Weak premating reproductive isolation despite divergence in secondary sexual traits in the Variable Seedeater

The likelihood of hybridization after secondary contact is reduced when assortative mating is strong and fitness of hybrids is low; thus, maintaining reproductive isolation. To this end, signals that convey population identity may enhance recognition and reduce hybridization by promoting assortative mating. Here, we studied visual and acoustic signals, plumage colour and song, that commonly mediate species recognition in birds to evaluate their role in reproductive isolation in a recently diverged clade of Neotropical birds. Subspecies of the Variable Seedeater (Sporophila corvina) that differ dramatically in plumage colour have established secondary contact at two independent contact zones in Costa Rica and Panama. We first evaluated divergence in song in allopatric populations close to the most recent contact zone (Costa Rica), where the two subspecies do not hybridize, and found significant differences in song structure and composition of song elements between subspecies. Then, we us..., Song Recording and measurement
We evaluated variation in song structure and element composition between two S. corvina subspecies, S. c. corvina (here after named as corvina) and S. c. hoffmanni (here after named as hoffmanni). Male songs were recorded in the field at sites in the Caribbean (corvina males) and Pacific (hoffmanni males) slopes of central and eastern Costa Rica. We also recorded a few hybrid individuals from Gamboa, Panama to evaluate how acoustic signals from this black-pied hybrid population compares to the allopatric populations. Songs were recorded in two consecutive seasons between April and May 2019, and between July and August 2020, using a Tascam DR-100MKIII Linear PCM Recorder (Tascam Corporation, Japan), coupled with a Sennheiser ME66/K6 directional microphone system (Sennheiser Electronic Corporation, Germany) housed in a Rycote 055208 standard Windshield, at 16 bits and a 48-kHz sampling rate in a WAV file. To supplement our field recordings, we included recor..., , # Data from: Weak premating reproductive isolation despite divergence in secondary sexual traits in the Variable Seedeater

[https://doi.org/10.5061/dryad.8gtht76x5](https://doi.org/10.5061/dryad.8gtht76x5)

The dataset comprises structural measurements of songs from two subspecies and hybrids of *Sporophila corvina*, along with behavioral responses recorded during playback and mount presentations. The song measurements are utilized to estimate song variation between and within subspecies, and to assess how hybrid individuals differ from allopatric populations. Behavioral responses to playback and mount experiments were documented to evaluate how territorial males of *S. corvina* subspecies respond to simulated intrusions from decoys bearing homotypic or heterotypic signals (song and plumage color) in all possible combinations. These behavioral responses are utilized to assess male-male aggression as a proxy for premating reproductive isolation.

## Description of the data and file stru...