Influence of behavioural tactics on recruitment and reproductive trajectory in the kittiwake

Many studies have provided evidence that, in birds, inexperienced breeders have a lower probability of breeding successfully. This is often explained by lack of skills and knowledge, and sometimes late laying dates in the first breeding attempt. There is growing evidence that in many species with deferred reproduction, some prebreeders attend breeding places, acquire territories and form pairs. Several behavioural tactics assumed to be associated with territory acquisition have been described in different species. These tactics may influence the probability of recruiting in the breeding segment of the population, age of first breeding, and reproductive success in the first breeding attempt. Here we addressed the influence of behaviour ('squatting') during the prebreeding period on demographic parameters (survival and recruitment probability) in a long-lived colonial seabird species: the kittiwake. We also investigated the influence of behaviour on reproductive trajectory. Squatters have a higher survival and recruitment probability, and a higher probability of breeding successfully in the first breeding attempt in all age-classes where this category is represented. The influence of behaviour is mainly expressed in the first reproduction. However, there is a relationship between breeding success in the first occasion and subsequent occasions. The influence of breeding success in the first breeding attempt on the rest of the trajectory may indirectly reflect the influence of behaviour on breeding success in the first occasion. The shape of the reproductive trajectory is influenced by behaviour and age of first breeding. There is substantial individual variation from the mean reproductive trajectory, which is accounted for by heterogeneity in performance among individuals in the first attempt, but there is no evidence of individual heterogeneity in the rate of change over time in performance in subsequent breeding occasions     

Defining the linear portion of a sigmoid‐shaped curve: bend points

Formulae are provided that define the ‘bend points’, the beginning and end of the essentially linear dose–response region, for the four‐parameter logistic model. The formulae are expressed in both response and dose units. The derivation of the formulae is shown in order to illustrate the general nature of the methodology. Examples are given that describe how the formulae may be used while planning and conducting bioassays. Copyright © 2003 John Wiley & Sons, Ltd.     

A MODEL OF "FAMILY FAIRNESS" AND ITS IMPLICATIONS FOR DEBT NEUTRALITY

Evidence suggests that a signcant proportion, though by no means all, of bequests is equally divided among the beneficiaries. This is inconsistent with standard models of bequests, which predict that equal division should occur only by chance. This paper proposes a modified model incorporating "family fairness" as well as utilitarianism as an influence on behavior. Various implications for debt neutrality are analyzed.     

The Ecology of Family Guidance in Low-Income Mexican-American and European-American Families*

This two-part study applied an ecocultural perspective to socialization of daily and long-term goals in low-income Mexican-American and European-American families with children in third, fifth, and seventh grades. The first part of the study examined family members' participation and parents' socialization goals and guidance strategies for their children's daily household chores and homework activities. The second part of the study examined parents' long-term aspirations and guidance strategies for their children's educational, vocational, and moral development. For daily activities, results showed that in Mexican-American families both parents and siblings played important roles, whereas in European-American families parents were the primary socialization agents. As predicted, in both groups parents' expertise influenced their guidance strategies. Finally, Mexican-American and European-American parents differed in their relative endorsement of gender, relational, and self-reliance goals for household chores. For long-term goals, parents in both groups held high educational, vocational, and moral aspirations for their children. However, some parents of seventh-graders had lower educational and vocational aspirations than those of fifth- and third-graders. Although expertise consistently influenced Mexican-American parents' guidance strategies, the pattern for European-American parents was mixed. The discussion highlights between- and within-group differences in daily and long-term socialization practices with an emphasis on resources and vulnerabilities in the families.     

The U.S. legalization program: a preliminary final report

The Immigration Reform and Control Act (IRCA) of 1986 made 4 types of aliens eligible to receive legalization benefits: 1) those who resided "continuously" in the US since January 1, 1982; 2) those who had worked in the US perishable-crop agriculture for 90 "man-days" in specified time periods (Special Agricultural Workers [SAWS]); 3) those who were in the US since before January 1, 1972; and 4) those classified as Cuban/Haitian entrants and who had been in the US since January 1, 1982. Estimates of the number of aliens eligible for legalization, not including SAWS, ranges from 1.834 million to 2.56 million. Estimates of undercounts of undocumented aliens are 10% for those who entered before 1975 and 37.5% for those who arrived after 1975. Other refinements in the estimates of undocumented aliens include adjustments for 1) ethnic group and location, 2) the growth of the undocumented population between the census date and the legalization eligibility date under IRCA, and 3) emigration and deportation rates. Out of the 1,581,800 applicants entered into the Immigration and Naturalization Service (INS) computers (from a total of 2.15 million applicants) as of May 20, 1988, 73.7% were Mexican nationals. Only 5 other countries contributed more than 1%: El Salvador (6.5%), Haiti (2.3%), Guatemala (2.2%), the Philippines (1%), and Colombia (1%). The Mexican percentage was unexpectedly high, perhaps because the legalization had been much more successful in the Southwest than anywhere else in the country. Reasons that Mexicans have a higher legalization participation rate than other nationalities include 1) the distant eligibility date; 2) ethnic differences among non-Mexican nationalities; 3) particularly in the northeast, fears of exposing one's illegal status to INS; 4) the difficulty of information reaching ethnic communities, 5) the reluctance of those already undergoing the naturalization process to risk the legalization process; and 6) the reluctance of employees to admit employment of undocumented aliens. In the end, more than 90% of applicants are expected to be granted temporary resident alien status (and about 70% of agricultural workers), for a total of more than 2 million people. Researchers estimate that 2.5 - 3 million more persons remain in an undocumented status in the US.     

Enrich marital inventory: a discriminant validity and cross-validation assessment

To assess the validity and clinical utility of the marital inventory ENRICH, a discriminant validity study was conducted using a national sample of 5039 married couples. The sample was randomly split in order to form a cross-validation group. ENRICH is a multidimensional scale and two types of analysis were conducted to assess the value of these various scales. Results from discriminant analysis indicated that using either the individual scores or couples' scores, happily married couples could be discriminated from unhappily married couples with 85–95% accuracy. These results were cross-validated with a second sample. Using regression analysis, it was clearly demonstrated that background factors account for little of the variance in discriminating happy from unhappily married couples compared to their relationship dynamics, i.e., scale scores. All ENRICH scales except equalitarian roles proved significant, indicating the validity of a multidimensional inventory.