Effects of egg order on organic and inorganic element concentrations and egg characteristics in tree swallows, Tachycineta bicolor

Abstract

The laying order of tree swallow eggs was identified from the Housatonic River, Berkshire County, Massachusetts, USA, and eggs were chemically analyzed individually to document possible effects of laying order on organic contaminant and inorganic element concentrations. Effects of laying order on other parameters such as egg weight, size, and lipid and moisture content also were assessed. Some effects of egg order on total polychlorinated biphenyls (PCBs) were detected, but the effect was not uniform across individual females or between years. In 2004, clutches with higher total PCBs tended to have concentrations decline across egg order, whereas clutches with lower concentrations of PCBs tended to increase across egg order. In contrast, in 2005, there was a tendency for concentrations to increase across egg order. Polychlorinated biphenyl concentrations were highly variable within and among clutches in both years. The directionality of egg order associations (i.e., slopes) for trace elements was element dependent, was positive for Mn and Zn, was negative for B, and had no slope for Cr. Whole egg weight increased across egg order. Percentage lipid was variable within a clutch, with no pattern common across all females. Percentage lipid was also correlated with organic contaminant concentration. In highly contaminated environments, higher lipid content could have the unanticipated corollary of having higher concentrations of lipophilic contaminants such as PCBs. To reduce the effect of high variation within a clutch when assessing contamination exposure, it is recommended that two eggs per clutch be collected and pooled for chemical analysis. We further recommend that, as long as the two eggs are randomly collected, the additional effort needed to identify and collect specific eggs is not warranted.

Individual variation in body burden, lipid status, and reproductive investment is related to maternal transfer of a brominated diphenyl ether (BDE-99) to eggs in the zebra finch

“…The relationships of contaminant exposure level and clutch mass with the reduction in maternal burden over the laying period could also have consequences on laying order effects, if the decreasing burden results in declining egg concentrations. Reviews of studies on laying order effects on egg contaminant concentrations have found that there is no consistent pattern for egg contaminants over the laying sequence, and the majority of studies show no significant laying order effects [7,39]. This is not surprising, as individual variation in maternal contaminant burden and reproductive investment could result in variation in laying order effects among individuals.…”

Changes in polychlorinated biphenyl (PCB) exposure in tree swallows (Tachycineta bicolor) nesting along the Sheboygan River, WI, USA

“…Eggs were collected shortly after the clutch was completed during the last week in May and the first week in June, the contents placed in chemically-clean jars, and frozen at -20°C until chemically analyzed. The specific eggs collected were taken haphazardly from the completed clutch; there is no evidence that laying order or stage of incubation affects total PCB concentrations in a predictable manner (Custer et al 1997(Custer et al , 2010b. In 1990s, eggs, 'pippers' consisting of pipping eggs or just-hatched nestlings within a day of hatching, and 12-day-old nestlings (±1 day of age) were collected, whereas in 2010s, eggs and 12-day-old nestlings were collected.…”

Effects of in ovo exposure to 3,3′,4,4′-tetrachlorobiphenyl (PCB 77) on heart development in tree swallow (Tachycineta bicolor)

“…The purpose of the present study was to determine whether PCB 77 increased mortality in tree swallows eggs and to assess other impacts of this congener, particularly heart defects in the developing embryo. The Upper Hudson River was considered contaminated based on previous studies and measurements of PCBs in eggs collected from nests in that region [29][30][31]. Embryos in these eggs were considered environmentally exposed and were not dosed with PCB 77 treatments.…”