For reasons that are not fully understood, some orchard orioles will nest close to the nests of eastern kingbirds. This might come as a surprise since eastern kingbirds have the reputation of aggressively defending their nests. Well, many experts believe that this is the reason why orchard orioles will choose nest sites sometimes within mere yards from the nests of eastern kingbirds.
It seems obvious that kingbirds do not feel threatened by North America’s smallest oriole. However, when kingbirds fly out to confront a crow, common grackle or other potential avian nest predator flying close to their nests, they unwittingly also defend the nearby nests of orchard orioles.
Some studies suggest that this behavior may translate into real benefits for the orchard orioles. Studies have shown that, when the nesting success of orchard orioles that nest close to eastern kingbirds was compared with the success of those that do not, they discovered the nesting success of orioles that nest some distance away from eastern kingbird nests was lower. In fact, there also seems to be a correlation between kingbird populations and orchard oriole populations. When eastern kingbird numbers are high orchard orioles are more abundant too.