Abstract
We examined effects of movement patterns and habitat use of female Wood Ducks (Aix sponsa) during incubation on incubation constancy and recess frequency. Incubating females (n = 41) were equipped with subcutaneous radiotransmitters and subsequently located during daily recess events. Using compositional analysis, we determined beaver ponds, creeks, ephemeral wetlands, and lake-influenced habitats ranked higher in preference than other available aquatic habitats (i.e. managed impoundments, farm pond, and lake habitats). An inverse relationship between female use of the top four ranked habitats and recess range size suggested that those were high-quality habitats. Mean (±SE) incubation constancy (n = 40 nests) was 81.3 ± 0.8%, and females took an average of 2.2 ± 0.3 recesses day−1. Incubation period averaged 31.8 ± 0.3 days, and there was a weak inverse relationship between incubation period and incubation constancy. Incubating females lost 3.9 ± 0.8% of early incubation body mass, but body-mass changes were not associated with use of preferred habitats (i.e. beaver ponds, creeks, ephemeral wetlands, and lake-influenced areas). Initiation date of incubation and percentage use of preferred habitats were the most important variables describing variation in incubation constancy. Constancy declined later in the breeding season and with increased use of preferred habitats. Recess frequency decreased with increasing variation in distances that females traveled from the nest. Wood Ducks nesting at southern latitudes generally are not energetically constrained during incubation, and nest attentiveness is only weakly associated with incubation period. We would expect stronger relationships between habitat use, body-mass dynamics, and incubation behavior under environmental conditions that are more severe or less predictable.
Are thyroid hormones mediators of incubation temperature-induced phenotypes in birds?