary power of the microsatellite panel was 0.99; no loci deviated from Hardy-Weinberg equilibrium; and we did not detect linkage disequilibrium following Bonferroni correction. This microsatellite panel will facilitate future studies of nest parasitism and extra-pair paternity in blue-footed boobies.

The behaviour that mediates divorce and partner change in socially monogamous species is largely unstudied and unknown, although roles and adaptive functions in some birds have been inferred from breeding outcomes, partial behavioural records and captive studies. Here, roles and functions of natural within-season mate switching of a colonial bird were characterized by describing interactions over many days during the whole daylight period. Switching occurred in 5.9% of bluefooted booby pairs and was initiated by desertion of males or, less commonly, females. Three male desertions were consistent with either the Errors of Mate Choice or Incompatibility hypotheses but were better explained by our new Unfaithful Mate hypothesis because infidelity of the mate preceded desertion. Another two male desertions were more consistent with the Better Options hypothesis because the males switched to their ongoing extra-pair (EP) partners. One female desertion was consistent with the Errors of Mate choice or Incompatibility hypotheses, and another with the Better Options hypothesis. All five deserted females switched promptly to their EP partners. Thus, most switches consisted of (1) males replacing a possibly unsatisfactory partner with a new (already identified or to be identified) partner, or (2) deserted females pairing with their EP partners. [ABSTRACT FROM AUTHOR]

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 life-history tactics for each sex and different ages, with birds likely trying to maximize their fitness by responding to the environmental contingencies of each year. [ABSTRACT FROM AUTHOR]

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-looted 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 I 1 years), the fewer fledglings it produced. A positive effect of density on long- term 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. [ABSTRACT FROM AUTHOR]

Philopatry over the lifetime and its relationship with reproductive success were examined using longitudinal records of nest location and reproduction of individual blue-footed boobies. Males showed shorter natal dispersal than females, and natal dispersal distance of both sexes were unrelated to either first reproductive success or lifetime reproductive success. Throughout the early lifetime, males and females nested closer to their first breeding sites than to their natal sites, and comparison with a simulation of successive breeding dispersals in random directions showed that male and female blue-footed boobies are philopatric to the first breeding site. Therefore, throughout the early lifetime, the first breeding site seems to function as a point of reference for breeding site use together with the previous season's site. Males and females with shorter natal dispersal distances showed stronger lifetime philopatry to their first breeding sites, suggesting stable individual variation in competitive ability or dispersal phenotype. However, early lifetime philopatry to first breeding sites was unrelated to annual breeding success. Compared with simple fidelity to previous breeding sites, lifetime philopatry to first breeding sites should result in increased kin interactions and greater selection for kin recognition, altruism and inbreeding avoidance, as well as long-term familiarity with neighbors. [ABSTRACT FROM PUBLISHER]

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. [Copyright &y& Elsevier]

Individual variation in sexual fidelity and extrapair paternity (EPP) is widely attributed to environmental heterogeneity, but the only variables known to be influential are food abundance and density of conspecific breeders (potential extrapair partners). Habitat structure is thought to impact EPP but is rarely measured and, when considered, is usually confounded with food abundance and predation pressure. To sidestep these confounds, we tested whether EPP is associated with habitat structure variables and with local conspecific density in a species whose nesting habitat is not used for feeding and lacks predators. In a blue-footed booby, Sula nebouxii , colony, the probability of EPP in a female's nest was highest in parts of the study plot where there were few obstacles to locomotion, and was quadratically related to local density of sexually active males, even though local males did not sire the EP chicks. The probability of a male breeder siring EP (extrapair) chicks elsewhere was quadratically related to local density of sexually active males around his nest. From these patterns we infer that both sexes may foray for EP interactions, that males and females nesting at intermediate density are most likely to be accessed by forayers, and that obstacles in the vicinity of a female's nest constrain access of foraying males. To our knowledge, this is the first demonstration that individual variation in EPP is associated with habitat structure in the absence of confounding variation in food availability, predation pressure or breeder quality, and the first evidence that EPP opportunities of female and male breeders are reduced by high density of conspecific breeders above a particular threshold. [ABSTRACT FROM AUTHOR]