Consequences of Dominance-Mediated Habitat Segregation in American Redstarts during the Nonbreeding Season

Abstract

ABSTRACT.-Several species of migratory songbirds exhibit a distinct form of habitat segregation while on their Neotropical wintering grounds in which males and females occupy different habitat types. In the American Redstart (Setophaga ruticilla), that sexual habitat segregation is a result of behavioral dominance of older males. In that study, we examined whether such dominance behavior and the resulting differential habitat segregation has consequences for the condition or survival of excluded individuals. We quantified the physical condition and survival of redstarts (both males and females) occupying two habitat types that differed in the proportion of males and females present in Jamaica. Both sexes of redstarts occupying female-biased habitat lost significantly more mass over-winter and had lower annual survival and longevity compared to individuals in male-biased habitat. These results suggest that nonbreeding habitats differed in suitability, with the least suitable habitat being occupied predominately by females. Because most female redstarts are forced to over-winter in these kinds of habitats, they may often be in poor physiological condition prior to departing on spring migration for the breeding grounds. This in turn may influence dynamics of the breeding period by determining their condition and perhaps reproductive success. Furthermore, because winter habitat segregation appears to lower female survivorship, it may also limit the number and availability of breeding females. These results implicate events that occur during the nonbreeding period as playing a critical role in the annual dynamics of this migratory species. Received 30 September 1999, accepted 8 August 2000 IDENTIFYING THE FACTORS that limit abundance of organisms is essential to understanding their population dynamics. Unfortunately, this is difficult because of the complex life cycles of most organisms and problems in assessing relative importance of factors such as weather, food, habitat, and intra-and interspecific interactions. The complexities associated with determining limiting processes becomes especially apparent for long-distance migratory birds that range over large geographical areas.Progress toward identifying factors that control population dynamics of migratory birds has been further hindered because most studies have focused on describing patterns (e.g. distribution and habitat associations: see papers in Keast and Morton 1980, Hagan and Johnston 1992, Martin and Finch 1995 rather than understanding population processes. This emphasis is especially true for research on migrant songbirds in their Neotropical wintering

Assessing the effect of seasonal agriculture on the condition and winter survival of a migratory songbird in Mexico

“…Site or habitat quality can be assessed directly by estimating winter survival, but this takes considerable time and effort. Body mass (Marra & Holmes, 2001;Angelier et al, 2011), leukocyte profiles (Cīrule, Krama, Vrublevska, Rantala, & Krams, 2012), and dates of departure for spring migration (Marra & Holmes, 2001) have all been used as metrics of winter habitat quality for migratory birds. However, in our study none of these metrics reflected the observed differences in winter survival of birds in the three habitats.…”

“…However, migratory birds can adjust the timing of departure from the wintering grounds according to ecological conditions (Marra, Francis, Mulvihill, & Moore, 2005) and each bird's ability to acquire the nutrient reserves required for long-distance migration (Smith et al, 2010;Studds & Marra, 2005). Birds wintering in habitats with limited resources delay migration onset, at the cost of decreased reproductive success (Marra, Hobson, & Holmes, 1998;Marra & Holmes, 2001;Rockwell, Bocetti, & Marra, 2012). Departure dates may therefore reflect habitat quality (Smith et al, 2010;Studds & Marra, 2005).…”

Benefits of Studies of Overwintering Birds for Understanding Resident Bird Ecology and Promoting Development of Conservation Capacity

“…Migratory-bird research on the wintering grounds must focus on identifying sites that support high annual survival of both sexes in as high abundance as possible, and management of wintering habitat must focus on maintenance of these sites (Faaborg et al 2009b), such that we avoid problems associated with low habitat quality that delay initiation of spring migration and potentially reduce reproductive success on the breeding grounds . Numerous studies are needed on the ecology of wintering migrants that equal the quality of those of Holmes et al (1989) and Marra and colleagues (Marra & Holberton 1998;Marra & Holmes 2001) on the American Redstart, Latta and Faaborg on Cape May Warbler (Dendroica tigrina) and Prairie Warbler (D. discolor) (Latta & Faaborg 2001, Wunderle (Wunderle 1995;Wunderle & Latta 2000) on Black-throated Blue Warbler, and Greenberg et al (1997Greenberg et al ( , 2000 on bird use of coffee plantations, but they need to cover a broad range of species, habitats, and geography.…”

Rainfall and habitat interact to affect the condition of a wintering migratory songbird in The Bahamas

“…Males and older individuals often occupy taller, wetter vegetation, while females and younger individuals are segregated to poorer-quality, drier habitats (Marra, 2000;Marra, Sherry, & Holmes, 1993;Mettke-Hofmann et al, 2015). Habitat segregation is important to consider because it can influence variation among age and sex classes in their ability to maintain body condition during the dry season (Marra & Holmes, 2001), and subsequently their capacity to survive or reproduce successfully (Marra, Hobson, & Holmes, 1998;Norris et al, 2004;Rockwell et al, 2017).…”