An Experimental Investigation of Nest Reuse and Nest Site Selection in an Open-Cup Nesting Passerine

摘要

Eastern Kingbirds (Tyrannus tyrannus) breed from coast to coast in North America and build open-cup nests in trees. They have been extensively studied across most of their range and have only on occasion been documented to reuse a nest from a previous season. However, at Malheur National Wildlife Refuge (MNWR), located in southeastern Oregon, ~10 % of female Eastern Kingbirds reuse old nests of mainly American Robins (Turdus migratorius). In an attempt to address why nest reuse is so common at MNWR, I used artificial nests to evaluate two hypotheses as to why nest reuse is common in this breeding population. The first hypothesis states that Eastern Kingbirds reuse nests to save time and/or energy (TES) and the second one states nest reuse occurs because there is a shortage of suitable nest sites (NSS). I was able to reject the TES hypothesis because artificial nests provided no apparent reproductive benefits to Eastern Kingbirds, except that if a nest had failed it took less time to lay a replacement clutch after an initial failure if an artificial nest was used instead of building a new nest. A more reasonable explanation is that Eastern Kingbirds face a limited availability of suitable nest sites. With this in mind, I took vegetation measurements to address the hypothesis that Eastern Kingbirds make adaptive choices when selecting a nest site, in which case they would choose sites that increase their probability of breeding successfully. Successful nests, both natural and artificial, were placed higher in a tree and on a steeper angled nest branch than their failed counterparts. Those findings suggest that Eastern Kingbirds make adaptive choices when selecting a nest site.