As the warm temperatures of spring start a little earlier each year due to climate change, bees and plants are keeping pace, according to a new study published online Dec. 5 in the Proceedings of the National Academy of Sciences.

An analysis of bee collection data over the past 130 years shows that spring arrives about 10 days earlier than in the 1880s, and bees and flowering plants have kept pace by arriving earlier in lock-step. The study also found that most of this shift has occurred since 1970, when the change in mean annual temperature has increased most rapidly.

The researchers compared flowering data from 106 native, bee-pollinated plant species over the last 130 years with collection data obtained for bees over the same time period. Data on bee activity was obtained from museum specimens from 10 major U.S. bee collections. A large proportion of the bee data came from the Cornell Insect Collection.

"It's an illustration of how valuable our natural history collections are at Cornell, even if you don't know in advance how these collections might be used," said Bryan Danforth, Cornell professor of entomology and a co-author of the paper. Danforth is also co-principal investigator of a project funded by the National Science Foundation (NSF) to create a database of the 10 bee collections used in this study. Lead author Ignasi Bartomeus and senior author Rachael Winfree are both entomologists at Rutgers University.

"What's amazing is that we can detect these shifting patterns of emergence phenology [timing of when a species emerges after winter] in data like this," Danforth added.

That's because each museum specimen includes such information as the collection date, host plant, precise location, habitat and collector's name. Most of the bees were collected as they hover over or sit on host plants. The study focused on 10 northeastern North American species -- including Mason bees, cellophane bees, digger bees and bumblebees -- that overwinter in a dormant state as adult bees and emerge in the early spring in step with the native plants they pollinate.