Differential changes in the onset of spring across US National Wildlife Refuges and North American migratory bird flyways

• DOI: 10.1371/journal.pone.0202495
• Publication Date: 2018-09-12T13:47:35Z
• Authors: Eric K. Waller; Theresa M. Crimmins; Jessica J. Walker; Erin E. Posthumus; Jake F. Weltzin
• Keywords: Flyway; Warbler

Warming temperatures associated with climate change can have indirect effects on migratory birds that rely seasonally available food resources and habitats vary across spatial temporal scales. We used two heat-based indices of spring onset, the First Leaf Index (FLI) Bloom (FBI), as proxies habitat for period 1901 to 2012 at three scales: US National Wildlife Refuge System; four major bird flyways in North America; seasonal ranges (i.e., breeding non-breeding grounds) species, Blue-winged Warbler (Vermivora cyanoptera) Whooping Crane (Grus americana). Our results show relative historical range variability, onset is now earlier 76% all wildlife refuges extremely early exceeding 95% conditions) 49% refuges. In but Pacific, rate advance generally greater higher latitudes than lower latitudes. This differential most pronounced Atlantic flyway, presumably because a "warming hole" southeastern US. Both FLI FBI advanced markedly ranges–but not ranges–of selected albeit considerable intra-range variation. Differences among species terms patterns location extent habitats, well shifts conditions over time, may complicate predictions vulnerability effects. study provides insight into how phenology disparate linked could inform local- landscape-scale management strategies conservation populations.