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Local density regulates migratory songbird reproductive success through effects on double‐brooding and nest predation
Author(s) -
Woodworth Bradley K.,
Wheelwright Nathaniel T.,
Newman Amy E. M.,
Norris D. Ryan
Publication year - 2017
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1002/ecy.1911
Subject(s) - fledge , nest (protein structural motif) , reproductive success , songbird , biology , ecology , predation , avian clutch size , population , density dependence , seasonal breeder , population density , reproduction , zoology , demography , biochemistry , sociology
Knowledge of the density‐dependent processes that regulate animal populations is key to understanding, predicting, and conserving populations. In migratory birds, density‐dependence is most often studied during the breeding season, yet we still lack a robust understanding of the reproductive traits through which density influences individual reproductive success. We used 27‐yr of detailed, individual‐level productivity data from an island‐breeding population of Savannah sparrows Passerculus sandwichensis to evaluate effects of local and total annual population density on female reproductive success. Local density (number of neighbors within 50 m of a female's nest) had stronger effects on the number of young fledged than did total annual population density. Females nesting in areas of high local density were more likely to suffer nest predation and less likely to initiate and fledge a second clutch, which led to fewer young fledged in a season. Fledging fewer young subsequently decreased the likelihood of a female recruiting offspring into the breeding population in a subsequent year. Collectively, these results provide insight into the scale and reproductive mechanisms mediating density‐dependent reproductive success and fitness in songbirds.