Large-scale disturbances such as ice storms may increase in frequency
and intensity as climate changes. While disturbances are a natural
component of forest ecosystems, climatically driven alteration to
historical patterns may impart fundamental change to ecosystem
function. At Hubbard Brook Experimental Forest, NH, experimental ice
storms of varying severity were applied to replicate plots of mature
northern hardwoods to quantify their effects on forested ecosystems.
We assessed ice storm treatment effects on insectivorous
foliage-gleaning birds and their interactions with larval Lepidoptera.
These birds are charismatic, of conservation concern, and are a major
predator of caterpillars. In turn, lepidopterans are the dominant
herbivores in temperate forests and are integral to ecosystem
function. We predicted that avian abundance would increase due to
additional structural heterogeneity caused by ice treatments, with a
concomitant increase in caterpillar predation.
Point counts were used to measure insectivorous bird activity in the
ice storm experiment plots and additional control plots before and
after treatments. Point counts were conducted in June 2015 and June
2016. Icing occurred in January-February 2016. We deployed and
retrieved plasticine model caterpillars and estimated predation from
characteristic marks to these surrogates. Abundance of
foliage-gleaning birds was higher in the ice storm plots and birds
responded to treatments as a single diffuse disturbance rather than on
an individual plot level. All species except one were observed both
before and after the ice treatments. Surprisingly, predation on
caterpillar models was unaffected by ice storm treatments but rather
was a function of caterpillar density. The increase in avian abundance
in the ice storm treatment plots corroborates other studies of bird
responses to relatively small-scale disturbances in forests and the
limited change in species composition was expected given the plot
size. We conclude that ice storms may provide beneficial changes for
foliage-gleaning birds in the growing season following the
disturbance.
These data were gathered as part of the Hubbard Brook Ecosystem Study
(HBES). The HBES is a collaborative effort at the Hubbard Brook
Experimental Forest, which is operated and maintained by the USDA
Forest Service, Northern Research Station.
A complete analysis of these data can be found in: Leuenberger, W. M.
(2017). Response of larval lepidoptera and their avian
predators to experimental ice storms in a northeastern
forest (Order No. 10282770). Available from ProQuest
Dissertations & Theses A&I. (1950488566).