Source data for: Nesting success of Red-winged Blackbirds (Agelaius phoeniceus) in marshes in an anthropogenic landscape

Recent analyses show significant population declines in many abundant
avian species, especially marsh-nesting species including the Red-winged
Blackbird (RWBL). Hypothesized causes include reduced nesting success
resulting from changing land use patterns and exposure to contaminants.
Our goal was to test the hypothesis that landscape and nest
characteristics as well as exposure to polychlorinated biphenyls (PCBs)
correlate with nesting success. From 2008-2014, we measured clutch size,
egg and nestling mass, hatching and fledging success, and daily survival
of 1293 RWBL nests from 32 marshes in the Hudson River valley of New York.
Using generalized linear effect and survival models, we found that: (1)
Julian date was negatively related to hatching success and clutch size but
positively related to egg mass; (2) nest height was negatively related to
hatching success; (3) nestling mass decreased with increased nest density
and distance to edges; (4) fledging success was significantly lower in
nests closer to the ground that were far from water; and (5) clutch size
and daily survival were higher in nests farther from  water.
Results showed that nesting success was correlated with variables
associated with flooding, population density, and predation and provided
no support for the predicted negative effects of PCB exposure.