Pre‐reproductive survival in a tropical bird and its implications for avian life histories

Abstract

The factors that affect survival until reproduction are essential to understanding the organization of life histories within and among species. Theory predicts, for example, that survival until reproduction influences the optimum level of reproductive investment by parents, which might partly explain prolonged parental care in species with high first-year survival. Tests and refinements of life-history theory have been hampered, however, by a lack of field-based estimates of pre-reproductive survival, especially for tropical species, which have been the subject of many comparative analyses. Tropical species are predicted to have higher first-year survival and delayed reproduction compared to Northern Hemisphere species. We estimated survival until reproduction, age at first reproduction, and sources of variation in juvenile survival in a Neotropical passerine, the Western Slaty-Antshrike (Thamnophilus atrinucha), in central Panama. We observed that fledged antshrikes had 76% survival through the dependent period and 48% survival to the age of 1 year; survival rate was lowest during the first week after leaving the nest. Timing of fledging within the breeding season, fledgling mass, and age at dispersal influenced survival, while sex of offspring and year did not. Individuals did not breed until two years of age, and post-fledging pre-reproductive survival was 41% of annual adult survival. High survival until reproduction in antshrikes balanced their low annual productivity, resulting in a stable population. Survival during the post-fledging period of dependence and the first year of independence in the Western Slaty-Antshrike exceeded estimates for Northern Hemisphere species. This difference appears to be associated with the extended post-fledging parental care, delayed dispersal, low costs of dispersal, and the less seasonal environment of antshrikes.

Age effects on survival of Amazon forest birds and the latitudinal gradient in bird survival

“…If this extended parental care results in increased survival of juvenile birds, it is conceivable that a latitudinal change in juvenile survival might offset the latitudinal change in clutch size. Indeed, when Tarwater et al (2011) estimated the survival of juveniles from fledgling to 1 yr of age in a Central American population of Black-crowned Antshrikes (Thamnophilus atrinucha), they obtained a value of nearly 50%, which is above the range of prereproductive survival for 7 species of North American birds that they used for comparison. Tarwater et al (2011) suggested that a relatively high pre-reproductive survival among tropical birds might resolve the apparent contradiction between the latitudinal trend in clutch size and the overlap of adult survival estimates across latitudes.…”

“…Indeed, when Tarwater et al (2011) estimated the survival of juveniles from fledgling to 1 yr of age in a Central American population of Black-crowned Antshrikes (Thamnophilus atrinucha), they obtained a value of nearly 50%, which is above the range of prereproductive survival for 7 species of North American birds that they used for comparison. Tarwater et al (2011) suggested that a relatively high pre-reproductive survival among tropical birds might resolve the apparent contradiction between the latitudinal trend in clutch size and the overlap of adult survival estimates across latitudes. Their reliance on a small number of species is a reflection of data availability; tropical studies of variation in survival as a function of age are rare and usually focus on single species (e.g., Anders et al 1997, Tarwater et al 2011, whereas information on clutch size can be mapped for thousands of species around the world (Jetz et al 2008).…”

“…Tarwater et al (2011) suggested that a relatively high pre-reproductive survival among tropical birds might resolve the apparent contradiction between the latitudinal trend in clutch size and the overlap of adult survival estimates across latitudes. Their reliance on a small number of species is a reflection of data availability; tropical studies of variation in survival as a function of age are rare and usually focus on single species (e.g., Anders et al 1997, Tarwater et al 2011, whereas information on clutch size can be mapped for thousands of species around the world (Jetz et al 2008). The scarcity of multispecies comparisons between juvenile and adult survival leaves open the possibility that there may, after all, be a latitudinal gradient in adult survival.…”

Stage-dependent survival in relation to timing of fledging in a migratory passerine, the Northern Wheatear (Oenanthe oenanthe)

“…Most if not all studies show a dip in daily survival during the first few days after fledging (Sullivan 1989, Anders et al 1997Sim et al 2013;Kershner et al 2004;Tarwater et al 2011 ;Yackel Adams et al 2006;NaefDaenzer et al 2001;Dybala et al 2013). In addition, some studies show a second dip after the nestlings have become independent (Sullivan 1989;Anders et al 1997;Sim et al 2013) although others do not (Kershner et al 2004;Tarwater et al 2011;Yackel Adams et al 2006;Naef-Daenzer et al 2001).…”

“…In addition, some studies show a second dip after the nestlings have become independent (Sullivan 1989;Anders et al 1997;Sim et al 2013) although others do not (Kershner et al 2004;Tarwater et al 2011;Yackel Adams et al 2006;Naef-Daenzer et al 2001). We divided survival into two periods (B4 and [4 weeks after fledging) and found some support for differential survival between them.…”