Stopover singing is common in migrating male New World warblers (Parulidae) but differs from song produced during breeding

Migratory singers dynamically overlap the signal space of a breeding warbler community

“…We conducted our study of the signal space of migrant and breeding warblers at natural areas in Kalamazoo and Van Buren Counties (42.290 N, 85.586 W), Michigan, U.S.A., between April and July, 2019 and 2020. Migrant warblers move through this region during April–June (Sblendorio & Gill, 2023); thus, we recorded birds when migrants were abundant and also when they had moved out of the region and only breeding species remained in the community. To explore signaling niches and patterns of overlap, we recorded songs of 30 warbler species, categorizing species as local breeders ( n = 11) or migrants ( n = 19) based on whether each was confirmed as breeding within Kalamazoo Co. (Chartier et al., 2011; http://www.ebird.org).…”

“…To minimize acoustic interference, co‐existing species are predicted to inhabit distinct, non‐overlapping regions of signal space, as observed in breeding communities across diverse taxa (birds: e.g., Luther, 2009, frogs: e.g., Chek et al., 2003, insects: e.g., Schmidt et al., 2013, bats: e.g., Kingston et al., 2000, and fish: e.g., Bertucci et al., 2020). In addition to the vocalizations of locally breeding species, migrant bird species often sing when they temporarily reside in a stopover habitat to refuel for the next leg of their journeys (Gahr, 2020; Sblendorio & Gill, 2023). Migrant species use the presence of seasonally breeding species (i.e., both other migrants that breed in an area and year‐round resident species) as cues to habitat quality and food availability in unfamiliar areas (Rodewald & Brittingham, 2002), such that breeding and migrant species commonly co‐occur.…”

“…The brevity of migration, paired with interspecific differences in both the timing of migration (Helm et al., 2009) and the extent of singing during stopovers (Sblendorio & Gill, 2023), may lead to dynamic patterns of overlap in and competition for signal space. Differences in the timing of arrival at stopovers could stagger and prolong acoustic overlap among migrant and breeding species, such that males of breeding species, singing to defend territories and attract mates, are likely to be confronted with a continuously changing acoustic community.…”

“…Migrant and breeding warblers are likely to co-occur and share signal space: migrant warblers join interspecific flocks (Zou et al, 2018), breeding warblers show high species co-occurrence (Cohen & Satterfield, 2020;Lovette & Hochachka, 2006), and critically, warblers sing during migratory stopovers (e.g. Cox, 1960;Janes, 2017;Morse, 1991;Sblendorio & Gill, 2023;Trautman, 1940).…”