Juvenile Mortality Increases with Clutch Size in a Neotropical Bird

• Published in: Ecology (Durham) Vol. 86; no. 12; pp. 3238 - 3244
• Main Authors: Styrsky, Jennifer Nesbitt, Brawn, Jeffrey D., Robinson, Scott K.
• Format: Journal Article
• Language: English
• Published: Washington, DC Ecology Society of America 01-12-2005; Ecological Society of America
• Subjects: Age; Animal and plant ecology; Animal nesting; Animal populations; Animal reproduction; Animal, plant and microbial ecology; Aves; Biological and medical sciences; Bird nesting; Birds; clutch manipulation; Clutch size; Ecological life histories; Eggs; Evolution; food limitation; Forest ecology; Fundamental and applied biological sciences. Psychology; General aspects; Hylophylax naevioides; juvenile mortality; life history; Mortality; Neotropics; nest predation; parental care; post-fledging; Predation; Spotted Antbird; Survival analysis; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Young animals; Panama; Parental care; food limitation; Life history; post-fledging; Mortality; Clutch size; Neotropics; Young animal; juvenile mortality; Feeding; clutch manipulation; Hylophylax naevioides; Vertebrata; nest predation; Manipulation; Spotted Anthird; Predation; Aves; Nest; Fledging
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/04-1613

The change in avian clutch size with latitude is a celebrated example of geographic variation in a vertebrate life-history trait. Alternative hypotheses for this pattern invoke nest predation, limited food for nestlings, or post-fledging juvenile mortality as selection pressures leading to small clutch size of tropical birds. We manipulated the clutch size of Spotted Antbirds (Hylophylax naevioides) in central Panama to test these hypotheses. We observed that rates of nest predation were not influenced by parental activity at nests and parents could successfully feed nestlings in enlarged broods. Although larger broods produced the most fledged juveniles, these individuals were less likely to survive to dispersal than were juveniles that fledged from smaller broods. Consequently, nest productivity did not vary with clutch size. Post-fledging mortality was not related to nestling mass two to three days prior to fledging. Rather, differences in the allocation of parental investment per juvenile among differently sized broods appeared to influence juvenile survival probability. These results identify parental care during the post-fledging period as a potential key factor influencing the evolution of small clutch size in tropical birds.