Observations of 2017 Tree Swallow Prey

While photographing purple martin prey being brought to their nestlings, I also briefly monitored prey brought to four tree swallow nests in our yard. The tree swallow nests each contained older nestlings capable of swallowing larger prey. Many feeding visits did display prey items too large to be completely hidden in the adult’s mouth.  However, sometimes the adult would place its closed beak into the wide gape of a nestling before opening its mouth, and, likely ejecting a bolus of tiny insects such as gnats or mosquitoes. These, of course, went unrecorded.  But, the larger prey closely mimicked the medium size prey that purple martins were bringing to their larger nestlings.  Both species had a field day with the swarming hover flies. And, both species brought a great variety of insects to the nests.  Perhaps a decrease in the numbers of flying insects is not the cause of our decreasing barn swallow population, since these two other species of aerial insectivores are doing fine here.  But, it still seems that we have had far fewer insects on our property in recent years.  I should try to monitor barn swallow prey in 2018 – a much harder task.