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There is growing interest in latitudinal effects on animal behaviour and life history. One recent focus is on birdsong, which is hypothesized to be more elaborated or complex in the north temperate zone compared with the tropics. Current evidence is mixed and based on cross-species comparisons, or single species with restricted distributions. We circumvent these limitations using a transcontinental sample of 358 songs from house wrens (Troglodytes aedon) at 281 locations spanning more than 1008 of latitude (528 N-558 S) across the Americas. We found a significant latitudinal gradient in several basic elements of song performance and complexity between north temperate and tropical populations. Furthermore, we document convergence in song patterns between populations at higher latitudes in the Northern and Southern Hemispheres. Effects were strongest for the number of elements in a song, and the rate of element production, both increasing towards the poles, with similar but weaker effects for other song dimensions (e.g. number of unique elements, trills and trill rate). We consider possible causes related to variable habitats and morphology, concluding that the shorter breeding seasons at higher latitudes in both hemispheres may favour greater song elaboration to mediate territory competition and mate choice.

Among songbirds with large song-type repertoires, there may be functional variation in how individuals organize and display song-type diversity over time. Past studies focusing on conventional measures of song production have been extremely productive. However, network analysis offers a novel set of tools to quantify additional, previously unstudied elements of song organization and display. We studied protracted bouts of singing by 10 male House Wrens (Troglodytes aedon) to (1) test functional hypotheses of variation in song diversity in this species, and (2) evaluate the utility of network metrics in such research. Our analysis included a variety of conventional measures of song production and several standard metrics from network theory to quantify how variably the many song types in a male's repertoire could be connected to one another and the limitations or diversity of their song sequences. Analysis of conventional variables showed that males produced more and longer songs, at shorter intervals, containing more syllables and more different syllable types, and also more different song types, prior to than after pairing and early in the morning regardless of breeding stage. These results are consistent with the hypothesis that song diversity functions in mate attraction and possibly in territory signaling. In contrast, analyses of network metrics revealed variety in song sequencing by males, but comparatively few and weak effects associated with either breeding stage or time of day. Overall, most song types connected to only a few others and a relatively small proportion of all possible song-type transitions actually occurred. Hence, much of the variety in song sequencing that was possible with the large song repertoires of males was not realized. The latter outcomes, brought to light via network analyses, highlight an important paradox for future research on this and related species with large song repertoires.

House Wrens (Troglodytes aedon Vieillot, 1809) are among the best studied songbirds in North America, but most of what is known about this model species derives from studies using artificial nestboxes. Consequently, we know comparatively little about the natural breeding biology of House Wrens and whether it corresponds to patterns reported from nestboxes. To address these issues, we report a study of nest site selection and breeding phenology in Western House Wrens (Troglodytes aedon parkmanii Audubon, 1839) using natural cavities in aspen forests in southwest Alberta, Canada. A total of 96 breeding pairs, representing 77 different banded males, were studied across a 4 year period (2011–2014). In total, 78% of arriving males paired, with 52% of nests successfully fledging. More than 30% of males attempted polygyny, but only 8% succeeded. Distinct patterns were observed for many characteristics of the nest site and cavity, including the type of tree used, as well as the cardinal direction and dimensions of the cavity entrance, its location on the nest tree, and its height above the ground, some of which were related to pairing and breeding success. Results are compared with studies of House Wrens using artificial nestboxes with broader application to many other model species likewise studied primarily using nestboxes.

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