Nestling Sex Ratio in the Southwestern Willow Flycatcher

Current Topics in Avian Conservation Genetics with Special Reference to the Southwestern Willow Flycatcher

It is sometimes said that scientists are entitled to their own opinions but not their own set of facts. This suggests that application of the scientific method ought to lead to a single conclusion from a given set of data. However, sometimes scientists have conflicting opinions about which analytical methods are most appropriate or which subsets of existing data are most relevant, resulting in ...

Appendix E. Willow Flycatcher Migration and Winter Ecology

Nestling testosterone is associated with begging behaviour and fledging success in the pied flycatcher, Ficedula hypoleuca.

Animal signals are hypothesized to be costly in order to honestly reflect individual quality. Offspring solicitation signals given by nestling birds are thought to have evolved to advertise either need or individual quality. We tested the potential role of testosterone (T) in controlling the intensity of these signals by measuring begging behaviour as: (i) duration of the begging display and (i...

Against the odds? Nestling sex ratio variation in green-rumped parrotlets

We investigated nestling sex ratio variation in the green-rumped parrotlet (Forpus passerinus), a small neotropical parrot breeding in central Venezuela. There are strong theoretical reasons to predict a female-biased sex ratio in this system according to the local resource hypothesis; juvenile males are philopatric and there are high levels of competition between male siblings for access to br...

Sex-specific effects of altered competition on nestling growth and survival: an experimental manipulation of brood size and sex ratio.

1. An increase of competition among adults or nestlings usually negatively affects breeding output. Yet little is known about the differential effects that competition has on the offspring sexes. This could be important because it may influence parental reproductive decisions. 2. In sexual size dimorphic species, two main contradictory mechanisms are proposed regarding sex-specific effects of c...