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The Nesting Biology of Some Passerines of Buenos Aires, Argentina

1985; Issue: 36 Linguagem: Inglês

10.2307/40168328

1941-2282

P.C. Mason,

Bird parasitology and diseases

Nesting data were collected over two seasons at two study sites approximately 20 km apart in Buenos Aires Province, Argentina. Community composition differed between sites. The data include brief descriptions of nests, eggs, and nestlings. The duration of incubation and nestling periods are also presented. Maximum likelihood estimators of nest survivorship are calculated separately for nests with eggs and nests with nestlings. Nestlings of eight species were parasitized with botfly larvae (probably Philornis sp.). Broadly speaking, species that nest in complex or closed nests have higher survivorship than species which build cup nests. However, a comparison of mortality of the Rufous Hornero and the Saffron Finch using nests of the former indicates that the behavior of the species contributes greatly to survivorship. Saffron Finches nesting in hornero nests show poorer survivorship than the horneros themselves. Nonetheless, Saffron Finches using these nest sites have superior survivorship to those which use other nests. The demographic data also permit the rejection of the hypothesis of prevention of total nest failure as the selective agent favoring asynchronous hatching in the Rufous Hornero. RESUMEN. Se colecciono informaci6n de anidaci6n durante dos temporadas en dos sitios distantes 20 km entre si, en la provincia de Buenos Aires, Argentina. La composici6n de la comunidad difiere entre ambos sitios. Los datos incluyen breves descripciones de nido, huevos y polluelos. Tambien se presenta informaci6n respecto a la duraci6n de la incubaci6n y el periodo de anidaci6n. Se calculan separadamente las estimaciones maximas de sobrevivencia, para nidos con huevos y nidos con polluelos. Polluelos de ocho especies estaban parasitados por larvas de la mosca (probablemente Philornos sp.). Generalmente, las especies que anidan en nidos complejos o cerrados tienen mayor tasa de sobrevivencia que las especies cuyos nidos tienen forma de copa. Sin embargo una comparaci6n de la mortalidad del hornero Rufous y el Pinz6n Saffron usando nidos de hornero indican que la sobrevivencia esta relacionada con el comportamiento de la especie. Pinzones Saffron que anidan en nidos de horneros, tienen menor sobrevivencia que los mismos horneros. A pesar de lo cual, los pinzones que usan nidos de hornero tienen mayor sobrevivencia que los pinzones que usan otros nidos. La informaci6n demografica tambien permite rechazar la hipotesis de prevenci6n de fracaso total de anidaci6n como un agente selectivo favoreciendo la incubaci6n asincr6nica del hornero Rufous. Studies of nesting biology contribute to the development of biological knowledge in a variety of ways. Descriptive natural history observations document the diversity of life, and the accumulation of such observations eventually allows the construction of general hypotheses. Some information can be interpreted immediately through its application to current theory. Many of the data collected at nests, such as egg size, clutch size, length of incubation and nestling periods, and nest survivorship are among the most fundamental of avian life-history attributes. The values of these parameters, which contribute to fitness and are subject to selection, are often unknown. The purpose of this paper is twofold. First, it supplies a body of descriptive data on events that occur at nests of temperate, South American passerines. Second, it interprets appropriate portions of the demographic data. In particular, these analyses examine the relationship between nest survivorship and nest placement, both interand intraspecifically. Finally, a comparison of survival rates during the egg and nestling phases is used to test a hypothesis of asynchronous hatching in the single passerine species observed here to display this trait.