This metadata record represents passive immunity components of six songbird species (Passeriformes) in a single taxonomic family, the New World blackbirds (Icteridae). Six immune elements were compared among blackbird eggs collected in North Dakota, South Dakota, and Puerto Rico, including immunoglobulins (Ig) in both yolk and albumen, lipopolysaccharide-specific immunoglobulins in both yolk and albumen, and ovotransferrin and lysozyme in albumen. The data were summarized and used in the analysis for a peer-reviewed journal publication entitled: "Do life history traits influence patterns of maternal immune elements in New World blackbirds (Icteridae)?" The data consist of two data sets. The first data set includes day, year, and ___location (county or municipality, U.S. State or Territory) of egg collection, a species code, a ratio between positive and negative values of immunoglobulin in egg yolk, and a ratio between positive and negative values of lipopolysaccharide-specific immunoglobulins in egg yolk. The second data set includes day, year, and ___location (county or municipality, U.S. State or Territory) of egg collection, a species code, a ratio between positive and negative values of immunoglobulin in egg albumen, a ratio between positive and negative values of lipopolysaccharide-specific immunoglobulins in egg albumen, concentration of lysozyme (an antimicrobial enzymen) in egg albumen, and concentration of ovotransferrin (an antimicrobial enzymen) in egg albumen. Both data sets also include information on parasitism rates in the northern Great Plains between 1990 to 2015 (L.D. Igl, unpublished data) and average incubation periods for blackbird species from the literature.