Abstract

Artificial nest box programs have frequently been initiated to increase breeding habitat and bolster Wood Duck (Aix sponsa) populations. However, Wood Duck colonies relying heavily on nest box programs are also prone to lower nest hatchability and increased nest abandonment, possibly due to extreme levels of conspecific brood parasitism (CBP). In 2010, 2012, and 2013 we monitored ~100 nest boxes in northern Utah, USA, for excessive brood parasitism. Data were gathered describing nest box visibility and the surrounding habitat attributes from nest box characteristics and land-cover datasets, then logistic regression was used to assess the factors affecting CBP in the population. Using two clutch size thresholds (14 and 16 eggs) to define extreme CBP, nest box mounting method was identified to have the greatest effect on CBP, with tree-mounted nest boxes having a lower probability of CBP than pole-mounted boxes in each year of the study. The effects of habitat attributes derived from land-cover datasets were not identified, likely because the 30 m resolution does not consistently identify narrow strips of riparian habitat where many nest boxes are located. Results agree with hypotheses that tree-mounted boxes offer more concealment for nest sites making them more difficult for parasites to locate. Placing nest boxes in trees, where possible, may increase egg hatchability and decrease nest abandonment by decreasing the occurrence of extreme CBP in artificially nesting Wood Duck populations.

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Hafen, K. and D. N. Koons. 2016. Factors affecting conspecific brood parasitism in Wood Duck Aix Sponsa of the intermountain region of North America. Wildfowl. 66:186-196.