Reproductive success of white-faced ibis (Plegadis chihi) was measured in nine colonies on marshes in northern Utah during 1979. The effects of pesticides and characteristics of colonies and sub-colonies on reproductive success were examined. DDE was present in all 80 eggs sampled and had a geometric mean concentration of 1.25 ppm. Shell thickness of 176 eggs was 4.3 percent below pre-1945 thickness. Shell thickness was weakly correlated with residues of DDT, DDE, Dieldrin, and heptachlor epoxide. Residues of these four pesticides were all correlated with each other. However, because of the stronger correlations between shell thickness and two residues, DDE and DDT, and because of studies in the literature, it was concluded that these two residues were responsible for the observed shell thinning. Observed levels of pesticides did not cause sufficient shell thinning to reduce hatching success, but clutch size was negatively correlated with pesticide residues. Only two characteristics of colonies were observed to be associated with differences in reproductive success. Earlier sub-colonies had larger clutches and larger colonies suffered higher rates of predation. If there are effects of subcolony size, degree of nesting synchrony, vegetation type, or avian species association on reproductive success, they may not be detectable with one year of data.

Made available in DSpace on 2016-06-02T20:21:25Z (GMT). No. of bitstreams: 1 3426.pdf: 1264050 bytes, checksum: 96e1848885552d495b4d4685cb57fba6 (MD5) Previous issue date: 2011-01-24 / Universidade Federal de Sao Carlos / The white-faced ibis, Plegadis chihi (Vieillot, 1817) (Pelecaniformes, Threskiornithidae) is a migratory waterbird that breeds in colonies in the southern of Brazil. In point of view of genetics, this species was not studied. In this study we genetically characterized two populations from Rio Grande do Sul, and we classified nestlings sampled inside the same nests in one category of relatedness (full-siblings, half-siblings or unrelated). We extracted DNA from 247 nestlings (either from growing feathers or muscle tissue) and amplified it by PCR. We screened 44 microsatellite heterologous loci developed for species belonging to: Threskiornithidae, Ciconiidae and Ardeidae families. Individuals were genotyped at successfully amplified loci, and six loci proved to be polymorphic. The number of alleles per locus ranged from two (NnNF5) to 10 (Aaju3), and average expected and observed heterozygosities were 0.572 and 0.552, respectively. NnNF5 and Eru6 were excluded from the analysis of genetic structure since they are in linkage disequilibrium with Eru5 and Eru4, respectively. The AMOVA analysis showed that most of the genetic diversity is distributed within populations, and not between populations. The FST value, although small, was significant (0.009, p = 0.05), indicating that there is low differentiation between colonies studied. The results suggest that populations are structured and that little gene flow occurs between them. The ratio between males and females in our samples was not different from the expected 1:1. One hundred and six pairs of nestlings taken from the same nests, using Aaju3, Eru2, Eru4, Eru5 e Eru6 loci, were inspected for relatedness. Our analytical procedure allowed us to identify the kinship of 55% of the pairs. Among the classified pairs of nestlings we found: 62% of fullsiblings, 5% of half-siblings and 33% of unrelated nestlings. Relatedness categories found between pairs of nestlings are showing that genetic monogamy is not the only mating system, but extra-pair fertilization and brood parasitism can be occurring. / O tapicuru, Plegadis chihi (Vieillot, 1817) (Pelecaniformes, Threskiornithidae) é uma ave aquática migratória que se reproduz em colônias no sul do Brasil. Essa espécie tem sido pouco estudada do ponto de vista genético. Nesse trabalho, nós caracterizamos geneticamente duas populações do Rio Grande do Sul e classificamos filhotes coletados no mesmo ninho em uma categoria de parentesco (irmão-completos, meio-irmãos ou não-relacionados). O DNA foi extraído a partir de penas em crescimento e tecidos musculares de amostras de 247 ninhegos e amplificado via PCR. Foram testados 44 locos de microssatélites desenvolvidos para espécies pertencentes a três famílias de aves: Threskiornithidae, Ciconiidae e Ardeidae. Os locos que amplificaram após as reações de PCR foram genotipados e seis deles se apresentaram polimórficos. O número de alelos variou de dois (NnNF5) a 10 (Aaju3) e a heterozigosidade média esperada e observada foram 0,572 e 0,552, respectivamente. Os locos NnNF5 e Eru6 foram excluídos das análises de estruturação genética por se apresentarem em desequilíbrio de ligação com os locos Eru5 e Eru4, respectivamente. A análise de AMOVA mostrou que a maior parte da diversidade está presente dentro das populações e não entre elas. O Fst foi pequeno, mas significativo (0,009, p = 0,05), mostrando uma baixa diferenciação genética entre as duas colônias. Os resultados sugerem que as populações estão pouco estruturadas e que ocorre fluxo gênico entre elas. A sexagem molecular não detectou desvio da razão observada entre machos e fêmeas em relação à razão esperada (1:1). O grau de parentesco foi determinado para 106 pares de ninhegos retirados do mesmo ninho, com os dados dos locos Aaju3, Eru2, Eru4, Eru5 e Eru6, sendo possível a classificação de 55% dos pares numa categoria de parentesco. Dentre os pares de ninhegos que foram classificados: 62% são irmãos-completos, 5% meio-irmãos e 33% não-relacionados. Esses padrões de parentesco evidenciam que o sistema de acasalamento não é apenas monogâmico, mas que também pode estar ocorrendo fertilização extra-par e parasitismo de ninho, em menor escala.