The Effects of Hackberry Psyllids on Refueling Migratory Songbirds and Autumnal Seed Rain
Hackberry psyllids (Pachypsylla sp) are a galling insect native to North America’s hackberry trees (Celtis sp). Hackberry leaf-galling psyllids are ephemerally abundant during autumn, a period of time when migratory songbirds are traveling from their breeding areas in temperate North America south to their winter ranges. These migrations are energetically taxing and many songbirds fuel their journey with resources like insects and fruits. I captured birds with mist nets, observed foraging behaviors, and captured avian-dispersed fleshy fruit seeds (hereafter, seed rain) rain during the autumn of 2016 and 2017 to determine how hackberry psyllids, an ephemerally abundant insect, affect migrating songbird refueling indices estimated from blood samples, foraging activity, and subsequent bird-dispersed seed rain patterns. I used end-point assays to measure bird metabolites to find that hackberry presence and hackberry psyllid were associated with increased protein metabolism and fat accumulation for insectivores and omnivores. I also found that hackberry seeds were most dispersed when hackberry psyllids were present. Allospecific seed rain was greater when eastern bacchharis (Baccharis hamifolia) shrubs were treated with hackberry leaves and hackberry psyllids, and allospecific seed rain was greater near hackberry trees and when hackberry psyllids were present within mixed-hardwood forests. This study adds to the growing support that insects play a crucial role for refueling migratory songbird stopover sites and that hackberry psyllids can increase the likelihood that hackberry seeds are dispersed away from the host tree and allospecific fruiting seeds are dispersed nearer the host tree.
Animal physiology, Avain biology, Community ecology, Mutualism, Plant-animal Interactions, Seed dispersal, Ecology and Evolutionary Biology, Natural Resources and Conservation, Natural Resources Management and Policy, Ornithology
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