PARENT SESSION
PT11 - PCB Fate & Effects in the Housatonic River
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P688) Spatial and Demographic Effects on Tree Swallow Nest Quality and Reproductive Success.
Robertson, Ralleigh1, Jones, Jason2, Henning, Miranda*,3, 1 Queen's University, Kingston, Ontario, Canada2 Dartmouth College, Hanover, NH, USA3 ARCADIS, Portland, ME, USA
ABSTRACT- Nest−box studies with tree swallows (Tachyneta bicolor) are often used to evaluate risks posed to birds by contaminated sediments. This study design is favored because tree swallows readily breed in nest boxes and may be exposed to chemicals in sediments via the food chain because they feed on emergent insects. However, many factors other than chemical exposures can influence productivity of tree swallows in nest−box studies. This study′s objective was to determine the effects of inter−nest spacing, proximity to forest edge, timing of settlement and nest building, availability of nesting material, age of the breeding pair, and history of the nest−box and grid on reproductive success and/or nest quality in birds not exposed to chemicals above background levels. Nests located close together had lower nest mass, later clutch initiation, shorter incubation periods and fewer fledglings than nests spaced farther apart. Nests located close to forest edge had lower nest mass, smaller clutch sizes and later initiation. Younger females and nests settled later in the year were both associated with lower reproductive success. The history of the nest−box and grid influenced first egg dates, incubation periods, clutch and brood size, and fledging success. This study also indicated little or no effect of nest quality on reproductive success. If meaningful conclusions are to be drawn about the effects of chemicals on tree swallow nesting behavior and reproductive success, it is critical that potential confounding factors such as those evaluated in this study be carefully controlled.
Key words: tree swallows, reproduction, nest box, study design