What can we learn about insect declines from studies of birds?

Most of the world’s bird species eat insects. Ornithologists, consequently, often collect insect data. Frequently, however, these data are not published in journals read by entomologists, and sometimes the details are not published at all. Using the developing EntoGEM database, which is derived from an ongoing systematic review of the scientific literature in an attempt to collate and synthesize studies that provide data on insect trends, we identified ornithological studies with potential to contribute useful data on insect trends. From these studies we asked what kinds of insects ornithologists study, where these studies have been done, and whether the studies have been included in entomological syntheses. We found many cases where ornithologists have published long-term data sets describing insect abundance that have not been included in reviews or meta-analyses on insect decline. Mapping those studies also suggests that there is potential to fill geographic knowledge gaps. Finally, bibliometric analyses supported our contention that ornithologists and entomologists often do not cite the same literature, even when writing on the same topic.